<%BANNER%>

Timing of climatic factors that may influence potato yield, quality, and potential nitrogen losses in a northeast Florid...

HIDE
 Title Page
 Dedication
 Acknowledgement
 Table of Contents
 List of Tables
 List of Figures
 Abstract
 Introduction
 Development of a growing degree...
 Yield and quality of 'Atlantic'...
 Summary, and future research
 Appendices
 References
 Biographical sketch
University of Florida Institutional Repository

PAGE 1

TIMING OF CLIMATIC FACTORS THAT MAY INFLUENCE POTATO YIELD, QUALITY, AND POTENTIAL NITROGEN LO SSES IN A NORTHEAST FLORIDA SEEPAGE-IRRIGATED POTATO PRODUCTION SYSTEM By CHRISTINE MARIA WORTHINGTON A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2006

PAGE 2

Copyright 2006 by Christine Maria Worthington

PAGE 3

To my two strongholds in life, Curtiss and Jevin.

PAGE 4

iv ACKNOWLEDGMENTS I would like to extend my d eepest and heartfelt gratitude to Chad M. Hutchinson, my advisor, for his unwavering support, patie nce and confidence in my ability to achieve my goal. I would also like to extend my sincere appreciation to my committee members, Drs. Bill Stall, Rao Mylavarapu, Tom Obreza, Kenneth Portier and James White, for their patience and guidance through th is life lesson. I would es pecially like to thank Dr. Portier for unselfishly assisting me in analyz ing all the data and his patience getting it completed. The completion of this work would not ha ve been possible if it werent for the dedicated staff at the Plant Science and Re search Unit, Hastings, FL., especially Doug Gergela, Pam Solano, Bart Harrington and Larry Miller. I sincerely appreciate the faculty and staff in the Horticultural Sciences Department for giving me the opportunity to accomplish my goal. I would like to thank my parents, Paul a nd Cecilia Worthington and Patti Hoff, for their unconditional love and support and believing I can. Finally, all this wouldnt have been possi ble if it werent for the support and love and years of patience from Curtiss and Jevin who I owe my deepest gratitude.

PAGE 5

v TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES...............................................................................................................x LIST OF FIGURES.........................................................................................................xvi ABSTRACT...................................................................................................................xvii i CHAPTER 1 INTRODUCTION........................................................................................................1 Florida Potato Production.............................................................................................1 Tri-County Agricultural Area................................................................................2 Potato Capital of Florida.......................................................................................3 Florida Chip Potato Varieties................................................................................4 Seasonal Environmental Stress Associated with IHN..................................................7 Moisture Stress......................................................................................................8 Nutrition................................................................................................................9 Rationale..............................................................................................................10 Organization of Dissertation.......................................................................................11 2 DEVELOPMENT OF A GROWING DEGREE DAY MODEL TO DETERMINE OPTIMAL PLANTING DATE AND E NVIRONMENTAL INFLUENCE ON POTATO YIELD AND QUALITY IN NORTHEAST FLORIDA...........................12 Introduction.................................................................................................................12 Growing Degree Days................................................................................................13 Materials and Methods...............................................................................................14 Site Description...................................................................................................14 Experimental Design...........................................................................................14 Crop Production Practices..........................................................................................15 Tuber Planting.....................................................................................................15 Irrigation..............................................................................................................15 Nutrient Management..........................................................................................16 Tuber Production Analysis..................................................................................16 Tuber Specific Gravity........................................................................................17 External Quality...................................................................................................17 Internal Quality....................................................................................................17

PAGE 6

vi Growing Degree Days................................................................................................18 Statistical Analysis......................................................................................................18 Results And Discussion..............................................................................................19 Tuber Yield for 2004...........................................................................................19 Planting date main effect..............................................................................19 Nitrogen rate main effect..............................................................................20 Variety main effect.......................................................................................20 Main effect interaction.................................................................................20 Tuber Yield for 2005...........................................................................................21 Planting date main effect..............................................................................21 Nitrogen rate main effect..............................................................................22 Variety main effect.......................................................................................22 Main effect interactions................................................................................23 Tuber External Quality for 2004.........................................................................23 Planting date main effect..............................................................................23 Nitrogen main effect.....................................................................................24 Variety main effect.......................................................................................24 Tuber External Quality for 2005.........................................................................24 Planting date main effect..............................................................................24 Nitrogen rate main effect..............................................................................24 Variety main effect.......................................................................................25 Tuber Internal Quality for 2004..........................................................................25 Planting date main effect..............................................................................25 Nitrogen rate main effect..............................................................................26 Variety main effect.......................................................................................26 Tuber Internal Quality for 2005..........................................................................26 Planting date main effect..............................................................................26 Nitrogen rate main effect..............................................................................27 Variety main effect.......................................................................................27 Growing Degree Day Model......................................................................................28 Growing Degree Day Model and Potato Plant Development.............................28 Growing Degree Day Model and Tuber Yield....................................................28 Growing Degree Day Model and Internal Tuber Quality...................................30 Conclusion..................................................................................................................31 3 YIELD AND QUALITY OF ATLANTIC POTATO ( SOLANUM TUBEROSUM L.) TUBERS AND OFF-FI ELD NUTRIENT MOVEMENT UNDER VARYING NITROGEN S OURCES AND STAGED LEACHING IRRIGATION EVENTS.............................................................................................49 Introduction.................................................................................................................49 Materials and Methods...............................................................................................53 Site Description...................................................................................................53 Experimental Design...........................................................................................53 Crop Production Practices..........................................................................................54 Tuber Planting.....................................................................................................54 Irrigation..............................................................................................................54 Nutrient Management.................................................................................................55

PAGE 7

vii Ammonium Nitrate Nitrogen..............................................................................55 Controlled Release Fertilizer...............................................................................56 Tuber Production Analysis.........................................................................................56 Tuber Specific Gravity........................................................................................57 External Quality...................................................................................................57 Internal Quality....................................................................................................57 Water Sample Collection and Nutrient Load..............................................................57 Surface Run-Off Volume....................................................................................57 Nutrient Load.......................................................................................................58 Wells....................................................................................................................58 Lysimeters...........................................................................................................58 Growing Degree Day Model......................................................................................59 Statistical Analysis......................................................................................................59 Results And Discussion..............................................................................................60 Tuber Yield for 2004...........................................................................................60 Irrigation date main effect............................................................................60 Fertilizer main effect....................................................................................61 Main effect interactions................................................................................61 Tuber Yield for 2005...........................................................................................62 Irrigation date main effect............................................................................62 Fertilizer main effect....................................................................................63 Sidedress main effect...................................................................................63 Main effect interactions................................................................................63 Tuber External Quality for 2004.........................................................................64 Irrigation date main effect............................................................................64 Fertilizer main effect....................................................................................64 Sidedress main effect...................................................................................64 Tuber External Quality for 2005.........................................................................64 Irrigation date main effect............................................................................64 Fertilizer main effect....................................................................................65 Sidedress main effect...................................................................................65 Tuber Internal Quality for 2004..........................................................................65 Irrigation date main effect............................................................................65 Fertilizer main effect....................................................................................67 Sidedress main effect...................................................................................68 Tuber Internal Quality for 2005..........................................................................69 Irrigation date main effect............................................................................69 Fertilizer source main effect.........................................................................70 Sidedress main effect...................................................................................70 Nitrate Nitrogen Concentration in Wells for 2004..............................................71 Irrigation main effect....................................................................................71 Fertilizer main effect....................................................................................71 Sidedress main effect...................................................................................72 Nitrate Nitrogen Concentration in Wells for 2005..............................................72 Irrigation main effect....................................................................................72 Fertilizer main effect....................................................................................73 Sidedress main effect...................................................................................73

PAGE 8

viii Nitrate Nitrogen Concentration in Lysimeters for 2004......................................73 Irrigation main effect....................................................................................73 Fertilizer main effect....................................................................................74 Sidedress main effect...................................................................................74 Nitrate Nitrogen Concentration in Lysimeters for 2005......................................74 Irrigation main effect....................................................................................74 Fertilizer main effect....................................................................................75 Sidedress main effect...................................................................................76 Nutrient Load Concentration in Surface Water...................................................76 Water volume: 2004....................................................................................76 Water volume: 2005....................................................................................77 Nutrient load: 2004......................................................................................77 Nutrient load: 2005......................................................................................77 Growing Degree Days.........................................................................................78 Conclusions.................................................................................................................79 4 SUMMARY, AND FUTURE RESEARCH.............................................................110 Optimum Planting Dates...........................................................................................111 Climatic Factors........................................................................................................112 Potato Varieties.........................................................................................................113 Fertilizer Source........................................................................................................113 Additional N Sidedress.............................................................................................114 Water Quality............................................................................................................114 Future Research........................................................................................................115 APPENDIX A ADDITIONAL DATA AND ANOVA TABLES FOR PLANTING DATE YIELD......................................................................................................................116 B ADDITIONAL DATA AND ANOVA TABLES FOR PLANT TISSUE FOR PLANTING DATE...................................................................................................135 C ADDITIONAL DATA AND ANOVA TABLE FOR POST HARVEST SOIL NUTRIENTS FOR PLANTING DATE...................................................................148 D ANOVA TABLES FOR YIELD AND Q UALITY FOR IRRIGATION STUDY..151 E ADDITIONAL DATA AND ANOVA TA BLES FOR SURFACE WATER NUTRIENT CONCENTRATION...........................................................................160 F ADDITIONAL DATA AND ANOVA TABLES FOR TISSUE NUTRIENT CONCENTRATION AND FUE FOR IRRIGATION STUDY...............................188 G ADDITIONAL DATA AND ANOVA TA BLES FOR SOIL NUTRIENT CONCENTRATION................................................................................................208

PAGE 9

ix LIST OF REFERENCES.................................................................................................219 BIOGRAPHICAL SKETCH...........................................................................................225

PAGE 10

x LIST OF TABLES Table page 2-1 Total and marketable yield and speci fic gravity production statistics for 2004 and 2005...................................................................................................................32 2-2 Two-way interaction between planting da te and nitrogen rate main effects for total and marketable tuber yields in 2004................................................................34 2-3 Two-way interaction between planting da te and variety main effects for total tuber yields in 2004 and 2005..................................................................................35 2-4 Size class distributi on and range (%) production statistics 2004 and 2005.............36 2-5 Two-way interaction between planting da te and nitrogen rate main effects for size class range (%) for A1 in 2004 and A3 and size class distribution for A1 to A2 in 2005................................................................................................................38 2-6 Two-way interaction between planting date and variety main effects for size class range (%) for A1, A2, A3 and A2 to A3 in 2004 and B, A1, A3 and A1 to A2 in 2005................................................................................................................39 2-7 External quality (green, growth cracks, mis-shaped, rot and total culls) % of total yield 2004 and 2005.........................................................................................40 2-8 Internal quality (%) of total yield 2004 and 2005....................................................42 2-9 Mean maximum and minimum temperat ure (C) for planting dates 1-6, 2004 and 2005..........................................................................................................................4 4 2-10 Accumulated GDD and calendar days to obtain emergence and full flower 2004 and 2005...................................................................................................................45 2-11 Early and late season yield reducti on and harvest date at 2000 GDD for 2004 and 2005...................................................................................................................46 3-1 Irrigation treatment (WAP), fertilizer tr eatment, fertilizer source and additional sidedress application (DAP) for 2004 and 2005 production seasons.......................80

PAGE 11

xi 3-2 Total and marketable tuber yields an d specific gravity for Atlantic potato under varying staged leaching irrigation treatments and fertilizer source in Hastings, FL in 2004 and 2005................................................................................82 3-3 Three-way interaction between irrigati on date, fertilizer source and side dress application main effects for total and marketable tuber yields and specific gravity for Atlantic potato under varyi ng staged leaching ir rigation treatments and fertilizer source in Ha stings, FL in 2004 and 2005...........................................84 3-4 Size class distribution an d range (%) production statistics for Atlanticpotato under varying staged leaching irrigation treatments and fertilizer source in Hastings, FL in 2004 and 2005................................................................................85 3-5 External tuber defects (%) of total yield for Atlantic under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005................................................................................87 3-6 Internal tuber defects (%) of total yield for Atla ntic under vary ing staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005................................................................................89 3-7 Well NO3-N concentration (mg L-1) under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005..........................................................................................................................9 1 3-8 Lysimeter NO3-N concentration (mg L-1) under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005..........................................................................................................93 3-9 Total NO3-N nutrient load by fertilizer sour ce and leaching irrigation date and percent reduction in load from CRF compared with AN 2004..............................95 3-10 Total NO3-N nutrient load by fertilizer sour ce and leaching irrigation date and percent reduction in load from CRF compared with AN 2005..............................95 3-11 Accumulated Growing Degree Days to leaching irrigation event, emergence and full flower.................................................................................................................96 A-1 Total and marketable yield and specifi c gravity production statistics for late harvest 2004 and 2005............................................................................................117 A-2 Size class distribution an d range (%) production statisti cs for late harvest 2004..119 A-3 Size class distribution an d range (%) production statisti cs for late harvest 2005..121 A-4 Size class distribution an d range (%) production statisti cs for late harvest 2005..122

PAGE 12

xii A-5 External quality (green, growth cracks, mis-shaped, rot and total culls) (%) of total yield late harvest 2004 and 2005....................................................................123 A-6 Internal quality (%) of tota l yield late harvest 2004 and 2005..............................125 A-7 2004 ANOVA table for potato yi eld in planting date study..................................127 A-8 2005 ANOVA table for potato total and mark etable yield and size distribution in planting date study.................................................................................................128 A-9 2004 ANOVA table for potato internal a nd external quality in planting date study.......................................................................................................................129 A-10 2005 ANOVA table for potato internal a nd external quality in planting date study.......................................................................................................................130 A-11 2004 ANOVA table for potato yield in planting date study late harvest...............131 A-12 2005 ANOVA table for potato yield in planting date study late harvest...............132 A-13 2004 ANOVA table for potato internal a nd external quality in planting date study late harvest....................................................................................................133 A-14 2005 ANOVA table for potato internal a nd external quality in planting date study late harvest....................................................................................................134 B-1 Haulm nutrient concentration (%) at tuber initiation in 2004 and 2005................136 B-2 Full flower (haulm) nutrient concentration (%) for 2004 and 2005.......................138 B-3 Tuber diced pieces nutrient concentration (kg ha-1) at harvest 2005.....................140 B-4 Ca++ and TKN fertilizer use efficiency (%) 2005..................................................141 B-5 2004 ANOVA table for haulm tissue at tuber initiation for planting date.............142 B-6 2004 ANOVA table for haulm tissue at full flower for planting date....................143 B-7 2005 ANOVA table for haulm tissue at tuber initiation for planting date.............144 B-8 2005ANOVA table for haulm tissue at full flower................................................145 B-9 2005ANOVA table for FUE..................................................................................146 B-10 2005ANOVA table for tuber diced pieces for planting date..................................147 C-1 Soil nutrient concentration (mg kg-1) post harvest 2005........................................149 C-2 2005 ANOVA table for post harvest soil planting date.........................................150

PAGE 13

xiii D-1 2004 ANOVA table for potato total and ma rketable yield and specific gravity....152 D-2 2004 ANOVA table for potato size class distribution and range...........................153 D-3 2005 ANOVA table for potato total and ma rketable yield and specific gravity....154 D-4 2005 ANOVA table for potato size class distribution and range...........................155 D-5 2004 ANOVA table for potato external quality.....................................................156 D-6 2004 ANOVA table for potato internal quality......................................................157 D-7 2005 ANOVA table for potato external quality.....................................................158 D-8 2005 ANOVA table for potato internal quality......................................................159 E-1 Well NH4-N concentration (mg L-1) under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005........................................................................................................................161 E-2 Lysimeter NH4-N concentration (mg L-1) under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005........................................................................................................163 E-3 2004 ANOVA table for well water sample 29 DAP..............................................165 E-4 2004 ANOVA table for well water sample 44 DAP..............................................166 E-5 2004 ANOVA table for well water sample 60 DAP..............................................167 E-6 2004 ANOVA table for well water sample 72 DAP..............................................168 E-7 2004 ANOVA table for well water sample 89 DAP..............................................169 E-8 2005 ANOVA table for well water sample 17 DAP..............................................170 E-9 2005 ANOVA table for well water sample 33 DAP..............................................171 E-10 2005 ANOVA table for well water sample 45 DAP..............................................172 E-11 2005 ANOVA table for well water sample 59 DAP..............................................173 E-12 2005 ANOVA table for well water sample 73 DAP..............................................174 E-13 2005 ANOVA table for well water sample 89 DAP..............................................175 E-14 2004 ANOVA table for lysimeter water sample 45 DAP......................................176 E-15 2004 ANOVA table for lysimeter water sample 65 DAP......................................177

PAGE 14

xiv E-16 2004 ANOVA table for lysimeter water sample 73 DAP......................................178 E-17 2004 ANOVA table for lysimeter water sample 90 DAP......................................179 E-18 2005 ANOVA table for lysimeter water sample 18 DAP......................................180 E-19 2005 ANOVA table for lysimeter water sample 34 DAP......................................181 E-20 2005 ANOVA table for lysimeter water sample 45 DAP......................................182 E-21 2005 ANOVA table for lysimeter water sample 60 DAP......................................183 E-22 2005 ANOVA table for lysimeter water sample 73 DAP......................................184 E-23 2005 ANOVA table for lysimeter water sample 89 DAP......................................185 E-24 2004 NO3-N concentration in surface water runoff (Figures 3.4-3.6)...................186 E-25 2005 NO3-N concentration in surface runoff (Figures 3.7-3.10)...........................187 F-1 Leaf Ca++ (%) under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005.......................189 F-2 Leaf TKN (%) under varying staged l eaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005.......................190 F-3 Full flower (haulm) nutrient uptake (kg ha-1) under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005........................................................................................................191 F-4 Tuber nutrient uptake (kg ha-1) at harvest under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005........................................................................................................192 F-5 Fertilizer use efficiency (%) of tota l fertilizer applied under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005..............................................................................193 F-6 SPAD leaf chlorophyll values under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005........................................................................................................................194 F-7 2004 ANOVA table for leaf tissue 36 DAP...........................................................196 F-8 2004 ANOVA table for leaf tissue 51 DAP...........................................................197 F-9 2004 ANOVA table for leaf tissue 67 DAP...........................................................198 F-10 2004 ANOVA table for full flower haulm.............................................................199

PAGE 15

xv F-11 2004 ANOVA table for tube r tissue at harvest......................................................200 F-12 2005 ANOVA table for leaf tissue 41 DAP...........................................................201 F-13 2005 ANOVA table for leaf tissue 74 DAP...........................................................202 F-14 2005 ANOVA table for full flower haulm tissue...................................................203 F-15 2005 ANOVA table for nutrient tuber tissue.........................................................204 F-16 2004 ANOVA table for FUE.................................................................................205 F-17 2005 ANOVA table for FUE.................................................................................206 F-18 2004 ANOVA table for SPAD 2004 and 2005......................................................207 G-1 Post harvest soil nutri ent concentration Ca, NH4-N, and NO3-N (mg kg -1) under varying staged leaching irrigation treatm ents, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005...........................................................209 G-2 2004 ANOVA table for post harvest soil nutrient concentration 106 DAP...........210 G-3 2005 NOVA table for post harvest soil nutrient concentration 106 DAP..............211 G-4 2004 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 2 WAP....................................................................................................212 G-5 2004 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 8 WAP....................................................................................................213 G-6 2004 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 12 WAP..................................................................................................214 G-7 2005 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 2 WAP....................................................................................................215 G-8 2005 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 4 WAP....................................................................................................216 G-9 2005 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 8 WAP....................................................................................................217 G-10 2005 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 12 WAP..................................................................................................218

PAGE 16

xvi LIST OF FIGURES Figure page 1-1. Loading potatoes onto railroad car in Hastings, Florida ca 1920s ...........................3 1-2 Internal heat necr osis in Atlantic.............................................................................6 2-1 Varieties a.Atlantic b.Harley Blackwell...........................................................13 2-2 Daily rainfall (cm) for a. 2004 a nd b. 2005 production season. Grouping of red bars denote a leaching rainfall event (7.6 cm in 3 days or 10.1 cm in 4 days). The yellow, pink, blue, green, orange a nd black lines denote planting dates 1-6, respectively, from emerge nce to tuber initiation......................................................47 2-3 Total and marketable yield at each planting date x variety and accumulated GDD at harvest. a. 2004 b. 2005.............................................................................48 3-1 Aerial photograph of pot ato production fields along the St. Johns River, St. Johns County, Florida. Courtesy of Pam Livingston-Way, SJRWMD...................50 3-2 Plot map leaching irrigation project.........................................................................81 3-3 Total water volume from each irrigation date a. 2004 and b. 2005.........................97 3-4 NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replication at leaching event 2 WAP, 2004....................................................................................98 3-5 NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replication at leaching event 8 WAP, 2004....................................................................................99 3-6 NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replication at leaching event 12 WAP, 2004................................................................................100 3-7 NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replication at leaching event 2 WAP, 2005..................................................................................101

PAGE 17

xvii 3-8 NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replication at leaching event 4 WAP, 2005..................................................................................102 3-9 NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replication at leaching event 8 WAP, 2005..................................................................................103 3-10 NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replication at leaching event 12 WAP, 2005................................................................................104 3-11 NO3-N load (kg ha-1) at 2, 8 and 12 WAP, 2004. a. 2 WAP b. 8 WAP c. 12 WAP.......................................................................................................................105 3-12 NO3-N load (kg ha-1) at 2, 4, 8 and 12 WAP, 2005. a. 2 WAP b. 4 WAP c. 8 WAP d. 12 WAP....................................................................................................107 3-13 Daily rainfall (cm) for the a. 2004 and b. 2005 production season. The group of red bars denote a leaching rainfall event (7.6 cm in 3 days or 10.1 cm in 4 days). The yellow, blue, pink and green arrows denote a stage leaching irrigation event at 2, 4, 8 and 12 WAP, respectively.......................................................................109

PAGE 18

xviii Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy TIMING OF CLIMATIC FACTORS THAT MAY INFLUENCE POTATO YIELD, QUALITY, AND POTENTIAL NITROGEN LO SSES IN A NORTHEAST FLORIDA SEEPAGE-IRRIGATED POTATO PRODUCTION SYSTEM By Christine Maria Worthington December 2006 Chair: Chad M. Hutchinson Major Department: Horticultural Sciences Potato, a cool season crop, is planted in Northeast Florida in January when temperatures are cool. As the season progr esses, daily temperatur es and incidence of leaching rainfall events increase which can a ffect yield and quality. Nutrient runoff from potato production land has thought to have been primarily responsible for the non-point source pollution into the St J ohns River watershed. Best Management Practices (BMPs) for potato production in the TCAA have been implemented. With over 7,000 ha in potato production in the TCAA, the main concern with the implementation of the BMPs are to not compromise yield and quality. The experi mental design in chapter 2 was a split-split design with four blocks. Planting dates (1-6) were main plots. The first split was the N rate (168 and 224 kg ha-1). The second split was potato variety, Atlantic and Harley Blackwell. The experimental design in ch apter 3 was a split-split design with four blocks. Irrigation treatments were main plots at 0, 2, 4, 8, and 12 WAP (weeks after

PAGE 19

xix planting). The first split was the nitrogen source (AN or CRF). The second split was an additional side-dress fertilizer application. Optimal yields for the TCAA occurred over a 4 week period (early to late February) in a twelve week planting window. Harley Blackwell demonstrated its effectiveness to produce quality t ubers under conditions when air temperatures and leaching rainfall events stressed plants. IHN was triggered by rainfall and nutritional conditi ons that stressed the plant ear ly in the season combined with increasing minimum daily temperatures late r in the season. Marketable yields in the CRF treatments were an average of 12% higher compared with the AN fertilizer treatment. The CRF treatments had a significa ntly higher incidence of tubers with IHN compared with the AN fertilizer treat ment at 22.3 and 15.6%, respectively. NO3-N loading from surface water runoff from potat o production was decreased an average of 43% with the use of the CRF compared with the AN fertilizer treatment. A CRF used in potato production, rather than a so luble N fertilizer, could reduce NO3-N loads into the St. Johns River watershed by 56,000 kg N per year.

PAGE 20

1 CHAPTER 1 INTRODUCTION Cultivated potatoes ( Solanum tuberosum L.) were introduced into Europe by the Spaniards who traveled to South America in the 1500s, but not until the late 1600s were they found throughout Europe. During the 18t h and 19th centuries the potato was an established major agronomic food crop througho ut Europe. Its acceptance was primarily due to the increasing cost of grain and th e demands for food to accommodate the growing populace (Burton, 1989a). Many believe the onsla ught of Irelands Great Potato Famine in 1845 spawned the beginning of the cultivated potato in America. Actually, the first Irish white potatoes were grown in Derry (previously Londonberry) New Hampshire in the spring of 1719 (Hawkins, 1967). Today, potatoes are not only important on a world-wide basis, but in the U.S as well. According to the National Potato C ouncil, 2002, the U.S. ranked third, worldwide, in potato production (24, 000,000 metric tons) following China and the Russian Federation which produced 65,052,000 and 31,900,000 me tric tons, respectively. Since its introduction as a cultivated crop, potato has become as economically and culturally important to society as wheat ( Triticum aestivum L.) and rice ( Oriza sativa L). (National Potato Council website). Florida Potato Production Florida potato production ( 9,659,000 cwt) ranks in the top 1/3 of the 36 states in commercial potato production (National Po tato Council website). Florida potato production (chip and fresh market) encomp asses approximately 12,550 ha (31,000 acres)

PAGE 21

2 extending as far south as Hendry County and north to Jackson County. According to Witzig and Pugh, (2004), potatoes continue to remain among the top five vegetables produced in Florida with a cash value of approximately $115 million (Witzig and Pugh, 2004). Tri-County Agricultural Area The largest concentration of potato producti on is in the tri-county agricultural area (TCAA; Flagler, Putnam and St. Johns countie s) of northeast Florida. Irrigation for the area is applied by seepage irrigation. V-shap ed furrows approximately 18 m apart and a hardpan clay layer approximately 61 cm belo w the soil surface allows water to move down and laterally across the bed and supply ne eded moisture to the potato crop (Hensel, 1964). Florida can also receive large amounts of rainfall in a very short amount of time. The 50 year average rainfall received duri ng the production season in the TCAA (January through June) is approximately 57 cm. Rainfa ll events as leaching rainfall events and defined as 7.6 cm in 3 days or 10.1 cm in 7 days are not uncommon during the production season. The 50 year average for a 7.6 cm leaching rainfall event to occur during the production season is 2.5 times while the 50 ye ar average for a 10.1 cm leaching rainfall event to occur is 5.3 times during the pr oduction season. In 2004, this area produced potatoes on approximately 18,000 acres (~ 7,300 ha) providing a cash value of 42,773,000 (Florida Agricultural Fast Facts, 2005). The majority of the potatoes grown in south Florida for winter harvest are fresh market varieties. Potatoes grown in the TCAA for spring harvest are primarily for chip (60%) with fresh market varieties accounting for about 40% of total production. In the TCAA, potato planting begins in late December and continues through mid-March. Harvest usua lly begins by late April and runs through June.

PAGE 22

3 Potato Capital of Florida Hastings, located in the southwest portion of St. Johns County, is referred to as the Potato Capital of Florida. The area has been in potat o production for over 100 years when Henry Flagler, a well known philanthropi st, railroad magnate, and real estate developer asked his cousin, Thomas Horace Hastings, (founder of Hastings ca. 1890) to grow winter vegetables for hi s hotel guests in St. Augustine. At his request, Thomas built the first greenhouses in Hastings establishing vegetable production in Northeast Florida. His production included cucumber ( Cucumus sativus L.), cabbage ( Brassica oleracea L., Capitata group), cauliflower ( Brassica oleracea L., Botrytis group), onions ( Allium cepa L.), potatoes, and rice. Pota to production acreage started out small 3 to 4 ha (7-9 acres), but in the following years acreage increased as Hastings became a major supplier for new potatoes for the northeastern U.S. By 1928, approximately 7,900 railcar loads of fresh spring potatoes were shipped out of the Hastings area for the northern markets (Weingartner and Hensel, 2003). Figure 1-1. Loading potatoes onto railroa d car in Hastings, Florida ca 1920s The standard cultivar grown for fresh ma rket in the TCAA during this time during the 20s and up until 1938 was Spaulding Rose. With its resistance to late blight, mild

PAGE 23

4 mosaic, net necrosis and brown rot, it wa s an excellent variety for Florida growing conditions (Folsom, 1945). In the 1950 s, Sebago was also found to be a good processing potato for the burgeoning chip indus try. From that point on, Hastings market went from 100% fresh to more than 80% chip. Florida Chip Potato Varieties The standard chip variety grown today in the TCAA is Atlantic which is noted for its light chip color, rela tively high yield (39-50 t ha-1);(350-450 cwt/A), and high specific gravity (1.090). Higher specific gravity allo ws for more processed product per unit of raw product used. Less fat is absorbed duri ng frying along with a shorter frying time. However, it is susceptible to internal heat necrosis (IHN), a physiological tuber disorder that causes an unacceptable browning of the tuber tissue Atlantic is resistant to scab ( Streptocmyces scabies ), Verticillium wilt, pink eye, caused by the bacterium Pseudomonas marginalia common races of the late blight fungus ( Phytothera infestans ) and race A of the golden nematode ( Globodera rostochiensis ) and is immune to virus X (Potato X potexvirus ) and tuber net necrosis. With its higher yields and specific gravity, Atlantic replaced Sebago as the primary chipping potato grown in the TCAA. In the early 1990s Snowden was released and appeared to be a promising ch ipping potato with comparable yields and specific gravities to Atlantic, but Snowden can accumu late unacceptable glycoalkaloid levels. Glycoalkaloids contribute to the potatoes fl avor, but in high concentrations can be toxic to humans causing nausea, headaches and diarrhea (Cantwell, 1996). Today, limited acreage of Snowden is gr own in the TCAA for chip and fresh market, since the primary chip acreage is planted in Atla ntic (Personal communication, Hutchinson, 2004).

PAGE 24

5 Atlantic was released July 16, 1976 by US DA, Florida, New Jersey and Maine Agricultural Experiment Stations and the Virginia Truck and Ornamentals Research Station, Norfolk Virginia. In replicated tria ls over three years, Atlantic was compared to the most popular variety grown for the afor ementioned states. Consistently, Atlantic yielded more (t ha-1), with exception of the Virginia si te, and had higher specific gravities in all states (Webb et al., 1978). Recently a potato variety was released th at may provide chip potato growers an alternative to Atlan tic and Snowden; Harley Blackwe ll, was released in 2003 by the USDA based on the cooperative research results of many institutions including the University of Florida. Plant size (vig or), maturity, canopy shape and flowering characteristics are all si milar to Atlantic. Yields and specific gravities of Harley Blackwell are lower than Atlantic, but are acceptable according to chipping standards (Beltsville Agricultural Research Center website) (United States Standards for Grades of Potatoes for Chipping, 1997). Another desirable characteristic of Harley Blackwell is its resistance to in ternal heat necrosis (IHN). IHN is described in the Compe ndium of Potato Diseases, 2nd edition, as a physiological disorder caused by elevated soil temperatures during the latte r stages of growth and development of the tuber. If th e vines and leaves are still actively growing and green during this period of elevated temperatures, water and nutrients are translocated from the tuber to supply the pl ant. The vascular sy stem of the tuber is stressed and cannot sustain th e evapotranspirational demands of the plant. Under these conditions, it is reported that the vascular ring deterior ates and becomes necrotic.

PAGE 25

6 Symptoms are most severe during hot, dry weather conditions in sandy, gravel, muck or peat soils. Necrotic areas are mostly found in and around the vascular ring usually coalescing and radiating to the center (pith). The symptoms are also more prevalent at the bud (apical) end of the tuber and not the st em end. Peterson et al. (1985) reported that as the tuber expands there is more xylem at the stem end of the t uber during growth and development. IHN does not affect the nutr itional value of the tuber, but the economic impact can be significant due to off-grade quality. The exterior of the potato tuber does not show visible signs of IHN. Accordi ng to the Department of Agriculture (1978), USDA no. 1 potatoes may not exceed 10 and 5% external and internal defects by weight, respectively. Figure 1-2. Internal heat necrosis in Atlantic Internal necrosis (physiol ogical necrosis) was first reported in 1937 by Larson and Albert when they recognized it as an economic concern for commercially grown potatoes. Internal necrosis ha s been referred to as internal brown spot (IBS), chocolate and rust spot, internal browning and internal brown fleck (Sterrett and Henninger, 1997). Unlike IBS that is reported to occur throughout the growing season, IHN of Atlantic has been reported to occur during the mid to late bulking period of the tuber.

PAGE 26

7 Seasonal Environmental Stress Associated with IHN Sterrett et al. (1991) reported that IHN is influenced by more than one environmental stress factor. During the 1986-1988 production years, seven planting dates in two locations (New Jersey and Virginia) and several harvests, beginning at 80 DAP and continuing to 147 DAP, were evaluate d using a step-wise regression model that included the variables temperature, rainfa ll, days after planting (DAP), yield and percentage of large tubers (>64mm in diam eter) to assess when potatoes become offgrade during the growing season. Accumulated heat units were evaluated in the model with a penalty imposed if the maximum a nd minimum temperatures were above 25 and 21C, respectively for a consecutive duration of three or more days (Lee et al., 1992). A weak correlation was observed with the occurrence of IHN due to DAP, yield and percentage of large tubers. Although rain fall was included in the model it was not assessed. The findings concluded that more than one environmental factor, such as, reduced solar radiation, reduced temperature and increased relative humidity and its role in photosynthesis, respiration could be i nvolved in the development of IHN. Henninger et al. (2000) also used the heat sum model by Lee to evaluate 19 different potato clones and their parents in cluding Atlantic for the occurrence of IHN over three years and in six loca tions in NJ and VA. Temperat ures during the later part of the 1991 and 1993 production years were above the maximum temperature allowed for potatoes going off-grade due to IHN accordi ng to the Lee heat sum model. Although Atlantic had the highest yield and specific gravity, it also had the highest incidence and severity of IHN. This result was in ag reement with (Sterrett and Henninger, 1997) who reported a higher incidence of IHN near harves t and generally in th e larger tubers (>76 mm). Lee et al. (1992) repor ted that IHN in Atlantic occurred earlier in plant

PAGE 27

8 development correlating with the highest mean maximum temperature during the 0-30 DAP and the highest mean minimum temperat ure during the remainder of the growing season up to 90 DAP. They concluded that th e high minimum temperatures had an effect on the occurrence of IHN. Moisture Stress Wannamaker and Collins (1992) evaluated nine cultivars, including Atlantic for its susceptibility to IHN, at two locations (Tidewater Research Station TRS, NC and Horticultural Crops Research Station HCRS Castle Hayne, NC), and two planting and harvest dates in 1989 and 1990. Occurrence of IHN was higher at the TRS site in 1989 (1.3 to 68.7%) when compared with HCRS with an occurr ence of IHN of 0 to 35.5%. Temperatures were similar for both locations and years, but rainfall was higher at the TRS site in 1989 and 1990. Although the occu rrence of IHN was lower in 1989 the TRS site still had the highest amount of rainfall a nd incidence of IHN. Sterrett et al. (1991) reported that during the growing season in 1989, IHN was delayed due to the increased rainfall during the first 60 DAP but incide nce increased during a dry, warm spring. Although IHN may be due to a combination of environmental stressors, Wannamaker and Collins report contradicts others that IHN typically occurs during dry conditions. While IBS is a similar physiological defect, a report by Iritani et al. (1984) supports Wannamaker and Collins findings suggesting that temperature and, most important of all, moisture fluctuations are suspected to cause IBS. Novak et al. (1986) studied brown fleck in potatoes in Queensland. They found an increase in brown fleck incidence when soil moisture levels were high late in the s eason. They suggested withholding irrigation as the crop reached maturity to reduce the di sorder that contradict s Sterret et al. (1991) that a higher incidence of IHN was noted wh en a hot dry weather later in the season.

PAGE 28

9 Nutrition Silva et al. (1991) evaluated varying gypsum and nitrogen rates in conjunction with three irrigation schedules ( no irrigation, required irrigati on, and excess irrigation) on specific gravity, yield, and internal defects of Atlantic over a three year period. Nitrogen rates had no significant effect on th e internal quality of tubers, but the application of gypsum did lowe r IBS occurrence in Atlantic tubers. They also found that excess irrigation increased the incidence of IBS in Atlantic pot atoes in two of the three years evaluated. Sterrett and Henninge r, (1997) reported th at Clough, (1994), found an increase in IHN incidence when lower N rates (68 or 84 kg N ha-1 were applied vs. 168 or 252 kg N ha-1). Sterrett and Henninger (1991) report supports Cloughs findings that IHN was slightly reduced with the higher N rates of 84 and 252 kg N ha-1 versus 64 kg N ha-1. Palta (1996), reported since tubers are naturally deficient in Ca++ especially those grown in sandy soil, applying Ca++ to the tuber-stolon junction improved Ca++ uptake in tuber peel and medullary tissue, suggesti ng that placement is key to improving uptake efficiency of Ca++. Ozgden et al. (2005) recently re ported potato plants that received split applications of calcium nitrat e throughout the season had sign ificantly lower incidence of IBS in 1997. They also reported that tuber ca lcium concentrations were higher in 1999, but the incidence of IBS was not significan tly different than the treatments without calcium nitrate. The authors mentioned th at a leaching rainfall (13cm) within 24 hrs occurred during the bulking peri od that may have had an effect on the incidence of IBS in Russet Burbank potatoes. Gunter et al (2000) reported solubl e sources of calcium applied in split applications was more e ffective at reducing the incidence of IBS compared with the application of gypsum. Tzeng et al. (1986) reported a negative

PAGE 29

10 correlation between the inciden ce of IBS and tuber peel calcium. Sterrett and Henninger (1991), evaluated different Ca++ rates and their effect on several cultivars for the occurrence of IHN. The cultivars included, Atlantic (non resist ant to IHN), Katahdin, (moderately resistant to IHN), and Kennebec and Superior, (moderate to high resistance to IHN). It was reported that Atlantic had significantly lower tuber tissue Ca++ compared with Superior. However, placement of Ca++ within the hill had no effect on the IHN occurrence. Sterrett et al., (in pre ss) reported a significant clone x calcium interaction for the inciden ce of IHN at two locations in 2001 and 2002. They reported that soil applied Ca++ increased Ca++ in two IHN susceptible clones and decreased Ca++ concentration in one IHN susceptible clone in 2001. However, in 2002, they reported the incidence of IHN decreased in three (2 IHN susceptible clones and 1 IHN resistant clone) of the 18 clones when Ca++ was applied to the soil. Although Ca++ is one of the most naturally abundant plant nutrients, it can be eas ily leached, especially in humid climatic conditions (Mengel and Kirkby, 1987). Ca++ can also be removed from the soil profile by the addition of N fertilizers, e.g. NH4NO3. The process of nitr ification releases H+ into the soil releasing Ca++ from exchange sites and eventual ly leaching below the root zone of the potato crop. It has been re ported that for every 100 kg of (NH4)2SO4 added to the soil, approximately 45 kg of Ca++ are leached (Mengel and Kirkby, 1987). Rationale Atlantic is the major commercial chippi ng variety grown in the TCAA encompassing 70% of the acreage grown making it economical ly vital to the area. Major chipping processors request Atlantic for their produc t for its chipping qua lity although Atlantic is susceptible to developing IHN. De veloping an understanding of the role environmental and nutritional stressors play on yield and quality, especially IHN of

PAGE 30

11 potato would benefit Florida farmers. Accordi ng to Sterrett and Henni nger, to date there have been no cultural management practices which alleviate the onset and progression of IHN. Therefore, the focus of this research is to determine at what stage IHN may be initiated and the correlation with cultural and/or environmental stressors throughout the growing season. Organization of Dissertation This work is organized into four chapte rs. The first chapter is an introduction describing the history of the potato from its Sout h American origin to its vital role as part of Floridas agriculture today. The second chapter descri bes the results of a two year study evaluating multiple planting dates with two N rates and two varieties and how the timing of climatic factors and cultural practic es effect tuber production and quality in the TCAA during the growing season. The third ch apter reports the results of a two year study which addresses the effect s of two nitrogen (N) ferti lizer sources and simulated leaching rainfalls during the growing season on yield, tuber quality and nitrate leaching (NO3-N). The fourth chapter summarizes the re sults and conclusions and suggests future research addressing yield and quality of potato production in the TCAA.

PAGE 31

12 CHAPTER 2 DEVELOPMENT OF A GROWING DEGREE DAY MODEL TO DETERMINE OPTIMAL PLANTING DATE AND ENVIRO NMENTAL INFLUENCE ON POTATO YIELD AND QUALITY IN NORTHEAST FLORIDA Introduction Potato production in Florida spans from as far south as Hendry County to Jackson County in the north. The largest area in production is northeast Floridas Tri-County Agricultural Area (TCAA) (St. Johns, Putnam and Flagler counties) with 7,300 ha (18,000 acres). Potatoes continually rank among the top five vegetabl es in production in Florida with annual value of approximate ly $125 million (Witzig and Pugh, 2004). Potatoes, a cool season crop, are planted in the TCAA beginning in late December when day length is short and temperatures c ool. As the season progresses and the potato progresses through key developmental stages, daylight hours lengthen and temperatures increase. Winkler (1971) reporte d that yields may suffer due to extended periods of cool temperatures (below 18C) as well as hi gher temperatures (above 20C) for extended periods. Cooler and higher temperatures reduce net assimilation to the tubers while higher temperatures may pr event tuber initiation. Atlantic is the most prevalent chip variety in northeast Florida. Atlantic is noted for its light chip color, relatively high yield and high specific gravity (Fig 2.1a). However, it is susceptible to internal heat necrosis (IHN), a physiological tuber disorder that causes an unacceptable browning of the tuber tissue (Fig 2.2).

PAGE 32

13 Figure 2-1. Varieties. a.Atlantic b.Harley Blackwell Harley Blackwell, a new va riety resistant IHN, was released in 2003 by the US Department of Agriculture (USDA, Beltsvi lle Md., 2004) (Fig 2.1b). Yield and specific gravity of Harley Blackwell are lower than Atlantic but are acceptable according to chipping standards (United States Standards fo r Grades of Potatoes for Chipping, 1978). Both Atlantic and Harley Blackwe ll were planted in this study. Growing Degree Days Growing Degree Days (GDD) are a useful t ool to determine harvest dates and yield in crops such as broccoli ( Brassica oleracea L.) (Dufault, 1997), peas ( Pisum sativum L.) (Hoover, 1955); corn ( Zea mays L.); cucumber ( Cucumis sativus L.) (Perry et al., 1986) and taro ( Colocasia esculenta L. Schott) (Lu et al., 2001). Sterrett et al. (1991) evaluated a revised accumulated heat unit system (Lee et al., 1992) to predict when potato tubers would go off-grade. With this system, growers could determine when to harvest to avoid economic losses du e to tuber quality issues. Historically, growers in the TCAA have used calendar days and experience to predict key potato developmental stages e.g. em ergence, full flower and full senescence. Developing and utilizing the growing degr ee day system may be a more accurate a b

PAGE 33

14 predictor of these stages throughout the seas on to determine optimal planting dates and yields compared with calendar da ys. It would also facilitate a more efficient fertilizer and pesticide appli cation schedule. This experiment was designed to evaluate and quantify the effects of multiple planting dates on the occurrence of IHN base d upon environmental stressors (rainfall and temperature) as well as determine the infl uence of growing degree day accumulation on the timing of key developmental stages and production of optimal yields over multiple planting dates typically experienced in the TCAA. The objectives of this study were to 1) determine the effects of multiple planting dates and N rates on yield and quality of potat o in Northeast Florida 2) determine when and what climatic factors influence yield and quality of potato in Northeast Florida 3) develop a model based on GDD to determin e key developmental stages of potato. Materials and Methods Site Description The experiment was conducted durin g production years 2004 and 2005 at the University of Florida, Plant Science Resear ch and Education Unit, Hastings, Florida on an Ellzey fine sand (sandy, siliceous, hyperthe rmic Arenic Ochraqualf; sand 90% to 95%, <2.5% clay, <5% silt). The soil profile is described as poorly drained although the top 94 cm have a very high permeability rate (5-10 cm hr-1). A restricting clayey layer lies below the sandy loam top layer of the profile. The water table is within 25 cm of the surface for one to six months of the year (S oil Survey, St Johns County, 1983) Experimental Design The experiment was arranged as a randomi zed complete block with a split-split design with four blocks in bed 16 NL at th e PSREU Hastings Farm. Planting dates (1-

PAGE 34

15 6) were assigned to main plots. Each ma in plot (planting da te) was 46.3 m by 6.0 m (6 rows) with a 12.1 m buffer between the north and south end of the main plots. The first split was the N rate at 168 and 224 kg ha-1. N rate plots were 4.8 m by 6.0 m (6 rows). The second split was potato variety, Atlantic and Harley Blackwell (Maine Farmers Exchange-MFX, Presque Isle, Maine). Potato variety plots were 4.8 m by 3.0 m (3 rows) Crop Production Practices Tuber Planting Potatoes were cut at planting to an a pproximate 71 g seed piece and dusted with fungicide [1.13 g a.i. fludioxonil and 21.82 g a.i. mancozeb per 45.4 kg seed pieces (Maxim MZ; Syngenta Crop Protection, Inc., Greensboro, N.C.)]. Azoxystrobin [0.1 L ha-1 a.i. (a.i., Amistar; Syngenta, Crop Prot ection, Greensboro, N.C.)] and aldicarb [3.36 kg ha-1 a.i (a.i., Temik, Bayer Corp., Kansas City Mo.)] was applied in-row at planting. All other pesticide applica tions during the growing season followed recommendations for Florida potato production (Hut chinson et al., 2004). Irrigation Plots were irrigated with seepage irriga tion throughout the growing season except during periods of sufficient rainfall. The seepage irrigation system is a semi-closed system. Water withdrawn from the confin ed aquifer is pumped through PVC (polyvinyl chloride) pipe to each V-shaped open water furrow in the field. Each water furrow is situated 18.2 m apart. Water seeps from the water furrow laterally, underground, across the bed and through capillarity reaches the ro oting system of the potato plant (Singleton, 1990). Water is controlled at each water furrow by a valve that can be turned on or off when necessary. Current research at the farm as estimated that each valve can deliver approximately (8.3 L min-1).

PAGE 35

16 Nutrient Management Fertilizer application was based on 100 and 75% of the best management practice (BMP) recommendations for Florida potato production [224 and 168 kg ha-1 N, respectively] (Hutchinson et al., 2004). In bot h seasons, pre-plant fertilizer (1 day before planting) was applied with a two-row hydrau lic fertilizer applicator (Kennco Mfg., Ruskin Fl, 33570) banded on top of the row at 112 kg N ha-1 as 14N-6.0 P2O5-12.0 K2O. Total P requirement 44.8 kg P2O5 ha-1 was applied in a single pre-plant application. Fertilizer was chopped and incorporated w ith a four-row chopper then each row was bedded prior to planting. One sidedr ess of remaining N [112 and 56 kg N ha-1, 34N-0P2O5-0 K2O] and K [60.4 kg K2O ha0N-0P2O5-50K2O] was applied approximately 30 d after each planting date when plants were 10 to 15 cm tall with a tworow, ground driven, belted fertilizer applicator that banded the fertilizer on each side of the plant. Rows were then single disked to c over the fertilizer on the shoulder of the row. Tuber Production Analysis At harvest potatoes were graded and sized into the following cl ass sizes; B = 3.8 to 4.4 cm, A1 = 4.4 to 6.4 cm, A2 = 6.4 to 8.3 cm A4 = > 10.2 cm. Culls (growth cracks, misshapen, sunburned and rotten tubers) we re removed and weighed before A size classes were separated. Mark etable yield is defined as no. 1 tubers with diameters between 4.4 and 10.2 cm (USDA, 1978) and without visible blemishes (rotten, green, misshapen, or containing growth cracks). One row of potato plants (5.8 meters) from each fertilizer rate by variety plot within each block and planti ng date were harvested at least 100 DAP as required by aldicarb labeling. A late season harvest, approximately 128 DAP, of one row of potato plants (5.8 m) from each fertilizer rate by vari ety plot within each block and planting date

PAGE 36

17 were also harvested. At both harvests, tubers were washed, graded and sized into five classes as described above. Tuber Specific Gravity Specific gravity was calculated from a s ub-sample of marketable tubers from each fertilizer by variety plot with in each block and planting date using weig ht in air/ weight in water method (Burton, 1989c). Atlantic potatoes are the standard for chipping in Florida, therefore, high tuber specific gravit y is desired. Specific gravities of at least 1.078 are considered good for production at the PSREU research farm in Hastings, FL (Hutchinson et al., 2002). External Quality Culls (green, growth cracks, misshapen, and rotten tubers) were removed and weighed at the grading line. External quality (green, growth cracks, misshaped and rot) were reported as a percentage of total yield. Internal Quality A 20 tuber sub-sample from each fertilizer by variety plot within each block and planting date were cut into quarters and ra ted for internal qualit y. Rated physiological disorders included hollow heart (HH), intern al heat necrosis (IHN) and brown center (BC). Disease induced disorders included co rky ring spot (CRS) and brown rot (BR). A twenty tuber sample from each plot was scor ed for percent hollow heart, IHN, and BC. IHN severity was scored on a one to six scale with a score of one to four relating to the number of quarters with IHN. A score of fi ve or six indicated th at all quarters had the disorder and up to 75 to 100% of all quarters were showed visual symptoms, respectively (Figure 23).

PAGE 37

18 Growing Degree Days Growing degree days (GDD) were calcu lated throughout the season for each planting date for the 2004 and 2005 production s eason with the following formula (Sands et al., 1979): GDD = [(minT + maxT)/2)-7C]. where minT and maxT are the minimum and ma ximum daily temperatures and the base is 7C. GDD totals were recorded for key growth and developmental stages (emergence, tuber initiation and full flower). Emergence wa s determined when the plantlets were just emerging from the soil. Tuber initiation was determined by the visual observance of the radial growth of the stolon tip and full fl ower was determined when approximately 9095% of the peduncals on plants in each plot had open flowers. Statistical Analysis Tuber production A general linear model was used to determine yield, internal and external quality responses of Atlantic and Harley Blackw ell potato varieties as a result of multiple planting dates a nd two N rates for the 2004 and 2005 production seasons. Normality for each potato class size was checked by residual analysis using the Shapiro-Wilk test as implemented in the PROC CAPABILITY procedure of SAS (SAS, Institute, 2004). Means were separated usi ng Tukey adjustment as implemented in SAS (SAS Institute, 2004) to separate individual f actor means and/or interaction means when significant.

PAGE 38

19 Results And Discussion This experiment was designed to determin e optimal yields over a typical growing season and the effects of nutrient and envir onmental stressors (rainfall, temperature) would have on yields and quality in the TC AA. Additionally, GDD we re also calculated for each planting date to determine optimal yields and key developmental stages and throughout the 2004 and 2005 growing season. Tuber Yield for 2004 Planting date main effect Planting date main effect significantly infl uenced total and marketable yields for 2004 and 2005 (Table 2-1). Plants in planting dates 5 and 6 (planted 9 Mar. and 24 Mar.) produced significantly lower total and marketable yields compar ed with plants in planting dates 3 and 4 (planted 9 Feb. and 23 Feb.), respectively, in 2004. Tubers in planting dates 5 and 6 were bulking under high temp eratures, 25.9 and 30.3C, respectively that increased respiration and d ecreased dry matter accumula tion compared with early plantings (Burton, 1989c). Tubers in planting dates 3 through 6 (9 and 23 Feb; 9 and 24 Mar), respectively, had significantly lower specific gravities compar ed with planting date 2 (planted 26 Jan.). Tubers from planting dates 3 and 4 (9 and 23 Feb), had (received) a higher percentage (amount) of water (rainfall) that contribut ed to their higher tuber yields. Rainfall accumulation from tuber initiation through harvest for planting dates 3 through 6 was three times higher compared with planting date 2 (planted 26 Jan.) for the same developmental stages. Tubers in the size cl ass distribution range A1 to A2 in planting dates 2 and 5 and A2 to A3 in planting date s 5 were significantly lower compared with planting date 4 (Table 2-4). This result was due to the cooler and warmer temperatures

PAGE 39

20 early and later in the growing season wh ich decreased tuber development caused by reduced net assimilation to the tubers. Nitrogen rate main effect Fertilizer main effect significantly infl uenced marketable tuber yields in 2004. Plants in the 224 kg N ha-1 treatment had significantly highe r marketable yields compared with plants in the 168 kg N ha-1 treatment at 23.2 and 20.5 t ha-1, respectively (Table 2-1). Variety main effect Variety main effect significantly influenced total and marketable yields in 2004. Total and marketable yields for Atlantic were 8% and 20% higher compared with Harley Blackwell, respectively, over all plan ting dates and nitrogen rates. Atlantic had higher specific gravity compared with Harley Blackwell (1.078 and 1.075), respectively, as well (Table 2-1). Varieties th at are resistant to I HN typically have lower specific gravities than varieties prone to IHN e.g. Atlantic (Ste rrett and Henninger who in 1991). Although Harley Blackwell had lo wer specific gravity, chipping companies will still accept them due to their internal quality. Main effect interaction The two-way interaction between planting date and fertilizer rate main effects was significant for the total and ma rketable tuber yields in 2004. A two-way interaction was also significant for the planting date by vari ety main effects. The two-way interaction term was calculated using LSMeans with th e slice option (planti ng date) (SAS 2004). This option enabled the comparison of the ferti lizer rates within each of the planting dates as well as the comparison of the va rieties within each planting date. The 224 kg ha-1 N rate had significantly higher total and marketable yields in planting dates 3, 5 and 6 (planted 9 Feb and 9 and 24 Mar, respectiv ely) compared with

PAGE 40

21 the 168 kg ha-1 N rate within each of the respect ive planting dates. These results indicated that planting late in the season (March) led to tuber bulking in warmer and wetter weather conditions that negatively imp acted total and marketable yields (Table 22). The interaction term for planting date by variety main effects was significant in 2004. Atlantic had significantl y higher total tuber yields in planting dates 1, 3, 5 and 6 compared with Harley Blackwell. Alt hough Atlantic had significantly higher total yields compared with Harley Blackwell in the later planting dates (planting dates 5 and 6), Atlantic had a significan tly higher incidence of ro ts compared with Harley Blackwell that would explain the non significant planting da te by variety interaction for marketable yield (Table 2-3 a nd Table 2-7). There were no ot her main effect interactions for yield. Tuber Yield for 2005 Planting date main effect Planting date main effect significantly infl uenced total and marketable yields in 2005. Planting dates 1, 2, 5 and 6 had signifi cantly lower marketable yields compared with planting dates 3 and 4 (pla nted 8 and 22 Feb) (Table 2-1) A leaching rainfall event occurred early in the season for planting date 6 (1 June) that delayed plant emergence (Figure 2-4). The significantly lower marketab le yields in planting dates 1 and 2 may be due to the lower temperatures early in the season, with average low temperatures of 11.4C which reduced net assimilation to the de veloping tubers and negatively impacted yield. Higher temperatures in planting date s 5 and 6 later in the season increased tuber respiration and decreased dry matter accu mulation during the bulking period with average high temperatures of 29C between fu ll flower and harvest (Figure 2-4). Size

PAGE 41

22 class distribution was also significantly influe nced by planting dates. Planting date 1 and 6 had the highest weight of B size tubers co mpared with all other planting dates. Additionally, planting dates 1 and 6 also had the lowest percenta ges of tubers in size class ranges A1 to A2 and A2 to A3 (Table 2-4) which are the marketable tuber size class range. Cooler temperatures early in the seas on as well as the higher temperatures late in the season also decreased and/or prevente d tuber initiation and development (Burton, 1989c). Nitrogen rate main effect Nitrogen rate main effect did not signifi cantly influence total or marketable tuber yields in 2005. Plants in the 224 kg N ha-1 had slightly higher tuber total yields compared with the 168 kg N ha-1 rate at 25.2 and 24.5 t ha-1, respectively. Total and marketable tuber yields were not signifi cantly different in the 224 kg N ha-1 treatment compared with plants in the 168 kg N ha-1 treatment at 19.4 and 19.1 t ha-1, respectively (Table 2-1). Three leaching rainfall events occurred duri ng the 2005 season compared with one in the 2004. This may explain the similarities in the total and marketable yields between fertilizer treatments in 2005 (Figure 2-4a a nd 2.4b). There were no significant nitrogen rate main effects interaction for tube r total and marketab le yields in 2005. Variety main effect The variety main effects significantly infl uenced total and marketable yields in 2005. Harley Blackwell had significantly hi gher total and marketable yields 26.1 and 20.0 t ha-1 compared with Atla ntic at 23.6 and 18.6 t ha-1, respectively. This result was most likely due to a higher tuber set per pl ant in Harley Blackw ell compared with Atlantic. Atlantic may also be more sens itive to colder temperatures early in the season and warmer temperatures later in the season, both of which would reduce net

PAGE 42

23 assimilation to developing tubers. Atlan tic had significantly hi gher specific gravity compared with Harley Blackwell at 1.078 and 1.076, respectively. Plants in planting dates 5 and 6 in 2004 and 2005 were bulking und er high temperatures that increased respiration and decreased dry matter accumula tion compared with early plantings that resulted in lower yields (Bur ton, 1989c). Optimum planting da tes to obtain highest yields in the TCAA, based on the results of this re search, encompassed a 4-week period in the middle of the traditional 12-w eek planting window. These da tes corresponded to planting dates 3 and 4 and extended from early February through the last week of February (Table 2-1). Main effect interactions The two-way interaction between planting date and variety main effects were significant for the total tuber yields in 2005. Harley Blackwell had significantly higher total yields in planting dates 2, 3, and 6 co mpared with Atlantic (Table 2-3). As discussed in the variety main effects, Harley Blackwell appears to tolerate environmental stress better compared with A tlantic early and later in the season. Tuber External Quality for 2004 Planting date main effect Planting date main effect significantly infl uenced the number of total culls in 2004. Tubers in planting dates 5 and 6 (planted 9 and 24 Mar) produced significantly higher total culls, 14.5 and 10.4%, respectively, compar ed with all other planting dates (Table 27). Since potatoes are a cool season crop, this was due to the warmer day and night temperatures with an average of 4 and 6 degrees warmer, respectively, as well as wetter weather conditions with an average additional rainfall amount of 5.3 cm.

PAGE 43

24 Nitrogen main effect Nitrogen rate main effect did not signifi cantly influence the occurrence of external defects. Percentages of total culls for th e 168 and 224 kg ha-1 N rate treatments were 3.2 and 2.4%, respectively (Table 2-7). Variety main effect Variety main effect significantly influenced the incidence of total culls. Atlantic had a significantly higher pe rcentage of total culls (2.9%) compared with Harley Blackwell (2.8%) (Table 2-7). The interaction term for th e planning date and variety main effects were significant for total culls. Atlantic had a significantly higher percentage of total culls comp ared with Harley Blackwell in planting date 2 at 3.1 and 0.3%, respectively. There were no other interaction effects for the 2004 production season. Tuber External Quality for 2005 Planting date main effect Planting date main effect in 2005 signifi cantly influenced total cull production Tubers in planting dates 5 and 6 had significan tly higher percentages of total culls (21.1 and 30.1% of total yields) compared with tubers from all other planting dates. A leaching rainfall event (17.0 cm) between 31 May and 1 June, 2005 (early to mid bulking) during planting dates 5 and 6 combined with highe r temperatures during these planting dates (average of 8 degrees) explai ned the significantly higher tota l culls, primarily rots, for both planting dates 5 and 6 (Table 2-7; Fig 2.5). Nitrogen rate main effect Nitrogen main effect did not significantly influence external defects in 2005.

PAGE 44

25 Variety main effect Variety main effect significantly influe nced total culls. Harley Blackwell had significantly lower tota l culls compared with Atlanti c (4.0 and 8.1%), respectively (Table 2-7). As mentioned previously, Atla ntic may be more sens itive to the warmer temperatures late in the season. Atlantic should be planted for early chipping contracts and Harley Blackwell should be planted to fill late season contracts when Atlantic quality can be suspect. Tuber Internal Quality for 2004 Planting date main effect Internal tuber defects are an important cl ass of defects. Unlike external tuber defects, internal defects cannot be seen on the grading table. Therefore, they cannot be picked-out before loading on the truck. The only recourse a grower has for a field of potatoes with high levels of inte rnal defects is to blend the load with tubers that do not have a high percentage of defects. Accord ing to the Department of Agriculture, 1978, USDA no. 1 potatoes may not exceed 10 and 5% external and internal defects by weight, respectively. Planting date main effect significantly infl uenced the occurrence of IHN in tubers in 2004. Tubers from planting date 4 (planted 23 Feb) had signifi cantly higher incidence of IHN compared with tubers from planti ng dates 1, 5 and 6 (planted 13 Jan., 9 and 24 Mar.) in 2004 (Table 2-8). IHN severity range d from a high of 1.5 in planting date 4 to a low of none in planting date 6. The signifi cantly higher incidence of IHN in tubers during planting date 4 could be explained in part to a leaching rainfall event in the first 30 DAP, between 200 and 400 GDD, which most likel y leached a majority of the preplant fertilizer (112 kg N ha-1) below the root zone. Although preplant N was applied in

PAGE 45

26 planting dates 1-4, planting date 4 had the shortest amount of time before a leaching rainfall event occurred after planting, approxi mately 21 DAP. Plants were in their early vegetative stage, which require d less nitrogen (approximately 15% of total N applied) (Ojala et al., 1990). N applied preplant may have gone through nitrification and subsequently leached below the root zone, th erefore, leaving only the N applied at the second sidedress for growth and developm ent the remainder of the season. Nitrogen rate main effect Nitrogen main effect did not significantly influence the occurren ce of tubers with IHN in 2004 (Table 2-8). Variety main effect Variety main effect significantly influen ced the incidence IHN in tubers in 2004. Atlantic had a significant highe r percentage of tubers with IHN compared with Harley Blackwell, 1.7 and 0.0% of total yi eld, respectively (Table 2-8). Tuber Internal Quality for 2005 Planting date main effect Planting date main effect significantly infl uenced the percentage of tubers with IHN in the 2005 production season. Similarly in 2004, tubers in planti ng date 4 (planted 22 Feb) had a significantly higher inciden ce of IHN (3.9%) compared with all other planting dates. Tubers in planting date 5 also had a higher incidence of IHN (3.1%) compared with planting dates 1, 2, 3, and 6. Severity was highest in planting dates 4 and 5, each having an IHN severity rating of 1.5. A leaching rainfall event (Potatoes horticulturally and environmentally sound fertilization of Hastings ar ea potatoes, brochure) occurred between emergence and tuber initiation (between 200 and 400 GDD for planting dates 4 and 5). NO3-N was most

PAGE 46

27 likely leached below the root zone leaving the sidedress applica tion as the primary N supply for the remainder of the season. A second and third leaching rainfall, 55-60 DAP; 10.26 cm and 85 DAP; 9.69 cm, respectively, occu rred during the early to mid and late bulking periods for planting date 5 (Fig 2.5). Th e two late seasons leaching rainfall events occurred during the period of highest N demand by the plant explaining the 15 fold increase in tuber IHN levels compared with the 2004 season (Table 2-4). Ojala et al. (1991) reported plants duri ng tuber initiation and bulking use approximately 30 and 58 to71%, respectively, of th e total N applied. Nitrogen rate main effect Nitrogen rate main effect did not significan tly influence IHN in tubers, with similar nitrogen rate main e ffect results in 2004, it would suggest that N rate alone is not the single cause of IHN development in tubers Variety main effect Variety main effect significantly influe nced the incidence of IHN in tubers. Atlantic had a significantly hi gher incidence of IHN compar ed with Harley Blackwell at 2.3 and 0.0%, respectively. Atlantic also had a higher severity rating (1.3) compared with Harley Blackwell (0.0) (Table 2-8). The percentage of tubers with IHN was highest in planting date 4 in 2004 and 2005. The highest mean maximum temperat ures during the first 30 DAP and mean minimum temperatures up to 90 DAP were obser ved starting in planting date 4. This supports the findings by Lee et al. (1992) that IHN in Atlant ic is highly correlated with high maximum temperatures in the first 30 DAP and high minimum temperatures for the remainder of the season up to 90 DAP (Table 29). Additionally, leaching rainfall events early in the season for planting date 4 in 2004 and 2005 as well as planting date 5 in 2005

PAGE 47

28 predisposed these tubers to IHN due to a combination of nutritional and environmental stress during early tuber development (Fig 2.4). Growing Degree Day Model Growing Degree Day Model and Potato Plant Development The key developmental stages evaluated for this study were emergence and full flower. Emergence and full fl ower occurred on average across planting dates at 213 and 804 accumulated GDD, respectively for th e 2004 production season. In 2005, the average across planting dates for emer gence and full flower were 210 and 813 accumulated GDD, respectively. GDD is a more predictive model compared with calendar days for determining key developmental stages for the potato plant. For instance, full flower occurred from 68 to 40 d after planting for 2004 and 71 to 42 DAP in 2005 over all planting dates. As planti ng dates progressed during the season, periods between developmental stages compressed (T able 2-10). This result would be an important concept to communicate to growers. Fertilizer an d pesticide applications, as well as, harvest dates should be timed by accumulated GDD and not calendar days as commonly done. Growing Degree Day Model and Tuber Yield During the 2004 production season, planting date 4 had the highest total and marketable yields, with accumulated GDD 2374. Marketable tuber yields were similar for planting date 1 through 3 (Table 2-1). Pl anting in January and March resulted in an average reduction in yield of 16 a nd 25%, respectively (Table 2-11). The 2005 production season also had the highe st yields in plan ting dates 3 and 4, with accumulated GDD of 1894 an 2160, respective ly. Optimum planting dates to obtain highest yields in the TCAA, based on the resu lts of this research, encompassed a 4-week

PAGE 48

29 period in the middle of the traditional 12-week planting window. Optimum period for highest yield extended from early to late February, 2004, which corresponded to 1951 to 2374 accumulated GDD for a 100 d season when plan ted during this part of the season. Planting before and after this 4 week period re sulted in an average decline in yield of 16 and 25% compared with planting date 4 respectively (Table 2-11). The optimum period for highest yields in 2005 extended from early February through the first week of March, 2005, which corresponded to 1894 to 2385 accumulated GDD for a 100 d season. Planting date 4 ha d the highest yields in 2005, as well. Planting before this date resulted in a reduc tion in yields from 48 to 55%. Planting later resulted in a decrease in yields from 36 to 73% (Table 2-11). Optimum planting dates for both the 2004 and 2005 season were planting dates 3 and 4. Planting before and after this 4-week period resulted in decreased yields for both Atlantic and H arley Blackwell for the 2004 and 2005 production seasons due to colder temperatures early in the season and warm er and wetter weather later in the season (Figure 2-4). In this experiment (and on many private farms), harvest was not determined by accumulated GDD but determined by calendar days. Aldicarb, a common soil applied insecticide/nematicide used in the area has a 100-d harvest interval. Growers time their harvest according to this required harvest in terval. The calendar method works better for the mid-season planting because Atlantic and Harley Blac kwell both have about a 100-d season. Timing harvest by calendar days does not work late in the season because as the season compresses, harvest should be accelerated. This concept would be important in later plantings because hot and we t weather in June incr eases rots in mature

PAGE 49

30 tubers as was demonstrated in this research. A grower that had late season contracts to fill, could theoretically harvest their crop from 92 to 83 DAP rather than the 100 day interval based upon aldicarb labeling requirement s if an alternative to aldicarb could be identified (Table 2-11). Growing Degree Day Model and Internal Tuber Quality The highest incidence of tubers with I HN in 2004 was during planting dates 3 and 4 with IHN values of 1.8 and 5.6% of total yi eld, respectively (Table 2-8). A leaching rainfall event occurred between 200 and 400 GDD for planting dates 3 and 4 in 2004 (emergence and tuber initiati on) (Figure 2-4). Accumula ted GDD for planting dates 3 and 4 at harvest were 1951 and 2374, respectively (Table 2-11). The GDD accumulated by harvest should not be used to predict the in cidence of IHN in tubers. IHN most likely is a combination of plants stresses that o ccur throughout the season a nd cannot be tied to a single GDD number at the end of the season. It would be useful to relate the accumulated GDD to the development stage of the potato plant and the timing of a perceived plant stress. This may provide insi ght to the development of IHN in tubers. The highest percentage of tubers with I HN in 2005 occurred in planting dates 4 and 5, with IHN values of 3.9 and 3.1% of total yiel d, respectively (Table 2-8). As is 2004, a leaching rainfall event occu rred between 200 and 400 accumulated GDD during planting dates 4 and 5 in 2005 (Figure 2-4). Lee et al. (1992) reported that IHN in Atlantic develope d early in the plant season and correlated with the highest mean ma ximum temperature from 0-30 DAP and the highest mean minimum temperature during th e remainder of the growing season up to 90 DAP. The results of this research indicated that a leaching event early in the season,

PAGE 50

31 between emergence and tuber initiation (200 to 400 GDD) also contributed to the occurrence of IHN in tubers. Conclusion This experiment was designed to determine seasonal environmental (rainfall, temperature) and nutrient constraints that imp act plant stress and, in turn, tuber quality as well as determining optimal yields over a typical growing season in the TCAA. Optimal yields for the TCAA occur over a 4 week period in a twelve week planting window from late January to late February. The results from this research suggest a couple of options for growers who need to m eet late season contracts. First, Harley Blackwell has demonstrated its effectivene ss to produce quality tubers under conditions when air temperatures and leaching rainfall even ts stress plants. Second, if an alternative to the pesticide aldicarb is identified, a gr ower could harvest at 79 to 90 DAP based on the GDD model. This alternat ive would reduce the incidence of rots due to the warmer and wetter weather conditions typically experienced later in the season. This research has also demonstrated that the internal physiological disorder, IHN is triggered by rainfall and nutri tional conditions that stress th e plant early in the season combined with increasing minimum daily te mperatures later in the season. Leaching rainfall events between 200 and 400 GDD after planting stressed the plants nutritionally by potentially leaching nutrients from the root zone when potato plants are at a stage of rapid growth and development as discussed in chapter 3.

PAGE 51

32Table 2-1. Total and marketable yield and sp ecific gravity production st atistics for 2004 and 2005 Total yield Marketable yield Specific gravity Total yield Marketable yield Specific gravity 2004 2005 Main Effect t ha-1 t ha-1 Planting Datez (PD) 1 28.0 bcy 24.0 ab 1.083 a 19.3 c 14.9 d 1.081 a 2 28.0 bc 21.2 bc 1.085 a 19.6 c 16.9 d 1.076 b 3 30.8 ab 23.7 ab 1.079 b 29.7 b 26.2 b 1.080 a 4 33.0 a 26.4 a 1.076 c 35.3 a 32.4 a 1.081 a 5 25.5 c 17.0 d 1.068 d 30.5 b 20.9 c 1.076 b 6 24.5 c 19.4 cd 1.066 d 17.4 c 9.0 e 1.069 c Nitrogen Rate (NR) 168 kg N ha-1 29.4 a 20.5 b 1.076 25.2 19.1 1.077 224 kg N ha-1 27.1 b 23.2 a 1.076 24.5 19.4 1.077 Variety (V) Atlantic 29.3 a 24.2 a 1.078 23.6 b 18.6 b 1.078 a Harley Blackwell 27.1 b 19.6 b 1.075 26.1 a 20.0 a 1.076 b

PAGE 52

33Table 2-1. Continued Total yield Marketable yield Specific gravity Total yield Marketable yield Specific gravity 2004 2005 t ha-1 t ha-1 Interaction effectsx PD*NR ** ** ns ns ns ns PD*V ns *** ** ns NR*V ns ns ns ns ns ns PD*NR*V ns ns ** ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were ( 13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005). yMeans are separated with column and main effect us ing Tukeys studentized range test. Means followed by different letters are si gnificantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001 using ANOVA

PAGE 53

34 Table 2-2. Two-way interaction between planting date and nitr ogen rate main effects for total and marketable tuber yields in 2004 Total yield Marketable yield 2004 PDz*N R Slicedy by PD t ha-1 1 168 27.8 23.8 1 224 28.2 24.0 2 168 27.0 20.7 2 224 28.9 21.7 3 168 28.0 bx 20.3 b 3 224 33.7 a 27.4 a 4 168 33.4 26.8 4 224 32.5 26.1 5 168 24.4 b 15.7 b 5 224 26.7 a 18.5 a 6 168 22.5 b 17.1 b 6 224 26.6 a 21.8 a zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004) ySliced by PD This option enabled the comparison of the fertilizer rates among each of the planting date treatments xMeans of the interaction effects followed by different letters within each planting date and column are significantly different at p 0.05. Means with no letters are not significantly different.

PAGE 54

35 Table 2-3. Two-way interacti on between planting date and variety main effects for total tuber yields in 2004 and 2005 Total yield Total yield 2004 2005 PDz*V Slicedy by PD t ha-1 t ha-1 1 Atlantic 29.3 ax 19.2 1 Harley Blackwell 26.8 b 19.4 2 Atlantic 27.5 16.8 b 2 Harley Blackwell 28.4 22.7 a 3 Atlantic 32.1 a 26.9 b 3 Harley Blackwell 29.4 b 32.6 a 4 Atlantic 33.8 35.1 4 Harley Blackwell 32.1 35.5 5 Atlantic 29.0 a 32.5 a 5 Harley Blackwell 22.2 b 28.5 b 6 Atlantic 24.5 14.9 b 6 Harley Blackwell 24.5 20.0 a zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005). ySliced by PD This option enabled the comparison of the varieties among each of the planting date treatments xMeans of the interaction effects followed by different letters within each planting date and column are significantly different at p 0.05. Means with no letters are not significantly different.

PAGE 55

36Table 2-4. Size class dist ribution and range (%) produc tion statistics 2004 and 2005 Size Distribution by class (%)z Size Class Range (%) Size Distribution by class (%)z Size Class Range (%) Main effects B A1 A2 A3 A1 to A2 A2 to A3 B A1 A2 A3 A1 to A2 A2 to A3 Planting Datez (PD) 2004 2005 1 7.5 aby 68.5 a 15.3 a 1.0 ab 84.4 a 17.1 ab 19.2 a 71.2 ab 5.9 d 0.0 b 78.3 b 6.3 d 2 9.7 a 61.4 b 13.9 ab0.7 ab 76.1 c 15.6 bc 10.1 b 73.6 a 13.0 c 0.2 b 87.3 a 13.9 c 3 9.2 a 62.0 b 15.5 a 0.0 b 78.8 bc 15.7 bc 8.8 bc 62.5 c 22.4 b 3.6 a 85.2 a 27.1 b 4 6.1 b 63.9 ab 18.6 a 1.1 ab 83.3 ab 15.6 ab 6.1 c 52.8 d 38.8 a 3.9 a 87.5 a 39.9 a 5 9.2 a 66.4 ab 9.1 b 0.0 ab 77.5 c 10.5 c 9.8 b 71.7 ab15.4 c 0.0 b 88.1 a 15.8 c 6 5.8 b 65.5 ab 18.6 a 1.6 a 86.4 a 21.7 a 22.3 a 68.2 b 2.8 d 0.0 b 75.1 b 3.6 d Nitrogen Rate (NR) (kg ha-1) 224 7.4 64.1 16.3 0.9 81.8 18.4 13.0 a 66.4 13.7 0.6 84.7 a 15.3 168 8.3 65.2 13.7 0.5 80.6 15.2 11.3 b 67.2 14.4 0.7 83.1 b 16.6 Variety (V) Atlantic 5.4 b 64.9 20.3 a 1.5 a 86.1 a 23.3 a 9.6 b 66.7 17.6 a 0.9 86.4 a 19.9 a Harley Blackwell 10.8 a 64.3 10.4 b 0.2 b 75.0 b 11.2 b 15.0 a 66.9 10.8 b 0.4 81.1 b 12.4 b

PAGE 56

37Table 2-4. Continued Size Distribution by class (%)z Size Class Range (%) Size Distribution by class (%)z Size Class Range (%) B A1 A2 A3 A1 to A2 A2 to A3 B A1 A2 A3 A1 to A2 A2 to A3 Interaction effectsx 2004 2005 PD*NR ns ns ns ns ns ns ns ns * ns PD*V ns *** ** ns *** ** ns *** ns NR*V ns ns ns ns ns ns ns ns ns ns PD*NR*V ns ns ns ns ns ns ns ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Ja n, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb 22 Feb, 7 Mar 22 Mar,2005). yMeans are separated with column and main effect using Tukeys studentiz ed range test. Means follow ed by different letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001 using ANOVA.

PAGE 57

38 Table 2-5. Two-way interaction between planting date and nitr ogen rate main effects for size class range (%) for A1 in 2004 and A3 and size class distribution for A1 to A2 in 2005 A1 A3 A1 to A2 2004 2005 PDz*N R Slicedy by PD % % 1 168 84.1 ax 0.0 79.6 1 224 77.4 b 0.0 76.1 2 168 71.9 0.5 88.8 2 224 72.9 0.0 85.4 3 168 71.1 2.0 b 86.1 3 224 74.2 5.2 a 84.0 4 168 76.5 5.9 a 85.4 b 4 224 74.7 2.4 b 88.8 a 5 168 76.1 0.0 88.1 5 224 81.3 0.0 87.5 6 168 80.8 0.2 76.9 a 6 224 73.6 0.0 72.6 b zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005) ySliced by PD This option enabled the comparison of the fertilizer rates among each of the planting date treatments xMeans of the interaction effects followed by different letters within each planting date and column are significantly different at p 0.05. Means with no letters are not significantly different.

PAGE 58

39Table 2-6. Two-way interaction between plan ting date and variety main effects for si ze class range (%) for A1, A2, A3 and A2 t o A3 in 2004 and B, A1, A3 and A1 to A2 in 2005 A1 A2 A3 A2 to A3 B A1 A3 A1 to A2 2004 2005 PDz*V Slicedy by PD % % 1 Atlantic 69.4 18.1 1.1 20.1 16.9 b 71.7 0.0 80.8 a 1 Harley Blackwell 67.6 12.4 0.9 14.3 21.7 a 69.8 0.0 75.2 b 2 Atlantic 64.7 ax 16.7 0.7 18.6 9.1 73.8 0.3 88.1 2 Harley Blackwell 58.0 b 11.3 0.8 12.8 11.1 73.4 0.1 86.1 3 Atlantic 62.4 20.8 a 0.0 21.2 a 6.6 b 60.7 6.4 a 84.7 3 Harley Blackwell 61.5 10.9 b 0.0 10.9 b 11.2 a 64.1 1.5 b 85.1 4 Atlantic 64.1 22.8 2.8 a 26.8 a 4.2 b 50.6 5.6 a 88.1 4 Harley Blackwell 63.7 14.6 0.2 b 15.6 b 8.3 a 55.0 1.6 b 86.1 5 Atlantic 70.8 a 12.9 a 1.9 a 16.5 a 7.7 b 67.9 b 0.0 90.6 a 5 Harley Blackwell 61.1 b 5.7 b 0.0 b 5.7 b 12.0 a 75.3 a 0.0 84.7 b 6 Atlantic 57.2 b 31.7 a 4.5 a 38.1 a 15.6 b 73.3 a 0.0 83.3 a 6 Harley Blackwell 72.6 a 8.3 b 0.1 b 9.0 b 29.7 a 62.9 b 0.2 65.7 b zPlanting dates 1 through 6 for 2004 and 2005 were (13 Ja n, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005) ySliced by PD This option enabled the comparison of th e varieties among each of th e planting date treatments xMeans of the interaction effects followed by different letter s within each planting date and column are significantly different at p 0.05. Means with no letters are not significantly different.

PAGE 59

40Table 2-7. External quality (green, gr owth cracks, mis-shaped, rot and total culls) % of total yield 2004 and 2005 External tuber defects (%) Main effects Green Growth crack Misshaped Rot Total cullz Green Growth crack Misshaped Rot Total cullz Planting Date (PD) 2004 2005 1 0.0 c 0.0 0.0 b 0.0 c 0.0 c 0.5 a 0.1 a 0.0 0.0 c 0.9 c 2 0.0 bc 0.3 a 0.2 a 0.0 c 0.0 c 0.3 a 0.1 a 0.1 0.1 c 1.5 c 3 0.1 ab 0.0 0.1 ab 0.4 c 0.4 c 0.5 ab 0.0 ab 0.1 0.0 c 1.4 c 4 0.5 a 0.0 0.0 b 4.6 b 4.6 b 0.3 b 0.0 b 0.0 0.0 c 0.5 c 5 0.0 bc 0.0 0.0 ab 13.8 a 14.5 a 0.5 ab 0.0 ab 0.0 19.9 b 21.1 b 6 0.0 c 0.0 0.0 ab 10.4 a 10.4 a 0.0 a 0.0 b 0.0 29.9 a 30.1 a Nitrogen Rate (NR) kg ha-1 224 0.20 0.0 0.0 2.4 2.4 0.3 0.0 0.0 8.20 5.7 168 0.39 0.0 0.0 3.2 3.2 0.3 0.0 0.0 9.18 6.0 Variety (V) Atlantic 0.4 0.0 0.1 a 2.9 2.9 a 0.4 0.0 a 0.1 a 9.87 8.1 a Harley Blackwell 0.1 0.0 0.0 b 2.8 2.8 b 0.2 0.0 b 0.0 b 7.52 4.0 b

PAGE 60

41Table 2-7. Continued Green Growth crack Misshaped Rot Total cullz Green Growth crack Misshaped Rot Total cullz Interaction effects 2004 2005 PD*NR ns ns ns ns ns ns ns ns ns PD*V ns ns ns ns ns ns ns ns ns PD*F ns ns ns ns ns ns ns ns ns PD*NR*V ns ns ns ns ns ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005). yMeans are separated with column and main effect using T ukeys studentized range test. Means followed by different letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 61

42Table 2-8. Internal quality (% ) of total yield 2004 and 2005 Internal Quality (%) Main effects HH IHN IHN severity CRS BCL HH IHN IHN severity CRS BCL Planting Date (PD) 2004 2005 1 0.9 b 0.0 b 1.0 14.3 a 0.0 b 0.0 0.0 b 0.1 b 0.3 a 6.0 2 3.8 a 1.2 ab 0.6 0.7 b 1.2 a 0.0 0.0 b 0.3 b 0.0 b 0.6 3 0.0 c 1.8 ab 0.5 3.9 ab 0.0 b 0.0 0.0 b 0.1 b 0.0 b 0.0 4 0.0 c 5.6 a 1.0 0.4 b 1.4 a 0.0 3.9 a 1.5 a 0.0 b 0.3 5 0.0 c 0.2 b 0.7 0.0 b 0.0 b 0.0 3.1 a 1.5 a 0.0 b 0.0 6 0.0 bc 0.8 b 0.6 0.0 b 0.0 b 0.0 0.2 b 0.5 b 0.0 b 0.0 Nitrogen Rate (NR) kg ha-1 224 0.3 1.0 0.9 0.8 b 0.2 0.0 0.4 0.7 0.0 0.4 168 0.2 1.1 0.5 2.6 a 0.1 0.0 0.8 0.6 0.0 0.7 Variety (V) Atlantic 1.0 a 3.2 a 0.6 1.6 0.4 a 0.0 2.3 a 1.3 a 0.0 2.1 Harley Blackwell 0.0 b 0.0 b 0.9 1.5 0.1 b 0.0 0.0 b 0.0 b 0.0 0.0

PAGE 62

43Table 2-8. Continued HH IHN IHN severity CRS BCL HH IHN IHN severity CRS BCL Interaction effects 2004 2005 PD*NR ns ns ns ns ns ns ns ns ns PD*V ns ns ns ns ns *** ns ns ** PD*F ns ns ns ns ns ns ns ns ns PD*NR*V ns ns ns ns ns ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005). yMeans are separated with column and main effect using T ukeys studentized range test. Means followed by different letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 63

44Table 2-9. Mean maximum and minimum temperat ure (C) for planting dates 1-6, 2004 and 2005 0-30 DAP 30-60 DAP 60-90 DAP 2004 Mean Mean Mean Planting Order Date of Planting Max Min Max Min Max Min 1 13 Jan 18.8 7.2 19.4 8.3 23.3 10.5 2 27 Jan 18.3 7.7 22.2 10.0 24.4 11.1 3 9 Feb 19.4 8.8 22.7 9.4 25.5 12.2 4 23 Feb 21.1 10.5 23.8 11.1 27.2 16.1 5 9 Mar 22.2 9.4 25.5 12.2 30.0 17.7 6 24 Mar 23.8 10.5 27.2 15.0 31.6 20.0 0-30 DAP 30-60 DAP 60-90 DAP 2005 Mean Mean Mean Planting Order Date of Planting Max Min Max Min Max Min 1 11 Jan 17.2 6.1 20.0 7.2 23.3 11.6 2 25 Jan 19.4 7.2 20.0 8.8 24.4 10.5 3 8 Feb 20.0 7.7 23.3 11.6 23.8 10.5 4 22 Feb 20.0 9.4 24.4 11.6 26.1 13.3 5 7 Mar 22.2 11.1 23.8 11.1 28.8 16.1 6 22 Mar 24.4 11.6 26.1 13.3 29.4 19.4

PAGE 64

45Table 2-10. Accumulated GDD and calendar days to obtain emergence and full flower 2004 and 2005 2004 Planting Order Date of Planting Date of emergence Days to emergence GDDy to emergence Calendar days to FF GDD to FF Calendar days to harvest GDD to harvest 1 13 Jan 6 Feb 24 240 68 841 104 1493 2 27 Jan 16 Feb 20 226 61 806 104 1676 3 9 Feb 25 Feb 16 178 52 749 106 1951 4 23 Feb 7 Mar 13 218 49 820 106 2374 5 9 Mar 22 Mar 13 202 47 816 104 2490 6 24 Mar 5 Apr 12 211 40 792 104 2840 Average 16 213 53 804 2137 2005 Planting Order Date of Planting Date of emergence Days to emergence GDD to emergence Calendar days to FFx GDD to FF Calendar days to harvest GDD to harvest 1 11 Jan 8 Feb 28 244 71 814 104 1442 2 25 Jan 15 Feb 21 213 61 794 106 1677 3 8 Feb 23 Feb 15 199 56 837 105 1894 4 22 Feb 12 Mar 18 211 48 801 106 2160 5 7 Mar 22 Mar 15 197 47 811 105 2385 6 22 Mar 31 Mar 9 198 42 826 105 2719 Average 18 210 54 813 2046

PAGE 65

46 Table 2-11. Early and late season yield re duction and harvest date at 2000 GDD for 2004 and 2005 2004 Planting Order Date of Planting Date of emergence Yield reduction Calendar days to 2000 GDD Harvest date at 2000 GDD 1 13 Jan 6 Feb -15 130 17 May 2 27 Jan 16 Feb -16 115 21 May 3 9 Feb 25 Feb -7 104 25 May 4 23 Feb 7 Mar 0 97 30 May 5 9 Mar 22 Mar -23 89 6 June 6 24 Mar 5 Apr -26 81 13 June 2005 Planting Order Date of Planting Date of emergence Yield reduction Calendar days to 2000 GDD Harvest date at 2000 GDD 1 11 Jan 8 Feb -55 130 21 May 2 25 Jan 15 Feb -48 118 23 May 3 8 Feb 23 Feb -20 110 29 May 4 22 Feb 12 Mar 0 101 3 June 5 7 Mar 22 Mar -36 94 9 June 6 22 Mar 31 Mar -73 84 14 June

PAGE 66

47 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.001/13/04 1/20/04 1/27/04 2/3/04 2/10/04 2/17/04 2/24/04 3/2/04 3/9/04 3/16/04 3/23/04 3/30/04 4/6/04 4/13/04 4/20/04 4/27/04 5/4/04 5/11/04 5/18/04 5/25/04 6/1/04 6/8/04 6/15/04 6/22/04 6/29/04 7/6/04DateRainfall (cm)0 5 10 15 20 25 30 35Daily average temperature (C) Rainfall events Average daily temperature Daily rainfall and average daily temperature -2004 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.001/12/05 1/19/05 1/26/05 2/2/05 2/9/05 2/16/05 2/23/05 3/2/05 3/9/05 3/16/05 3/23/05 3/30/05 4/6/05 4/13/05 4/20/05 4/27/05 5/4/05 5/11/05 5/18/05 5/25/05 6/1/05 6/8/05 6/15/05 6/22/05 6/29/05DateRainfall (cm)0 5 10 15 20 25 30 35Average daily temperature (C) Rainfall events Average daily temperature Daily rainfall and average daily temperature 2005 Figure 2-2. Daily rainfall (cm) for a. 2004 and b. 2005 production season. Grouping of red bars denote a leaching rainfall event (7.6 cm in 3 days or 10.1 cm in 4 days). The yellow, pink, blue, green, or ange and black lines denote planting dates 1-6, respectively, from em ergence to tuber initiation a. b

PAGE 67

48 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 AtlAtlAtlAtlAtlAtlHBHBHBHBHBHB 123456123456 Planting Date x VarietyYield (t/ha)0 500 1000 1500 2000 2500 3000Accumulated GDD Total yield Marketable yield Accumulated GDD 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 AtlAtlAtlAtlAtlAtlHBHBHBHBHBHB 123456123456 Planting date x VarietyYield (t/ha)0 500 1000 1500 2000 2500 3000Accumulated GDD Total yield Marketable yield Accumulated GDD Figure 2-3. Total and marketable yield at each planting date x variety and accumulated GDD at harvest. a. 2004 b. 2005 a. b.

PAGE 68

49 CHAPTER 3 YIELD AND QUALITY OF ATLANTIC POTATO ( SOLANUM TUBEROSUM L.) TUBERS AND OFF-FIELD NUTRIE NT MOVEMENT UNDER VARYING NITROGEN SOURCES AND STAGED LEACHING IRRIGATION EVENTS Introduction The St. Johns River has been identified by th e state of Florida as a priority water body in need of restoration under the auspi ces of the Surface Water Improvement and Management Act implemented by the Florida le gislature in 1987. Pers onnel from the St. Johns River Water Management District (S JRWMD), University of Florida, multiple state government agencies, and the North Fl orida Growers Exchange have developed Best Management Practices (BMP) fo r potato production in the Tri-County Agricultural Area (St. Johns, Putnam, a nd Flagler Counties, TCAA). The purpose of implementing BMPs is to reduce nitrate run-off from the approximately 7,300 ha of land in potato production in the St Johns River watershed. The SJRWMD has estimated that as much as 36% of the pollutant load entering the river basin today is related to human activities that include agricultural production. Algal blooms in the St. Johns River have coincided with peak runoff associated with the TCAA potato season (SJRWMD, 1996). Bailey and Wadell (1979) reported non-point source pollution from agricultural runoff contributes approximately 9.5 million t ons of N and P to U.S. surface waters annually. The EPA reports that non-point s ource pollution from agriculture has impaired 60% of the river miles and half of the lake acreage surveyed by states, territories and tribes (EPA website).

PAGE 69

50 Figure 3-1. Aerial photograph of potato production fields alo ng the St. Johns River, St. Johns County, Florida. Courtesy of Pam Livingston-Way, SJRWMD Growers in Northeast Florida typica lly apply approximately 308 kg N ha-1 for commercial potato production (H ochmuth, et al., 1993). Grow ers participating in the BMP program are encouraged to apply the IFAS recommended nitrogen rate of 224 kg N ha-1. In the event of a leaching rain, grower s are allowed, under th e provisions of the program, to apply an additional 34 kg N ha-1 (Hutchinson et al., 2002). It has generally been accepte d that leaching rains are res ponsible for the majority of nitrate movement out of potato production ground IFAS research defines a leaching rain as 7.6 cm of rain in three days or 10 cm of rain over seven days. After a leaching event, growers are encouraged to a pply an additional 34 kg N ha-1 (Kidder et al., 1992) Potatoes are typically grown in sandy, course textured soils that have a low water holding capacity, which exacerbates the potential of NO3-N leaching below the root system of the potato plant. Potato plants have a relatively sha llow root system with greater than 90% of the total root area located in the uppe r 25 cm of the soil profile (Munoz, 2004; Rosen, 2001). Heavy rain washes fertilizer out of the potato row and either into the furrow or into the perched water table. Fertilizer washed into the furrow

PAGE 70

51 moves in surface water off the potato beds and into tail-water or drainage canals. The amount of fertilizer th at potentially could be leached from the row is dependent on the type and amount of fertilizer a pplied within the row, as well as the time between fertilizer application and a leaching event occurs. Controlling NO3-N leaching can be difficult under the best management practices due to unforeseen leaching rainfall events. Wang and Alva (1996), evaluated soil columns with a Wabasso sand and reported approximately 88 to 100% of ammonium nitrate was lost due to leaching compar ed to 11.5 to 11.7% of a polymer-coated controlled release fertilizer (CRF). Maynard and Lorenz, (1979); Elkashif and Locascio, (1983) reported the release of N from sulfur coated urea (SCU, slow release fertilizer) was too slow to sufficiently meet the demands of the potato crop. Wa ddell et al. (1999) reported the tuber N uptake in SCU treatment s was the lowest compared with other fertilizer treatments and attributed this to th e lack of release of the coated urea when the plant N demand was high. While CRFs have been on the market for several years (Trenkel, 1997), vegetable gr owers require a CRF with a more predictable release pattern, one that is customi zed for individual crop growth and development stages. Fertilizer manufacturers addresse d this with the release of a polymer-coated urea (PCU). Unlike SCU that is affected by soil propertie s (moisture or microbial activity), PCUs are dependent upon temperature and moisture perm eability of the resin coating, therefore, making the release rate more predictable or controlled (Shoji and Gandeza, 1992). Studies have reported the benefits of polymer-coated CRFs in potato production systems. CRFs maintained quality a nd yield while reducing nutrient leaching. Hutchinson et al. (2003), reporte d that yield and quality of Atlantic on an Ellzey fine

PAGE 71

52 sand in FL was not adversely affected, alt hough, two leaching rainfall events occurred during the production season (713 DAP and 92-98 DAP). Hutchinson (2005) reported a 69% reduction in tubers with IHN with the use of a blended polymer coated urea product (168 kg N ha-1) with an approximate release rate of 45, 75 and 120 DAP, compared with ammonium nitrate (AN) at th e BMP rate (224 kg N ha-1). Similar results were also reported by Pack (2004), in which the average reduction of tubers with IHN was68% with CRF (168 kg N ha-1) treatments compared with the BMP rate of AN (224 ha N ha-1). Zvomuya and Rosen (2001) reported in 1996 and 1997, PCU treatments produced signifi cantly higher total and mark etable tuber yields of Russet Burbank on a Hubbard loamy sand in MN when compared with AN fertilizer. Leaching events (> 5cm within a 48 hr pe riod) were recorded in 1996 (20 and 50 DAP) and 1997, (40, 50 and 75 DAP). IHN was not reported, although the incidence of HH remained the same over both production seasons for the CRF treatmen t and decreased in 1997 in the AN fertilizer treatment. Zvomuya et al. (2003) reported a decrease in NO3-N leaching of 34-49% after leaching irrigation events in CRF plots. To tal and marketable tuber yields of Russet Burbank were 12 to 19% higher with CRFs compared with multiple applications of urea on a Hubbard loamy sand in Becker, MN. CRF could be the N management tool for Northeast Florida potato production that reduces NO3-N leaching while, at the same ti me, maintaining acceptable yields. However, the relationships between fertilizer source, leaching irri gation timing, and tuber quality and yield are not well understood.

PAGE 72

53 The objectives of this study were to 1) determine the influence of fertilizer source (soluble and controlled release) and timing of leaching irrigation on yield and quality of Atlantic 2) determine the influence of fertilizer source (soluble and controlled release) and timing of leaching irrigation on nutrient leaching and nutrients in surface water runoff during a leaching event. Materials and Methods Site Description The experiment was conducted during the 2004 and 2005 production years at the University of Florida, Plant Science Res earch and Education Unit (PSREU), Hastings, Florida on an Ellzey fine sand (sandy, sili ceous, hyperthermic Arenic Ochraqualf; sand 90% to 95%, <2.5% clay, <5% si lt). The soil profile is described as poorly drained although the top 94 cm have a very high perm eability rate (5-10 cm/hr). A restricting clayey layer lies below the sandy loam top layer of the profile. The water table is within 25 cm of the surface for one to six months of the year (Soil Survey, St Johns County, 1983) Experimental Design The experiment was arranged as a factoria l randomized complete block as a splitsplit design with four blocks. Each of the four blocks were located in a single bed at the PSREU (beds 12-15 NL). The study was conducte d at the same location for the 2004 and 2005 production years. The main effects were irrigation event, nitr ogen source, and sidedress fertilizer application. Main plots were 16 rows wide (102 cm centers) by 18.3 m (60 ft) long running south to north with a 6.1 m (20 ft) buffer between main plots. Irrigation treatments were applied to main plots at 0, 2, 4, 8, and 12 WA P (weeks after planting). Nitrogen source

PAGE 73

54 was applied to eight row sub-plots in each main plot. Ammonium nitrate (AN) and polymer coated urea (controlled release fert ilizer; CRF) were the fertilizer sources. The last main effect, side-dress fert ilizer application, was applied to four of the eight rows in each sub-plot. Ammonium nitrate (34-0-0) was applied with a hydraulic fertilizer applicator as a band on either side of the potato plant after each l eaching irrigation date event (Table 3-1 and Fig 3.1). Crop Production Practices Tuber Planting Potatoes were cut at planting to an a pproximate 71 g seed piece and dusted with fungicide [1.13 g a.i., fludioxonil and 21.8 g a.i. mancozeb per 45.4 kg seed pieces] (Maxim MZ; Syngenta Crop Protection, Inc., Greensboro, N.C.)]. Azoxystrobin, a.i.[0.1 L ha-1 (Amistar; Syngenta, Crop Protection, Gree nsboro, N.C.)] and aldicarb a.i. [3.4 kg ha-1 (Temik, Bayer Corp., Kansas City, Mo.)] was applied in-row at planting. All other pesticide applications during the growing season followed recommendations for Florida potato production (Hutch inson et al., 2004). Potatoes were planted 19 and 22 Feb 2004 and 2005 and harvested 1 and 8 June 2004 and 2005 (106 and 108 DAP), respectively. Between and within row spacing was 102 and 20 cm (40 and 8 inches), respectivel y. This resulted in a plant density of approximately 48,400 plants ha-1. Irrigation Overhead solid set sprinkler irrigation system with #4 mini-wobblers (127 L hr-1 or 0.6 gpm at 25 psi; Senninger Irrigation, Inc., Cl ermont, FL) was installed to apply each leaching irrigation event (2, 4, 8 and 12 WAP) 7.6 cm of simulated rainfall to main plots.

PAGE 74

55 Irrigation was collected in U. S. Weathe r Bureau approved rain gauges (Forestry Suppliers, Inc., Jackson, MS) placed in each irrigation main plot. Plots were irrigated with seepage irriga tion throughout the growing season except during leaching irrigation events and periods of sufficient rainfall. The seepage irrigation system is a semi-closed system. Wa ter withdrawn from the confined aquifer is pumped through PVC (polyvinyl chloride) pipe to each V-shaped open water furrow in the field. Each water furrow is situated 18.2 m apart. Water seeps from the water furrow laterally, underground, across the bed and throug h capillarity reaches the root system of the potato plant (Singleton, 1990). A perc hed water table was maintained at approximately 45-60 cm from the top of the potato row. Nutrient Management Ammonium Nitrate Nitrogen Fertilizer application was based on best management practice (BMP) recommendations for Florida potato production (224 kg.N ha-1; Hutchinson et al., 2004). Pre-plant fertilizer was applied as a 15 cm wide band on top of the row at a rate of 112 kg N ha-1 as 14N-6P2O5-12K2O with a John Deere 6615 and a two-row hydraulic fertilizer applicator (Kennco Mfg., Ruskin FL,). Fertil izer was incorporated into each row with a four-row chopper then rows were bedded prio r to planting. Two additional sidedress applications of 56 kg N ha-1 as 30-0-0 were banded on either side of the potato plants with a two row hydraulic fertilizer applic ator at 34 and 43 DAP in 2004 and 37 and 43 DAP in 2005 to AN plots to achieve the BMP rate of 224 kg ha-1. Following each sidedress application, a four row covering disk was used to cover the fertilizer banded along side the potato plants in each row. This is not the side dress ni trogen main effect.

PAGE 75

56 After a leaching irrigation ev ent, a third side dress nitrogen application of 34 kg N ha-1 (30-0-0 NPK) was mechanically applied to four of the eight row main fertilizer treatments (treatments 2 and 4) followi ng the BMP recommendation for fertilizer application after a leaching ra in. (Table 3-1, Fig 3.1). This is the sidedress nitrogen application main effect. Controlled Release Fertilizer All CRF fertilizer was applied in a si ngle preplant application at 196 kg N ha-1 (380-0, The Scotts Company, Marysville, OH) on 12 and 21 Feb 2004 and 2005, respectively (Fig 3.1). CRF is a polymer-sulfu r coated urea product designed to release 75% of the nitrogen by 75 DAP. All CRF treatments received 78 kg ha-1 P2O5 as 0-20-0 and 202 kg ha-1 K2O as 0-0-50 preplant. Tuber Production Analysis. At harvest, two rows (6.1 meters each) from each fertilizer source by additional sidedress application plot were harvested, washed, and mechanically graded and sized into the following class sizes ; B = 3.8 to 4.4 cm, A1 = 4.4 to 6.4 cm, A2 = 6.4 to 8.3 cm, A3=8.3 cm to 10.2 cm, A4 = > 10.2 cm at the PSREU. Marketable yield is defined as no. 1 tubers with diameters between 4.4 a nd 10.2 cm (USDA, 1978) and without visible blemishes (rotten, green, misshapen, or growth cracks).

PAGE 76

57 Tuber Specific Gravity. Specific gravity was calculated on a sub-sa mple of marketable tubers from each fertilizer source by additional sidedress applicat ion plot using the wei ght in air/weight in air-weight in water method (Burton, 1989a). A tlantic potatoes are the standard chip variety. High specific gravity is desired. Specific grav ities of at least 1.078 are considered good for production at the PSREU re search farm in Hastings, FL (Hutchinson et al., 2002). External Quality. Culls (green, growth cracks, misshapen, and rotten tubers) were removed and weighed at the grading line. External quality (green, growth cracks, misshaped and rot) were reported as a percentage of total yield. Internal Quality. A 20 tuber sub-sample from each fertilizer source by additional sidedress application plot was cut into quarters and rated for internal quality. Rated physiological disorders included hollow heart (HH), intern al heat necrosis (IHN) and brown center (BC). Disease induced disorders included co rky ring spot (CRS) and brown rot (BR). IHN severity was scored on a one to six scale with a score of one to four relating to the number of quarters with IHN. A score of fi ve or six indicated th at all quarters had the disorder and up to 75 to 100% of all quarters were covered, respectively. Water Sample Collection and Nutrient Load Surface Run-Off Volume Surface run-off volume was collected from a fertilizer source main plot during each irrigation event. A 7.1 cm (18 in) PVC pipe was placed perpendicular to each of the

PAGE 77

58 eight plots at the water furrow to route su rface water flow. Water volume was collected every ten minutes from the pipe for ten seconds and the water volume was recorded. Nutrient Load A 20 mL water sample was collected ev ery 10 min as runoff started from each fertilizer source main plot, (8 total) at each 10 minute sample interval using the system described for surface water volume. Samp le collection stopped once irrigation was turned off and runoff ceased from each of the fe rtilizer plots. Water samples were stored in a freezer at -15C until analyzed. Samples were analyzed for NO3-N and NH4-N (EPA method 353.2), P, K (EPA method 200.7), and EC at the University of Florida/IFAS Analytical Research Laboratory, Gainesvi lle, FL (Mylavarapu and Kennelley, 2002). Wells Observation wells (10 cm diameter by 0.9 m long) were installed (10 and 8 Mar, 2004 and 2005 (23 and 15 DAP), respectively in each fertilizer source by sidedress application plot (80 total) so th at the top of the wells were fl ush with the top of the row. This allowed access to the perched water table for water samples during the growing season. A 20 mL water sample was collected biweekly and at 24 hours post irrigation event. Water samples were processed and stored as described previously. Lysimeters Porous cup suction lysimeters (model 1900 Soil Water Sample rs) (SoilMoisture Equipment Corp., Santa Barbara, CA) were installed (10 and 9 Mar, 2004 and 2005; 23 and 16 DAP, respectively) in each fertilizer so urce by sidedress appli cation plot (80 total) to a depth of 30 cm. At sampling, a vacuum (50-60 kPa) was drawn on each lysimeter. A 46 cm plastic tube attached to a 50cc syringe was used to extract the water from each lysimeter. Samples (20 mL) were taken biw eekly and at 24 hours pos t leaching irrigation

PAGE 78

59 event from each fertilizer source plot. Wa ter samples were processed and stored as described previously. Growing Degree Day Model Growing degree days (GDD) were calcu lated throughout the season in 2004 and 2005 with the following formula (Sands et al., 1979): GDD = [(minT + maxT)/2)-7C]. where minT and maxT are the minimum and ma ximum daily temperatures and the base is 7C or 45F. GDD totals were recorded for key growth and developmental stages (emergence, and full flower). Emergence was determined when the plantlets were just emerging from the soil. Full flower was determined when approximately 90-95% of the peduncals on plants in each plot had open flowers. Statistical Analysis Tuber production. A general linear model was used to determine yield and internal and external quality responses of potato as a result of fertilizer source and leaching irrigation events for the 2004 and 2005 production seasons. Normality for each potato class size was checked by residual anal ysis using the Shapiro-Wilk test as implemented in the PROC CAPABILITY pr ocedure of SAS (SAS Institute, 2004). Means were separated using Tukey adjustment as implemented in SAS (SAS Institute, 2004) to separate individual factor means a nd/or interaction means when significant. Interactions were calculated using LSM eans with the slice option (SAS 2004). Water analysis. A general linear model was used to determine water nutrient concentrations in the water table (wells and ly simeters) as well as nutrient load from each irrigation date treatment for 2004 and 2005 pr oduction years. Normality for each water

PAGE 79

60 nutrient analyzed was checked by residual an alysis using the Shapiro-Wilk test as implemented in the PROC CAPABILITY pr ocedure of SAS (SAS, Institute, 2004). Concentrations of nutrients were log transformed and checked for normality then back transformed. Means were separated using Tukey adjustment as implemented in SAS (SAS Institute, 2004) to separate individual f actor means and/or interaction means when significant. Results And Discussion Tuber Yield for 2004 Irrigation date main effect Irrigation date main effect significantly in fluenced total and marketable tuber yields for the 2004 season (Table 3-2). The later in the season a leaching event occurred, total and marketable tuber yields and specific gr avity were more negatively impacted. Total and marketable tuber yields for the 8 a nd 12 WAP irrigation date were 10 and 11 % lower, respectively, than the 0 WAP irriga tion date. Ojala et al. (1990), reported nutritional and/or environmental stress at or near full flower can negatively impact total and marketable tuber yields as well as speci fic gravity. This is due to the high nitrogen requirement during the tuber bulking stage. Approximately, 58 to 71% of total nitrogen uptake by the potato crop occurs from early to mid tuber bulking. Optimal yield for this study should be in 0 WAP irrigation plots since no supplemental irrigation was applied. The 4 WA P irrigation date was not applied due to a naturally occurring leaching rainfa ll at the scheduled irrigation event in 2004. It received the same rainfall and irrigation schedule as the 0 WAP plot. Total and marketable tuber yields for plants in the 0 WAP treatme nt were a respectable 29.5 and 25.0 t ha-1, respectively in 2004.

PAGE 80

61 Tubers from plants in the 8 and 12 WA P irrigation treatment had significantly lower specific gravities compared with tubers in the 0, 2 and 4 WAP irrigation treatments in 2004 (Table 3-2). The percent of tuber we ight in the A2 to A3 size class range was also negatively impacted in the 8 and 12 WAP irrigation date treatments. A 45% decrease in this tuber classi fication was observed compared with the 0 WAP date (Table 3-4). The scheduled leaching rainfall in comb ination with frequent rainfall events after the 8 and 12 WAP irrigation treatments negativ ely influenced tuber specific gravity. Fertilizer main effect The fertilizer source main effect demonstrated the effectiveness of the CRF in potato production. Total and marketable tuber yields for plants in the CRF fertilizer treatments were 8 and 10 % higher, resp ectively, compared with plants in the conventional AN treatment for the 2004 production season (Table 3-2). The sidedress main effect treatment did not significantly influence total a nd marketable tuber yields nor tuber size and specific gravity (Table 3-2). Main effect interactions The three-way interaction between irrigation date, fertilizer source, and side dress application main effects was significant for total and marketable tuber yields. The threeway interaction term was calculated using LSMeans with the slice option (irrigation treatment*side) (SAS 2004). This option enable d the comparison of the fertilizer source with or without the extra sidedress treatment among each of the irrigation date treatments Plants in the CRF 2 WAP irrigatio n date treatment with the 34 kg N ha-1 sidedress application had significantly higher marketable tuber yields (28%) compared with plants in the AN fertilizer plots with the same side dress amount (Table 3-3). Lower yield from plants in the AN fertilizer--extra sidedress application plots may be explained by a large

PAGE 81

62 amount of AN leached from the plot (Table 3-9) at the 2 WAP irrigation date. Potato plants were just starting to emerge and the root system of the pl ant was not large enough to utilize the applied fertilizer. The CRF pl ots did not leach as much nitrogen (data to follow). Therefore, the sidedress nitrogen a dded to the overall nitr ogen load instead of replacing lost nitrogen as in the AN plots. Al l other irrigation treatm ents with or without the extra sidedress were not significantly different among each irrigation treatment. Tuber Yield for 2005 Irrigation date main effect Irrigation date main effect significantly in fluenced total and marketable tuber yields during the 2005 season. Plants in the 12 WAP irrigation date treatment had the lowest marketable yield followed by plants in irriga tion treatments 4 and 8 WAP plots (Table 32). The leaching rainfall event that occurr ed at the scheduled 4 WAP irrigation date treatment, negatively affected marketable tuber yields, since tubers ar e usually initiated at this time (Figure 3-12). Plants in the 8 and 12 WAP irrigation trea tments also produced the lowest percentage of tubers in the size class range A2 to A3 compared with the 0 WAP treatment (Table 3-4). The additional plant stress (too much water) in plants in irrigation treatments 4, 8 and 12 WAP resulted in an average decline of marketable tubers weight by 18% compared with the 0 WAP irrigation da te treatment. Specific gravities for tubers from plants in the 4 and 12 WAP irrigation treatments (1.080) were significantly lower th an in tubers from plants in the 0 WAP irrigation date treatment (1.082). A leaching rainfall event o ccurred within 7 to 10 days of the 4 and 12 WAP scheduled leaching irrigation events (Figure 3-13). As in 2004, the additional leaching irrigation events in conjunction with the wetter weather conditions later in the season reduced tube r specific gravity.

PAGE 82

63 Fertilizer main effect Fertilizer main effect demonstrated th e effectiveness of CRF in potato production in 2005. Plants in the CRF treatment produced 10.0 and 13.0% more total and marketable tuber yields than plants in the standard ammonium nitr ate treatment (Table 32). A 16% increase in the percent of tubers in size class range A2 to A3 was also observed for the CRF treatments compared with the AN fertilizer treatment in 2005 (Table 3-4). Specific gravity was also influenced by th e fertilizer main effect treatments. Tubers from plants in the AN fertilizer treat ment had significantly higher specific gravity, 1.079 compared with tubers from plants in the CRF fertilizer treatment, 1.077 (Table 32). Sidedress main effect The sidedress main effect did not signifi cantly influence total and marketable tuber yield, specific gravity or size class distribution (Table 3-2 and 3.4). Main effect interactions The three-way interaction between irrigati on date, fertilizer source and side dress application main effect was significant for th e total and marketable tuber yields in 2005. In 2005, plants in the CRF additional 34 kgN ha-1 treatment had higher total and marketable tuber yields, 28 and 26%, respectivel y compared with yield from plants in the AN additional 34 kg N ha-1 (Table 3-3) in the 2 WAP irri gation date treatment. This is a similar result to 2004. Nitrogen in the CRF is protected early in the season compared with AN. The sidedress N application adds positively to the CRF treatment but does not make up for that which is leached in the AN treatment. As the season progressed, the

PAGE 83

64 ability for the sidedress N to add positively to yield decreased. The extra side dress application should be examined further. Tuber External Quality for 2004 Irrigation date main effect Irrigation treatment main effect had limite d influence on external tuber quality such as green, growth cracks, misshapes, and total cu lls. Green tubers were reduced in the 8 and 12 WAP irrigation treatments in 2004 (Table 3-5). This is because the irrigation treatment plots were middle busted and hilled later in the season compared with the 0 WAP irrigation date plots resulting in be tter soil coverage of the tubers. Fertilizer main effect Fertilizer main effect did not significantly influence exte rnal tuber quality in 2004. Sidedress main effect Sidedress main effect had no influence on external tuber quality. There were no interaction effects for exte rnal tuber defects for th e 2004 production season. Tuber External Quality for 2005 Irrigation date main effect Irrigation date main effect significantly influenced all external tuber defects in 2005. The 12 WAP irrigation date in 2005 resulte d in significantly hi gher percentages of green, rotten and total culled tube rs compared with the 0 WAP i rrigation date (Table 3-5). Late in the season, the 12 WAP irrigation date washed soil from the potato row exposing tubers and resulting in green tubers. The co mbination of late seas on irrigation and heat resulted in a high number of rots in the 12 WAP irrigation date. Tubers in the 12 WAP irrigation date had significantl y higher total culls 16.6% comp ared with the 0, 2, 4 and 8 WAP irrigation treatments at 4.8, 5.9, 7.5 a nd 7.5%, respectively (Table 3-5).

PAGE 84

65 Fertilizer main effect Fertilizer main effect significantly influen ced external tuber defects in 2005. Plants in CRF plots had a higher percentage of t uber rots compared with plants in the AN fertilizer plots (3.4 and 2.7 % respectively; Table 3-5). The additional water applied at the 12 WAP irrigation date combined with a leac hing rainfall event 7 to 10 days prior to harvest (Figure 3-13) and warm er temperatures negatively imp acted tuber quality late in the season. Sidedress main effect Sidedress main effect did not significantly influence tuber external quality. There were no interaction effects for external tuber defects for the 2005 production season (Table 3-5). Tuber Internal Quality for 2004 Irrigation date main effect Internal defects include physiological disorders which are hollow heart (HH), internal heat necrosis (IHN) and brown cente r (BC). Disease induced disorders include corky ring spot (CRS) and brown rot (BR). BC and HH occur when sudden growing c onditions change during the growing season. This occurs when the potato plant reco vers too quickly after an environmental or nutritional stress during the grow ing season. As the tubers st art to grow and expand the pith tissue in the center of the tuber turns n ecrotic or can split ope n leaving a void in the center of the potato. IHN is characterized by necrotic ar eas mostly in and around the vascular ring usually coalesci ng and radiating to the center (p ith) at the bud (apical) end of the tuber and not the stem end. IHN is t hought to occur late in the growing season due to elevated temperatures and hot dry weathe r conditions, but may be initiated earlier in

PAGE 85

66 the growing season as discussed in chapte r 2. BC, HH, nor IHN affects the potato nutritionally, but can negatively impact the chip processing potatoes. CRS is a viral disease (tobacco rattle vi rus; TRV) transmitted by the stubby-root nematode ( Paratrichodorus minor ). As the nematode feeds on the tuber the virus transmitted causes concentric brown necrotic arcs in the tuber flesh. Brown rot also known as bacterial wilt is cau sed by a soil borne pathogen ( Ralstonia solanacearum ). The pathogen infects the potato roots through wounds and at emergence of lateral roots. In this study, both percent affected and severi ty were calculated for IHN. Severity is based upon a score on a scale of one to six. A score of one to four indicates that 0 to 25% of all four quarters had the diso rder. A score of five or six indicated that all quarters had the disorder and up to 75 to 100% of all quarters were covered, respectively. Irrigation date main effect treatments signi ficantly influenced the development of internal heat necrosis in tubers (IHN) in 2004. IHN appears to be initiated by early season plant stress (too much water and poor nutrition) and is exacerbated by increased temperatures later in the season as discusse d in chapter 2. Plants in the 8 and 12 WAP irrigation treatments produced tubers with significantly lower pe rcentages of IHN, 3.3 and 4.3% of total tuber yield, respectively, co mpared with the 2WAP irrigation date at 16.3%. The 2 WAP irrigation event occurred at emergence and was followed by another natural leaching rainfall even t that occurred approximate ly 2 weeks later around tuber initiation. This corresponded to approxima tely 200 to 400 GDD, respectively. This is supported by the findings in chapter 2. The pl ots with the highest incidence of tubers with IHN experienced a leaching rainfall ev ent between 200 and 400 GDD. Plant stress (too much water) in conjunction with a nutr itional loss (nutrient leaching) early in the

PAGE 86

67 season, between 200 and 400 GDD, may predispose th e tubers to IHN. IHN severity was highest as well in tubers from the 2 WAP i rrigation treatment at 2.3. IHN severity in tubers in the 2 WAP irrigation treatment was si gnificantly different from levels in tubers at 8 and 12 WAP (1.3 and 1.7), respectively, but the same as 0 and 4 WAP irrigation treatments (Table 3-6). The natural rainfall event described above that was devastating to plants in the 2 WAP irrigation treatment occurred at the 4 WA P irrigation date. Ther efore, the irrigation treatment was not applied at 4 WAP. Intere stingly, the percentages of tubers with IHN and their IHN severity were similar in the 0 WAP and 4 WAP irrigation treatments. Therefore, this provides evidence that the 2 WAP irrigation event stressed (too much water) plants causing the increase in the percen tage of tubers with IHN and the severity of IHN. Although this early plant stress at 2 WA P was necessary for the development of IHN, it may have only been part of the neces sary events for the development of IHN by the end of the season. In other words, creati ng potato plant stress by excessive irrigation and the resulting reduced nutrition early in th e season (emergence to tuber initiation) may predispose the developing tubers to the occurrence of IHN. However, a late season stress may be necessary to exa cerbate the symptoms. Fertilizer main effect Fertilizer main effect significantly influen ced the incidence of tubers with IHN. CRF treatment had a significantly higher incide nce of tubers with I HN compared with the AN fertilizer treatment, 11.0 and 5.6% of tota l tuber yield, respectively. IHN severity was not significantly different among fertilizer treatments (Table 3-6). The higher incidence of IHN may be caused by the time needed for the CRF treatments to recharge

PAGE 87

68 the nutrient levels in the soil af ter a leaching event. CRF with a faster release rate will recharge sooner than one that has a slower release rate. A slow recharge rate would result in sub-optimal soil nutrient conditions resulting in plant nutri ent stress. Studies have related IHN development in tubers to nitrogen stress as reported by (Sterrett and Henninger, 1997; Sterrett and Henninger, 1991 and Clough, 1994). Sidedress main effect Interestingly, the sidedress main effect did not significantly reduce the occurrence of tubers with IHN in 2004. Tubers with IHN and the IHN severity rating for the CRF treatment was 9.8% and 1.9 respectively compar ed with the AN fertilizer treatment at 7.1% and 1.8, respectively. If nutrient stress doe s relate to IHN, th en additional nitrogen should reduce the occurrence and se verity of IHN. Three items relating to the application of additional nitrogen in this study may have prevented the optimal use of the sidedress application. First, the app lication method applied a dry soluble fertilizer to the row shoulders. However, this application method pl aces the fertilizer in the dry area of the bed above the capillary zone of the seepage irrigation and where few potato roots are located (Munoz, 2004). This means that rainfa ll is necessary to pus h the fertilizer into the root zone of the crop. If the rainfall is too heavy, fertilizer w ill move in surface water runoff into the drainage canals. Secondly, in order for fertilizer to be us ed by the plant, it needs to be available prior to full flower (30 to 50 DAP). Certai nly, the 8 and 12 WAP application treatments are well past full flower and not expected to be beneficial to the crop. And as noted, the 0, 2, and 4 WAP sidedress applications could on ly be beneficial if natural rainfall pushed the fertilizer into the row and not off the row in surface water movement. The leaching

PAGE 88

69 rainfall event that occurred at 4 WAP wash ed the soil away from the hill exposing the potato roots as well as washi ng the fertilizer away from the hill and into the alley. Lastly, the BMP recommendation of 34 kg N ha-1 may not be enough N to make a difference in yield or quality. The functionality of the application is related to placement and rate. For instance, if it were placed properly, less N would be needed to impact quality and/or yield. However, this study did not examine rate; therefore, a conclusion on the influence of rate and placement on the eff ectiveness of the sidedress application can only be presumed. There were no significant ma in effect interactions in 2004 (Table 36). Tuber Internal Quality for 2005 Irrigation date main effect Irrigation date main effect treatments did not significantly influence the internal tuber quality in 2005. Occurrence of IHN in tubers for the 2005 season was 71% higher compared with the 2004 production season (T able 3-6). There was no significant differences among the irrigation da te treatments for the incide nce or severity of tubers with IHN. Tubers with IHN ranged from a high of 35.5% in the 2 WAP irrigation date treatment to a low of 24.9 in the 0 WAP irri gation treatment. Pl ants in the 2 WAP irrigation treatment received water/nutrient stress early in the s eason with the staged leaching irrigation event followed by an addi tional leaching rainfall event near 4 WAP (Figure 3-13); (Table 3-6). IHN seve rity among irrigation treatments was not significantly different. IHN se verity rating ranged from 3.4 in the 2 WAP irrigation date treatment down to 3.0 in the 12 WAP irrigation date treatment.

PAGE 89

70 Fertilizer source main effect Fertilizer source main effect significantly influenced the development of tubers with IHN. The incidence of IHN was 24% higher in tubers in the CRF treatments compared with tubers in the AN fertilizer tr eatment (Table 3-6). IHN severity was not significantly different between the CRF and AN treatment at 3.3 and 3.1, respectively. Although CRF had significantly more tubers with IHN, the severity rating was similar. As in 2004, this was most likely caused by th e CRF treatments to recharge the nutrient levels in the soil that is related to CRF type and release rate. CRF treatments had significantly higher inci dences of tubers with IHN in 2004 and 2005 compared with the AN fertilizer treatments that contradicts the results reported by Hutchinson, 2005 and Pack, 2004. The difference in results may be due to the timing of the leaching event and its relation to the growth stage of the potato plant. In 2004, the highest incidence of tubers with IHN was in the 2 WAP irrigation treatment while the lowest incidence of tubers with IHN were the late season irrigation events, 8 and 12 WAP. Similarly, in 2005, th e 2 WAP irrigation treatment also had the highest incidence of tubers with IHN compared with the other irrigation treatments. Although leaching rainfall events occurred during both seasons, the time when leaching rainfall events occured in conjunction w ith the growth stage of the potato crop may determine when IHN in tubers is initiated due to nutritional and envi ronmental stressors. Sidedress main effect Sidedress main effect treatment did not significantly influence the occurrence of tubers exhibiting IHN. The IHN severity rating for the sidedress treatments were identical at 3.2. Quality (particularly IHN) did not improve with the BMP recommended

PAGE 90

71 side dress application. The BMP should be re examined to make sure the side dress methodology is beneficial to potato crop in the production system (Table 3-6). Nitrate Nitrogen Concentr ation in Wells for 2004 Irrigation main effect Irrigation treatment main eff ect significantly influenced NO3-N concentrations in well water samples in 2004. During the 2004 production season, well water NO3-N concentrations were highest at the 29 DAP sa mple date and decreased exponentially over time. A leaching rainfall event occurred th e night before that would explain the high NO3-N values. The 4 WAP irrigation treatm ent had the highest well NO3-N value at the 29 DAP sample date at 30.2 mg L-1. All other irrigation treatments had well NO3-N concentrations between 17.1 and 29.5 mg L-1. Well water NO3-N concentrations at 72 DAP were significantly higher at the 8 WAP irrigation date compared with the 0 and 2 WAP irrigation date. All sample dates except at 29 DAP had well NO3-N levels 8.2 mg L-1 (Table 3-7). The relatively low NO3-N concentrations in the observation wells may be due to a couple of factors. First, most of the nutrients were most likely moved out of the bed due to surface water flow. Second, the amount of water applied at the leaching events may not have been enough and/or had been diluted by the time the nutrients reached the depth of the observati on wells as it moved down through the soil profile. Fertilizer main effect The fertilizer main effect significantly influenced well water NO3-N concentrations in 2004. The 89 DAP well water NO3-N concentrations were si gnificantly higher in the CRF compared with the AN fertiliz er treatment, 0.5 and 0.2 mg L-1, respectively. This

PAGE 91

72 may indicate that the CRF was still releasing N late in the season. Similarly to the irrigation treatments, well water NO3-N concentrations were highest at the 29 DAP sample date and decreased exponentially over time. Sidedress main effect The sidedress main effect did not si gnificantly influence well water NO3-N concentrations at any of the sampling dates. There were no significan t interaction effects for the 2004 production season (Table 3-7). Nitrate Nitrogen Concentr ation in Wells for 2005 Irrigation main effect The irrigation treatment main effects did not significantly influence well water NO3-N concentrations in 2005. At th e 17 DAP sample date, well water NO3-N concentration ranged from a high of 7.4 mg L-1 in the 2 WAP irrigation treatment, followed by 12, 4, 8 and 0 WAP irrigation treatments at 7.3, 6.4, 5.2 and 4.1 mg L-1, respectively. This result was due to the 2 WAP irrigation treatment that was applied 24 h prior to the 17 DAP sample acquisition. Well water NO3-N concentrations increased up to 45 DAP. Since no irrigation treatment wa s applied before this sample date, the increase in NO3-N concentration in the wells was th e result of a 2.8 cm rainfall event at 44 DAP. Well water NO3-N concentrations ranged from a high of 3.4 mg L-1in the 8 WAP irrigation date treatme nt to a low of 1.4 mg L-1 in the 0 WAP irrigation treatment at the 59 DAP sample event. This result was due to the 8 WAP irrigation treatment applied 24 h previous to the 59 DAP well sample (Table 3-7). This shows that leaching events do have an impact on the movement of nutrients down through th e soil profile into the water table.

PAGE 92

73 Fertilizer main effect Fertilizer main effect did not significantly influence well NO3-N concentrations in 2005. CRF treatments consistently had lower NO3-N levels throughout each of the sampling dates compared with the AN fertilizer treatments. Overall sample dates, the average reduction of well NO3-N in the CRF treatments was approximately 19% lower compared with the AN fertilizer treatment. Sidedress main effect The sidedress main effect did not significantly influence well NO3-N concentrations in 2005. The 0 and 34 kg N ha-1 sidedress treatments were similar throughout all sample dates (Table 3-7). A decreasing trend in lysimeter NO3-N concentration was no ted after the 29 and 45 DAP sampling dates for 2004 and 2005, respec tively. This may be due to the combination of the scheduled leaching irrigati on events and the leaching rainfall events during the latter part of the season in 2005 (Figure 3-13). Nitrate Nitrogen Concentrat ion in Lysimeters for 2004 Irrigation main effect Irrigation date main effects significantly influenced lysimeter NO3-N concentrations in 2004. The highest valu es observed during the 2004 production season were at the 30 DAP sampling event w ith an average value of 216.4 mg L-1. The flush of NO3-N was most likely due to the leaching rain fall received the prev ious night (11 cm) (29 DAP). At the 45 DAP sample date the 8 WAP irrigation treatm ent had the highest lysimeter NO3-N concentration at 41.9 mg L-1 followed by irrigation treatments, 12, 2, 0 and 4 WAP with NO3-N values of 34.4, 26.1, 25.2, and 22.1 mg L-1, respectively. A sharp decline in lysimeter NO3-N concentrations were observed at the 90 DAP sample

PAGE 93

74 date in all irrigation treatments with the exception of the 12 WAP irrigation treatment had lysimeters NO3-N concentrations below 1.1 mg L-1. The 12 WAP irrigation date at the 90 DAP sample date had signi ficantly higher lysimeter NO3-N concentration, 9.3 mg L-1 that was most likely due to the 12 WAP irri gation treatment applied 24 h before the 90 DAP sample acquisition (Table 3-8). Fertilizer main effect Fertilizer main effect did not significantly influence lysimeter NO3-N concentrations. CRF treatment consistently had lower NO3-N nutrient concentrations throughout all sampling dates compared with the AN fertilizer treatment for the 2004 production season. CRF treatments had an average 30% lower lysimeter NO3-N concentration compared with AN fertilizer tr eatment over all lysimeter sampling dates in 2004 (Table 3-8). A decreasing trend was noted over the season until the last sample date (90 DAP) when lysimeter NO3-N concentrations increased. This may be due to the flush of nutrients from the potato crop late in the season due to the lack of nutrient uptake by the senesced plants. Sidedress main effect Sidedress main effect did not sign ificantly influence lysimeters NO3-N concentrations. Similarly to the fertilizer main effects, a downward trend was also noted over the season until the last sample date 90 DAP when lysimeter NO3-N concentrations increased. There were no othe r significant interaction e ffects for 2004 (Table 3-8). Nitrate Nitrogen Concentrat ion in Lysimeters for 2005 Irrigation main effect Irrigation date main effect significantly influenced NO3-N concentrations in lysimeter water samples in treatment plots in 2005. Although not si gnificant, at the 18

PAGE 94

75 DAP sample date, the 2 WAP irrigati on treatment had higher lysimeter NO3-N concentration (39.6 mg L-1) compared with all other irrigation treatments at 18 DAP. The lysimeter water sample at 18 DAP was within 24 h of the 2 WAP irrigation treatment that would explain the higher lysimeter NO3-N concentration. NO3-N concentrations in lysimeter water samples continued to rise until the 45 DAP sample date, then again lysimeter NO3-N concentrations began to decline a nd were lowest at the 89 DAP sample date. Similarly to the discussion above, at the 34 DAP which was within 24 h of the 4 WAP irrigation treatment, lysimeter NO3-N concentrations we re higher (60.8 mg L-1) compared with all other irrigation treatments. Again, lysimeter NO3-N concentrations peaked at 45 DAP followed by a decreasing tre nd to a low at the 89 DAP sample date in which all lysimeter NO3-N concentrations were 3.6 mg L-1. This indicated that a majority of the N applied was either taken up by the plant or leached below the root zone (Table 3-8). Fertilizer main effect Fertilizer main effect significan tly influenced again lysimeter NO3-N concentrations in 2005. CRF had agai n, significantly lower lysimeter NO3-N concentrations for the 18, 34 45 and 60 DAP sampling dates. After the 45 DAP sample date again lysimeter NO3-N concentrations in the CRF and AN fertilizer treatments declined to a low of 2.8 and 3.3 mg L-1, respectively. Overall, the CRF decreased lysimeter water NO3-N by 32% compared with the AN fe rtilizer treatment. This shows the benefits of the CRF throughout the season, bu t especially early in the season when the risks of nutrient leaching is at its highest.

PAGE 95

76 Sidedress main effect Sidedress main effect did not signif icantly influence again, lysimeter NO3-N concentrations for any of the lysimeter samp le dates in 2005. Ther e were no significant main effects interactions in 2005 (Table 3-8). Therefore, this is anot her argument that the placement of a dry soluble fertilizer on th e shoulder of the row is not the proper application method. The produc tion BMPs for potato production may need to be revised to create an effective sidedre ss treatment after a leaching rain. Overall, the lysimeter NO3-N nutrient concentrations in 2004 and 2005 again for CRF treatments was 29 and 25% less, respectively, compared with the AN fertilizer treatments. Theoretically, if growers in th e TCAA used a CRF, based upon this research, reduction of N into the St. Johns River could be 56,000 kg N per year. Nutrient Load Concentration in Surface Water Water volume: 2004 The volume of water flow from the field va ried with irrigation treatments in 2004. Surface water flow during the 2 WAP irrigatio n treatment was highest peaking between 300 and 350 L compared with the 8 and 12 WAP irrigation treatments. High surface flow from the plot was most likely due to the wetter weather c onditions prior to the irrigation event as well as the lack of crop c over since potato plants were just starting to emerge at 2 WAP. Additionally, at this st age of growth and deve lopment of the potato plant, high surface water flow from the plots wo uld have carried ferti lizer out of the bed into the drainage canals creating a nutrient a nd water stress early in the season. This can be seen due to the higher incidence of tubers with IHN in the 2 WAP irrigation treatment and would also support the theory that IHN ma y be initiated early in the season due to a combination of plant stress caused by too much water and too low nut ritent concentration

PAGE 96

77 followed by hot dry weather late in the s eason. At the 12 WAP irrigation treatment, surface water flow was lowest because of hot dry weather conditions (Figure 3-3a). Although IHN has been reported to be caused by hot dry weather condi tions late in the season and when tubers are near maturity (S tevenson et al., 1987; Sterrett and Henninger, 1991), tubers from the 12 WAP irrigation treatm ent had the lowest incidence of IHN. Water volume: 2005 The volume of water flow also varied with irrigation treatments in 2005. The surface water runoff was the highest during the 4 WAP irrigation date, peaking around 375 L that may be attributed to the wetter weather conditions two days prior to the irrigation event. The 12 WAP irrigation date surface water flow was the lowest due to drier conditions prior to the irriga tion event and (Figure 3-3b). Nutrient load: 2004 CRF treatments had consistently lower NO3-N nutrient loads (kg ha-1) compared with the AN fertilizer treatments at the 2, 8 and 12 WAP irrigation treatments in 2004. NO3-N nutrient loading from surface water runoff in the CRF treatments were reduced by 35, 28 and 32% compared with the AN fe rtilizer treatments at 2, 8 and 12 WAP, respectively in 2004. Overall, the average reduction in NO3-N loading from the CRF treatments was 31% less compared with AN fertilizer treatments (Table 3-9; Figure 311). Nutrient load: 2005 As in 2004, the CRF had consistently lower NO3-N nutrient loads (kg ha-1) over time compared with the AN fertilizer treatm ent in 2005. The CRF treatment during the 2005 production season also decreased NO3-N nutrient loads from surface water runoff by 55, 22, 63 and 79% for the 2, 4, 8 and 12 WA P irrigation treatments, respectively

PAGE 97

78 (Table 3-10; Figure 3-12). Nutrient runoff over time in each leaching irrigation event in 2004 and 2005 was variable within replications but overall, the CRF treatment had less NO3-N runoff (Figure 3.4-3.6; Appendix E-24 pg 189) and (Figure 3-7-3.10; Appendix E-25 pg. 190). Overall the average reduction in NO3-N nutrient loading from the CRF treatment was 54% compared with AN fertilizer treatment (Table 3-10). This data has shown the benefits using a CRF that can significantly reduce the amount of nutrient loading into the watersheds and reduce the negative impacts th at nutrient loading w ould have on sensitive environmental areas in the TCAA. Based upon this research, if growers in the TCAA used a CRF in their production practices, N in to the St. Johns River could be reduced by 56,000 kg per year, a substantial sa vings of pollutant into the river. This was determined by the average NO3-N load (kg ha-1) for AN and CRF treatments in 2004 and 2005 (Table 3.9 and 3.10) multiplied by the total potat o production area in the TCAA (8,000) hectares. Growing Degree Days Potato plant emergence in 2004 and 2005 o ccurred at 18 and 19 DAP, respectively. The accumulated GDD to reach emergence in 2004 and 2005 was 225 and 228, respectively. Full flower in 2004 and 2005 occurred 53 and 49 DAP, respectively that corresponded to 807 and 798, respectively (T able 3-11). The accumulated GDD to reach emergence and full flower are in agreement with the findings discussed in chapter two. The highest incidence of tubers with IHN in 2004 and 2005 occurred in the 2 WAP irrigation treatment. The 2 WAP irrigation event occurred at 193 accumulated GDD. As in chapter two, the higher incidence of t ubers with IHN experienced a leaching event between 200 and 400 accumulated GDD for both 2004 and 2005.

PAGE 98

79 Conclusions This research has demonstrated the eff ectiveness of a CRF in potato production compared with a soluble N fertilizer. Market able yields in the CRF treatments were an average of 12% higher compared with the AN fertilizer treatment. Additionally, 13% less N fertilizer was applied in the CRF treatment compared with the AN fertilizer treatment. Overall, the sidedress main e ffect of the additional 34 kg N ha-1 after a leaching rainfall event did not significantly influen ce total or marketable yields in 2004 or 2005. Although, the three-way interact ion between irrigation date, fertilizer source and side dress application main effect was significant fo r the total and marketable tuber yields in 2004 and 2005 in the CRF treatment at the 2 WAP irrigation treatment da te. Internal and external quality were unaffected with the additional N application after a leaching event, therefore, the BMP rate was not adequate to prevent IHN. The CRF treatments had a significantly higher incidence of tubers with IHN compared with the AN fertilizer treatment at 22.3 and 15.6%, respectively. The CRF treatment had a 31% higher incidence of tubers with IHN compared with the AN fertilizer treatment. This also supports the hypothesis that the CRF needed to have a faster release rate earlier in the season. NO3-N loading from surface water runoff fr om potato production was decreased by an average of 43% with the use of the CRF compared with the AN fertilizer treatment. Therefore, if growers in the TCAA used a CRF in potato production, ra ther than a soluble N fertilizer at the BMP rate of 224 kg N ha-1, NO3-N loads into the St. Johns River watershed could be reduced by 56,000 kg N per year.

PAGE 99

80Table 3-1. Irrigation treatment (WAP), fert ilizer treatment, fertilizer source and additional sidedress application (DAP) for 2004 and 2005 production seasons Irrigation treatment WAPz Fertilizer treatment Fertilizer sourcey Irrigation date Timing DAPx Additional N side dressw kg N ha-1 Additional sidedress DAP 2004 2005 2004 2005 0 1 ANy 0 0 0 0 2 AN 0 0 34 43 43 0 3 CRF 0 0 0 0 4 CRF 0 0 34 43 43 2 1 AN 17 16 0 2 2 AN 17 16 34 43 43 2 3 CRF 17 16 0 2 4 CRF 17 16 34 43 43 4 1 AN 28 30 0 4 2 AN 28 30 34 43 43 4 3 CRF 28 30 0 4 4 CRF 28 30 34 43 43 8 1 AN 59 58 0 8 2 AN 59 58 34 67 64 8 3 CRF 59 58 0 8 4 CRF 59 58 34 67 64 12 1 AN 91 88 0 12 2 AN 91 88 34 N/A N/A 12 3 CRF 91 88 0 12 4 CRF 91 88 34 N/A N/A zWAP Weeks after planting yAN Ammonium nitrate; CRF C ontrolled release fertilizer xDAP Days after planting wAdditional sidedress applied as 30-0-0.

PAGE 100

81 E -12 D -8 C -4 B -2 A -No irrigation Irrigation treatment (WAP) 4 -CRF 30-0-0 3 -CRF No additional N 2 -AN 30-0-0 1 -AN No additional N N source and additional N treatment Rep 2 Rep 1Rep 3Rep 4N 2143 A 3412 A 2134 A 2143 A 3412 B 1234 B 1234 B 4312 B 4321 C 2143 C 3421 C 1234 C 1234 D 4321 D 4312 D 3412 D 3412 E 4321 E 1234 E 2143 E Figure 3-2. Plot map leach ing irrigation project

PAGE 101

82Table 3-2. Total and marketable tuber yiel ds and specific gravity for Atlantic po tato under varying staged leaching irrigati on treatments and fertilizer sour ce in Hastings, FL in 2004 and 2005 Total yield Marketable yield Specific gravity Total yield Marketable yield Specific gravity 2004 2005 Main Effect t ha-1t ha-1 Date (D) (WAP)x 0 WAP 29.5 abw 25.0 ab 1.079a 28.2 ay 24.9 a 1.082a 2 WAP 28.5 ab 24.9 ab 1.079a 26.3 ab 22.9 ab 1.081b 4 WAP 30.3 a 25.7 a 1.079a 24.3 b 20.5 cd 1.080b 8 WAP 26.7 b 21.9 b 1.077b 26.6 ab 22.0 bc 1.082a 12 WAP 27.1 b 22.7 ab 1.077b 25.1 ab 18.8 d 1.080b Fertilizer (F) CRFv 29.7 a 25.2 a 1.077b 27.4 a 23.2 a 1.081 AN 27.3 b 22.9 b 1.079a 24.8 b 20.4 b 1.081 Sidedress (S) 0.0 (kg N ha-1) 29.1 24.6 1.078 25.7 21.9 1.080 34.0 (kg N ha-1) 28.1 23.6 1.078 26.3 21.7 1.081

PAGE 102

83 Table 3-2. Continued Total yield Marketable yield Specific gravity Total yield Marketable yield Specific gravity 2004 2005 t ha-1t ha-1 Interaction effectsu D*F ns ns ns ns D*S ns ns ns ns ns ns F*S ns ns ns ns ns ns D*S*F * ns * ns zMarketable Yield: Sum of size classes A1 to A3. ySize classes: B = 3.8 to 4.4 cm, A1 = 4.4 to 6.4 cm, A2 = 6.4 to 8.3 cm, A3 = 8.3 to 10.2 cm. Size Distribution by Class: Class (w t)/(Total Yield (wt) culls (wt)) xWAP = Weeks after planting. wMeans followed by a different letter are significant at the p 0.05 using Tukeys studentized range test. vCRF = Controlled release fertilizer, AN = Ammonium nitrate. uns, *, **, *** nonsignificant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 103

84Table 3-3. Three-way interaction between irrigation date, fertilizer source and side dress application main effects for total and marketable tuber yields and specific gr avity for Atlantic potato unde r varying staged leaching irrigation treatments and fertilizer source in Hastings, FL in 2004 and 2005 Total yield Marketable yield Specific gravity Total yield Marketable yield Specific gravity 2004 2005 Trmt*fert*side t ha-1 t ha-1 Slicedz by trmt*side A AN 0 25.5 b 20.3 b 1.082 a 29.3 25.2 1.083 A CRF 0 31.2 a 27.3 a 1.078 b 28.3 25.7 1.083 A AN 30 32.2 27.8 1.079 27.0 23.9 1.081 A CRF 30 29.2 24.3 1.078 28.5 25.2 1.081 B AN 0 27.5 23.6 1.078 28.0 25.1 1.080 B CRF 0 28.6 24.4 1.080 26.7 22.8 1.080 B AN 30 24.8 b 21.7 b 1.079 21.5 b 18.9 b 1.081 B CRF 30 33.4 a 29.8 a 1.078 29.7 a 25.5 a 1.081 C AN 0 29.1 24.9 1.079 22.1 b 18.3 b 1.080 C CRF 0 33.0 28.5 1.078 28.4 a 25.0 a 1.079 C AN 30 28.6 23.5 1.080 21.3 b 17.2 b 1.081 C CRF 30 30.4 25.7 1.080 26.2 a 22.4 a 1.081 D AN 0 28.3 23.9 1.078 a 26.2 21.7 1.084 D CRF 0 25.2 19.7 1.075 b 27.3 23.0 1.082 D AN 30 26.0 21.1 1.079 a 26.4 21.6 1.082 D CRF 30 27.8 23.2 1.076 b 26.9 22.1 1.082 E AN 0 25.4 21.4 1.078 a 23.8 17.1 b 1.080 E CRF 0 28.6 24.2 1.076 b 26.5 20.9 a 1.081 zSliced trmt*fert This option enabled the comparison of the fe rtilizer source with or without the extra sidedress treatment am ong each of the irrigation date treatments

PAGE 104

85Table 3-4. Size class distribu tion and range (%) production stat istics for Atlanticpotato unde r varying staged leaching irri gation treatments and fertilizer source in Hastings, FL in 2004 and 2005 Size Distribution by class (%)z Size Class Range (%) Size Distribution by class (%)z Size Class Range (%) B A1 A2 A3 A1 to A2 A2 to A3 B A1 A2 A3 A1 to A2 A2 to A3 Main effects 2004 2005 Date (D) (WAP)x 0 WAP 7.1 b 62.1 b 23.6a 1.3 87.1 a 25.0 a 6.0 b 48.6 b 32.5 a 11.2 ab 93.0 a 44.0 a 2 WAP 6.0 b 62.0 b 26.0a 0.9 88.9 a 26.8 a 6.0 b 46.6 b 31.6 ab 14.0 a 93.2 a 46.2 a 4 WAP 7.0 b 65.2 ab 20.8ab 0.8 87.1 a 21.7 ab 7.7 ab 52.1 ab 26.7 a-c 10.7 a-c 91.1 ab 38.5 ab 8 WAP 9.8 a 68.6 ab 14.1c 0.2 83.1 b 14.3 c 8.7 a 55.7 a 25.2 c 8.2 bc 89.9 b 34.1 b 12 WAP 7.8 ab 69.9 a 16.2bc 0.1 86.4a 16.4 bc 8.1 ab 56.7 a 25.8 bc 6.5 c 90.6 ab 33.2 b Fertilizer (F) CRFv 7.5 63.7 b 21.7 1.1 86.8 22.9 a 6.5b 49.5 b 29.4 12.5 a 92.4 a 42.5 a AN 7.5 67.4 a 18.5 0.2 86.2 18.8 b 8.1a 54.5 a 27.3 7.7 b 90.8 b 35.9 b Sidedress (S) 0.0 ( kg N ha-1) 7.4 64.1 21.9 0.5 86.7 22.5 7.1 51.2 28.5 11.0 91.5 40.0 34.0 ( kg N ha-1) 7.6 66.5 18.9 0.8 86.4 19.7 7.4 52.5 28.2 9.3 91.7 38.6

PAGE 105

86Table 3-4. Continued Size Distribution by class (%)z Size Class Range (%) Size Distribution by class (%)z Size Class Range (%) B A1 A2 A3 A1 to A2 A2 to A3 B A1 A2 A3 A1 to A2 A2 to A3 Interaction effectsu 2004 2005 D*F ns ns ns ns ns ns ns ns ns D*S ns ns ns ns ns ns ns ns ns ns ns ns F*S ns ns ns ns ns ns ns ns ns ns ns ns D*S*F ns ns ns ns ns ns ns ns ns ns ns zMarketable Yield: Sum of size classes A1 to A3. ySize classes: B = 3.8 to 4.4 cm, A1 = 4.4 to 6.4 cm, A2 = 6.4 to 8.3 cm, A3 = 8.3 to 10.2 cm. Size Distribution by Class: Class (w t)/(Total Yield (wt) culls (wt)) xWAP = Weeks after planting. wMeans followed by a different letter are significant at the p 0.05 using Tukeys studentized range test. vCRF = Controlled release fertilizer, AN = Ammonium nitrate. uns, *, **, *** nonsignificant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 106

87Table 3-5. External tuber defects (%) of total yield for Atlantic under varying st aged leaching irrigation treatments, ferti lizer source and additional sidedress in Hastings, FL in 2004 and 2005 External tuber defects (%) Sun burned Growth crack Misshaped Rot Total cullz Sun burned Growth crack Misshaped Rot Total cullz Date (D) (WAP)x 2004 2005 0 WAP 0.7 0.0 0.2 1.6 3.0 2.7 by 0.0 b 0.0 b 1.1 b 4.8 b 2 WAP 0.4 0.0 0.1 1.3 2.2 2.7 b 0.0 ab 0.0 b 2.7 b 5.9 b 4 WAP 0.5 0.0 0.0 1.6 2.6 3.4 ab 0.3 a 0.8 ab 1.9 b 7.5 b 8 WAP 0.3 0.0 0.1 1.1 1.9 3.4 ab 0.1 ab 1.3 a 1.7 b 7.5 b 12 WAP 0.3 0.0 0.1 1.6 2.7 4.4 a 0.0 ab 0.3 ab 10.7 a 16.6 a Fertilizer (F) ANw 0.4 0.0 0.1 1.4 2.5 3.0 0.0 0.2 2.7 b 8.4 CRF 0.5 0.0 0.1 1.4 2.4 3.5 0.0 0.5 3.4 a 7.8 Sidedress (S) 0.0 (kg N ha-1) 0.4 0.0 0.1 1.6 2.6 3.3 0.0 0.3 3.9 9.0 34.0 (kg N ha-1) 0.5 0.0 0.1 1.2 2.2 3.2 0.0 0.4 1.9 6.7

PAGE 107

88Table 3-5. Continued External tuber defects (%) Sun burned Growth crack Misshaped Rot Total cullz Sun burned Growth crack Misshaped Rot Total cullz Interaction effectsv 2004 2005 D*F ns ns ns ns ns ns ns ns ns ns D*S ns ns ns ns ns ns ns ns ns ns F*S ns ns ns ns ns ns ns ns ns ns D*S*F ns ns ns ns ns ns ns ns ns ns zTotal culls are the sum of growth cracks, mi sshaped, green, and rotten categories and are calculated as a percent of total yield. Cate gories may not appear additive due to rounding yMeans separated within columns using Tukeys studentized range test at p 0.05. Means with no letters were not significantly different. xWAP = Weeks after planting. wAN = Ammonium nitrate CRF = Controlled release fertilizer vns, *, **, *** nonsignificant or significant at p 0.05, 0.01, 0.001.

PAGE 108

89Table 3-6. Internal tuber defects (%) of total yield for Atlantic under varying st aged leaching irrigation treatments, ferti lizer source and additional sidedress in Hastings, FL in 2004 and 2005 Internal tuber defects (%) HHz IHN IHN severity CRS BCL HH IHN IHN severity CRS BCL 2004 2005 Date (D) (WAP)y 0 WAP 0.18 10.9 abx 2.2 a 0.5 0.3 0.0 24.9 3.1 0.0 0.0 2 WAP 0.38 16.7 a 2.3 a 0.1 0.7 0.0 35.5 3.4 0.0 0.0 4 WAP 0.00 8.8 ab 1.8 ab 0.1 0.4 0.0 30.0 3.1 0.0 0.3 8 WAP 0.19 3.3 b 1.3 b 0.0 0.0 0.0 30.9 3.2 0.0 0.5 12 WAP 0.19 4.3 b 1.7 b 0.0 0.1 0.0 26.6 3.0 0.0 0.0 Fertilizer (F) ANw 0.15 5.6 b 1.6 0.1 0.3 0.0 25.6 b 3.1 0.0 0.1 CRF 0.23 11.0 a 2.0 0.1 0.2 0.0 33.6 a 3.3 0.0 0.3 Sidedress (S) 0.0 (kg N ha-1) 0.19 7.1 1.8 0.2 b 0.2 0.0 30.0 3.2 0.0 0.1 34.0 (kg N ha-1) 0.19 9.8 1.9 0.0 a 0.3 0.0 28.8 3.2 0.0 0.4

PAGE 109

90Table 3-6. Continued Internal tuber defects (%) HHz IHN IHN-S CRS BCL HH IHN IHN-S CRS BCL Interaction effectsv 2004 2005 D*F ns ns ns ns ns ns ns ns ns D*S ns ns ns ns ns ns ns ns ns F*S ns ns ns ns ns ns ns ns ns ns D*S*F ns ns ns ns ns ns ns ns ns ns zHH Hollow heart, IHN Internal heat necrosis; IHN-S internal heat necrosis severity; CRS Corky ring spot; BCLBrown center (light) yWAP = Weeks after planting. xMeans separated within columns using Tukeys studentized range test at p 0.05. Means with no letters were not significantly different. wAN = Ammonium nitrate CRF = Controlled release fertilizer vns, *, **, *** nonsignificant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 110

91Table 3-7. Well NO3-N concentration (mg L-1) under varying staged leaching irrigation tr eatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005 2004 (DAP) 2005 (DAP) Main Effects 29 44 64 72 89 17 33 45 59 73 89 Datey (D) 0 WAP 24.1 5.1 1.3 az 0.3 b 0.3 4.1 9.0 14.4 1.4 4.1 1.9 2 WAP 27.5 6.8 1.5 a 0.3 b 0.3 7.4 16.9 23.7 2.9 7.2 1.9 4 WAP 30.2 4.6 1.5 a 0.5 ab 0.5 6.4 13.2 25.4 2.6 6.3 2.0 8 WAP 17.1 4.4 1.4 a 0.7 a 0.4 5.2 12.9 18.5 3.4 7.4 2.4 12 WAP 29.5 8.2 0.9 b 0.4 ab 0.3 7.3 10.6 20.2 3.1 5.4 1.8 Fertilizerx (F) CRF 24.7 5.8 1.2 0.4 0.5 a 5.4 11.3 17.8 2.0 4.7 2.2 AN 25.7 5.5 1.4 0.4 0.2 b 6.5 13.3 22.6 3.4 7.5 1.8 Sidedress (S) 0.0 (kg N ha-1) 6.0 1.2 0.4 0.3 20.0 2.9 5.8 2.0 34.0 (kg N ha-1) 5.0 1.5 0.4 0.4 20.2 2.1 6.3 2.0

PAGE 111

92Table 3-7. Continued 2004 (DAP) 2005 (DAP) 29 44 64 72 89 17 33 45 59 73 89 Interaction effectsw D*F ns ns ns ns ns ns ns ns ns ns ns D*S ns ns ns ns ns ns ns ns F*S ns ns ns ns ns ns ns ns D*S*F ns ns ns ns ns ns ns ** zMeans followed by a different letter within columns are significant at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 112

93Table 3-8. Lysimeter NO3-N concentration (mg L-1) under varying staged leaching irrigati on treatments, fertilizer source and additional sidedress in Ha stings, FL in 2004 and 2005 2004 (DAP) 2005 (DAP) Main Effects 30 45 65 73 90 18 34 45 60 73 89 Datey (D) 0 WAP 242.4 25.2 0.8 0.3 0.4 bz 26.7 48.4 b 77.9 8.4 b 10.3 c 2.2 2 WAP 190.5 26.1 0.5 0.2 0.6 b 39.6 60.8 ab 93.4 24.8 a 27.4 ab 3.5 4 WAP 22.1 1.0 0.3 0.6 b 29.2 64.1 a 87.4 27.7 a 18.4 bc 2.8 8 WAP 41.9 1.1 0.2 0.9 b 26.1 51.4 ab 76.7 32.6 a 53.0 a 3.6 12 WAP 34.4 0.7 0.2 9.3 a 32.4 55.0 ab 85.5 24.6 a 29.1 ab 3.3 Fertilizerx (F) CRF 205.5 21.7 1.25 0.2 2.89 22.4 b 49.2 b 72.1 b 16.9 b 18.6 2.8 AN 224.7 38.4 1.69 0.3 4.34 42.8 a 62.9 a 97.0 a 27.5 a 31.1 3.3 Sidedress (S) 0.0 (kg N ha-1) 21.6 1.50 0.6 5.17 91.1 20.0 24.5 3.6 34.0 (kg N ha-1) 32.4 1.45 0.3 1.00 81.4 22.3 23.7 2.9

PAGE 113

94Table 3-8. Continued 2004 (DAP) 2005 (DAP) 30 45 65 73 90 18 34 45 60 73 89 Interaction effectsw D*F ns ns ns ns ns ns ns ns ns ns D*S ns ns ns ns ns ns ns ns F*S ns ns ns ns ns ns ns ns D*S*F ns ns ns ns ns ns ns ns zMeans followed by a different letter within co lumns are significantly different at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 114

95 Table 3-9. Total NO3-N nutrient load by fertilizer sour ce and leaching irrigation date and percent reduction in load fr om CRF compared with AN 2004 NO3-N load (kg ha-1) % Date AN CRF CRF/AN 2 WAP 2.91 a 1.90 b 35 4 WAP na na na 8 WAP 6.04 a 4.36 b 28 12 WAP 4.59 a 3.13 b 32 Season Total 13.54 a 9.39 b 31 zMeans within rows followed by a different letter are significantly different at the p 0.05 using the least significant difference mean separation test. Table 3-10. Total NO3-N nutrient load by fertilizer source and leaching irrigation date and percent reduction in load fr om CRF compared with AN 2005 NO3-N load (kg ha-1) % Date AN CRF CRF/AN 2 WAP 3.55 a 1.59 b 55 4 WAP 4.02 a 3.10 b 22 8 WAP 10.25 a 3.72 b 63 12 WAP 0.39 a 0.08 b 79 Season Total 18.16 8.49 54 zMeans within rows followed by a different letter are significantly different at the p 0.05 using the least significant difference mean separation test.

PAGE 115

96Table 3-11. Accumulated Growing Degr ee Days to leaching irrigation event, emergence and full flower 2004 Irrigation Date GDDy at irrigation date IHNx IHN severity Days to emergence GDD to emergence Calendar days to FFw GDD to FF GDD to harvest 0 WAPz 10.9 abx 2.2 a 18 225 53 807 2107 2 WAP 198 16.7 a 2.3 a 18 225 53 807 2107 4 WAP 371 8.8 ab 1.8 ab 18 225 53 807 2107 8 WAP 979 3.3 b 1.3 b 18 225 53 807 2107 12 WAP 1666 4.3 b 1.7 b 18 225 53 807 2107 2005 Irrigation Date GDD at irrigation date IHN IHN severity Days to emergence GDD to emergence Calendar days to FFx GDD to FF GDD to harvest 0 WAP 24.9 3.1 19 228 49 798 2144 2 WAP 188 35.5 3.4 19 228 49 798 2144 4 WAP 408 30.0 3.1 19 228 49 798 2144 8 WAP 948 30.9 3.2 19 228 49 798 2144 12 WAP 1629 26.6 3.0 19 228 49 798 2144 zWAP = Weeks after Planting yGDD = Growing Degree Days xIHN = Internal Heat Necrosis % of total yield wFF = Full Flower

PAGE 116

97 0 50 100 150 200 250 300 350 400 0102030405060708090100110120130140150160170180190200210220 Time (minutes)H2O (L/10min) 2 WAP 8 WAP 12 WAP 0 50 100 150 200 250 300 350 400 0102030405060708090100110120130140150160170180190200210 Time (minutes)H20 (L/10min) 2 WAP 4 WAP 8 WAP 12 WAP Figure 3-3. Total water volume from each irrigation date a. 2004 and b. 2005 a. b.

PAGE 117

98 rep=1 fertANC R F 0 1000 2000 3000 4000 5000 6000 Fertilizer Type 020406080100120140160180200220240 rep=2 fertANC R F 0 1000 2000 3000 4000 5000 6000 Fertilizer Type 020406080100120140160180200220240 rep=3 fertANC R F 0 1000 2000 3000 4000 5000 6000 Fertilizer Type 020406080100120140160180200220240 rep=4 fertANC R F 0 1000 2000 3000 4000 5000 6000 Fertilizer Type 020406080100120140160180200220240 Figure 3-4. NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replicati on at leaching event 2 WAP, 2004

PAGE 118

99 rep=1 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Fertilizer Type 020406080100120140160180200220240 rep=2 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Fertilizer Type 020406080100120140160180200220240 rep=3 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Fertilizer Type 020406080100120140160180200220240 rep=4 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Fertilizer Type 020406080100120140160180200220240 Figure 3-5. NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replicati on at leaching event 8 WAP, 2004

PAGE 119

100 rep=1 fertANC R F 1000 2000 3000 4000 5000 6000 7000 8000 9000 Fertilizer Type 020406080100120140160180200220240 rep=2 fertANC R F 1000 2000 3000 4000 5000 6000 7000 8000 9000 Fertilizer Type 020406080100120140160180200220240 rep=3 fertANC R F 1000 2000 3000 4000 5000 6000 7000 8000 9000 Fertilizer Type 020406080100120140160180200220240 rep=4 fertANC R F 1000 2000 3000 4000 5000 6000 7000 8000 9000 Fertilizer Type 020406080100120140160180200220240 Figure 3-6. NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replicati on at leaching event 12 WAP, 2004

PAGE 120

101 rep=1 fertANC R F 0 1000 2000 3000 4000 5000 Fertilizer Type 020406080100120140160180200220240 rep=2 fertANC R F 0 1000 2000 3000 4000 5000 Fertilizer Type 020406080100120140160180200220240 rep=3 fertANC R F 0 1000 2000 3000 4000 5000 Fertilizer Type 020406080100120140160180200220240 rep=4 fertANC R F 0 1000 2000 3000 4000 5000 Fertilizer Type 020406080100120140160180200220240 Figure 3-7. NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replicati on at leaching event 2 WAP, 2005

PAGE 121

102 rep=1 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 Fertilizer Type 020406080100120140160180200220240 rep=2 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 Fertilizer Type 020406080100120140160180200220240 rep=3 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 Fertilizer Type 020406080100120140160180200220240 rep=4 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 Fertilizer Type 020406080100120140160180200220240 Figure 3-8. NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replicati on at leaching event 4 WAP, 2005

PAGE 122

103 rep=4 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 Fertilizer Type 020406080100120140160180200220240 rep=1 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 Fertilizer Type 020406080100120140160180200220240 rep=2 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 Fertilizer Type 020406080100120140160180200220240 rep=3 fertANC R F 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 Fertilizer Type 020406080100120140160180200220240 Figure 3-9. NO3-N nutrient concen tration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replicati on at leaching event 8 WAP, 2005

PAGE 123

104 rep=4 fertANC R F 0 1000 2000 3000 Fertilizer Type 020406080100120140160180200220240 rep=1 fertANC R F 0 1000 2000 3000 Fertilizer Type 020406080100120140160180200220240 rep=2 fertANC R F 0 1000 2000 3000 Fertilizer Type 020406080100120140160180200220240 rep=3 fertANC R F 0 1000 2000 3000 Fertilizer Type 020406080100120140160180200220240 Figure 3-10. NO3-N nutrient concentration (mg 10min-1) of AN fertilizer treatment (blue lines) and CRF treatments (red lines) with parameter estimates by replicati on at leaching event 12 WAP, 2005

PAGE 124

105 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0102030405060708090100110120130140150160170180 Time (minutes)NO3-N load (kg/ha) AN CRF 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 010203040506070809010011012013014015016017018019020021022 0 Time (minutes)NO3-N load (kg/ha) AN CRF Figure 3-11. NO3-N load (kg ha-1) at 2, 8 and 12 WAP, 2004. a. 2 WAP b. 8 WAP c. 12 WAP b. a.

PAGE 125

106 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0102030405060708090100110120130140150160170180190 Time (minutes)NO3-N load (kg/ha) CRF AN Figure 3-11. Continued c.

PAGE 126

107 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0102030405060708090100110120130140150160170180190200 Time (minutes)NO3-N load (kg//ha) AN CRF 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0102030405060708090100110120130140150160170 Time (minutes)NO3-N load (kg//ha) AN CRF Figure 3-12. NO3-N load (kg ha-1) at 2, 4, 8 and 12 WAP, 20 05. a. 2 WAP b. 4 WAP c. 8 WAP d. 12 WAP b. a.

PAGE 127

108 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0102030405060708090100110120130140150160170180190200210 Time (minutes)NO3-N load (kg//ha) AN CRF 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 01020304050607080 Time (minutes)NO3-N load (kg//ha) AN CRF Figure 3-12. Continued c. d.

PAGE 128

109 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.002/17/04 2/24/04 3/2/04 3/9/04 3/16/04 3/23/04 3/30/04 4/6/04 4/13/04 4/20/04 4/27/04 5/4/04 5/11/04 5/18/04 5/25/04DateRainfall (cm)0 5 10 152025 30Average daily temperature (C) Rainfall events Average daily temperature 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.002/23/05 3/2/05 3/9/05 3/16/05 3/23/05 3/30/05 4/6/05 4/13/05 4/20/05 4/27/05 5/4/05 5/11/05 5/18/05 5/25/05 6/1/05 6/8/05DateRainfall (cm)0 5 10 15 20 25 30Average daily temperature (C) Rainfall events Average daily temperature Figure 3-13. Daily rainfall (cm) for the a. 2004 and b. 2005 production season. The group of red bars denote a leaching rainfa ll event (7.6 cm in 3 days or 10.1 cm in 4 days). The yellow, blue, pink a nd green arrows denote a stage leaching irrigation event at 2, 4, 8 and 12 WAP, respectively a. b

PAGE 129

110 CHAPTER 4 SUMMARY, AND FUTURE RESEARCH The St. Johns River in the state of Florida has been recognized as a priority water body in need of restoration. Best Management Practices (BMPs) for potato production in the TCAA have been implemented in response to the water quality concerns in the St. Johns River. With over 7,000 ha in potato pr oduction in the TCAA, nutrient runoff from potato production land has thought to have been primarily responsible for the non-point source pollution into the St Johns River wate rshed. Potato production BMPs to reduce nutrients entering the watershed have include d a reduction of N fertilizer applied to the potato crop, from a grower standa rd of 286 kg N ha-1 to 224 kg N ha-1. Second, the use of alternative N fertilizers, e.g. controlled release fertilizer s which would supply N to the potato crop as it is needed throughout the s eason. Third, in the event of a leaching rainfall event which is defined as 7.6 cm in 3 days or 10.2 cm in 7 days an additional 34 kg N ha-1 may be applied to the po tato crop to compensate for what potential N losses were incurred after the leaching rainfall event. The concerns of the grower with the implementation of the BMPs are first, to not compromise yield and second to maintain quali ty both externally and internally which are related to nutrition and/or environmental st ress (high temperatures and large amounts of rainfall) during the growing season. Potato, a cool season crop, is planted in the TCAA beginning in January when day length is s hort and temperatures cool. As the season progresses, daylight hours lengthen and temp eratures increase as the potato goes through key developmental stages. Leaching rainfall events during the production season are also

PAGE 130

111 common and can affect yield and quality of potato. The 50 year average for leaching rainfall events during the production seas on in the TCAA from 1954 to 2004 is 2.5 times for a 7.6 cm rainfall in 3 days and 5.3 times for a 10.2 cm rainfall in 7 days during the 6 month production season. Addressing these environmental and nutritional issues is important to the grower since approximately 70% of the acreage in the TCAA is planted in Atlantic which is a po tato that typically requires higher amounts of nitrogen to maintain quality and yield. This research ad dressed the concerns of the grower from a BMP standpoint as well as evaluating the envi ronmental factors which could impact both yield and quality of the potato crop throughout the production season. This research has found: Optimum Planting Dates Based upon this research the optimum plan ting dates in the TCAA are a four week period (early to late February) in the typi cal twelve week planting window from January through March. Planting in January, in orde r to meet early Apr il chipping contracts, could reduce yields by approximately 34%. Th e earlier planting dates also had little to no external and internal defects. Planting in March, a grower could exp ect an average reduction in yield of approximately 38%. This was primarily due to the increased percenta ges of rots due to the warmer day and night temperatures later in the season. Day and night time temperatures during tuber bulking (between full flower and harvest) in planting dates 5 and 6 were 8 and 10 degrees warmer, respec tively, compared with all other planting dates. Furthermore, the average amount of rainfall received during planting dates 5 and 6 was 58% more rainfall compared with the other planting dates 1 through 4 during the production season.

PAGE 131

112 Growing degree days evaluated thro ughout the growing season in 2004 and 2005 for each of the planting dates demonstrated optimal yields were obtained for Atlantic and Harley Blackwell at approximatel y 2000 GDD. Additionally, key growth and developmental stages were determined using GDD. Average GDD to reach emergence and full flower in 2004 and 2005 was 212 a nd 808 GDD, respectively. Atlantic and Harley Blackwell are generally harvest at or soon after 100 days after plating. This is primarily due to the aldicarb, an insecticid e/nematicide, labeling restrictions. This harvest date works for early to mid season plan tings, but not for late season plantings in March. As planting dates extend further in to the season, average daily temperatures increase, therefore, developmental stages occur sooner and the growing season is compressed based on accumulated growing degree days. Therefore, if a grower were to base the harvest of the late season plantings upon GDD and changed the insecticide/nematicide program, harvest could th eoretically be 10 to 21 days sooner rather than the 100 day harvest interval potentially reducing the incidence of rots in the field and therefore higher marketable yields. Climatic Factors This research also demonstrated that a leaching rainfall event between 200 and 400 GDD predisposed Atlantic to the onset of IHN due to plant stress caused by excess water which leads to low soil nutrient con centration early in the season followed by warmer temperatures later in the season. The average number of leaching rainfall events occurring between Jan and July over the last 50 years in the TCAA is 2.5 times for a 7.6 cm rainfall in 3 days and 5 times for a 10.1 cm rainfall in 7 days. Therefore, the influence of leaching rains on potato growth and production is imperative information to relay to the grower.

PAGE 132

113 Potato Varieties Although Harley Blackwell typi cally has lower yields co mpared with Atlantic it has proven to be a viable option for a chippi ng stock because of its desirable internal quality characteristics. Average marketable yields for Harley Black well and Atlantic were 19.8 and 21.4 t ha-1, respectively. Although, averag ed marketable yields were lower, Harley Blackwell had significantly lowe r total culls compared with Atlantic in 2004 and 2005. Adverse weather conditions during the growing season in the TCAA have certainly made Harley Blackwell a viab le option as an altern ative chipping variety in the TCAA. Its ability to withstand the warmer temperatures later in the season while maintaining its internal quality makes it a be tter chipping variety for late season contracts compared with Atlantic. Fertilizer Source This research has additionally demonstrat ed the effectiveness of a CRF in potato production compared with solubl e N fertilizer. CRF treatme nts had an average increase in marketable yields of 12% with 13% less N fertilizer applied compared with the AN fertilizer treatment. FUE was also signifi cantly higher in the CRF treatments, with an average increase in nitrogen FUE of 18% co mpared with the AN fertilizer treatments (data in appendix, F-5 page 6). Additionally, CRF was applied just prior to planting which means less time spent in the field appl ying additional fertili zer and a savings on fuel costs. External tuber defects, particularly IHN, was higher in the CRF treatments compared with the AN fertilizer treatments. This is most likely due to two conditions, first, the formulation of the CRF and its abil ity to recharge in the soil. Therefore, a blend should be created that contains a thi nner coated material to release faster and

PAGE 133

114 reduce the recharge timing. Second, the pla cement of the CRF so that more of the material is in the root zone of the plant. Similarly to the multiple planting date st udy, the incidence of IHN was also highest in the leaching irrigation treatments which occurred between 200 and 400 GDD, followed by the warmer temperatures later in the seas on. The additional pl ant stress (leaching irrigation event) at 8 and 12 WAP coupled with the warmer temperatures late in the season significantly impacted marketable yields. Additional N Sidedress Overall, the BMP of 34 kg N ha-1 after a leaching irrigation event did not significantly influence total or marketable tuber yields or external or internal tuber quality in 2004 or 2005. The three way interaction between irrigation main e ffects, fertilizer source and side dress did result in significantly higher tuber to tal and marketable yields in the CRF treatments at the 2 WAP irrigation date event. This was not the result in the AN fertilizer treatment in which the additional side dress did not make up for what was lost to leaching. At this time, this BMP does not app ear to be a sufficient amount to compensate for what nutrient losses were incurred during a leaching even t. Therefore, this BMP should be reevaluated for potato production in the TCAA which may be an issue of N rate and/or placement. Water Quality Use of CRF in potato production has also de monstrated it effectiveness in reducing the potential of nutrients movi ng into the water table. In 2005, the use of CRF reduced well NO3-N approximately 19% compared with the AN fertilizer treatment. Additionally, the use of CRF in potato production in 2004 and 2005 demonstrated a reduction in NO3-N in lysimeters by an average of 14 and 32%, respectively.

PAGE 134

115 This research demonstrated that nutrient loading from surface water runoff was significantly reduced with the use of CRF co mpared with the AN fertilizer treatment. The average reduction of NO3-N removed from the field due to surface water runoff was 43% compared with the AN fertilizer treatment. Based upon this research, NO3-N loads into the St. John River watershed from potat o production in the TC AA can be reduced by 56, 000 kg per year with the use of a CRF vs. an AN fertilizer. Future Research Based upon the results of this dissertation, possible future resear ch topics include: Growth and developmental characteristics as well as yield and quality of potato should be further investigated in a cont rolled environment (greenhouse or rainout shelter) instrumented to further evaluate the nutritional and environmental stressors which affect potato production in the TCAA. Based upon the results of this dissertation, in the event of an early season leaching rainfall, a CRF with a faster release rate to alleviate early season nutritional stress should be further investigated with particul ar attention to the incidence of tubers with IHN. A nutritional study including Ca++ related to placement, timing and rate during the production season and how these factors relate to Ca++ distribution in the tuber tissue of Atlantic. The reevaluation of the BMP of 34 kg N ha-1 after a leaching rainfall event should be studied in regards to placement and N rate applied for potato production in the TCAA. Further investigate the movement and concen tration of nutrients from surface water flow from potato production acreage into the St. Johns River watershed.

PAGE 135

116 APPENDIX A ADDITIONAL DATA AND A NOVA TABLES FOR PLANTING DATE YIELD In this appendix are reported additional data and ANOVA tables for planting date yield and late harvest yield. The tables in clude potato size dist ribution and external and internal quality.

PAGE 136

117Table A-1. Total and marketable yield and specific gr avity production statistics fo r late harvest 2004 and 2005 Total yield Marketable yield Specific gravity Total yield Marketable yield Specific gravity 2004 2005 Main Effect t ha-1 t ha-1 Planting Datez (PD) 1 31.8 ay 27.1 a 1.077 a 24.2 c 21.1 b 1.074 c 2 27.4 a 19.8 b 1.075 ab 20.1 d 17.6 bc 1.075 bc 3 27.7 a 20.2 b 1.076 a 25.3 bc 21.1 b 1.079 a 4 28.6 a 22.6 ab 1.073 b 34.0 a 25.7 a 1.076 b 5 18.8 b 10.8 c 1.066 c 28.1 b 16.0 c 1.069 d 6 11.5 c 6.1 d 1.063 d 12.7 e 6.2 d 1.061 e Nitrogen Rate (NR) 168 kg N ha-1 24.7 a 17.9 a 1.079 a 23.9 17.4 1.072 224 kg N ha-1 22.5 b 15.9 b 1.071 b 23.4 17.1 1.072 Variety (V) Atlantic 23.3 18.6 a 1.073 a 21.2 b 15.0 1.074 a Harley Blackwell 23.9 15.3 b 1.070 b 26.1 a 19.6 1.071 b

PAGE 137

118Table A-1. Continued Total yield Marketable yield Specific gravity Total yield Marketable yield Specific gravity 2004 2005 t ha-1 t ha-1 Interaction effectsx PD*NR ns ns ns ns ns PD*V ** ns *** ** ns NR* V ns ns ns ns ns ns PD*NR*V ns ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar, 2005). yMeans are separated with column and main effect usi ng Tukeys studentized range test. Means followed by different letters are sign ificantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 138

119 Table A-2. Size class distribu tion and range (%) production st atistics for late harvest 2004 Size Distribution by class (%)z Size Class Range (%) Main effects B A1 A2 A3 A1 to A2 A2 to A3 Planting Datey (PD) 2004 1 5.5 bcx 61.3 24.0 0.7 86.2 ab 25.9 2 9.1 a 60.4 12.3 0.9 75.1 c 14.3 3 7.7 ab 60.7 14.8 0.8 78.8 c 16.9 4 4.7 c 66.3 20.9 2.5 88.2 a 24.7 5 7.9 ab 68.3 10.3 0.5 81.7 bc 14.4 6 5.1 bc 67.8 12.8 0.1 89.7 a 11.5 Nitrogen Rate (NR) (kg ha-1) 224 6.9 61.9 b 17.8 a 1.1 83.3 20.7 a 168 6.3 66.4 a 13.4 b 0.5 83.7 14.8 b Variety Atantic 3.8 b 62.6 24.7 a 1.4 a 89.3 a 27.7 a Harley Blackwell 9.9 b 65.7 8.2 b 0.3 b 76.7 b 9.5 b zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar, 2005). yMeans are separated with column and main effect using Tukeys studentized range test. Means followed by differe nt letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA

PAGE 139

120 Table A-2. Continued Size Distribution by class (%)z Size Class Range (%) B A1 A2 A3 A1 to A2 A2 to A3 Interaction effectsw 2004 PD*NR ns *** ns ns ** PD*V ns ns * * NR*V ns ns ns ns ns ns PD*NR*V ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar, 2005). yMeans are separated with column and main effect using Tukeys studentized range test. Means followed by different letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 140

121 Table A-3. Size class distribu tion and range (%) production st atistics for late harvest 2005 Size Distribution by class (%)z Size Class Range (%) Main effects B A1 A2 A3 A1 to A2 A2 to A3 Planting Datey (PD) 2005 1 6.6 c 55.9 cd 28.7 a 5.8 a 91.9 a 35.4 ab 2 8.0 c 63.6 ac 23.8 ab 0.6 b 90.2 a 25.9 b 3 7.3 c 60.6 bc 29.0 a 0.4 b 91.6 a 30.6 ab 4 7.5 c 47.8 d 35.4 a 5.2 a 91.7 a 43.4 a 5 12.2 b 70.3 a 14.0 bc 0.0 c 86.5 b 14.0 c 6 18.9 a 67.0 ab 8.1 c 0.0 c 79.3 c 9.2 c Nitrogen Rate (NR) (kg ha-1) 224 10.3 59.5 23.1 1.4 88.4 26.6 168 9.3 62.3 21.5 0.9 89.3 24.1 Variety Atantic 7.6 59.7 25.1 a 1.6 91.2 a 29.0 a Harley Blackwell 12.1 62.1 19.7 b 0.8 86.3 b 22.0 b zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar, 2005). yMeans are separated with column and main effect using Tukeys studentized range test. Means followed by differe nt letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA

PAGE 141

122 Table A-4. Size class distribu tion and range (%) production st atistics for late harvest 2005 Size Distribution by class (%)z Size Class Range (%) B A1 A2 A3 A1 to A2 A2 to A3 Interaction effectsw 2005 PD*NR ns ns ns ns ns ns PD*V ns ns ns ns ns ns NR*V ns ns ns ns ns ns PD*NR*V ns ns ns ns ns ns zSize class: B = 3.8 to 4.4 cm (1.5 to 1 7/8 in), A1 =4.4 to 6.4 cm (1 7/8 to 2.5 in), A2 = 6.4 to 8.3 cm (2.5 to 3.25 in), A3 = 8.3 to 10.2 cm (3.25 to 4 in). yPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar), respectively. xMeans are separated with column and main effect using Tukeys studentized range test. Means followed by differe nt letters are significantly different at p 0.05. Means with no letters are not significantly different. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 142

123Table A-5. External quality (gre en, growth cracks, mis-shaped, rot and total cu lls) (%) of total yield late harvest 2004 and 2 005 External tuber defects (%) Main effects Green Growth crack Misshaped Rot Total cullz Green Growth crack Misshaped Rot Total cullz Planting Date (PD)z 2004 2005 1 0.0 0.7 ay 0.2 b 0.1 d 1.9 d 2.8 a 0.0 0.1 0.0 d 3.7 cd 2 1.2 0.0 b 0.0 b 3.4 c 6.2 c 0.3 b 0.0 0.0 0.4 d 2.2 d 3 0.0 0.0 b 1.9 a 6.3 c 9.0 bc 2.1 a 0.0 0.0 3.8 c 7.0 c 4 0.0 0.0 b 0.0 b 12.8 b 13.3 b 2.6 a 0.0 0.0 12.6 b 16.2 b 5 0.0 0.0 b 0.0 b 28.7 a 28.9 a 1.5 a 0.0 0.0 30.8 a 33.1 a 6 1.0 0.0 b 0.0 b 33.0 a 35.7 a 0.0 b 0.0 0.0 38.7 a 39.1 a Nitrogen Rate (NR) kg ha-1 224 0.2 0.0 0.0 b 10.2 13.1 1.5 0.0 0.0 9.3 14.4 168 0.1 0.0 0.1 a 11.1 14.3 1.2 0.0 0.0 10.5 14.6 Variety (V) Atlantic 0.1 0.0 0.2 a 10.2 13.5 2.5 a 0.0 a 0.0 13.6 a 21.1 a Harley Blackwell 0.2 0.0 0.0 b 11.1 13.9 0.6 b 0.0 b 0.0 6.9 b 9.2 b

PAGE 143

124Table A-5. Continued External tuber defects (%) Green Growth crack Misshaped Rot Total cullz Green Growth crack Misshaped Rot Total cullz Interaction effectsx 2004 2005 PD*NR ns ns ns ns ns ns ns ns * PD*V ns ns *** ns ns ns ** ns NR* V ns ns ns ns ns ns ns ns ns ns PD*NR*V ns ns ns ns ns ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar, 2005). yMeans are separated with column and main effect using T ukeys studentized range test. Means followed by different letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 144

125Table A-6. Internal qua lity (%) of total yield late harvest 2004 and 2005 Internal quality (%) Main effects HH IHN IHN severity CRS BCL HH IHN IHN severity CRS BCL Planting Datez (PD) 2004 2005 1 2.1 by 5.3 a-c 1.3 ab 4.9 ab 1.1 0.0 3.9 0.0 c 0.2 0.4 2 5.1 a 8.1 a 1.7 a 6.5 a 1.7 0.0 5.3 0.0 c 0.0 0.0 3 0.0 c 1.1 b-d 0.7 bc 3.2 a-c 1.0 0.0 3.8 1.2 ab 0.0 0.0 4 0.0c 7.0 ab 1.5 a 0.3 bc 0.9 0.0 9.0 1.7 a 0.0 0.0 5 0.0 c 0.1 d 0.3 c 0.0 c 0.0 0.0 3.6 1.1 a 0.0 0.0 6 3.3 ab 0.4 cd 0.0 c 0.0c 0.0 0.0 0.7 0.6 b 0.0 0.0 Nitrogen Rate (NR) kg ha-1 224 0.7 2.5 0.9 1.5 0.6 0.0 4.1 0.7 0.0 0.0 168 0.9 3.0 0.9 1.4 0.5 0.0 3.8 0.6 0.0 0.0 Variety (V) Atlantic 1.5 a 9.6 a 1.7 a 0.4 b 1.5 a 0.0 16.0 a 1.3 a 0.0 0.0 a Harley Blackwell 0.3 b 0.0 b 0.1 b 3.2 a 0.1 b 0.0 0.0 b 0.0 b 0.0 0.0 b

PAGE 145

126Table A-6. Continued HH IHN IHN severity CRS BCL HH IHN IHN severity CRS BCL Interaction effects 2004 2005 PD*NR ns ns ns ns ns *** ns ns PD*V *** *** ns ** ** ns ** ns ns NR* V ns ns ns ns ns ns ns ns ns PD*NR*V ** ns ns ns ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar, 2005). yMeans are separated with column and main effect using T ukeys studentized range test. Means followed by different letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 146

127Table A-7. 2004 ANOVA table for potat o yield in planting date study Type III Mean Squarez Source of Variation DFTotal Mkt B A1 A2 A3 A12 A23 SG Replication 3 0.88 390.9 0.00 0.00 0.00 0.00 0.01 0.00 0.00 Planting Date 5 12.57 3026.6 0.01 0.01 0.04 0.02 0.04 0.04 0.00 Replication*Planting Date 15 0.80 579.7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Nitrogen Rate 1 10.10 7200.6 0.00 0.00 0.02 0.01 0.00 0.04 0.00 Planting Date*Nitrogen Rate 5 1.75 1387.4 0.00 0.00 0.01 0.02 0.00 0.01 0.00 Replication*Planting Date *Nitrogen Rate 18 0.36 282.8 0.00 0.00 0.01 0.00 0.00 0.01 0.00 Variety 1 8.83 400.0 0.24 0.00 0.46 0.14 0.41 0.63 0.00 Planting Date*Variety 5 2.45 1206.3 0.00 0.03 0.02 0.02 0.00 0.04 0.00 Nitrogen Rate*Variety 1 0.00 56.2 0.00 0.02 0.00 0.03 0.01 0.01 0.00 Planting Date*Nitrogen Rate*Variety 5 0.53 5359.8 0.00 0.00 0.01 0.01 0.00 0.01 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 147

128Table A-8. 2005 ANOVA table for potato total and marketable yield and si ze distribution in planting date study Type III Mean Squarez Source of Variation DFTotal Mkt B A1 A2 A3 A12 A23 SG Replication 3 2.07 1.44 0.00 0.00*** 0.00 0.02 0.00 0.00 0.00 Planting Date 5 77.74***129.91***0.14*** 0.10 0.42*** 0.12*** 0.08*** 0.53*** 0.00*** Replication*Planting Date 15 0.61 0.87 0.00 0.00 0.00 0.01* 0.00 0.00 0.00 Nitrogen Rate 1 1.09 0.23 0.01** 0.00 0.00 0.00 0.01 0.00 0.00 Planting Date*Nitrogen Rate 5 0.94 1.69 0.00* 0.00 0.00 0.01** 0.00 0.00 0.00 Replication*Planting Date *Nitrogen Rate 18 0.89 0.54 0.00 0.00 0.01 0.00 0.00 0.01 0.00 Variety 1 13.51***5.26* 0.16*** 0.00 0.22*** 0.01 0.12*** 0.25*** 0.00 ** Planting Date*Variety 5 6.21*** 3.28* 0.00** 0.01* 0.01 0.01* 0.02*** 0.00 0.00*** Nitrogen Rate*Variety 1 0.63 1.03 0.00 0.00 0.01 0.00 0.00 0.01 0.00** Planting Date*Nitrogen Rate*Variety 5 1.29 2.22 0.00 0.00 0.02 0.01 0.00 0.01 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 148

129Table A-9. 2004 ANOVA table for pot ato internal and external qua lity in planting date study Type III Mean Squarez Source of Variation DFGC Green Mis shapen Rot Total cull CRS HH IHN BC(l) Replication 3 0.00 0.00 0.00 0.00 0.00 0.12** 0.00 0.00 0.00 Planting Date 5 0.00* 0.01** 0.00 0.42*** 0.29*** 0.34*** 0.10*** 0.10*** 0.05*** Replication*Planting Date 15 0.00 0.00 0.00 0.00 0.00 0.06** 0.00 0.01 0.00 Nitrogen Rate 1 0.00 0.00 0.00 0.01 0.01 0.12* 0.00 0.00 0.00 Planting Date*Nitrogen Rate 5 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.05* 0.00 Replication*Planting Date*Nitrogen Rate 18 0.00 0.00 0.00 0.00* 0.00** 0.01 0.00 0.01 0.00 Variety 1 0.00 0.00 0.01** 0.00 0.03** 0.00 0.25*** 0.57*** 0.07** Planting Date*Variety 5 0.00 0.00 0.00 0.00 0.01 0.00 0.10*** 0.09** 0.03** Nitrogen Rate*Variety 1 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.00 Planting Date*Nitrogen Rate*Variety 5 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.02 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 149

130 Table A-10. 2005 ANOVA table for pot ato internal and external qua lity in planting date study Type III Mean Squarez Source of Variation DFGC Green Mis shapen Rot Total cull CRS HH IHN BC(l) Replication 3 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.01 0.00 Planting Date 5 0.00* 0.00 0.00 1.08***0.79***0.00***0.00 0.12***0.12*** Replication*Planting Date 15 0.00 0.00 0.00 0.44 0.00 0.00 0.00 0.00 0.00 Nitrogen Rate 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 Planting Date *Nitrogen Rate 5 0.00 0.00 0.00 0.00 0.00* 0.00 0.00 0.01* 0.00 Replication*Planting Date*Nitrogen Rate 18 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Variety 1 0.01** 0.01 0.01** 0.04** 0.18***0.00 0.00 0.53***0.52*** Planting Date*Variety 5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.10***0.12*** Nitrogen Rate*Variety 1 0.00 0.00 0.00 0.03* 0.00 0.00 0.00 0.00 0.01 Planting Date*Nitrogen Rate*Variety 5 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 150

131Table A-11. 2004 ANOVA table fo r potato yield in planting date study late harvest Type III Mean Squarez Source DFTotal Mkt B A1 A2 A3 A12 A23 SG Replication 3 3.63* 2.53 0.00 0.02 0.04 0.00 0.00 0.04 0.00 Planting Date 5 108.11***148.29***0.00** 0.02 0.08** 0.02 0.09***0.09** 0.00*** Replication*Planting Date 15 2.52* 2.97 0.00 0.01 0.05* 0.01 0.00 0.05* 0.00 Nitrogen Rate 1 11.62** 12.04* 0.00 0.05 0.08 0.02 0.00 0.14* 0.00** Planting Date*Nitrogen Rate 5 1.21 1.93 0.00 0.01 0.01 0.00 0.00 0.02 0.00* Replication*Planting Date*Nitrogen Rate 18 0.53 0.72 0.00 0.00 0.00 0.01 0.00 0.00 0.00 Variety 1 0.73 34.96*** 0.00***0.02 1.24***0.09** 0.70***1.39***0.00*** Planting Date*Variety 5 5.90** 3.61 0.00 0.02 0.06* 0.02* 0.03* 0.05* 0.00* Nitrogen Rate*Variety 1 0.493 0.75 0.00 0.00 0.00 0.01 0.00 0.00 0.00 Planting Date*Nitrogen Rate*Variety 5 1.63 2.58 0.00 0.016 0.00 0.03* 0.01 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 151

132Table A-12. 2005 ANOVA table fo r potato yield in planting date study late harvest Type III Mean Squarez Source DFTotal Mkt B A1 A2 A3 A12 A23 SG Replication 3 3.15 3.16 0.00 0.00 0.00 0.01 0.00 0.01 0.00 Planting Date 5 83.93***114.15***0.08***0.10***0.27***0.17*** 0.08***0.38***0.00*** Replication*Planting Date 15 1.65* 2.39 0.00 0.01 0.03** 0.00 0.00 0.03* 0.00 Nitrogen Rate 1 0.57 0.32 0.00 0.01 0.00 0.00 0.00 0.01 0.00 Planting Date*Nitrogen Rate 5 1.74* 1.47 0.00 0.00 0.01 0.00 0.00 0.01 0.00 Replication*Planting Date*Nitrogen Rate 18 0.68 0.79 0.00 0.00 0.010 0.00 0.00 0.01 0.00 Variety 1 52.45***58.74*** 0.14***0.01 0.10** 0.03 0.15***0.15** 0.00*** Planting Date*Variety 5 8.65*** 5.29** 0.00 0.00 0.02 0.02 0.00 0.02 0.00 Nitrogen Rate*Variety 1 2.31 0.96 0.00 0.01 0.01 0.00 0.00 0.02 0.00 Planting Date*Nitrogen Rate*Variety 5 0.54 1.03 0.00 0.00 0.01 0.00 0.00 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 152

133Table A-13. 2004 ANOVA table for potato internal and external quality in planting date study late harvest Type III Mean Squarez Source of Variation DFGC Green Mis shapen Rot Total cull CRS HH IHN BC(l) Replication 3 0.00 0.00 0.00 0.00 0.00 0.11*** 0.00 0.01 0.01 Planting Date 5 0.01*** 0.03* 0.04*** 0.84*** 0.58*** 0.19*** 0.17*** 0.18*** 0.04** Replication*Planting Date 15 0.00 0.0 0.00 0.00 0.00 0.02 0.00 0.02 0.02* Nitrogen Rate 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Planting Date*Nitrogen Rate 5 0.00 0.01* 0.00 0.00 0.00 0.01 0.00 0.02 0.01 Replication*Planting Date*Nitrogen Rate 18 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.02 0.01 Variety 1 0.00 0.00 0.01** 0.00 0.00 0.32*** 0.09*** 2.09*** 0.21*** Planting Date*Variety 5 0.00 0.00 0.00 0.00 0.00 0.06** 0.25*** 0.12*** 0.03** Nitrogen Rate*Variety 1 0.00 0.00 0.00 0.00 0.00 0.036 0.01* 0.00 0.00 Planting Date*Nitrogen Rate*Variety 5 0.00 0.00 0.00 0.00 0.001 0.00 0.00* 0.00 0.01 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 153

134Table A-14. 2005 ANOVA table for potato internal and external quality in planting date study late harvest Type III Mean Squarez Source of Variation DFGC Green Mis shapen Rot Total cull CRS HH IHN BC(l) Replication 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.00 Planting Date 5 0.00 0.05*** 0.00 1.15*** 0.72*** 0.00* 0.00 0.09** 0.00 Replication*Planting Date 15 0.00 0.00 0.00 0.01 0.012 0.00 0.00 0.03 0.00 Nitrogen Rate 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Planting Date*Nitrogen Rate 5 0.00 0.00 0.00 0.01 0.01 0.00* 0.00 0.04 0.00 Replication*Planting Date*Nitrogen Rate 18 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Variety 1 0.01* 0.14*** 0.00 0.20*** 0.55*** 0.000 0.00 3.96*** 0.04** Planting Date*Variety 5 0.00 0.01* 0.00* 0.02** 0.01 0.00* 0.00 0.09** 0.00 Nitrogen Rate*Variety 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Planting Date*Nitrogen Rate*Variety 5 0.00 0.00 0.00 0.00 0.00 0.00* 0.00 0.04 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 154

135 APPENDIX B ADDITIONAL DATA AND A NOVA TABLES FOR PLANT TISSUE FOR PLANTING DATE In this appendix are reported additional data and ANOVA tables for planting date plant and tuber tissue nutr ient concentrations.

PAGE 155

136Table B-1. Haulm nutrient concentrati on (%) at tuber init iation in 2004 and 2005 Haulm Nutrient Concentration (%) 2004 2005 Main Effect TKN K P Ca TKN K P Ca Planting Datez (PD) 1 9.5 ay 18.0 bc0.8 a 1.4 d 9.7 a 1.4 d 2 8.7 ab 18.8 ab0.7 ab 2.1 b 8.4 b-d 2.0 c 3 8.0 bc 14.2 d 0.7 a-c 1.9 c 7.8 d 2.3 b 4 8.5 a-c 17.2 c 0.8 a 2.4 a 9.1 ab 2.1 bc 5 7.5 cd 19.4 a 0.6 c 2.2 b 8.1 cd 2.2 b 6 6.6 d 15.1 d 0.6 bc 1.9 c 8.6 bc 2.6 a Nitrogen Rate (NR) 168 kg N ha-1 7.9 b 17.3 0.7 1.9 8.6 2.1 224 kg N ha-1 8.2 a 16.7 0.7 1.9 8.6 2.1 Variety (V) Atlantic 8.1 17.1 0.7 1.8 b 8.6 1.9 b Harley Blackwell 8.0 16.9 0.7 2.1 a 8.6 2.2 a

PAGE 156

137Table B-1. Continued Haulm Concentration (%) 2004 2005 TKN K P Ca TKN K P Ca Interaction Effectsx PD*NR ** ns ns ns ns PD*V ns ns ns ns ns PD*NR*V ns ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar, 2005). yMeans are separated with column and main effect usi ng Tukeys studentized range test. Means followed by different letters are sign ificantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 157

138Table B-2 Full flower (haulm) nut rient concentration (%) for 2004 and 2005 Haulm Nutrient Concentration (%) 2004 2005 Main Effect TKN K P Ca TKN K P Ca Planting Datez (PD) 1 6.4 ay 14.7 ab 0.3 b 2.4 bc 6.9 ab 2.3 bc 2 5.8 ab 14.1 b 0.3 b 2.5 ab 7.6 a 2.6 ab 3 6.5 a 15.0 ab 0.5 a 2.4 bc 5.9 c 2.0 cd 4 4.7 c 13.8 b 0.2 b 3.1 a 7.3 ab 2.3 b-d 5 5.3 bc 16.2 a 0.4 a 2.6 ab 6.9 ab 2.9 a 6 6.4 a 13.8 b 0.5 a 2.0 c 6.8 b 2.0 d Nitrogen Rate (NR) 168 kg N ha-1 5.5 b 14.8 0.3 2.6 6.7 b 2.3 224 kg N ha-1 6.1 a 14.3 0.3 2.4 7.0 a 2.4 Variety (V) Atlantic 5.9 14.5 0.4 2.3 b 7.0 2.2 b Harley Blackwell 5.8 14.6 0.3 2.7 a 6.8 2.5 a

PAGE 158

139Table B-2. Continued Haulm Nutrient Concentration (%) 2004 2005 TKN K P Ca TKN K P Ca Interaction Effectsx PD*NR ns ns ns ns ns ns PD*V ns ns ns ns ns ns PD*NR*V ns ns ns ns ns ns zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar, 2005). yMeans are separated with column and main effect usi ng Tukeys studentized range test. Means followed by different letters are sign ificantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 159

140 Table B-3 Tuber diced pieces nutrient concentration (kg ha-1) at harvest 2005 Ca TKN Planting Datez (PD) ------kg ha-1------1 1.1 bc 74.3 cd 2 1.0 bc 64.6 d 3 1.4 b 87.3 bc 4 2.5 a 107.6 a 5 1.5 b 92.9 ab 6 0.7 c 47.2 e Nitrogen Rate (NR) kg ha-1 168 1.2 73.9 b 224 1.4 81.6 a Variety Atly 1.2 b 75.1 b HB 1.5 a 80.3 a Interaction effects PD*NR ns ns PD*V ns ** PD*NR*V ns ns zPlanting dates 1 through 6 for 2005 were (11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar), respectively. yMeans are separated with column and main effect using Tukeys studentized range test. Means followed by different letters are significan tly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 160

141 Table B-4. Ca++ and TKN fertilizer use efficiency (%) 2005 Ca++ TKN Planting Date (PD) -------%------1 6.5 c 62.9 c 2 4.9 cd 52.2 d 3 4.4 d 63.1 c 4 11.2 ab 91.6 a 5 13.6 a 81.8 b 6 9.8 b 61.4 c Nitrogen Rate (NR) kg ha-1 168 7.6 66.6 b 224 8.5 70.9 a Variety Atlantic 7.0 b 65.3 b Harley Blackwell 9.3 a 72.0 a Interaction effects PD*NR ns ns PD*V ns ns PD*NR*V ns ns zPlanting dates 1 through 6 for 2005 were (11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar), respectively. yMeans are separated with column and main effect using Tukeys studentized range test. Means followed by different letters are significantly different at p 0.05. Means with no letters are not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 161

142 Table B-5. 2004 ANOVA table for haulm tissue at tuber initiation for planting date Type III Mean Squarez Source of Variation DF Ca TKN Replication 3 0.01 0.02 Planting Date 5 0.60*** 0.27*** Replication*Planting Date 15 0.00 0.01 Nitrogen Rate 1 0.00 0.01 Planting Date*Nitrogen Rate 5 0.00 0.02 Replication*Planting Date*Nitrogen Rate 18 0.00 0.00 Variety 1 0.64*** 0.00 Planting Date*Variety 5 0.01* 0.01 Nitrogen Rate*Variety 1 0.00 0.00 Planting Date*Nitrogen Rate*Variety 5 0.01 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 162

143 Table B-6. 2004 ANOVA table for haulm tissu e at full flower for planting date Type III Mean Squarez Source DF Ca TKN Replication 3 0.00 0.00 Planting Date 5 0.30*** 0.24*** Replication*Planting Date 15 0.03 0.02 Nitrogen Rate 1 0.06 0.20*** Planting Date*Nitrogen Rate 5 0.01 0.01 Replication*Planting Date*Nitrogen Rate 18 0.01 0.01 Variety 1 0.44*** 0.00 Planting Date*Variety 5 0.00 0.00 Nitrogen Rate*Variety 1 0.01 0.00 Planting Date*Nitrogen Rate*Variety 5 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 163

144 Table B-7. 2005 ANOVA table for haulm tissue at tuber initiation for planting date Type III Mean Squarez Source of Variation DF Ca TKN Replication 3 0.00 0.00 Planting Date 5 0.64*** 0.09*** Replication*Planting Date 15 0.01 0.11 Nitrogen Rate 1 0.01 0.00 Planting Date*Nitrogen Rate 5 0.01 0.00 Replication*Planting Date*Nitrogen Rate 18 0.01 0.01 Variety 1 0.47*** 0.00 Planting Date*Variety 5 0.01 0.00 Nitrogen Rate*Variety 1 0.01 0.02 Planting Date*Nitrogen Rate*Variety 5 0.00 0.01 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 164

145 Table B-8. 2005ANOVA table for haulm tissue at full flower Type III Mean Squarez Source of Variation DF Ca TKN Replication 3 0.01 0.00 Planting Date 5 0.32*** 0.11*** Replication*Planting Date 15 0.02 0.00 Nitrogen Rate 1 0.08** 0.03 Planting Date*Nitrogen Rate 5 0.03* 0.00 Replication*Planting Date*Nitrogen Rate 18 0.01 0.00 Variety 1 0.45*** 0.02 Planting Date*Variety 5 0.01 0.00 Nitrogen Rate*Variety 1 0.01 0.00 Planting Date*Nitrogen Rate*Variety 5 0.02 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 165

146 Table B-9. 2005ANOVA table for FUE Type III Mean Squarez Source DF Ca TKN Replication 3 0.00 0.03* Planting Date 5 0.07*** 0.40*** Replication*Planting Date 15 0.00 0.00 Nitrogen Rate 1 0.00 0.09** Planting Date*Nitrogen Rate 5 0.00 0.01 Replication*Planting Date*Nitrogen Rate 18 0.00 0.00 Variety 1 0.04*** 0.07** Planting Date*Variety 5 0.00 0.01 Nitrogen Rate*Variety 1 0.00 0.00 Planting Date*Nitrogen Rate*Variety 5 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 166

147 Table B-10. 2005ANOVA table for tube r diced pieces for planting date Type III Mean Squarez Source of Variation DF Ca TKN Replication 3 0.03 0.81 Planting Date 5 1.02*** 24.98*** Replication*Planting Date 15 0.04 0.48 Nitrogen Rate 1 0.04 4.62** Planting Date*Nitrogen Rate 5 0.03 0.44 Replication*Planting Date*Nitrogen Rate 18 0.04 0.45 Variety 1 0.40** 2.02* Planting Date*Variety 5 0.07 1.72** Nitrogen Rate*Variety 1 0.08 0.06 Planting Date*Nitrogen Rate*Variety 5 0.02 0.27 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 167

148 APPENDIX C ADDITIONAL DATA AND A NOVA TABLE FOR POST HARVEST SOIL NUTRIENTS FOR PLANTING DATE In this appendix are reported ANOVA tables for post harvest soil sample planting date 2005.

PAGE 168

149 Table C-1. Soil nutrient concentration (mg kg-1) post harvest 2005 Ca NH4-N NO3-N EC pH Main Effect Planting Datez (PD) ------------mg kg-1-----------dS/M 1 428.7 a 1.8 a 13.2 a 0.0 d 5.1 2 339.0 ab 1.8 a 2.1 b 0.1 c 5.8 3 289.2 b 1.1 b 1.3 b 0.4 a 5.7 4 395.5 a 1.0 b 2.3 b 0.2 bc 5.4 5 399.6 a 0.5 c 1.3 b 0.3 ab 5.2 6 414.0 a 0.5 c 1.0 b 0.3 a 5.5 Nitrogen Rate (NR) kg ha-1 168 377.7 1.0 1.9 b 0.2 5.5 224 370.9 1.0 2.5 a 0.2 5.4 Variety Atly 367.5 1.0 2.3 0.2 5.4 HB 381.2 1.0 2.1 0.2 5.5 Interaction effects PD*NR ns ns ns ns ns PD*V ns ns ns ns ns PD*NR*V ns ns ns ns ns zPlanting dates 1 through 6 for 2005 were (11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar), respectively. yMeans are separated with column and ma in effect using Tukeys studentized range test. Means followed by different letters are sign ificantly different at p 0.05. Means with no letters ar e not significantly different. xns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA

PAGE 169

150Table C-2. 2005 ANOVA table for post harvest soil planting date Type III Mean Squarez Source of Variation DFCa NH4-N NO3-N pH EC Replication 3 0.07 0.10 0.09 0.74*** 0.00 Planting Date 5 0.24*** 15.07***16.74*** 0.58*** 0.11** Replication*Planting Date 15 0.07 0.04 0.20 0.05 0.01 Fertilizer 1 0.07 0.00 1.00 0.08 0.00 Planting Date*Nitrogen Rate 5 0.04 0.04 0.16 0.02 0.00 Replication*Planting Date*Nitrogen Rate 18 0.03 0.17 0.10 0.04 0.00 Variety 1 0.05 0.00 0.00 0.00 0.00 Planting Date*Variety 5 0.04 0.04 0.06 0.01 0.00 Nitrogen Rate*Variety 1 0.03 0.16 0.01 0.02 0.00 Planting Date*Nitrogen Rate*Variety 5 0.04 0.04 0.14 0.01 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 170

151 APPENDIX D ANOVA TABLES FOR YIELD AND Q UALITY FOR IRRIGATION STUDY In this appendix are reported ANOVA ta bles for irrigation study potato yield, potato external and internal quality 2004 and 2005.

PAGE 171

152 Table D-1. 2004 ANOVA table for potato total and marketable yield and specific gravity Type III Mean Squarez Source of Variation DF Total Mkt SG Replication 3 958.67 390.90 0.00 Treatment 4 2671.36* 3026.64* 0.00 Replication*Treatment 12 539.41 579.74 0.00 Fertilizer 1 8025.67** 7200.62** 0.00 Treatment*Fertilizer 4 1380.67* 1387.41** 0.00 Replication*Treatment* Fertilizer 15 309.05 282.82 0.00 Side 1 310.64 400.00 0.00 Treatment*Side 3 840.93 1206.37 0.00 Fertilizer*Side 1 43.89 56.25 0.00 Treatment*Fertilizer *Side 3 4332.01* 5359.87* 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 172

153Table D-2. 2004 ANOVA table for potato size class distri bution and range Type III Mean Squarez Source of Variation DF C B A1 A2 A3 A12 A23 Replication 3 7.43** 16.98**43.60 77.54 10.14* 43.97** 106.41 Treatment 4 9.88** 32.03**184.13 361.13** 4.83 70.64** 431.37** Replication*Treatment 12 1.18 4.07 34.33 22.42 2.15 7.21 31.28** Fertilizer 1 3.92 0.05 282.67 230.31** 16.93 9.81 375.96 Treatment*Fertilizer 4 3.98 3.78 39.06 58.28* 5.47 11.65 87.17 Replication*Treatment* Fertilizer 15 2.00 2.75 18.24 18.54 3.98** 8.37 36.16 Side 1 0.76 0.06 9.76 40.64 6.25* 2.25 18.06 Treatment*Side 3 6.64 5.10 7.76 53.47 1.12 18.37 47.39 Fertilizer*Side 1 1.26 3.06 3.51 43.89 2.25 7.56 25.00 Treatment*Fertilizer *Side 3 8.97 16.35 23.93 93.55 1.45 47.10 117.83 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 173

154 Table D-3. 2005 ANOVA table for potato total and marketable yield and specific gravity Type III Mean Squarez Source of Variation DF Total Mkt SG Replication 3 6693.88** 7750.64** 0.00* Treatment 4 3041.49* 7074.20** 0.00** Replication*Treatment 12 626.10 320.84 0.00 Fertilizer 1 11539.24**12278.88**0.00 Treatment*Fertilizer 4 1578.61 1602.44 0.00 Replication*Treatment* Fertilizer 15 697.75 758.68 0.00 Side 1 1650.39 1969.14 0.00 Treatment*Side 3 177.39 123.59 0.00 Fertilizer*Side 1 1991.39 1130.64 0.00 Treatment*Fertilizer *Side 3 1886.55* 1860.01* 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 174

155Table D-4. 2005 ANOVA table for potato size class distri bution and range Type III Mean Squarez Source of Variation DF C B A1 A2 A3 A12 A23 Replication 3 0.31 20.77 172.17* 67.01 188.31** 25.24* 233.03* Treatment 4 0.13 26.73* 293.96** 185.60** 104.63** 39.38** 512.41** Replication*Treatment 12 0.22 6.36 29.033 28.76 12.04 7.08 48.49 Fertilizer 1 0.07 47.02**435.59** 76.83 345.86** 45.11* 766.95** Treatment*Fertilizer 4 0.09 12.26 50.46 32.83 12.51 14.37 75.95 Replication*Treatment* Fertilizer 15 0.11 5.29 38.22 25.00 14.62 5.55 32.40 Side 1 0.14 0.39 10.56 11.39 0.01 6.25 21.39 Treatment*Side 3 0.14 1.55 48.72 53.59 3.93 2.62 53.76 Fertilizer*Side 1 0.01 3.51 18.06 0.14 8.26 2.25 6.89 Treatment*Fertilizer *Side 3 0.01 3.76 89.39 79.59* 22.09 2.45 100.76 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 175

156 Table D-5. 2004 ANOVA table fo r potato external quality Type III Mean Squarez Source of Variation DF GC Green Mis shapen Rot Total cull Replication 3 0.045 1.21* 0.08 9.04** 11.47** Treatment 4 0.022 0.86* 0.41* 1.23 3.42 Replication*Treatment 12 0.035 0.22 0.08 0.98 1.43 Fertilizer 1 0.004 0.30 0.30 0.18 0.11 Treatment*Fertilizer 4 0.053 0.36 0.03 0.42 0.91 Replication*Treatment *Fertilizer 15 0.037 0.52 0.21 1.21 2.44 Side 1 0.015 0.14 0.01 0.76 1.26 Treatment*Side 3 0.057 0.26 0.05 0.34 0.01 Fertilizer*Side 1 0.140 0.39 0.14 1.26 0.76 Treatment*Fertilizer *Side 3 0.015 1.43 0.18 2.68 4.84 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 176

157 Table D-6. 2004 ANOVA table fo r potato internal quality Type III Mean Squarez Source of Variation DF CRS HH IHN BC(l) Replication 3 7.01 1.61 746.91** 1.35 Treatment 4 17.11 0.28 471.83* 3.49 Replication*Treatment 12 11.87 0.58 110.03 2.36 Fertilizer 1 0.18 0.11 782.20** 2.55 Treatment*Fertilizer 4 1.65 1.07 79.08 7.95 Replication*Treatment *Fertilizer 15 2.52 0.78* 71.24 2.72 Side 1 33.06* 0.00 28.89 0.39 Treatment*Side 3 14.77 0.37 124.22 5.80 Fertilizer*Side 1 1.56 0.56 13.14 4.51 Treatment*Fertilizer *Side 3 5.85 0.18 139.39 6.43 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 177

158 Table D-7. 2005 ANOVA table fo r potato external quality Type III Mean Squarez Source of Variation DF GC Green Mis shapen Rot Total cull Replication 3 0.41 13.63** 3.56 18.81 55.95 Treatment 4 1.37* 9.32** 7.55* 239.34* 339.18** Replication*Treatment 12 0.37 1.50 1.63 21.65 29.32 Fertilizer 1 0.01 4.90 2.90* 0.14 12.01 Treatment*Fertilizer 4 0.39 2.04 0.34 23.44 28.17 Replication*Treatment *Fertilizer 15 0.34 2.30 0.59 14.57 24.58 Side 1 0.06 2.64 0.06 2.25 7.56 Treatment*Side 3 0.06 3.68 1.27 5.79 0.89 Fertilizer*Side 1 0.06 6.89 0.06 2.25 10.56 Treatment*Fertilizer *Side 3 0.06 1.76 0.10 2.20 3.39 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 178

159 Table D-8. 2005 ANOVA table fo r potato internal quality Type III Mean Squarez Source of Variation DF CRS HH IHN BC(l) Replication 3 3.40** 31.97 3.04 Treatment 4 0.29 286.35 5.17 Replication*Treatment 12 0.36 113.94 3.57 Fertilizer 1 0.92 1084.19* 0.73 Treatment*Fertilizer 4 0.13 178.72** 1.63 Replication*Treatment *Fertilizer 15 1.62 41.95 2.18 Side 1 1.00 110.25 0.39 Treatment*Side 3 2.12 317.29* 1.43 Fertilizer*Side 1 1.00 105.06 2.64 Treatment*Fertilizer *Side 3 0.12 272.18 1.93 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 179

160 APPENDIX E ADDITIONAL DATA AND ANO VA TABLES FOR SURFACE WATER NUTRIENT CONCENTRATION In this appendix are reported additional data and ANOVA tables for surface water nutrient concentrations in surface wells, lysi meters as well as regression equations for surface NO3-N runoff in 2004 and 2005. Each sample time is reported separately. The tables include wa ter nutrient concentrations of NO3-N, NH4N, P, K, and electrical conductivity.

PAGE 180

161Table E-1. Well NH4-N concentration (mg L-1) under varying staged leaching irrigation tr eatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005 2004 (DAP) 2005 (DAP) Main Effects 29 44 64 72 89 17 33 45 59 73 89 Datey (D) 0 WAP 2.3 1.1 0.2 0.2 0.3 2.0 0.4 bz 0.4 0.3 0.5 0.5 2 WAP 2.4 1.1 0.1 0.2 0.2 2.3 1.5 a 1.5 0.4 0.6 0.3 4 WAP 2.5 1.4 0.3 0.4 0.4 2.0 0.9 ab 1.4 0.4 0.5 1.0 8 WAP 1.8 1.3 0.4 0.3 0.3 2.1 1.0 a 0.8 0.6 0.6 0.6 12 WAP 1.6 1.4 0.2 0.2 0.4 2.0 0.6 ab 0.5 0.5 0.6 0.4 Fertilizerx (F) CRF 2.2 1.7 0.2 0.3 0.3 1.9 0.9 0.5 0.3 0.5 0.5 AN 2.0 0.9 0.3 0.2 0.3 2.3 0.8 0.8 0.6 0.6 0.6 Sidedress (S) 0.0 kg N ha-1 1.3 0.2 0.2 0.3 0.6 0.6 0.6 0.6 34.0 kg N ha-1 1.1 0.2 0.3 0.3 0.6 0.2 0.5 0.4

PAGE 181

162Table E-1. Continued 2004 (DAP) 2005 (DAP) 29 44 64 72 89 17 33 45 59 73 89 Interaction effectsw D*F ns ns ns ns ns ns ns ns ns ns ns D*S ns ns ns ns ns ns ns ns F*S ns ns ns ns ns ns ns ns D*S*F ns ns ns ns ns ns ns ns zMeans followed by a different letter within co lumns are significantly different at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 182

163Table E-2. Lysimeter NH4-N concentration (mg L-1) under varying staged leaching irrigati on treatments, fertilizer source and additional in Hastings, FL in 2004 and 2005 2004 (DAP) 2005 (DAP) Main Effects 30 45 65 73 90 18 34 45 60 73 89 Datey (D) 0 WAP 5.8 0.2 0.1 0.1 bz 0.1 6.3 1.6 c 1.4 b 0.1 0.4 0.0 2 WAP 5.6 1.2 0.1 0.1 b 0.2 19.5 8.4 a 6.1 a 0.2 0.6 0.0 4 WAP 0.2 0.1 0.1 b 0.2 13.2 3.3 b 2.2 b 0.5 0.5 0.0 8 WAP 0.1 0.1 0.4 a 0.2 11.6 1.9 c 1.7 b 0.2 0.8 0.0 12 WAP 0.2 0.1 0.2 ab 0.3 14.0 2.2 bc 1.7 b 0.2 0.8 0.0 Fertilizerx (F) CRF 6.8 0.2 0.1 0.2 0.2 12.6 2.5 1.9 0.2 0.7 0.0 AN 4.7 0.1 0.1 0.1 0.2 11.6 3.4 2.6 0.2 0.5 0.0 Sidedress (S) 0.0 kg N ha-1 0.1 0.1 0.2 0.2 1.2 0.3 0.6 0.0 34.0 kg N ha-1 0.2 0.1 0.1 0.2 0.6 0.2 0.6 0.0

PAGE 183

164Table E-2. Continued 2004 (DAP) 2005 (DAP) 30 45 65 73 90 18 34 45 60 73 89 Interaction effectsw D*F ns ns ns ns ns ns ns ns ns ns D*S ns ns ns ns ns ns ns ns F*S ns ns ns ns ns ns ns ns D*S*F ns ns ns ns ns ns ns ns zMeans followed by a different within columns letter are significantly different at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 184

165 Table E-3. 2004 ANOVA table for well water sample 29 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.33 0.69 0.29* 1134.85 3.49* Treatment 4 21.39 1.81 0.69** 1442.61 4.50* Replication*Treatment 12 1.33 1.16 0.07 852.26 0.87 Fertilizer 1 3.07 0.23 0.05 193.92 0.99 Treatment*Fertilizer 4 1.95 0.35 0.13 54.82 2.00 Replication*Treatment *Fertilizer 15 1.47 0.70 0.12 551.52 0.72 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 185

166 Table E-4. 2004 ANOVA table for well water sample 44 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.81 0.27 0.25 738.38 3.23* Treatment 4 16.63**1.03 0.69** 1009.75 3.99* Replication*Treatment 12 1.51 0.58 0.10 1094.02 0.93 Fertilizer 1 4.15 0.01 0.00 1217.28 0.26 Treatment*Fertilizer 4 1.89 0.02 0.11 206.05 1.42 Replication*Treatment *Fertilizer 15 1.60 0.21 0.13 592.14 0.70 Side 1 0.00 0.00 0.13 636.09 0.13 Treatment*Side 3 0.72 0.025 0.14 421.48 0.39 Fertilizer*Side 1 2.54 0.20 0.00 125.29 0.27 Treatment*Fertilizer *Side 3 3.60* 0.09 0.60 3580.70 0.83 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 186

167 Table E-5. 2004 ANOVA table for well water sample 60 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.81 0.57 0.25 0.13 3.23 Treatment 4 16.63**1.76 0.69* 0.26 3.99* Replication*Treatment 12 1.51 1.25 0.10 0.25 0.93 Fertilizer 1 4.15 0.00 0.00 0.37 0.26 Treatment*Fertilizer 4 1.89 0.40 0.11 0.08 1.42 Replication*Treatment *Fertilizer 15 1.60 0.71 0.13 0.11 0.70 Side 1 0.00 0.00 0.13 0.43 0.13 Treatment*Side 3 0.720 0.17 0.14 0.13 0.39 Fertilizer*Side 1 2.54 0.88 0.00 0.03 0.27 Treatment*Fertilizer *Side 3 3.60* 0.33 0.60 0.96* 0.83 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 187

168 Table E-6. 2004 ANOVA table for well water sample 72 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.69 4.31* 0.12 0.24 0.57** Treatment 4 1.45* 1.04 0.18 0.20 0.43* Replication*Treatment 12 0.22 1.18 0.24 0.08 0.09 Fertilizer 1 0.00 0.97 0.00 0.03 0.03 Treatment*Fertilizer 4 0.68 4.24 0.18 0.12 0.29 Replication*Treatment *Fertilizer 15 0.67 2.95 0.21 0.20 0.15 Side 1 0.69 0.04 0.02 0.13 0.16 Treatment*Side 3 0.33 0.10 0.22 0.04 0.00 Fertilizer*Side 1 0.89 1.49 0.29 0.50 0.61 Treatment*Fertilizer *Side 3 1.63 1.29 0.12 1.27 0.89 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 188

169 Table E-7. 2004 ANOVA table for well water sample 89 DAP Type III Mean Squarez Source of Variation DFNO3-NNH4N P K EC Replication 3 2.92* 10.50**3.10** 0.18 1.30** Treatment 4 0.56 0.99 0.05 0.12 0.14 Replication*Treatment 12 0.72 0.55 0.10 0.07 0.06 Fertilizer 1 7.71* 0.00 0.00 0.13 0.03 Treatment*Fertilizer 4 0.62 0.21 0.08 0.13 0.38 Replication*Treatment *Fertilizer 15 1.15* 0.70 0.15 0.20 0.29 Side 1 1.83 0.17 0.27 0.00 0.00 Treatment*Side 3 0.26 0.77 0.14 0.39 0.31 Fertilizer*Side 1 2.14 0.84 0.07 0.10 0.06 Treatment*Fertilizer *Side 3 0.21 2.13 0.33 0.82 0.88 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 189

170 Table E-8. 2005 ANOVA table for well water sample 17 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 1.22 1.78 1.32 Treatment 4 1.02 0.07 0.36 Replication*Treatment 12 0.61 0.95 0.20 Fertilizer 1 0.53 1.16 0.03 Treatment*Fertilizer 4 0.32 0.84 0.23 Replication*Treatment *Fertilizer 15 0.82 0.86 0.50 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 190

171 Table E-9. 2005 ANOVA table for well water sample 33 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.68 4.61* 0.84 Treatment 4 0.89 3.66* 0.38 Replication*Treatment12 0.30 0.89 0.39 Fertilizer 1 0.55 0.39 0.02 Treatment*Fertilizer 4 1.01 3.33* 0.02 Replication*Treatment *Fertilizer 15 0.79 1.88 0.23 Side 1 0.04 0.01 0.58 Treatment*Side 4 0.37 0.97 0.08 Fertilizer*Side 1 0.71 0.48 0.00 Treatment*Fertilizer *Side 4 0.88 0.86 0.59 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 191

172 Table E-10. 2005 ANOVA table for well water sample 45 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.33 9.29***1.00 Treatment 4 0.79 4.61** 0.51 Replication*Treatment12 0.43 1.61 0.33 Fertilizer 1 0.90 3.28 0.11 Treatment*Fertilizer 4 0.44 2.96* 0.09 Replication*Treatment *Fertilizer 15 0.33 1.53 0.23 Side 1 0.01 0.01 0.14 Treatment*Side 4 0.22 0.08 0.11 Fertilizer*Side 1 0.61 1.25 0.24 Treatment*Fertilizer *Side 4 0.53 0.32 0.68 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 192

173 Table E-11. 2005 ANOVA table for well water sample 59 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 3.95** 4.98* 0.04 Treatment 4 0.63 0.27 0.22 Replication*Treatment 12 0.70 1.55 0.25 Fertilizer 1 2.80 0.02 0.11 Treatment*Fertilizer 4 1.41 1.70 0.14 Replication*Treatment *Fertilizer 15 3.38***1.63 0.40 Side 1 0.03 4.57 0.16 Treatment*Side 4 0.32 0.20 0.06 Fertilizer*Side 1 0.25 2.48 0.00 Treatment*Fertilizer *Side 4 0.16 0.73 0.49 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 193

174 Table E-12. 2005 ANOVA table for well water sample 73 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.97 1.21 0.52 Treatment 4 0.86 0.15 0.39 Replication*Treatment 12 0.36 0.62 0.22 Fertilizer 1 3.83* 0.80 0.04 Treatment*Fertilizer 4 0.95 0.58 0.02 Replication*Treatment *Fertilizer 15 3.23***0.72 0.29 Side 1 0.04 0.04 0.09 Treatment*Side 4 0.42 0.17 0.02 Fertilizer*Side 1 0.90 0.00 0.92 Treatment*Fertilizer *Side 4 0.31 0.74 1.49* z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 194

175 Table E-13. 2005 ANOVA table for well water sample 89 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.94* 1.45 0.33 Treatment 4 0.27 0.74 0.41 Replication*Treatment12 0.61 1.20 0.14 Fertilizer 1 0.23 1.03 0.00 Treatment*Fertilizer 4 0.31 0.84 0.22 Replication*Treatment *Fertilizer 15 1.09** 0.82 0.47 Side 1 0.16 0.01 0.00 Treatment*Side 4 0.18 0.33 0.06 Fertilizer*Side 1 0.66 0.11 2.07* Treatment*Fertilizer *Side 4 2.92** 1.04 0.01 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 195

176 Table E-14. 2004 ANOVA table for lysimeter water sample 45 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 1741.48 1.15 4.85 0.15 10.67* Treatment 4 719.29 0.95 4.28 0.00 0.56 Replication*Treatment 12 991.13 2.23 3.09 0.04 0.21 Fertilizer 1 2377.45 1.86 0.00 0.03 0.18 Treatment*Fertilizer 4 613.84 3.50 0.83 0.01 1.50 Replication*Treatment *Fertilizer 13 3077.44* 1.95** 4.71 0.05 1.08* Side 1 4758.24 1.87* 3.07 0.08 0.30 Treatment*Side 2 1264.63 1.08 0.80 0.01 0.15 Fertilizer*Side 1 166.015 0.72 0.52 0.00 0.22 Treatment*Fertilizer *Side 2 3657.40 0.43 2.93 0.13 0.68 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 196

177 Table E-15. 2004 ANOVA table for lysimeter water sample 65 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 1.60 0.55 1.11 0.26 0.17 Treatment 4 0.85 0.85 1.67 0.07 4.88** Replication*Treatment 12 1.46 0.48 1.70 0.11 0.68 Fertilizer 1 0.45 0.20 1.180 0.61* 0.37 Treatment*Fertilizer 4 2.74* 0.58 1.89 0.08 2.22 Replication*Treatment *Fertilizer 13 0.87 0.39 2.91 0.12 0.77 Side 1 0.00 0.72 0.01 0.00 0.14 Treatment*Side 2 0.01 0.27 0.03 0.08 0.05 Fertilizer*Side 1 0.56 6.11** 1.63 0.10 0.10 Treatment*Fertilizer *Side 2 1.03 0.02 1.13 0.39 1.40 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 197

178 Table E-16. 2004 ANOVA table for lysimeter water sample 73 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.11 2.12 32.13**0.034 2.10 Treatment 4 0.85 4.29* 3.77 0.22 0.52 Replication*Treatment 12 0.47 1.11 2.57 0.09 0.70 Fertilizer 1 1.14 1.92 2.28 0.35 0.74 Treatment*Fertilizer 4 0.38 0.99 2.90 0.20 0.58 Replication*Treatment *Fertilizer 13 0.38 1.07 4.59* 0.21 1.11 Side 1 1.77 0.07 18.69**0.04 0.57 Treatment*Side 2 0.48 0.35 0.65 0.24 0.79 Fertilizer*Side 1 0.30 0.20 0.33 0.47 1.58 Treatment*Fertilizer *Side 2 0.49 2.29 2.38 0.17 0.92 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 198

179 Table E-17. 2004 ANOVA table for lysimeter water sample 90 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.81 0.57 0.25 738.38 3.23* Treatment 4 16.63** 1.76 0.69** 1009.75 3.99* Replication*Treatment 12 1.51 1.25* 0.10 1094.02 0.93 Fertilizer 1 4.15 0.00 0.00 1217.28 0.26 Treatment*Fertilizer 4 1.89 0.40 0.11 206.05 1.42 Replication*Treatment *Fertilizer 13 1.60 0.71 0.13 592.14 0.70 Side 1 0.00 0.00 0.13 636.09 0.13 Treatment*Side 2 0.72 0.17 0.14 421.48 0.39 Fertilizer*Side 1 2.54 0.88 0.00 125.29 0.27 Treatment*Fertilizer *Side 2 3.60* 0.33 0.60 3580.70 0.83 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 199

180 Table E-18. 2005 ANOVA table for lysimeter water sample 18 DAP Type III Mean Squarez Source of Variation DFNO3-N NH4N P K EC Replication 3 4.14** 9.63***0.31 Treatment 4 0.35 2.29* 0.52 Replication*Treatment 12 0.28 0.74 0.73 Fertilizer 1 6.59** 0.67 0.61 Treatment*Fertilizer 4 0.36 0.73 1.03 Replication*Treatment *Fertilizer 13 0.27 1.06 0.48 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 *** significant at Type I error<0.001

PAGE 200

181 Table E-19. 2005 ANOVA table for lysimeter water sample 34 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 1.34*** 7.22** 0.93 Treatment 4 0.28 6.56** 0.13 Replication*Treatment12 0.07 0.42 0.28 Fertilizer 1 1.46** 2.60 1.90* Treatment*Fertilizer 4 0.49* 2.03 0.35 Replication*Treatment *Fertilizer 13 0.16 0.98 0.58 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 201

182 Table E-20. 2005 ANOVA table for lysimeter water sample 45 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.22 10.16**0.58 Treatment 4 0.07 4.71 0.14 Replication*Treatment12 0.08 0.93 0.41 Fertilizer 1 1.58* 1.55 1.65 Treatment*Fertilizer 4 0.10 1.49 0.44 Replication*Treatment *Fertilizer 13 0.23 0.81 0.41 Side 1 0.09 1.44 0.05 Treatment*Side 2 0.00 0.07 0.60 Fertilizer*Side 1 0.04 0.48 0.00 Treatment*Fertilizer *Side 2 0.50 2.03 0.26 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 202

183 Table E-21. 2005 ANOVA table for lysimeter water sample 60 DAP Type III Mean Squarez Source of Variation DFNO3-N NH4N P K EC Replication 3 0.78 13.24**0.24 Treatment 4 3.63* 0.47 0.09 Replication*Treatment12 0.85 2.60 0.40 Fertilizer 1 5.49* 6.39 1.70* Treatment*Fertilizer 4 0.39 2.61 0.23 Replication*Treatment *Fertilizer 13 1.16 2.09 0.68 Side 1 0.28 5.27 0.02 Treatment*Side 2 0.00 2.22 0.23 Fertilizer*Side 1 1.43 0.14 0.00 Treatment*Fertilizer *Side 2 1.98 1.66 0.80 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 203

184 Table E-22. 2005 ANOVA table for lysimeter water sample 73 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 1.34 5.71***3.04*** Treatment 4 5.92* 1.27* 0.43 Replication*Treatment 12 0.57 0.46 0.87 Fertilizer 1 4.18 2.14* 1.98* Treatment*Fertilizer 4 0.80 0.11 0.46 Replication*Treatment *Fertilizer 13 1.10 0.51 0.80 Side 1 0.29 0.88 0.12 Treatment*Side 2 0.65 0.04 0.07 Fertilizer*Side 1 0.70 0.63 1.39 Treatment*Fertilizer *Side 2 2.32 0.90 0.34 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 204

185 Table E-23. 2005 ANOVA table for lysimeter water sample 89 DAP Type III Mean Squarez Source of Variation DF NO3-N NH4N P K EC Replication 3 0.11 0.16 0.24 Treatment 4 0.18 0.93 0.67* Replication*Treatment 12 0.62 1.20 0.46 Fertilizer 1 0.27 0.04 1.75* Treatment*Fertilizer 4 0.74 0.99 1.02 Replication*Treatment *Fertilizer 13 1.29 0.09 0.04 Side 1 0.05 0.66 2.43** Treatment*Side 2 0.00 0.75 0.53 Fertilizer*Side 1 0.16 0.00 0.49 Treatment*Fertilizer *Side 2 0.00 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 205

186 Table E-24. 2004 NO3-N concentration in surface water runoff (Figures 3.4-3.6) 2004 2 WAP Fertilize r source NO3-N Conc. Intercept Linear Quadratic Cubic Rep 1 AN NO3-N =1257.2690 5.9756*t + 0.5535*t2 0.0028*t3 Rep 1 CRF NO3-N = 881.7719 +1.7616*t + 0.3773*t2 0.0021*t3 Rep 2 AN NO3-N =1507.6540 2.4254*t + 0.6182*t2 0.0033*t3 Rep 2 CRF NO3-N = 748.9925 12.0316*t + 0.5366*t2 0.0026*t3 Rep 3 AN NO3-N = 919.5608 32.8086*t + 1.1328*t2 0.0052*t3 Rep 3 CRF NO3-N =1200.1280 25.3434*t + 0.5808*t2 0.0025*t3 Rep 4 AN NO3-N = 944.6789 36.4154*t + 0.8500*t2 0.0037*t3 Rep 4 CRF NO3-N = 550.9728 28.3725*t + 0.7326*t2 0.0032*t3 8 WAP Rep 1 AN NO3-N = 362.5155 +117.4689*t 1.1955*t2 + 0.0035*t3 Rep 1 CRF NO3-N =2209.9310 + 30.2345*t 0.4384*t2 + 0.0015*t3 Rep 2 AN NO3-N =1364.8200 + 73.7360*t 0.7496*t2 + 0.0024*t3 Rep 2 CRF NO3-N =2810006.9 +102.5645*t 1.1692*t2 + 0.0035*t3 Rep 3 AN NO3-N =1614040.6 +187.1749*t 2.0690*t2 + 0.0060*t3 Rep 3 CRF NO3-N = -8.9727 + 79.5071*t 0.7062*t2 + 0.0019*t3 Rep 4 AN NO3-N =2017.4450 + 56.2952*t 0.6288*t2 + 0.0019*t3 Rep 4 CRF NO3-N = 832.0742 + 54.8061*t 0.6290*t2 + 0.0020*t3 12 WAP Rep 1 AN NO3-N = 4753.4020 69.4826*t + 0.7071*t2 0.0024*t3 Rep 1 CRF NO3-N = 2043.1230 + 14.6515*t 0.1201*t2 + 0.0002*t3 Rep 2 AN NO3-N = 3709.1410 + 7.0360*t 0.2137*t2 + 0.0008*t3 Rep 2 CRF NO3-N = 3163.8050 12.0354*t + 0.0129*t2 + 0.0000*t3 Rep 3 AN NO3-N =-10912.7600 +425.4301*t 3.7789*t2 + 0.0106*t3 Rep 3 CRF NO3-N = 3710.6010 22.5319*t + 0.2206*t2 0.0008*t3 Rep 4 AN NO3-N = 6152.6640 87.7657*t + 0.7504*t2 0.0019*t3 Rep 4 CRF NO3-N = 3135.3690 60.0477*t + 0.6820*t2 0.0021*t3

PAGE 206

187 Table E-25. 2005 NO3-N concentration in surfa ce runoff (Figures 3.7-3.10) 2005 2 WAP Fertilizer source NO3-N Conc. Intercept Linear Quadratic Cubic Rep 1 AN NO3-N =629.0319 4.1902*t + 0.5733*t2 0.0028*t3 Rep 1 CRF NO3-N =441.6106 + 1.4065*t + 0.1690*t2 0.0009*t3 Rep 2 AN NO3-N =586.369 + 51.3664*t 0.0595*t2 0.0010*t3 Rep 2 CRF NO3-N =454.3027 + 1.8442*t + 0.1989*t2 0.0010*t3 Rep 3 AN NO3-N =905.4893 + 47.8330*t 0.0834*t2 0.0008*t3 Rep 3 CRF NO3-N =202.4595 2.6875*t + 0.3177*t2 0.0015*t3 Rep 4 AN NO3-N =949.1000 + 4.4425*t + 0.4574*t2 0.0025*t3 Rep 4 CRF NO3-N =260.8549 + 19.0567*t + 0.1400*t2 0.0012*t3 4 WAP Rep 1 AN NO3-N =2164.3520 25.3937*t + 0.8207*t2 0.0044*t3 Rep 1 CRF NO3-N = 258.0521 + 3.6491*t + 0.5734*t2 0.0036*t3 Rep 2 AN NO3-N =4647.8880 42.1462*t + 0.7983*t2 0.0042*t3 Rep 2 CRF NO3-N =1601.3040 + 4.1128*t + 0.6093*t2 0.0041*t3 Rep 3 AN NO3-N =3555.8490 23.4154*t 1 1.0305*t2 0.0061*t3 Rep 3 CRF NO3-N =3325.5890 10.2819*t + 0.4723*t2 0.0031*t3 Rep 4 AN NO3-N =3993.9000 14.7692*t + 0.6681*t2 0.0043*t3 Rep 4 CRF NO3-N =2376.4190 + 38.7546*t + 0.0210*t2 0.0020*t3 8 WAP Rep 1 AN NO3-N =1973.5780 + 16.4043*t + 1.2525*t2 0.0067*t3 Rep 1 CRF NO3-N = 923.6566 + 19.9737*t + 0.2075*t2 0.0015*t3 Rep 2 AN NO3-N =2071.8450 + 143.2060*t + 0.0084*t2 0.0036*t3 Rep 2 CRF NO3-N =1666.8170 + 23.7082*t + 0.1669*t2 0.0015*t3 Rep 3 AN NO3-N =3316.2380 + 15.9283*t + 1.2506*t2 0.0067*t3 Rep 3 CRF NO3-N =2440.5110 60.3510*t + 1.0669*t2 0.0040*t3 Rep 4 AN NO3-N =1585.3940 + 3.9408*t + 1.3436*t2 0.0068*t3 Rep 4 CRF NO3-N = 889.6320 + 23.6046*t + 0.2521*t2 0.0018*t3 12 WAP Rep 1 AN NO3-N = 22.0378 + 143.3538*t 3.3031*t2 + 0.0192*t3 Rep 1 CRF NO3-N = -75.5371 + 37.5613*t 1.0098*t2 + 0.0069*t3 Rep 2 AN NO3-N = 79.4959 + 23.2340*t 0.5233*t2 + 0.0029*t3 Rep 2 CRF NO3-N = 25.7384 + 11.5464*t 0.2624*t2 + 0.0014*t3 Rep 3 AN NO3-N =244.3768 + 68.7815*t 1.4406*t2 + 0.0071*t3 Rep 3 CRF NO3-N =228.4069 + 17.5211*t 0.7683*t2 + 0.0071*t3 Rep 4 AN NO3-N = 76.9183 + 51.4944*t 0.9448*t2 + 0.0038*t3 Rep 4 CRF NO3-N = 75.0206 4.6057*t + 0.3283*t2 0.0036*t3

PAGE 207

188 APPENDIX F ADDITIONAL DATA AND A NOVA TABLES FOR TISSUE NUTRIENT CONCENTRATION AND FUE FOR IRRIGATION STUDY In this appendix are reported additional data tables and ANOVA tables for tissue nutrient concentrations in leaf samples, full flower haulm, tuber Ca++ and tuber TKN nutrient concentration at harvest and FUE in 2004 and 2005.

PAGE 208

189 Table F-1. Leaf Ca++ (%) under varying staged leach ing irrigation treatments, fertilizer source and additional side dress in Hastings, FL in 2004 and 2005 2004 (DAP) 2005 (DAP) Main Effects 36 51 67 41 74 Datey (D) 0 WAP 0.8 bz 1.0 1.6 b 0.5 b 1.3 b 2 WAP 1.0 a 1.0 1.5 b 0.6 a 1.3 b 4 WAP 0.8 b 1.0 1.6 b 0.6 ab 1.4 ab 8 WAP 0.8 b 1.1 1.9 a 0.5 b 1.5 a 12 WAP 0.8 b 1.1 1.6 b 0.5 ab 1.4 b Fertilizerx (F) CRF 0.9 1.1 1.7 a 0.6 1.4 AN 0.8 1.0 1.6 b 0.6 1.4 Sidedress (S) 0.0 kg N ha-1 1.0 1.7 1.3 34.0 kg N ha-1 1.1 1.6 1.4 Interaction effectsw D*F ns ns ns ns ns D*S ns ns ns F*S ns ns ns D*S*F ns ns ns zMeans followed by a different letter within columns and main effects are significantly different at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 209

190 Table F-2. Leaf TKN (%) under varying staged leaching irrigation treatments, fertilizer source and additional side dress in Hastings, FL in 2004 and 2005 2004 (DAP) 2005 (DAP) Main Effects 36 51 67 41 74 Datey (D) 0 WAP 5.2 az 4.6 3.8 5.5 4.3 2 WAP 5.0 ab 4.9 3.7 5.3 4.4 4 WAP 5.0 ab 4.7 3.7 5.1 4.3 8 WAP 5.1 a 4.5 3.9 5.2 4.2 12 WAP 4.8 b 4.6 3.7 5.3 4.3 Fertilizerx (F) CRF 5.1 4.6 b 3.7 b 5.2 4.2 b AN 4.9 4.8 a 3.8 a 5.4 4.4 a Sidedress (S) 0.0 kg N ha-1 4.9 3.8 4.3 34.0 kg N ha-1 4.6 3.7 4.3 Interaction effectsw D*F ns ns ns ns D*S ns ns ns F*S ns ns ns D*S*F ns ns ns zMeans followed by a different lette r are significantly different within columns at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 210

191 Table F-3. Full flower (haulm) nutrient uptake (kg ha-1) under varying staged leaching irrigation treatments, fertili zer source and additional sidedress in Hastings, FL in 2004 and 2005 2004 2005 Main Effects K P Ca TKN Ca TKN Datey (D) 0 WAP 50.1 1.5 22.1 24.1 14.1 60.3 2 WAP 65.1 1.9 27.1 30.0 15.8 55.6 4 WAP 52.7 1.7 24.7 25.6 16.4 60.4 8 WAP 65.5 1.9 30.2 31.8 13.6 53.3 12 WAP 54.3 1.7 23.9 26.2 14.5 57.3 Fertilizerx (F) CRF 53.4 1.6 b 24.4 24.7 b 17.2 a 59.7 AN 60.9 1.9 a 26.3 30.2 a 12.6 b 55.0 Sidedress (S) 0.0 kg N ha-1 54.9 1.6 23.4 26.3 14.6 58.3 34.0 kg N ha-1 58.6 1.8 26.7 28.0 15.0 56.7 Interaction effectsw D*F * ns ns ns ns D*S ns ns ns ns ns ns F*S ns ns ns ns ns ns D*S*F ns ns ns ns ns ns zMeans followed by a different letter within columns are significantly different at the p 0.05 using Tukeys stud entized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 211

192 Table F-4. Tuber nutrient uptake (kg ha -1) at harvest under varying staged leaching irrigation treatments, fertili zer source and additional sidedress in Hastings, FL in 2004 and 2005 2004 2005 Main Effects K P Ca TKN Ca TKN Datey (D) 0 WAP 142.8 ab 11.7 az 1.5 ab 97.0 ab 1.2 75.6 2 WAP 133.4 ac 11.5 ab 1.5 ab 94.7 ab 1.1 70.5 4 WAP 154.2 a 12.8 a 1.7 a 110.3 a 0.9 65.6 8 WAP 117.5 c 9.3 c 1.3 b 92.5 b 1.1 73.4 12 WAP 128.8 bc 9.7 bc 1.6 ab 92.3 b 1.1 70.1 Fertilizerx (F) CRF 135.4 11.1 1.5 97.4 1.1 71.3 AN 135.0 10.8 1.5 96.9 1.0 70.7 Sidedress (S) 0.0 kg N ha-1 137.6 11.4 1.5 101.0 1.1 72.8 34.0 kg N ha-1 133.6 10.6 1.5 94.7 1.0 69.8 Interaction effectsw D*F ns ns ns ns ns ns D*S ns ns ns ns ns ns F*S ns ns ns ns ns ns D*S*F ns ns ns ns ns ns zMeans followed by a different letter within co lumns are significantl y different at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 212

193 Table F-5. Fertilizer use efficiency (%) of total fertilizer applied under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005 2004 2005 Main Effects Ca TKN Ca TKN Datey (D) 0 WAP 14.7 64.4 abz 7.4 66.3 2 WAP 13.4 61.2 bc 8.1 61.8 4 WAP 14.7 68.2 a 8.4 62.4 8 WAP 12.2 56.8 c 7.1 62.1 12 WAP 12.4 55.2 c 7.5 62.4 Fertilizerx (F) CRF 15.0 a 66.8 a 9.4 a 68.7 a AN 12.0 b 54.9 b 6.1 b 57.2 b Sidedress (S) 0.0 kg N ha-1 13.0 63.1 7.6 64.8 34.0 kg N ha-1 13.8 60.0 7.8 61.8 Interaction effectsw D*F ns ** ns ns D*S ns ns ns ns F*S ns ns ns ns D*S*F ns ns ns ns zMeans followed by a different letter within columns are significantly different at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 213

194Table F-6. SPAD leaf chlorophyll va lues under varying staged leaching irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and 2005 2004 (DAP) 2005 (DAP) Main Effects 42 60 73 85 38 51 68 84 Datey (D) 0 WAP 43.4 43.6 bcz 52.9 33.3 47.4 a 77.0 47.1 36.4 2 WAP 43.3 45.1 a 36.1 36.4 43.2 c 50.1 48.3 37.6 4 WAP 43.0 43.4 bc 34.9 34.9 42.9 c 50.2 48.4 37.3 8 WAP 42.3 42.4 c 45.0 b 50.3 46.5 37.1 12 WAP 42.2 43.9 b 34.6 34.6 44.9 b 50.6 46.7 37.8 Fertilizerx (F) CRF 41.9 b 42.4 b 46.7 34.6 47.1 a 59.8 46.6 b 36.1 b AN 43.8 a 44.9 a 34.9 35.0 42.2 b 51.5 48.2 a 38.3 a Sidedress (S) 0.0 kg N ha-1 43.6 34.0 34.2 50.2 469 36.7 b 34.0 kg N ha-1 43.7 48.8 35.7 69.1 48.2 37.9 a

PAGE 214

195Table F-6. Continued 2004 2005 42 60 73 85 38 51 68 84 Interaction effectsw D*F ns ns ns ns ns ns ns ns D*S ns ns ns ns ns ns ns ns F*S ns ns ns ns ns ns ns ns D*S*F ns ns ns ns ns ns ns ns zMeans followed by a different letter within co lumns are significantly different at the p 0.05 using Tukeys studentized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 215

196 Table F-7. 2004 ANOVA table for leaf tissue 36 DAP Type III Mean Squarez Source of Variation DF P K Ca TKN Replication 3 0.02** 0.01 0.02 0.01* Treatment 4 0.00 0.00 0.09** 0.01 Replication*Treatment 12 0.00 0.00 0.00 0.00 Fert 1 0.01 0.00 0.01 0.02 Treatment*Fertilizer 4 0.00 0.00* 0.00 0.00 Replication*Treatment *Fertilizer 15 0.00 0.00 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 216

197 Table F-8. 2004 ANOVA table for leaf tissue 51 DAP Type III Mean Squarez Source of Variation DF P K Ca TKN Replication 3 0.14** 0.02* 0.06** 0.05** Treatment 4 0.00 0.00 0.00 0.00 Replication*Treatment 12 0.00 0.00 0.00 0.00** Fertilizer 1 0.01 0.10** 0.00 0.04** Treatment*Fertilizer 4 0.01 0.00 0.01 0.00 Replication*Treatment *Fertilizer 15 0.01** 0.00 0.01 0.00 Side 1 0.00 0.00 0.00 0.01* Treatment*Side 2 0.00 0.00 0.00 0.00 Fertilizer*Side 1 0.00 0.00 0.00 0.00 Treatment*Fertilizer *Side 2 0.00 0.01 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 217

198 Table F-9. 2004 ANOVA table for leaf tissue 67 DAP Type III Mean Squarez Source of Variation DF P K Ca TKN Replication 3 0.04** 0.05** 0.09** 0.05** Treatment 4 0.01** 0.02** 0.12** 0.00 Replication*Treatment 12 0.00 0.00 0.01 0.00 Fertilizer 1 0.00 0.10** 0.09** 0.02* Treatment*Fertilizer 4 0.00 0.00 0.00 0.01* Replication*Treatment *Fertilizer 15 0.00 0.00 0.00 0.00 Side 1 0.00 0.00 0.02 0.00 Treatment*Side 2 0.00 0.00 0.00 0.00 Fertilizer*Side 1 0.00 0.00 0.00 0.00 Treatment*Fertilizer *Side 2 0.00 0.01 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 218

199 Table F-10. 2004 ANOVA table for full flower haulm Type III Mean Squarez Source of Variation DF P K Ca TKN Replication 3 0.17 0.02 0.20 8.70 Treatment 4 0.17 0.22 0.22 249.61 Replication*Treatment 12 0.12 0.15 0.12 128.44 Fertilizer 1 0.72* 0.44 0.32 873.39* Treatment*Fertilizer 4 0.52* 0.56* 0.38 367.30 Replication*Treatment *Fertilizer 15 0.14 0.15 0.19 172.02 Side 1 0.36 0.13 0.52 175.88 Treatment*Side 3 0.07 0.15 0.11 24.82 Fertilizer*Side 1 0.00 0.12 0.00 5.144 Treatment*Fertilizer *Side 3 0.13 0.10 0.15 227.23 z*Significant at Type I error<0.05

PAGE 219

200 Table F-11. 2004 ANOVA table for tuber tissue at harvest Type III Mean Squarez Source of Variation DF P K Ca TKN Replication 3 0.19** 0.12* 0.11 0.19** Treatment 4 0.26** 0.16** 0.19* 0.08* Replication*Treatment 12 0.02 0.02 0.04 0.02 Fertilizer 1 0.01 0.00 0.00 0.00 Treatment*Fertilizer 4 0.02 0.03 0.05 0.03 Replication*Treatment *Fertilizer 15 0.02 0.04 0.07 0.04 Side 1 0.01 0.00 0.08 0.04 Treatment*Side 3 0.00 0.01 0.01 0.00 Fertilizer*Side 1 0.01 0.02 0.22 0.00 Treatment*Fertilizer *Side 3 0.12 0.09 0.11 0.02 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 220

201 Table F-12. 2005 ANOVA table for leaf tissue 41 DAP Type III Mean Squarez Source of Variation DF Ca TKN P K Replication 3 0.11** 0.00 Treatment 4 0.09** 0.00 Replication*Treatment 12 0.01 0.00 Fertilizer 1 0.04 0.01* Treatment*Fertilizer 4 0.00 0.00 Replication*Treatment *Fertilizer 15 0.02 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 221

202 Table F-13. 2005 ANOVA table for leaf tissue 74 DAP Type III Mean Squarez Source of Variation DF Ca TKN P K Replication 3 0.00 0.01*** Treatment 4 0.02* 0.00 Replication*Treatment 12 0.00 0.00 Fertilizer 1 0.00 0.03*** Treatment*Fertilizer 4 0.01* 0.00 Replication*Treatment *Fertilizer 15 0.01 0.00 Side 1 0.02 0.00 Treatment*Side 3 0.00 0.00 Fertilizer*Side 1 0.00 0.00 Treatment*Fertilizer *Side 3 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error < 0.001

PAGE 222

203 Table F-14. 2005 ANOVA table fo r full flower haulm tissue Type III Mean Squaresz Source of Variation DF Ca TKN P K Replication 3 0.14*** 0.00 Treatment 4 0.08*** 0.00 Replication*Treatment 12 0.00 0.00 Fertilizer 1 0.70*** 0.01* Treatment*Fertilizer 4 0.00 0.00 Replication*Treatment*F ertilizer 15 0.01* 0.00 Side 1 0.07*** 0.00 Treatment*Side 3 0.01 0.00 Fertilizer*Side 1 0.00 0.00 Treatment*Fertilizer *Side 3 0.00 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error< 0.001

PAGE 223

204 Table F-15. 2005 ANOVA table for nutrient tuber tissue Type III Mean Squarez Source of Variation DF Ca TKN P K Replication 3 0.10 1.88* Treatment 4 0.03 0.78 Replication*Treatment 12 0.04 0.20 Fertilizer 1 0.04 0.04 Treatment*Fertilizer 4 0.02 0.78 Replication*Treatment*F ertilizer 15 0.01 0.67 Side 1 0.00 0.56 Treatment*Side 3 0.03 0.04 Fertilizer*Side 1 0.00 0.80 Treatment*Fertilizer *Side 3 0.00 1.02 z*Significant at Type I error<0.05

PAGE 224

205 Table F-16. 2004 ANOVA table for FUE Type III Mean Squarez Source of Variation DF P K Ca TKN Replication 3 0.18** 0.16** 0.63* 0.19** Treatment 4 0.23** 0.22** 0.20 0.08 Replication*Treatment 12 0.02 0.02 0.11 0.02 Fertilizer 1 0.48** 0.35** 1.37** 0.32** Treatment*Fertilizer 4 0.02 0.01 0.04 0.03 Replication*Treatment*F ertilizer 15 0.02 0.02 0.07 0.02 Side 1 0.00 0.00 0.06 0.01 Treatment*Side 3 0.01 0.03 0.17 0.01 Fertilizer*Side 1 0.00 0.00 0.00 0.00 Treatment*Fertilizer *Side 3 0.07 0.01 0.15 0.00 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 225

206 Table F-17. 2005 ANOVA table for FUE Type III Mean Squarez Source of Variation DF Ca TKN P K Replication 3 0.01*** 0.06* Treatment 4 0.00 0.00 Replication*Treatment 12 0.00 0.01 Fertilizer 1 0.07*** 0.28*** Treatment*Fertilizer 4 0.00 0.01 Replication*Treatment*F ertilizer 15 0.00 0.01 Side 1 0.00 0.01 Treatment*Side 3 0.00 0.00 Fertilizer*Side 1 0.00 0.01 Treatment*Fertilizer *Side 3 0.00 0.01 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error< 0.001

PAGE 226

207 Table F-18. 2004 ANOVA tabl e for SPAD 2004 and 2005 Type III Mean Squarez Source of Variation DF 2004 2005 Replication 3 16.37 11.83 Treatment 8 29.47* 10.09 Replication*Treatment 24 9.34 4.59 Fertilizer 1 136.71* 14.52 Treatment*Fertilizer 8 13.88 3.48 Replication*Treatment*F ertilizer 27 19.52** 4.93 Time 3 1441.04** 2403.60** Treatment*Time 20 9.13 13.43* z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 227

208 208 APPENDIX G ADDITIONAL DATA AND ANOVA TA BLES FOR SOIL NUTRIENT CONCENTRATION In this appendix are reported additional data tables and ANOVA tables for soil nutrient concentrations at post harvest a nd pre/post irrigation events. The data tables include soil nutrient concen trations at post harvest of Ca, NO3-N and NH4N. The ANOVA tables include soil nutrient concentrations at post harvest of P, K, Ca, Mg, NO3-N, NH4N, EC, pH, and OM.

PAGE 228

209 Table G-1. Post harvest soil nutrient concentration Ca, NH4-N, and NO3-N (mg kg -1) under varying staged leaching irrigati on treatments, fertilizer source and additional sidedress in Ha stings, FL in 2004 and 2005 2004 2005 Main Effects Ca NH4-NNO3-N Ca NH4-N NO3-N Datey (D) 0 WAP 503.0 9.6 9.9 326.3 1.6 1.6 bz 2 WAP 517.5 8.8 10.5 326.1 1.3 1.7 b 4 WAP 476.1 10.2 9.2 293.3 1.3 1.7 b 8 WAP 471.6 8.2 9.7 306.2 1.3 2.6 ab 12 WAP 484.5 7.9 6.5 296.6 1.5 3.4 a Fertilizerx (F) CRF 498.5 9.0 9.6 319.2 1.8 a 2.8 a AN 482.2 8.8 8.5 299.9 1.1 b 1.6 b Sidedress (S) 0.0 kg N ha-1 488.1 10.1 a 11.2 a 305.3 1.4 1.8 34.0 kg N ha-1 491.7 8.2 b 7.8 b 312.2 1.5 2.4 Interaction effectsw D*F ns ns ns ns ns ns D*S ns ns ns ns ns F*S ns ns ns ns ns ns D*S*F ns ns ns ns ns ns zMeans followed by a different letter within columns are significantly different at the p 0.05 using Tukeys student ized range test. yWAP = weeks after planting. xCRF = controlled release ferti lizer, AN = ammonium nitrate. wns, *, **, *** non-significant or significant at p 0.05, 0.01, 0.001, respectively using ANOVA.

PAGE 229

210 210Table G-2. 2004 ANOVA table for post harv est soil nutrient concentration 106 DAP Type III Mean Squarez Source DFP C M NH4N NO3-N EC pH OM Replication 3 0.18** 0.04* 0.17** 0.70** 0.21 0.96** 0.76** 0.01 Treatment 4 0.00 0.02 0.05 0.12 0.24 0.05** 0.00 0.04 Replication*Treatment12 0.00 0.00 0.02 0.07 0.08 0.00 0.05 0.017 Fertilizer 1 0.00 0.02 0.04 0.00 0.32 0.03 0.01 0.00 Treatment*Fertilizer 4 0.00 0.00 0.00 0.08 0.13 0.11 0.11 0.02 Replication*Treatment *Fertilizer 15 0.01 0.00 0.02 0.07 0.14 0.07 0.08 0.01 Side 1 0.01 0.00 0.03 0.55 1.07 0.00 0.00 0.01 Treatment*Side 3 0.03 0.01 0.02 0.22 0.04 0.11 0.08 0.01 Fertilizer*Side 1 0.00 0.00 0.00 0.14 0.00 0.01 0.01 0.00 Treatment*Fertilizer *Side 3 0.02 0.01 0.07 0.09 0.03 0.05 0.00 0.01 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01

PAGE 230

211 211Table G-3 2005 NOVA table for post harves t soil nutrient con centration 106 DAP Type III Mean Squarez Source DF Ca NH4N NO3-N pH Ec Replication 3 0.28*** 0.07 0.18 0.77*** 0.04** Treatment 4 0.04** 0.14 1.32*** 0.06 0.01 Replication*Treatment 12 0.00 0.17 0.19 0.01 0.00 Fertilizer 1 0.06** 4.74*** 5.65*** 0.06 0.02 Treatment*Fertilizer 4 0.04** 0.18 0.15 0.04 0.00 Replication*Treatment *Fertilizer 15 0.07*** 0.26 0.16 0.08** 0.00 Side 1 0.03 0.04 0.11 0.20** 0.00 Treatment*Side 3 0.01 0.34 0.17 0.00 0.02 Fertilizer*Side 1 0.00 0.14 0.02 0.01 0.00 Treatment*Fertilizer *Side 3 0.01 0.22 0.09 0.00 0.01 z*Significant at Type I error<0.05 **Significant at Type I error < 0.01 ***Significant at Type I error<0.001

PAGE 231

212 Table G-4. 2004 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 2 WAP Equality of Variances Variable Method Numerator DF Denominator DF F Value Pr>F P Folded F 3 3 5.36 0.2016 K Folded F 3 3 12.77 0.0650 Ca Folded F 3 3 4.00 0.2850 Mg Folded F 3 3 2.09 0.5596 EC Folded F 3 3 13.89 0.0579 pH Folded F 3 3 2.84 0.4145 NH4N Folded F 3 3 1.95 0.5976 NO3-N Folded F 3 3 1.62 0.7009 OM Folded F 3 3 10.21 0.0880

PAGE 232

213 Table G-5. 2004 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 8 WAP Equality of Variances Variable Method Numerator DF Denominator DF F Value Pr>F P Folded F 3 3 3.80 0.3017 K Folded F 3 3 6.45 0.1601 Ca Folded F 3 3 1.04 0.9767 Mg Folded F 3 3 1.42 0.7802 EC Folded F 3 3 6.23 0.1673 pH Folded F 3 3 6.81 0.1493 NH4N Folded F 3 3 2.07 0.5648 NO3-N Folded F 3 3 2.04 0.5740 OM Folded F 3 3 2.23 0.5268

PAGE 233

214 Table G-6. 2004 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 12 WAP Equality of Variances Variable Method Numerator DF Denominator DF F Value Pr>F P Folded F 3 3 10.06 0.0897 K Folded F 3 3 1.30 0.8336 Ca Folded F 3 3 4.38 0.2565 Mg Folded F 3 3 2.70 0.4358 EC Folded F 3 3 1.52 0.7392 pH Folded F 3 3 10.55 0.0843 NH4N Folded F 3 3 1.91 0.6073 NO3N Folded F 3 3 2.26 0.5205 OM Folded F 3 3 1.34 0.8142

PAGE 234

215 Table G-7. 2005 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 2 WAP Equality of Variances Variable Method Numerator DF Denominator DF F Value Pr>F P Folded F 3 3 2.28 0.5167 K Folded F 3 3 4.65 0.2388 Ca Folded F 3 3 2.02 0.5780 Mg Folded F 3 3 1.06 0.9617 NH4N Folded F 3 3 5.09 0.2144 NO3-N Folded F 3 3 7.43 0.1336

PAGE 235

216 Table G-8. 2005 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 4 WAP Equality of Variances Variable Method Numerator DF Denominator DF F Value Pr>F P Folded F 3 3 2.78 0.4239 K Folded F 3 3 50.90 0.0090 Ca Folded F 3 3 2.15 0.5466 Mg Folded F 3 3 1.25 0.8574 NH4N Folded F 3 3 2.45 0.4804 NO3-N Folded F 3 3 7.47 0.1328

PAGE 236

217 Table G-9. 2005 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 8 WAP Equality of Variances Variable Method Numerator DF Denominator DF F Value Pr>F P Folded F 3 3 6.20 0.1684 K Folded F 3 3 1.42 0.7809 Ca Folded F 3 3 1.72 0.6662 Mg Folded F 3 3 1.37 0.8014 NH4N Folded F 3 3 3.63 0.3181 NO3-N Folded F 3 3 3.77 0.3048

PAGE 237

218 Table G-10. 2005 Equality of variances for pre-post soil nutrient concentration at irrigation treatment 12 WAP Equality of Variances Variable Method Numerator DF Denominator DF F Value Pr > F P Folded F 3 3 2.64 0.4457 K Folded F 3 3 1.95 0.5959 Ca Folded F 3 3 1.15 0.9127 Mg Folded F 3 3 1.88 0.6161 NH4N Folded F 3 3 415.17 0.0004 NO3-N Folded F 3 3 2.62 0.4492

PAGE 238

219 LIST OF REFERENCES Bailey, G.W., and T.E. Wadell. 1979. Best management practices for agriculture and silviculture: An integrated overview. p. 33-56. In R.C. Loehr et al. (ed.) Best management practices for agriculture and silviculture. Scie nce Publishers, Ann Arbor, MI. Beltsville Agricultural Research Center. 2004. Vegetable lab ne ws. ww.barc.usda.gov. (last accessed Apr. 2005). Burton, W.G. 1989a. The origin and spread of the potato pp 1-34. In The Potato 3rd (ed.) New York: John Wiley & Sons. 1989. Burton, W. G. 1989b. Specific gravity as a gui de to the content of dry matter and of starch in potato tubers, p. 599-601. In : W. G. Burton, 3rd (ed.), The Potato. John Wiley and Sons, Inc., New York. Burton, W. G. 1989c. Yield and co ntent of dry matter:1. pp. 85-155. In : W. G. Burton, 3rd (ed.), The Potato. John Wile y and Sons, Inc., New York. Cantwell, M. 1996. A review of importa nt facts about potato glycoalkaloids. Perishables handling newsle tter. August 87:26-27. Clough, G.H. 1994. Potato tuber yield, minera l concentration and quality after calcium fertilization. J. Amer. So c. of Hort. Sci. 119:175-179. Dufault, R. J. 1997. Determining heat unit requirements for broccoli harvest in coastal South Carolina. J. Amer. Soc. Hort. Sci. 122(2):169-174. Elkashif, M.E., and S.J. Locascio. 1983. Is obutylidene diurea and su lfur-coated urea as N sources for potatoes. J. of Amer. Soc. of Hort. Sci. 108(4):523-526. Environmental Protection Agency. Non-point source pollution: The nations largest water quality problem. Po inter No. 1. Website: www.epa.gov (last accessed 02/15/06). Errebhi, M., C. J. Rosen, S. C. Gupta, and D. E. Birong. 1998. Potato yield response and nitrate leaching as influenced by nitr ogen management. Agron. J. 90 (1) 10-15 Jan/Feb. Folsom, D. 1945. Potato varieties: The newly named, the commercial, and some that are useful in breeding. Amer. Potato J. 22:229-242.

PAGE 239

220 Gunter, C., S. Ozgen, B. Karlsson and J. P. Paltoa. 2000. Calcium application at preemergence and during bulking may improve tuber quality and grade. HortSci. 35:498. Hawkins, A. 1967. From Lake Titicaca to New England The trail of the Irish potato to its new national monument. Amer. Potato J. 44:224-226. Henninger, M.R., S. B. Sterrett and K. G. Haynes. 2000. Broad-sense heritability and stability of internal heat n ecrosis and specific gravity in tetraploid potatoes. Crop Sci. 40:977-984. Hensel, D. R. 1964. Irrigation of potatoes at Hastings, Florida. Soil and Crop Sci. Soc. of Florida. 24: 105-110. Hochmuth, G., E. Hanlon, G. Kidder, D. Hensel W. Tilton, J. Dilbeck, and D. Schrader. 1993. Fertilization demonstrations for the Tri-County potato production area of Northeast Florida. Proceedings of the Fl orida State Horticultu ral Society. 106: 190-198. Hochmuth G., E. Hanlon, B. Hochmuth, G. Kidde r, and D. Hensel. 1993. Field fertility research with P and K for vegetables interpretations and recommendations. Soil Crop Science Society Florida Proceedings 52:95-101. Hoover, M. W. 1955. Some effects of temp erature upon the growth of southern peas. Proc. Amer. Soc. Hort. Sci. 668:308-314. Hutchinson, C.M., J.M. White, and D.P. Weinga rtner. 2002. Chip potato varieties for commercial production in Northeast Flor ida. EDIS, Florida Cooperative Extension Service Publication HS878. http://edis.ifas.ufl.edu/cv280 (last accessed 01/02/06). Hutchinson, C. M., W. A. Tilton, P. K. Li vingston-Way, and G. J. Hochmuth. 2002. Best management practices for potato pr oduction in Northeast Florida. EDIS, Florida Cooperative Extension Servi ce Publication HS877. Last accessed 01/02/06. Hutchinson C. M., and E. H. Simonne. 2003. Controlled-release fertilizer opportunities and costs for potato producti on in Florida. EDIS, Florida Cooperative Extension Service Publication HS-941. Hutchinson, C. M., E. H. Simonne, G. J. Hoch muth, D. N. Maynard, W.M. Stall, T. A. Kucharek, Se. E. Webb, T. G. Taylor, and S. A. Smith. 2004. Potato production in Florida, p. 259-272. In: Vegeta ble production handbook for Florida. Hutchinson, C. M. 2005. Influence of a contro lled release nitrogen fe rtilizer program on potato (Solanum tuberosum L.) on tuber yi eld and quality. ActaHort. 684:99-102.

PAGE 240

221 Iritani, W. M., L. D. Weller, and N. R. Know les. 1984. Factors influencing incidence of internal brown spot in Russet Burba nk potatoes. Amer. Potato J. 61:335-343 Lee, G. S., S. B. Sterrett, and M. R. Henni nger. 1992. A heat-sum model to determine yield and onset of internal heat necrosis for Atlantic potato. Amer. Potato J. 69:353-362. Larson, R. H., and A. R. Albert. 1949. Re lation of potato varie ties to incidence of physiological internal tuber necrosis. Amer. Potato J. 26:427-431. Lu, Hsiu-Ying, Chun-Tang Lu, Lit-Fu Chan, and Meng-Li Wei. 2001. Seasonal variation in linear increase of taro harvest index explained by growing degree days. Agron. J. 93:1136-1141. Maynard, D. N., and O. A. Lorenz. 1979. Cont rolled-release fertilizers for horticultural crops. Horticultural Reviews. 1:79-140. Mengel, K. and E. A. Kirkby. 1987. Calcium. In Mendel and Kirbys(4th ed). Principles of Plant Nutrition (pp 455-480) International Potash In stitute. Bern, Switzerland Munoz, F. 2004. Improving nitrogen manageme nt in potatoes through crop rotation and enhanced uptake. Ph.D Dissertation. Mylavarapu, R.S., and E.S. Kennelley. 2002. UF/IFAS Extension Soil Testing Laboratory (ESTL) Analytical procedures and training manual. University of Florida, IFAS. Extension Circular 1248. 18pp National Potato Council. The potato. Website: http://www.nationalpotatocouncil.org (last accessed April 2004). Novak, V.J.,G. D. Mann, and G. N. Schradter. 1986. Effects of age at harvest and irrigation near maturity on the incidence of internal brown fleck in potato tubers. Aust. J. Exp Agric. 26:129-132. Ojala, J.C., J.C. Stark, and G. E. Kleinkopf. 1990. Influence of irrigation and nitrogen management on potato yield and quality. Amer. Potato J. 67: 29-43. Ozgen, S. B., H. Karlsson, and J. P. Palta 2006. Response of potatoes (cv. Russet Burbank) to supplemental calcium applications under field conditions: Tuber calcium, yield and cncidence of internal brown spot. Amer. J. of Potato Res. 83:195-204. Palta J. P. 1996. Role of calcium in plant res ponses to stresses: Link ing basic research to the solution of practical probl ems. HortSci. 31(1):51-57. Perry K. B., T. C. Wehner, and G. L. Johnson. 1986. Comparison of 14 methods to determine heat unit requirements for cucu mber harvest. HortSci. 21(3):419-423.

PAGE 241

222 Peterson, R. L. W. G. Barker, and M. J. Howarth. 1985. Development and structure of tubers. In Potato Physiology pp 123-152. Academic Press, Inc., London. Sands, P. J., C. Hackett, and H. A. Nix. 1979. A model of the development and bulking of potatoes ( Solanum tuberosum L.). I. Derivation from well-managed field crops. Field Crops Res. 2:309-331. SAS Institue. 2004. SAS/STAT statistical an alysis system manual (V. 9.0) SAS Inst., Cary, N.C. Shoji, S., and A. T. Gandeza. 1992. Controll ed Release Fertilizers wi th Polyolefin Resin Coating, Development, Properties and U tilization. Konno Printing Co., Ltd. Japan. pp.92. Silva, G.H., R. W. Chase, R. Hammerschmidt, M. L. Vitosh, and R. B. Kitchen. 1991. Irrigation, nitrogen and gypsum effects on sp ecific gravity and in ternal defects of Atlantic potatoes. Amer. Potato J. 68:751-765 Singleton, V.D. 1990. Investigation of potat o water use in the Tri-County area of Putnam, St. Johns, and Flagler Counties, Florida. St. Johns River Water Management District Techni cal Publication SJ 90-13. Sterrett, S. B., M. R. Henninger, and G. S. Lee. 1991. Relationship of internal heat necrosis of potato to time and temperature after planting. J. Amer. Soc. Hort. Sci 116(4):697-700. Sterrett, S.B., G. L. Lee, M. R. Henninger, and M. Lentner 1991. Predictive model for onset and development of internal heat necr osis of Atlantic potato. J. Amer Soc. Hort. Sci. 116(4):701-705. Sterrett, S.B., and M.R. Henninger. 1991. Infl uence of calcium on internal heat necrosis of Atlantic potato. Amer. Potato J. 68:467-477. Sterrett, S.B., and C.P. Savage. 1993. Yield and development of internal heat necrosis affected by foliar fertilization. Amer. Potato J. 70:844 (Abstract) Sterrett, S.B., and M.R. Henninger. 1997. In ternal heat necrosis in the MidAtlantic region influence of environment and cultural management. Am. Potato J. 74: 233-243. Sterrett. S. B., K. G. Haynes, G. C. Yenc ho, M. R. Henninger and B. T. Vinyard. 2006. 4x-2x potato clones with resistan ce or susceptibility to inte rnal heat necrosis differ in tuber mineral status. Crop Science. 46: 1471-1478. Stevenson, W.R., R. Loria, G.D. Franc, a nd D.P. Weingartner. 2001. Physiological disorders of tubers: Internal symptoms. In Compendium of potato diseases 2nd ed. Minnesota: American Phytopathological Society.

PAGE 242

223 Tisdale S.L., W. L. Nelson, J. D. Beaton, a nd J. L. Havlin. 1993. Soil Fertility and Fertilizers. Prentice-Hall, Englewood Cliffs, NJ. pp90-91. Trenkel, M. E. 1997. Controll ed-release and stabilized fe rtilizers in agriculture. In Improving Fertilizer Use Efficiency. Intern ational Fertilizer I ndustry Association. Paris. pp151. Tzeng, K.C., A. Kelman, K.E. Simmons, and K.A. Kelling. 1986. Relationship of calcium nutrition to internal brown spot of potato tubers and sub-apical necrosis of sprouts. Amer. Potato J. 63: 87-97. United States Department of Agriculture. 1978. United States standards for grades of potatoes for chipping http://www.ams .usda.gov/standards/potatoch.pdf (last accessed Apr 2005). U. S. Department of Agriculture (USDA) 1983. Soil survey St. Johns County, Soil Conservation Service. 196 pp. Varvel, G. E., and T. A. Peterson. 1991. N itrogen fertilizer rec overy by grain sorghum in monoculture and rotation Systems. Agron. J. 83(3):617-622. Waddell, J. T., S. C. Gupta, J. F. Moncri ef, C. J. Rosen, and D. D. Steele. 1999. Irrigation and nitrogen management e ffects on potato yield, tuber quality, and nitrogen uptake. Agron. J. 91(6) 991-997 November/December. Wang, F. L., and A. K. Alva. 1996. Leaching of nitrogen from slow-release urea sources in sandy soils. Soil Science Society of America. Journal. 60: 1454-1458. Wannamaker, M.J., and W.W. Collins. 1992. Effect of year, location and harvest on susceptibility of cultivars to internal heat necrosis in North Carolina. Amer. Potato J. 69: 221-228. Webb, R.E., D. R. Wilson, J.R. Shumaker, B. Graves, M.R. Henninger, J. Watts, J.A. Frank, and H.J. Murphy. 1978. Atlantic: A new potato variety with high solids, good processing quality, and resistance to pests. Amer. Potato J. 55:141-145. Weingartner, D.P., and D.R. Hensel. 2003. Hi story and agricultural contributions o f the University of Florida, IFAS, Hastings Research and Education Center, 1923 to 2002. Proc. Fla. State Hort. Soc. 116:143-151. Winkler, E. 1971. Kartoffelbau in Tirol. II. Photosynthesevermgen and respiration von verschiedenen Kartoffelsorte n. Potato Res. 14:1-18. Witzig, J.D., and N.L. Pugh. 2004. Florida Agri cultural Statistics Serv ice. Quick stats vegetables. Website: http://www.nass.usda.gov/fl (last accessed 05/04)

PAGE 243

224 Zvomuya, F, C. J. Rosen, M. P. Russelle, and S. C. Gupta. 2003. Nitrate leaching and nitrogen recovery following a pplication of polyolefin-coated urea to potato. J. Env. Qual 32(2) 480-489 Mar/Apr.

PAGE 244

225 BIOGRAPHICAL SKETCH Christine M. Worthington was born in Omaha, Nebraska, on August 15, 1964. In 1983 she completed high school in Hewitt, Texas. Soon after high school she married and had two children: Ashley, born in 1984, and Jevin, born in 1986. In 1989 she was divorced with two small children. She made th e decision to go back to college in 1994 at Richland Community College in Dallas, Te xas, from 1994 to 1996. She was accepted to Texas A & M University in College Station, Texas, in 1996, where she received a B. S. in agronomy in 1999. She moved to Canyon, Texas, in December of 1999 to pursue a Master of Science in agriculture. She receiv ed her M.S. in envir onmental soil and plant science from West Texas A & M University in 2001. Upon graduati on from West Texas A & M, she and her children moved to Gain esville, Florida, to pursue a Doctor of Philosophy in horticultural scien ces. After getting her degree she plans to continue her professional career in agricultura l and environmental research.


Permanent Link: http://ufdc.ufl.edu/UFE0015765/00001

Material Information

Title: Timing of climatic factors that may influence potato yield, quality, and potential nitrogen losses in a northeast Florida seepage-irrigated Potato Production System
Physical Description: Mixed Material
Creator: Worthington, Christine Maria ( Dissertant )
Hutchinson, Chad M. ( Thesis advisor )
Stall, Bill ( Reviewer )
Mylavarapu, Rao ( Reviewer )
Obreza, Tom ( Reviewer )
Portier, Kenneth ( Reviewer )
White, James ( Reviewer )
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2006
Copyright Date: 2006

Subjects

Subjects / Keywords: Horticultural Science thesis, Ph. D.
Dissertations, Academic -- UF -- Horticulture

Notes

Abstract: Potato, a cool season crop, is planted in Northeast Florida in January when temperatures are cool. As the season progresses, daily temperatures and incidence of leaching rainfall events increase which can affect yield and quality. Nutrient runoff from potato production land has thought to have been primarily responsible for the non-point source pollution into the St Johns River watershed. Best Management Practices (BMPs) for potato production in the TCAA have been implemented. With over 7,000 ha in potato production in the TCAA, the main concern with the implementation of the BMPs are to not compromise yield and quality. The experimental design in chapter 2 was a split-split design with four blocks. Planting dates (1-6) were main plots. The first split was the N rate (168 and 224 kg ha⁻¹). The second split was potato variety, 'Atlantic' and 'Harley Blackwell'. The experimental design in chapter 3 was a split-split design with four blocks. Irrigation treatments were main plots at 0, 2, 4, 8, and 12 WAP (weeks after planting). The first split was the nitrogen source (AN or CRF). The second split was an additional side-dress fertilizer application. Optimal yields for the TCAA occurred over a 4 week period (early to late February) in a twelve week planting window. 'Harley Blackwell' demonstrated its effectiveness to produce quality tubers under conditions when air temperatures and leaching rainfall events stressed plants. IHN was triggered by rainfall and nutritional conditions that stressed the plant early in the season combined with increasing minimum daily temperatures later in the season. Marketable yields in the CRF treatments were an average of 12% higher compared with the AN fertilizer treatment. The CRF treatments had a significantly higher incidence of tubers with IHN compared with the AN fertilizer treatment at 22.3 and 15.6%, respectively. NO₃-N loading from surface water runoff from potato production was decreased an average of 43% with the use of the CRF compared with the AN fertilizer treatment. A CRF used in potato production, rather than a soluble N fertilizer, could reduce NO₃-N loads into the St. Johns River watershed by 56,000 kg N per year.
Subject: best, days, degree, growing, heat, internal, management, necrosis, practices
General Note: Title from title page of source document.
General Note: Document formatted into pages; contains 244 pages.
General Note: Includes vita.
Thesis: Thesis (Ph.D.)--University of Florida, 2006.
Bibliography: Includes bibliographical references.
General Note: Text (Electronic thesis) in PDF format.

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0015765:00001

Permanent Link: http://ufdc.ufl.edu/UFE0015765/00001

Material Information

Title: Timing of climatic factors that may influence potato yield, quality, and potential nitrogen losses in a northeast Florida seepage-irrigated Potato Production System
Physical Description: Mixed Material
Creator: Worthington, Christine Maria ( Dissertant )
Hutchinson, Chad M. ( Thesis advisor )
Stall, Bill ( Reviewer )
Mylavarapu, Rao ( Reviewer )
Obreza, Tom ( Reviewer )
Portier, Kenneth ( Reviewer )
White, James ( Reviewer )
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2006
Copyright Date: 2006

Subjects

Subjects / Keywords: Horticultural Science thesis, Ph. D.
Dissertations, Academic -- UF -- Horticulture

Notes

Abstract: Potato, a cool season crop, is planted in Northeast Florida in January when temperatures are cool. As the season progresses, daily temperatures and incidence of leaching rainfall events increase which can affect yield and quality. Nutrient runoff from potato production land has thought to have been primarily responsible for the non-point source pollution into the St Johns River watershed. Best Management Practices (BMPs) for potato production in the TCAA have been implemented. With over 7,000 ha in potato production in the TCAA, the main concern with the implementation of the BMPs are to not compromise yield and quality. The experimental design in chapter 2 was a split-split design with four blocks. Planting dates (1-6) were main plots. The first split was the N rate (168 and 224 kg ha⁻¹). The second split was potato variety, 'Atlantic' and 'Harley Blackwell'. The experimental design in chapter 3 was a split-split design with four blocks. Irrigation treatments were main plots at 0, 2, 4, 8, and 12 WAP (weeks after planting). The first split was the nitrogen source (AN or CRF). The second split was an additional side-dress fertilizer application. Optimal yields for the TCAA occurred over a 4 week period (early to late February) in a twelve week planting window. 'Harley Blackwell' demonstrated its effectiveness to produce quality tubers under conditions when air temperatures and leaching rainfall events stressed plants. IHN was triggered by rainfall and nutritional conditions that stressed the plant early in the season combined with increasing minimum daily temperatures later in the season. Marketable yields in the CRF treatments were an average of 12% higher compared with the AN fertilizer treatment. The CRF treatments had a significantly higher incidence of tubers with IHN compared with the AN fertilizer treatment at 22.3 and 15.6%, respectively. NO₃-N loading from surface water runoff from potato production was decreased an average of 43% with the use of the CRF compared with the AN fertilizer treatment. A CRF used in potato production, rather than a soluble N fertilizer, could reduce NO₃-N loads into the St. Johns River watershed by 56,000 kg N per year.
Subject: best, days, degree, growing, heat, internal, management, necrosis, practices
General Note: Title from title page of source document.
General Note: Document formatted into pages; contains 244 pages.
General Note: Includes vita.
Thesis: Thesis (Ph.D.)--University of Florida, 2006.
Bibliography: Includes bibliographical references.
General Note: Text (Electronic thesis) in PDF format.

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0015765:00001


This item has the following downloads:


Table of Contents
    Title Page
        Page i
        Page ii
    Dedication
        Page iii
    Acknowledgement
        Page iv
    Table of Contents
        Page v
        Page vi
        Page vii
        Page viii
        Page ix
    List of Tables
        Page x
        Page xi
        Page xii
        Page xiii
        Page xiv
        Page xv
    List of Figures
        Page xvi
        Page xvii
    Abstract
        Page xviii
        Page xix
    Introduction
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
    Development of a growing degree day model to determine optimal planting date and environmental influence on potato yield and quality in northeast Florida
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
    Yield and quality of 'Atlantic' potato (solanum tuberosum L.) tubers and off-field nutrient movement under varying nitrogen sources and staged leaching irrigation events
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
        Page 109
    Summary, and future research
        Page 110
        Page 111
        Page 112
        Page 113
        Page 114
        Page 115
    Appendices
        Page 116
        Page 117
        Page 118
        Page 119
        Page 120
        Page 121
        Page 122
        Page 123
        Page 124
        Page 125
        Page 126
        Page 127
        Page 128
        Page 129
        Page 130
        Page 131
        Page 132
        Page 133
        Page 134
        Page 135
        Page 136
        Page 137
        Page 138
        Page 139
        Page 140
        Page 141
        Page 142
        Page 143
        Page 144
        Page 145
        Page 146
        Page 147
        Page 148
        Page 149
        Page 150
        Page 151
        Page 152
        Page 153
        Page 154
        Page 155
        Page 156
        Page 157
        Page 158
        Page 159
        Page 160
        Page 161
        Page 162
        Page 163
        Page 164
        Page 165
        Page 166
        Page 167
        Page 168
        Page 169
        Page 170
        Page 171
        Page 172
        Page 173
        Page 174
        Page 175
        Page 176
        Page 177
        Page 178
        Page 179
        Page 180
        Page 181
        Page 182
        Page 183
        Page 184
        Page 185
        Page 186
        Page 187
        Page 188
        Page 189
        Page 190
        Page 191
        Page 192
        Page 193
        Page 194
        Page 195
        Page 196
        Page 197
        Page 198
        Page 199
        Page 200
        Page 201
        Page 202
        Page 203
        Page 204
        Page 205
        Page 206
        Page 207
        Page 208
        Page 209
        Page 210
        Page 211
        Page 212
        Page 213
        Page 214
        Page 215
        Page 216
        Page 217
        Page 218
    References
        Page 219
        Page 220
        Page 221
        Page 222
        Page 223
        Page 224
    Biographical sketch
        Page 225
Full Text












TIMING OF CLIMATIC FACTORS THAT MAY INFLUENCE POTATO YIELD,
QUALITY, AND POTENTIAL NITROGEN LOSSES IN A NORTHEAST FLORIDA
SEEPAGE-IRRIGATED POTATO PRODUCTION SYSTEM














By

CHRISTINE MARIA WORTHINGTON


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


2006

































Copyright 2006

by

Christine Maria Worthington

































To my two strongholds in life, Curtiss and Jevin.















ACKNOWLEDGMENTS

I would like to extend my deepest and heartfelt gratitude to Chad M. Hutchinson,

my advisor, for his unwavering support, patience and confidence in my ability to achieve

my goal. I would also like to extend my sincere appreciation to my committee members,

Drs. Bill Stall, Rao Mylavarapu, Tom Obreza, Kenneth Portier and James White, for their

patience and guidance through this life lesson. I would especially like to thank Dr.

Portier for unselfishly assisting me in analyzing all the data and his patience getting it

completed.

The completion of this work would not have been possible if it weren't for the

dedicated staff at the Plant Science and Research Unit, Hastings, FL., especially Doug

Gergela, Pam Solano, Bart Harrington and Larry Miller.

I sincerely appreciate the faculty and staff in the Horticultural Sciences Department

for giving me the opportunity to accomplish my goal.

I would like to thank my parents, Paul and Cecilia Worthington and Patti Hoff, for

their unconditional love and support and believing I can.

Finally, all this wouldn't have been possible if it weren't for the support and love

and years of patience from Curtiss and Jevin who I owe my deepest gratitude.
















TABLE OF CONTENTS



A C K N O W L E D G M E N T S ................................................................................................. iv

L IST O F T A B L E S .. ............ ................................................... ............... x...... .... ..x

LIST OF FIGURES ................................................ xvi

ABSTRACT ......................... ................................................ xviii

CHAPTER

1 IN TR O D U C T IO N ........ .. ......................................... ..........................................1.

F lorida P otato P reduction ................................................................ ...............1......
T ri-C county A agricultural A rea........................................................... ...............2...
P otato C capital of F lorida ........................................ ....................... ...............3...
F lorida C hip P otato V varieties ........................................................... ...............4...
Seasonal Environmental Stress Associated with IHN............................................7...
M o istu re S tre ss .............................................................................................. 8
N nutrition .............. ................................................ ..................... ...... ...... . 9
R a tio n a le .............................................................................................................. 1 0
O organization of D issertation ........................................ ....................... ............... 11

2 DEVELOPMENT OF A GROWING DEGREE DAY MODEL TO DETERMINE
OPTIMAL PLANTING DATE AND ENVIRONMENTAL INFLUENCE ON
POTATO YIELD AND QUALITY IN NORTHEAST FLORIDA ........................... 12

In tro d u ctio n ............................................................................................................... .. 12
Growing Degree Days .............. ................................. 13
M materials and M ethods .. ..................................................................... ............... 14
S ite D e scrip tio n ................................................................................................... 14
E x p erim ental D esig n ........................................................................................... 14
Crop Production Practices ................. ............................................................. 15
T u b er P lan tin g ..................................................................................................... 15
Irrig atio n ......................................................................................................... . 1 5
N utrient M anagem ent......................................... ......................... .............. 16
Tuber Production A analysis ..................................... ..................... ............... 16
Tuber Specific G ravity ................. ........................................................... 17
E xternal Q quality ............................................................................................. 17
In tern al Q u ality .................................................................................................... 17

v









G row ing D degree D ays ............... ................ ............................................ 18
Statistical A analysis ..... ............... ...................................... ............... ... 18
R results A nd D discussion .............. .................. .............................................. 19
Tuber Y ield for 2004 ............. ............... ............................................... 19
P planting date m ain effect......................................................... ............... 19
N itrogen rate m ain effect......................................................... ................ 20
V variety m ain effect ...................................... .. ........ .......... .. .............. ... 20
M ain effect interaction ......................................................... 20
Tuber Y ield for 2005 .............. .. ............ ............................................. 21
P planting date m ain effect......................................................... ................ 2 1
N itrogen rate m ain effect......................................................... ................ 22
V variety m ain effect ...................................... .. ........ .......... .. .............. ... 22
M ain effect interactions........................................................... ................ 23
Tuber External Q quality for 2004 .................................................... ................ 23
P planting date m ain effect......................................................... ................ 23
N itrogen m ain effect....................................... ...................... ................ 24
V variety m ain effect ...................................... .. ........ .......... .. .............. ... 24
Tuber External Q quality for 2005 .................................................... ................ 24
P planting date m ain effect......................................................... ................ 24
N itrogen rate m ain effect......................................................... ................ 24
V variety m ain effect ...................................... .. ........ .......... .. .............. ... 25
Tuber Internal Quality for 2004 ...................................................25
P planting date m ain effect......................................................... ................ 25
N itrogen rate m ain effect......................................................... ................ 26
V variety m ain effect ...................................... .. ........ .......... .. .............. ... 26
Tuber Internal Q quality for 2005 ..................................................... ................ 26
P planting date m ain effect......................................................... ................ 26
N itrogen rate m ain effect......................................................... ................ 27
V variety m ain effect ...................................... .. ........ .......... .. .............. ... 27
G row ing D egree D ay M odel .................................................................... ............... 28
Growing Degree Day Model and Potato Plant Development .............................28
Growing Degree Day Model and Tuber Yield...............................................28
Growing Degree Day Model and Internal Tuber Quality ..............................30
C o n c lu sio n ............................................................................................................... .. 3 1

3 YIELD AND QUALITY OF 'ATLANTIC' POTATO (SOLANUM
TUBEROSUML.) TUBERS AND OFF-FIELD NUTRIENT MOVEMENT
UNDER VARYING NITROGEN SOURCES AND STAGED LEACHING
IR R IG A T IO N E V E N T S .............................................................................................49

In tro d u ctio n ................................................................................................................ 4 9
M materials and M ethods .. ..................................................................... ................ 53
Site Description ............................. .... ........ ...... ...............53
E xperim ental D esign .......................................... ......................... ................ 53
Crop Production Practices ................. .............................................................. 54
T u b er P lan tin g ..................................................................................................... 54
Irrig atio n .............................................................................................................. 5 4
N utrient M anagem ent ...................... ............................................................... 55









A m m onium N itrate N itrogen ......................................................... ................ 55
C controlled R release Fertilizer.................. .................................................... 56
T uber P reduction A naly sis ........................................ ........................ ................ 56
Tuber Specific G ravity. ................ ............................................................ 57
E external Q quality ...................................................................................................57
Internal Quality ......................................................57
Water Sample Collection and Nutrient Load.........................................................57
Surface R un-O ff V olum e ...................................... ...................... ................ 57
N utrient L oad .................................................................................................. 58
Wells ............................................................................. 58
L y sim e te rs ...........................................................................................................5 8
G row ing D egree D ay M odel ....................................... ....................... ................ 59
Statistical A analysis ................................................................................................ 59
R results A nd D iscu ssion ..................................................................... ................ 60
Tuber Y field for 2004 ........................................................................ ............. 60
Irrigation date m ain effect ....................................................... ................ 60
F ertilizer m ain effect ...................................... ...................... ................ 6 1
M ain effect interactions........................................................... ................ 6 1
T ub er Y ield for 2005 .......................................... ......................... ................ 62
Irrigation date m ain effect ....................................................... ................ 62
F ertilizer m ain effect ...................................... ...................... ................ 63
Sidedress m ain effect ........................................................ 63
M ain effect interactions........................................................... ................ 63
Tuber External Q quality for 2004 .................................................... ................ 64
Irrigation date m ain effect ....................................................... ................ 64
F ertilizer m ain effect ...................................... ...................... ................ 64
Sidedress m ain effect ........................................................ 64
Tuber External Q quality for 2005 .................................................... ................ 64
Irrigation date m ain effect ....................................................... ................ 64
F ertilizer m ain effect ...................................... ...................... ................ 65
Sidedress m ain effect ........................................................ 65
Tuber Internal Quality for 2004 ....................... .......................................... 65
Irrigation date m ain effect ....................................................... ................ 65
F ertilizer m ain effect ...................................... ...................... ................ 67
Sidedress m ain effect ........................................................ 68
Tuber Internal Q quality for 2005 ..................................................... ................ 69
Irrigation date m ain effect ....................................................... ................ 69
Fertilizer source m ain effect.................................................... ................ 70
Sidedress m ain effect ................................................................. ............... 70
Nitrate Nitrogen Concentration in Wells for 2004.........................................71
Irrigation m ain effect.................................... .. .......... .......... ................. 71
F ertilizer m ain effect ...................................... ...................... ................ 7 1
Sidedress m ain effect ......................... ............................ 72
Nitrate Nitrogen Concentration in Wells for 2005 .........................................72
Irrigation m ain effect................................... ...................... ................ 72
F ertilizer m ain effect ...................................... ...................... ................ 73
Sidedress m ain effect .................................... .. ........... .......... .. ...... ..... 73









Nitrate Nitrogen Concentration in Lysimeters for 2004.................................73
Irrigation m ain effect................................... ...................... ................ 73
F ertilizer m ain effect ...................................... ...................... ................ 74
Sidedress m ain effect ........................................... ................. ................ 74
Nitrate Nitrogen Concentration in Lysimeters for 2005................................74
Irrigation m ain effect................................... ...................... ................ 74
F ertilizer m ain effect ...................................... ...................... ................ 75
Sidedress m ain effect .............................................................. ................ 76
Nutrient Load Concentration in Surface Water..............................................76
W ater volum e: 2004 ...................................... ...................... ................ 76
W ater volum e: 2005 ...................................... ...................... ................ 77
N utrient load: 2004...................................... .. .......... .......... ................. 77
N utrient load: 2005 ...................................... .. .......... .......... ................. 77
G row ing D egree D ay s ......................................... ........................ ................ 78
C o n c lu sio n s............................................................................................................... .. 7 9

4 SUMMARY, AND FUTURE RESEARCH...... .... .....................................110

O ptim u m P planting D ates ..................................................................................... 111......
C lim atic F acto rs ........................................................................................................ 1 12
P otato V arieties......................................................................................................... 1 13
F fertilizer S ou rce..................................................................... ..... . ...............113
A additional N Sidedress .... ............................................................... ............... 114
W ater Q u ality ............................................................................................................ 1 14
F u tu re R e search ........................................................................................................ 1 15

APPENDIX

A ADDITIONAL DATA AND ANOVA TABLES FOR PLANTING DATE
Y IE L D ................................................................................................................... ... 1 1 6

B ADDITIONAL DATA AND ANOVA TABLES FOR PLANT TISSUE FOR
PLA N TIN G D A TE .... .................................................................... ............... 135

C ADDITIONAL DATA AND ANOVA TABLE FOR POST HARVEST SOIL
NUTRIENTS FOR PLANTING DATE............... .........................148

D ANOVA TABLES FOR YIELD AND QUALITY FOR IRRIGATION STUDY .. 151

E ADDITIONAL DATA AND ANOVA TABLES FOR SURFACE WATER
NUTRIENT CONCENTRATION ................ ........ ......................160

F ADDITIONAL DATA AND ANOVA TABLES FOR TISSUE NUTRIENT
CONCENTRATION AND FUE FOR IRRIGATION STUDY ............................... 188

G ADDITIONAL DATA AND ANOVA TABLES FOR SOIL NUTRIENT
C O N C E N T R A T IO N ................................................................................................208









LIST O F R EFEREN CE S ... ................................................................... ................ 219

BIOGRAPH ICAL SKETCH .................. .............................................................. 225















LIST OF TABLES


Table page

2-1 Total and marketable yield and specific gravity production statistics for 2004
a n d 2 0 0 5 ............................................................................................................ .. 3 2

2-2 Two-way interaction between planting date and nitrogen rate main effects for
total and m arketable tuber yields in 2004 ........................................... ................ 34

2-3 Two-way interaction between planting date and variety main effects for total
tuber yields in 2004 and 2005 ..................................... ..................... ................ 35

2-4 Size class distribution and range (%) production statistics 2004 and 2005 ............36

2-5 Two-way interaction between planting date and nitrogen rate main effects for
size class range (%) for Al in 2004 and A3 and size class distribution for Al to
A 2 in 2 0 0 5 .............. ................................................ ....................... .. 3 8

2-6 Two-way interaction between planting date and variety main effects for size
class range (%) for Al, A2, A3 and A2 to A3 in 2004 and B, Al, A3 and Al to
A 2 in 2 0 0 5 .............. ................................................ ....................... .. 3 9

2-7 External quality (green, growth cracks, mis-shaped, rot and total culls) % of
total yield 2004 and 2005 ........................................ ........................ ................ 40

2-8 Internal quality (%) of total yield 2004 and 2005. ..............................................42

2-9 Mean maximum and minimum temperature (C) for planting dates 1-6, 2004 and
2 0 0 5 ........................................................................................................ ........ .. 4 4

2-10 Accumulated GDD and calendar days to obtain emergence and full flower 2004
a n d 2 0 0 5 .............................................................................................................. .. 4 5

2-11 Early and late season yield reduction and harvest date at 2000 GDD for 2004
a n d 2 0 0 5 ............................................................................................................ .. 4 6

3-1 Irrigation treatment (WAP), fertilizer treatment, fertilizer source and additional
sidedress application (DAP) for 2004 and 2005 production seasons.................... 80









3-2 Total and marketable tuber yields and specific gravity for 'Atlantic' potato
under varying staged leaching irrigation treatments and fertilizer source in
H astings, FL in 2004 and 2005 ........................................................... ................ 82

3-3 Three-way interaction between irrigation date, fertilizer source and side dress
application main effects for total and marketable tuber yields and specific
gravity for 'Atlantic' potato under varying staged leaching irrigation treatments
and fertilizer source in Hastings, FL in 2004 and 2005 ......................................84

3-4 Size class distribution and range (%) production statistics for 'Atlantic'potato
under varying staged leaching irrigation treatments and fertilizer source in
H astings, FL in 2004 and 2005 ........................................................... ................ 85

3-5 External tuber defects (%) of total yield for 'Atlantic' under varying staged
leaching irrigation treatments, fertilizer source and additional sidedress in
H astings, FL in 2004 and 2005 ........................................................... ................ 87

3-6 Internal tuber defects (%) of total yield for 'Atlantic' under varying staged
leaching irrigation treatments, fertilizer source and additional sidedress in
H astings, FL in 2004 and 2005 ........................................................... ................ 89

3-7 Well NO3-N concentration (mg L-1) under varying staged leaching irrigation
treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and
2 0 0 5 ........................................................................................................ .......... 9 1

3-8 Lysimeter NO3-N concentration (mg L-1) under varying staged leaching
irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in
2 0 0 4 an d 2 0 0 5 .......................................................................................................... 9 3

3-9 Total NO3-N nutrient load by fertilizer source and leaching irrigation date and
percent reduction in load from CRF compared with AN 2004...........................95

3-10 Total NO3-N nutrient load by fertilizer source and leaching irrigation date and
percent reduction in load from CRF compared with AN 2005...........................95

3-11 Accumulated Growing Degree Days to leaching irrigation event, emergence and
fu ll flo w e r ................................................................................................................ 9 6

A-i Total and marketable yield and specific gravity production statistics for late
harvest 2004 and 2005 .......................................... .. ...................... ........... 117

A-2 Size class distribution and range (%) production statistics for late harvest 2004 ..119

A-3 Size class distribution and range (%) production statistics for late harvest 2005 ..121

A-4 Size class distribution and range (%) production statistics for late harvest 2005 ..122









A-5 External quality (green, growth cracks, mis-shaped, rot and total culls) (%) of
total yield late harvest 2004 and 2005....... ... ......................................... 123

A-6 Internal quality (%) of total yield late harvest 2004 and 2005........................... 125

A-7 2004 ANOVA table for potato yield in planting date study ................................127

A-8 2005 ANOVA table for potato total and marketable yield and size distribution in
planting date study ............. ................. .............................................. 128

A-9 2004 ANOVA table for potato internal and external quality in planting date
stu d y .................................................................................................... .......... 12 9

A-10 2005 ANOVA table for potato internal and external quality in planting date
stu d y .................................................................................................... ........... 13 0

A-11 2004 ANOVA table for potato yield in planting date study late harvest .............131

A-12 2005 ANOVA table for potato yield in planting date study late harvest .............132

A-13 2004 ANOVA table for potato internal and external quality in planting date
stu dy late h arv est .................................................................................................... 13 3

A-14 2005 ANOVA table for potato internal and external quality in planting date
study late harvest ............................. .......... ....................... 134

B-i Haulm nutrient concentration (%) at tuber initiation in 2004 and 2005 ..............136

B-2 Full flower haulmm) nutrient concentration (%) for 2004 and 2005.................... 138

B-3 Tuber diced pieces nutrient concentration (kg ha-1) at harvest 2005 ...................140

B-4 Ca+ and TKN fertilizer use efficiency (% ) 2005 ............................... ................ 141

B-5 2004 ANOVA table for haulm tissue at tuber initiation for planting date.......... 142

B-6 2004 ANOVA table for haulm tissue at full flower for planting date..................143

B-7 2005 ANOVA table for haulm tissue at tuber initiation for planting date.......... 144

B-8 2005ANOVA table for haulm tissue at full flower ..................... .................. 145

B-9 2005ANOVA table for FUE ......................................................... 146

B-10 2005ANOVA table for tuber diced pieces for planting date............................... 147

C-i Soil nutrient concentration (mg kg-1) post harvest 2005 ..................................149

C-2 2005 ANOVA table for post harvest soil planting date ............... ...................150









D-1 2004 ANOVA table for potato total and marketable yield and specific gravity.... 152

D-2 2004 ANOVA table for potato size class distribution and range .........................153

D-3 2005 ANOVA table for potato total and marketable yield and specific gravity.... 154

D-4 2005 ANOVA table for potato size class distribution and range.........................155

D-5 2004 ANOVA table for potato external quality ......................... .................. 156

D-6 2004 ANOVA table for potato internal quality......................... .................. 157

D-7 2005 ANOVA table for potato external quality ......................... .................. 158

D-8 2005 ANOVA table for potato internal quality.......................... .................. 159

E-1 Well NH4-N concentration (mg L1) under varying staged leaching irrigation
treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and
2 0 0 5 ...................................................................................................... ........ .. 16 1

E-2 Lysimeter NH4-N concentration (mg L-1) under varying staged leaching
irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in
2 0 0 4 an d 2 0 0 5 ........................................................................................................ 16 3

E-3 2004 ANOVA table for well water sample 29 DAP................ ... .............165

E-4 2004 ANOVA table for well water sample 44 DAP......................... ............ 166

E-5 2004 ANOVA table for well water sample 60 DAP......................... ............ 167

E-6 2004 ANOVA table for well water sample 72 DAP......................... .............168

E-7 2004 ANOVA table for well water sample 89 DAP......................... .............169

E-8 2005 ANOVA table for well water sample 17 DAP......................... .............170

E-9 2005 ANOVA table for well water sample 33 DAP......................... .............171

E-10 2005 ANOVA table for well water sample 45 DAP......................................172

E-11 2005 ANOVA table for well water sample 59 DAP......................................173

E-12 2005 ANOVA table for well water sample 73 DAP......................................174

E-13 2005 ANOVA table for well water sample 89 DAP ................ ...............175

E-14 2004 ANOVA table for lysimeter water sample 45 DAP ................................... 176

E-15 2004 ANOVA table for lysimeter water sample 65 DAP ................................... 177









E-16 2004 ANOVA table for lysimeter water sample 73 DAP ............... ............... 178

E-17 2004 ANOVA table for lysimeter water sample 90 DAP ............... ...............179

E-18 2005 ANOVA table for lysimeter water sample 18 DAP ............... ...............180

E-19 2005 ANOVA table for lysimeter water sample 34 DAP ............... ............... 181

E-20 2005 ANOVA table for lysimeter water sample 45 DAP ............... ............... 182

E-21 2005 ANOVA table for lysimeter water sample 60 DAP ............... ...............183

E-22 2005 ANOVA table for lysimeter water sample 73 DAP ............... ...............184

E-23 2005 ANOVA table for lysimeter water sample 89 DAP................... ............ 185

E-24 2004 NO3-N concentration in surface water runoff (Figures 3.4-3.6) ................ 186

E-25 2005 NO3-N concentration in surface runoff (Figures 3.7-3.10)........................ 187

F-i Leaf Ca+ (%) under varying staged leaching irrigation treatments, fertilizer
source and additional sidedress in Hastings, FL in 2004 and 2005 .....................189

F-2 Leaf TKN (%) under varying staged leaching irrigation treatments, fertilizer
source and additional sidedress in Hastings, FL in 2004 and 2005 .................... 190

F-3 Full flower haulmm) nutrient uptake (kg ha-1) under varying staged leaching
irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in
2 0 0 4 an d 2 0 0 5 ........................................................................................................ 19 1

F-4 Tuber nutrient uptake (kg ha-1) at harvest under varying staged leaching
irrigation treatments, fertilizer source and additional sidedress in Hastings, FL in
2 0 0 4 an d 2 0 0 5 ........................................................................................................ 19 2

F-5 Fertilizer use efficiency (%) of total fertilizer applied under varying staged
leaching irrigation treatments, fertilizer source and additional sidedress in
H astings, FL in 2004 and 2005 ....... ........ .......... ..................... 193

F-6 SPAD leaf chlorophyll values under varying staged leaching irrigation
treatments, fertilizer source and additional sidedress in Hastings, FL in 2004 and
2 0 0 5 ...................................................................................................... .......... 19 4

F-7 2004 ANOVA table for leaf tissue 36 DAP....... ... ...................................... 196

F-8 2004 ANOVA table for leaf tissue 51 DAP....... ... ...................................... 197

F-9 2004 ANOVA table for leaf tissue 67 DAP....... ... ...................................... 198

F-10 2004 ANOVA table for full flower haulm.......... .....................................199









F-11 2004 ANOVA table for tuber tissue at harvest ......................... ...................200

F-12 2005 ANOVA table for leaf tissue 41 DAP...... .... ..................................... 201

F-13 2005 ANOVA table for leaf tissue 74 DAP...... .... ..................................... 202

F-14 2005 ANOVA table for full flower haulm tissue........................ ...................203

F-15 2005 ANOVA table for nutrient tuber tissue ....... ... .................................... 204

F-16 2004 ANOVA table for FUE ........................................................ 205

F-17 2005 ANOVA table for FUE ......................................................... 206

F-18 2004 ANOVA table for SPAD 2004 and 2005 ........................... ..................... 207

G-1 Post harvest soil nutrient concentration Ca, NH4-N, and NO3-N (mg kg -1) under
varying staged leaching irrigation treatments, fertilizer source and additional
sidedress in Hastings, FL in 2004 and 2005...... .... ................. ................... 209

G-2 2004 ANOVA table for post harvest soil nutrient concentration 106 DAP ...........210

G-3 2005 NOVA table for post harvest soil nutrient concentration 106 DAP............211

G-4 2004 Equality of variances for pre-post soil nutrient concentration at irrigation
treatm ent 2 W A P ............... .................. ............................................... 212

G-5 2004 Equality of variances for pre-post soil nutrient concentration at irrigation
treatment 8 WAP ........................... .......... ........................ 213

G-6 2004 Equality of variances for pre-post soil nutrient concentration at irrigation
treatm ent 12 W A P ... ..................................................................... ............... 2 14

G-7 2005 Equality of variances for pre-post soil nutrient concentration at irrigation
treatm ent 2 W A P ............... .................. ............................................... 215

G-8 2005 Equality of variances for pre-post soil nutrient concentration at irrigation
treatment 4 WAP ........................... .......... ........................ 216

G-9 2005 Equality of variances for pre-post soil nutrient concentration at irrigation
treatment 8 WAP ........................... .......... ........................ 217

G-10 2005 Equality of variances for pre-post soil nutrient concentration at irrigation
treatm ent 12 W A P ... ..................................................................... ............... 2 18















LIST OF FIGURES


Figure page

1-1. Loading potatoes onto railroad car in Hastings, Florida ca 1920's ........................3...

1-2 Internal heat necrosis in 'A tlantic' .................................. ................... ...............6...

2-1 V varieties a.'Atlantic' b.'H arley Blackw ell' ...................... ............. ............... 13

2-2 Daily rainfall (cm) for a. 2004 and b. 2005 production season. Grouping of red
bars denote a leaching rainfall event (7.6 cm in 3 days or 10.1 cm in 4 days).
The yellow, pink, blue, green, orange and black lines denote planting dates 1-6,
respectively, from emergence to tuber initiation................................. ................ 47

2-3 Total and marketable yield at each planting date x variety and accumulated
G D D at harvest, a. 2004 b. 2005 ........................................................ ................ 48

3-1 Aerial photograph of potato production fields along the St. Johns River, St.
Johns County, Florida. Courtesy of Pam Livingston-Way, SJRWMD ...................50

3-2 Plot m ap leaching irrigation project.................................................... ................ 81

3-3 Total water volume from each irrigation date a. 2004 and b. 2005 ......................97

3-4 NO3-N nutrient concentration (mg 10min-1) of AN fertilizer treatment (blue
lines) and CRF treatments (red lines) with parameter estimates by replication at
leaching event 2 W A P 2004 ............................................................... ................ 98

3-5 NO3-N nutrient concentration (mg 10min-1) of AN fertilizer treatment (blue
lines) and CRF treatments (red lines) with parameter estimates by replication at
leaching event 8 W A P 2004 ............................................................... ................ 99

3-6 NO3-N nutrient concentration (mg 10min-1) of AN fertilizer treatment (blue
lines) and CRF treatments (red lines) with parameter estimates by replication at
leaching event 12 W AP, 2004....... ......... ......... ..................... 100

3-7 NO3-N nutrient concentration (mg 10min-1) of AN fertilizer treatment (blue
lines) and CRF treatments (red lines) with parameter estimates by replication at
leaching event 2 W AP, 2005 ......................................................... 101









3-8 NO3-N nutrient concentration (mg 10min-1) of AN fertilizer treatment (blue
lines) and CRF treatments (red lines) with parameter estimates by replication at
leaching event 4 W AP, 2005 .......................................................... 102

3-9 NO3-N nutrient concentration (mg 10min-1) of AN fertilizer treatment (blue
lines) and CRF treatments (red lines) with parameter estimates by replication at
leaching event 8 W AP, 2005 .......................................................... 103

3-10 NO3-N nutrient concentration (mg 10min-1) of AN fertilizer treatment (blue
lines) and CRF treatments (red lines) with parameter estimates by replication at
leaching event 12 W AP, 2005 ....... ........... ............ ..................... 104

3-11 N03-N load (kg ha-1) at 2, 8 and 12 WAP, 2004. a. 2 WAP b. 8 WAP c. 12
W A P .................................................................................................... .......... 10 5

3-12 N03-N load (kg ha-) at 2, 4, 8 and 12 WAP, 2005. a. 2 WAP b. 4 WAP c. 8
W AP d. 12 W AP ................ .............. .... ........ .... ............... 107

3-13 Daily rainfall (cm) for the a. 2004 and b. 2005 production season. The group of
red bars denote a leaching rainfall event (7.6 cm in 3 days or 10.1 cm in 4 days).
The yellow, blue, pink and green arrows denote a stage leaching irrigation event
at 2, 4, 8 and 12 W AP, respectively ....... ... ......................... 109















Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

TIMING OF CLIMATIC FACTORS THAT MAY INFLUENCE POTATO YIELD,
QUALITY, AND POTENTIAL NITROGEN LOSSES IN A NORTHEAST FLORIDA
SEEPAGE-IRRIGATED POTATO PRODUCTION SYSTEM


By

Christine Maria Worthington

December 2006

Chair: Chad M. Hutchinson
Major Department: Horticultural Sciences

Potato, a cool season crop, is planted in Northeast Florida in January when

temperatures are cool. As the season progresses, daily temperatures and incidence of

leaching rainfall events increase which can affect yield and quality. Nutrient runoff from

potato production land has thought to have been primarily responsible for the non-point

source pollution into the St Johns River watershed. Best Management Practices (BMPs)

for potato production in the TCAA have been implemented. With over 7,000 ha in potato

production in the TCAA, the main concern with the implementation of the BMPs are to

not compromise yield and quality. The experimental design in chapter 2 was a split-split

design with four blocks. Planting dates (1-6) were main plots. The first split was the N

rate (168 and 224 kg ha-1). The second split was potato variety, 'Atlantic' and 'Harley

Blackwell'. The experimental design in chapter 3 was a split-split design with four

blocks. Irrigation treatments were main plots at 0, 2, 4, 8, and 12 WAP (weeks after


xviii









planting). The first split was the nitrogen source (AN or CRF). The second split was an

additional side-dress fertilizer application. Optimal yields for the TCAA occurred over a

4 week period (early to late February) in a twelve week planting window. 'Harley

Blackwell' demonstrated its effectiveness to produce quality tubers under conditions

when air temperatures and leaching rainfall events stressed plants. IHN was triggered by

rainfall and nutritional conditions that stressed the plant early in the season combined

with increasing minimum daily temperatures later in the season. Marketable yields in the

CRF treatments were an average of 12% higher compared with the AN fertilizer

treatment. The CRF treatments had a significantly higher incidence of tubers with IHN

compared with the AN fertilizer treatment at 22.3 and 15.6%, respectively. NO3-N

loading from surface water runoff from potato production was decreased an average of

43% with the use of the CRF compared with the AN fertilizer treatment. A CRF used in

potato production, rather than a soluble N fertilizer, could reduce NO3-N loads into the

St. Johns River watershed by 56,000 kg N per year.














CHAPTER 1
INTRODUCTION

Cultivated potatoes (Solanum tuberosum L.) were introduced into Europe by the

Spaniards who traveled to South America in the 1500's, but not until the late 1600's were

they found throughout Europe. During the 18th and 19th centuries the potato was an

established major agronomic food crop throughout Europe. Its acceptance was primarily

due to the increasing cost of grain and the demands for food to accommodate the growing

populace (Burton, 1989a). Many believe the onslaught of Ireland's Great Potato Famine

in 1845 spawned the beginning of the cultivated potato in America. Actually, the first

'Irish' white potatoes were grown in Derry (previously Londonberry) New Hampshire in

the spring of 1719 (Hawkins, 1967).

Today, potatoes are not only important on a world-wide basis, but in the U.S as

well. According to the National Potato Council, 2002, the U.S. ranked third, worldwide,

in potato production (24,000,000 metric tons) following China and the Russian

Federation which produced 65,052,000 and 31,900,000 metric tons, respectively. Since

its introduction as a cultivated crop, potato has become as economically and culturally

important to society as wheat (Triticum aestivum L.) and rice (Oriza sativa L). (National

Potato Council website).

Florida Potato Production

Florida potato production (9,659,000 cwt) ranks in the top 1/3 of the 36 states in

commercial potato production (National Potato Council website). Florida potato

production (chip and fresh market) encompasses approximately 12,550 ha (31,000 acres)









extending as far south as Hendry County and north to Jackson County. According to

Witzig and Pugh, (2004), potatoes continue to remain among the top five vegetables

produced in Florida with a cash value of approximately $115 million (Witzig and Pugh,

2004).

Tri-County Agricultural Area

The largest concentration of potato production is in the tri-county agricultural area

(TCAA; Flagler, Putnam and St. Johns counties) of northeast Florida. Irrigation for the

area is applied by seepage irrigation. V-shaped furrows approximately 18 m apart and a

hardpan clay layer approximately 61 cm below the soil surface allows water to move

down and laterally across the bed and supply needed moisture to the potato crop (Hensel,

1964). Florida can also receive large amounts of rainfall in a very short amount of time.

The 50 year average rainfall received during the production season in the TCAA (January

through June) is approximately 57 cm. Rainfall events as leaching rainfall events and

defined as 7.6 cm in 3 days or 10.1 cm in 7 days are not uncommon during the production

season. The 50 year average for a 7.6 cm leaching rainfall event to occur during the

production season is 2.5 times while the 50 year average for a 10.1 cm leaching rainfall

event to occur is 5.3 times during the production season. In 2004, this area produced

potatoes on approximately 18,000 acres (-7,300 ha) providing a cash value of 42,773,000

(Florida Agricultural Fast Facts, 2005). The majority of the potatoes grown in south

Florida for winter harvest are fresh market varieties. Potatoes grown in the TCAA for

spring harvest are primarily for chip (60%) with fresh market varieties accounting for

about 40% of total production. In the TCAA, potato planting begins in late December

and continues through mid-March. Harvest usually begins by late April and runs through

June.









Potato Capital of Florida

Hastings, located in the southwest portion of St. Johns County, is referred to as the

'Potato Capital of Florida'. The area has been in potato production for over 100 years

when Henry Flagler, a well known philanthropist, railroad magnate, and real estate

developer asked his cousin, Thomas Horace Hastings, (founder of Hastings ca. 1890) to

grow winter vegetables for his hotel guests in St. Augustine. At his request, Thomas built

the first greenhouses in Hastings establishing vegetable production in Northeast Florida.

His production included cucumber (Cucumus sativus L.), cabbage (Brassica oleracea L.,

Capitata group), cauliflower (Brassica oleracea L., Botrytis group), onions (Allium cepa

L.), potatoes, and rice. Potato production acreage started out small 3 to 4 ha (7-9 acres),

but in the following years acreage increased as Hastings became a major supplier for new

potatoes for the northeastern U.S. By 1928, approximately 7,900 railcar loads of fresh

spring potatoes were shipped out of the Hastings area for the northern markets

(Weingartner and Hensel, 2003).
















Figure 1-1. Loading potatoes onto railroad car in Hastings, Florida ca 1920's .

The standard cultivar grown for fresh market in the TCAA during this time during

the 20's and up until 1938 was Spaulding Rose. With its resistance to late blight, mild









mosaic, net necrosis and brown rot, it was an excellent variety for Florida growing

conditions (Folsom, 1945). In the 1950's, 'Sebago' was also found to be a good

processing potato for the burgeoning chip industry. From that point on, Hastings market

went from 100% fresh to more than 80% chip.

Florida Chip Potato Varieties

The standard chip variety grown today in the TCAA is 'Atlantic' which is noted for

its light chip color, relatively high yield (39-50 t ha-1);(350-450 cwt/A), and high specific

gravity (1.090). Higher specific gravity allows for more processed product per unit of

raw product used. Less fat is absorbed during frying along with a shorter frying time.

However, it is susceptible to internal heat necrosis (IHN), a physiological tuber disorder

that causes an unacceptable browning of the tuber tissue

'Atlantic' is resistant to scab (Streptocmyces scabies), Verticillium wilt, pink eye,

caused by the bacterium Pseudomonas marginalia, common races of the late blight

fungus (Phytothera infestans) and race A of the golden nematode (Globodera

rostochiensis) and is immune to virus X (Potato Xpotexvirus) and tuber net necrosis.

With its higher yields and specific gravity, 'Atlantic' replaced 'Sebago' as the primary

chipping potato grown in the TCAA. In the early 1990's 'Snowden' was released and

appeared to be a promising chipping potato with comparable yields and specific gravities

to 'Atlantic', but 'Snowden' can accumulate unacceptable glycoalkaloid levels.

Glycoalkaloids contribute to the potatoes flavor, but in high concentrations can be toxic

to humans causing nausea, headaches and diarrhea (Cantwell, 1996). Today, limited

acreage of 'Snowden' is grown in the TCAA for chip and fresh market, since the

primary chip acreage is planted in 'Atlantic' (Personal communication, Hutchinson,

2004).









'Atlantic' was released July 16, 1976 by USDA, Florida, New Jersey and Maine

Agricultural Experiment Stations and the Virginia Truck and Ornamentals Research

Station, Norfolk Virginia. In replicated trials over three years, 'Atlantic' was compared

to the most popular variety grown for the aforementioned states. Consistently, 'Atlantic'

yielded more (t ha-1), with exception of the Virginia site, and had higher specific gravities

in all states (Webb et al., 1978).

Recently a potato variety was released that may provide chip potato growers an

alternative to 'Atlantic' and 'Snowden'; 'Harley Blackwell', was released in 2003 by the

USDA based on the cooperative research results of many institutions including the

University of Florida. Plant size (vigor), maturity, canopy shape and flowering

characteristics are all similar to 'Atlantic'.

Yields and specific gravities of 'Harley Blackwell' are lower than 'Atlantic', but

are acceptable according to chipping standards (Beltsville Agricultural Research Center

website) (United States Standards for Grades of Potatoes for Chipping, 1997). Another

desirable characteristic of 'Harley Blackwell' is its resistance to internal heat necrosis

(IHN).

IHN is described in the Compendium of Potato Diseases, 2nd edition, as a

physiological disorder caused by elevated soil temperatures during the latter stages of

growth and development of the tuber. If the vines and leaves are still actively growing

and green during this period of elevated temperatures, water and nutrients are

translocated from the tuber to supply the plant. The vascular system of the tuber is

stressed and cannot sustain the evapotranspirational demands of the plant. Under these

conditions, it is reported that the vascular ring deteriorates and becomes necrotic.









Symptoms are most severe during hot, dry weather conditions in sandy, gravel, muck or

peat soils. Necrotic areas are mostly found in and around the vascular ring usually

coalescing and radiating to the center (pith). The symptoms are also more prevalent at

the bud (apical) end of the tuber and not the stem end. Peterson et al. (1985) reported that

as the tuber expands there is more xylem at the stem end of the tuber during growth and

development. IHN does not affect the nutritional value of the tuber, but the economic

impact can be significant due to off-grade quality. The exterior of the potato tuber does

not show visible signs of IHN. According to the Department of Agriculture (1978),

USDA no. 1 potatoes may not exceed 10 and 5% external and internal defects by weight,

respectively.
















Figure 1-2. Internal heat necrosis in 'Atlantic'

Internal necrosis (physiological necrosis) was first reported in 1937 by Larson and

Albert when they recognized it as an economic concern for commercially grown

potatoes. Internal necrosis has been referred to as internal brown spot (IB S), chocolate

and rust spot, internal browning and internal brown fleck (Sterrett and Henninger, 1997).

Unlike IBS that is reported to occur throughout the growing season, IHN of 'Atlantic' has

been reported to occur during the mid to late bulking period of the tuber.









Seasonal Environmental Stress Associated with IHN

Sterrett et al. (1991) reported that IHN is influenced by more than one

environmental stress factor. During the 1986-1988 production years, seven planting

dates in two locations (New Jersey and Virginia) and several harvests, beginning at 80

DAP and continuing to 147 DAP, were evaluated using a step-wise regression model that

included the variables temperature, rainfall, days after planting (DAP), yield and

percentage of large tubers (>64mm in diameter) to assess when potatoes become off-

grade during the growing season. Accumulated heat units were evaluated in the model

with a penalty imposed if the maximum and minimum temperatures were above 25 and

21C, respectively for a consecutive duration of three or more days (Lee et al., 1992). A

weak correlation was observed with the occurrence of IHN due to DAP, yield and

percentage of large tubers. Although rainfall was included in the model it was not

assessed. The findings concluded that more than one environmental factor, such as,

reduced solar radiation, reduced temperature and increased relative humidity and its role

in photosynthesis, respiration could be involved in the development of IHN.

Henninger et al. (2000) also used the heat sum model by Lee to evaluate 19

different potato clones and their parents including 'Atlantic' for the occurrence of IHN

over three years and in six locations in NJ and VA. Temperatures during the later part of

the 1991 and 1993 production years were above the maximum temperature allowed for

potatoes going off-grade due to IHN according to the Lee heat sum model. Although

'Atlantic' had the highest yield and specific gravity, it also had the highest incidence and

severity of IHN. This result was in agreement with (Sterrett and Henninger, 1997) who

reported a higher incidence of IHN near harvest and generally in the larger tubers (>76

mm). Lee et al. (1992) reported that IHN in 'Atlantic' occurred earlier in plant









development correlating with the highest mean maximum temperature during the 0-30

DAP and the highest mean minimum temperature during the remainder of the growing

season up to 90 DAP. They concluded that the high minimum temperatures had an effect

on the occurrence of IHN.

Moisture Stress

Wannamaker and Collins (1992) evaluated nine cultivars, including 'Atlantic' for

its susceptibility to IHN, at two locations (Tidewater Research Station TRS, NC and

Horticultural Crops Research Station HCRS, Castle Hayne, NC), and two planting and

harvest dates in 1989 and 1990. Occurrence of IHN was higher at the TRS site in 1989

(1.3 to 68.7%) when compared with HCRS with an occurrence of IHN of 0 to 35.5%.

Temperatures were similar for both locations and years, but rainfall was higher at the

TRS site in 1989 and 1990. Although the occurrence of IHN was lower in 1989 the TRS

site still had the highest amount of rainfall and incidence of IHN. Sterrett et al. (1991)

reported that during the growing season in 1989, IHN was delayed due to the increased

rainfall during the first 60 DAP but incidence increased during a dry, warm spring.

Although IHN may be due to a combination of environmental stressors, Wannamaker and

Collins' report contradicts others that IHN typically occurs during dry conditions. While

IBS is a similar physiological defect, a report by Iritani et al. (1984) supports

Wannamaker and Collins findings suggesting that temperature and, most important of all,

moisture fluctuations are suspected to cause IBS. Novak et al. (1986) studied brown

fleck in potatoes in Queensland. They found an increase in brown fleck incidence when

soil moisture levels were high late in the season. They suggested withholding irrigation

as the crop reached maturity to reduce the disorder that contradicts Sterret et al. (1991)

that a higher incidence of IHN was noted when a hot dry weather later in the season.









Nutrition

Silva et al. (1991) evaluated varying gypsum and nitrogen rates in conjunction with

three irrigation schedules (no irrigation, required irrigation, and excess irrigation) on

specific gravity, yield, and internal defects of 'Atlantic' over a three year period.

Nitrogen rates had no significant effect on the internal quality of tubers, but the

application of gypsum did lower IBS occurrence in 'Atlantic' tubers. They also found

that excess irrigation increased the incidence of IBS in 'Atlantic' potatoes in two of the

three years evaluated. Sterrett and Henninger, (1997) reported that Clough, (1994), found

an increase in IHN incidence when lower N rates (68 or 84 kg N ha-1 were applied vs.

168 or 252 kg N ha-1). Sterrett and Henninger (1991), report supports Clough's findings

that IHN was slightly reduced with the higher N rates of 84 and 252 kg N ha-1 versus 64

kg N ha-1.

Palta (1996), reported since tubers are naturally deficient in Ca+ especially those

grown in sandy soil, applying Ca+ to the tuber-stolon junction improved Ca+ uptake in

tuber peel and medullary tissue, suggesting that placement is key to improving uptake

efficiency of Ca+. Ozgden et al. (2005) recently reported potato plants that received split

applications of calcium nitrate throughout the season had significantly lower incidence of

IBS in 1997. They also reported that tuber calcium concentrations were higher in 1999,

but the incidence of IBS was not significantly different than the treatments without

calcium nitrate. The authors mentioned that a leaching rainfall (13cm) within 24 hrs

occurred during the bulking period that may have had an effect on the incidence of IBS in

'Russet Burbank' potatoes. Gunter et al. (2000) reported soluble sources of calcium

applied in split applications was more effective at reducing the incidence of IBS

compared with the application of gypsum. Tzeng et al. (1986), reported a negative









correlation between the incidence of IBS and tuber peel calcium. Sterrett and Henninger

(1991), evaluated different Ca+ rates and their effect on several cultivars for the

occurrence of IHN. The cultivars included, 'Atlantic' (non resistant to IHN), Katahdin,

(moderately resistant to IHN), and Kennebec and Superior, (moderate to high resistance

to IHN). It was reported that 'Atlantic' had significantly lower tuber tissue Ca+

compared with Superior. However, placement of Ca+ within the hill had no effect on the

IHN occurrence. Sterrett et al., (in press) reported a significant clone x calcium

interaction for the incidence of IHN at two locations in 2001 and 2002. They reported

that soil applied Ca+ increased Ca+ in two IHN susceptible clones and decreased Ca+

concentration in one IHN susceptible clone in 2001. However, in 2002, they reported the

incidence of IHN decreased in three (2 IHN susceptible clones and 1 IHN resistant clone)

of the 18 clones when Ca+ was applied to the soil. Although Ca+ is one of the most

naturally abundant plant nutrients, it can be easily leached, especially in humid climatic

conditions (Mengel and Kirkby, 1987). Ca+ can also be removed from the soil profile by

the addition of N fertilizers, e.g. NH4N03. The process of nitrification releases H+ into

the soil releasing Ca+ from exchange sites and eventually leaching below the root zone

of the potato crop. It has been reported that for every 100 kg of (NH4)2SO4 added to the

soil, approximately 45 kg of Ca+ are leached (Mengel and Kirkby, 1987).

Rationale

'Atlantic' is the major commercial chipping variety grown in the TCAA encompassing

70% of the acreage grown making it economically vital to the area. Major chipping

processors request 'Atlantic' for their product for its chipping quality although 'Atlantic'

is susceptible to developing IHN. Developing an understanding of the role

environmental and nutritional stressors play on yield and quality, especially IHN of









potato would benefit Florida farmers. According to Sterrett and Henninger, to date there

have been no cultural management practices which alleviate the onset and progression of

IHN. Therefore, the focus of this research is to determine at what stage IHN may be

initiated and the correlation with cultural and/or environmental stressors throughout the

growing season.

Organization of Dissertation

This work is organized into four chapters. The first chapter is an introduction

describing the history of the potato from its South American origin to its vital role as part

of Florida's agriculture today. The second chapter describes the results of a two year

study evaluating multiple planting dates with two N rates and two varieties and how the

timing of climatic factors and cultural practices effect tuber production and quality in the

TCAA during the growing season. The third chapter reports the results of a two year

study which addresses the effects of two nitrogen (N) fertilizer sources and simulated

leaching rainfalls during the growing season on yield, tuber quality and nitrate leaching

(NO3-N). The fourth chapter summarizes the results and conclusions and suggests future

research addressing yield and quality of potato production in the TCAA.














CHAPTER 2
DEVELOPMENT OF A GROWING DEGREE DAY MODEL TO DETERMINE
OPTIMAL PLANTING DATE AND ENVIRONMENTAL INFLUENCE ON POTATO
YIELD AND QUALITY IN NORTHEAST FLORIDA

Introduction

Potato production in Florida spans from as far south as Hendry County to Jackson

County in the north. The largest area in production is northeast Florida's Tri-County

Agricultural Area (TCAA) (St. Johns, Putnam and Flagler counties) with 7,300 ha

(18,000 acres). Potatoes continually rank among the top five vegetables in production in

Florida with annual value of approximately $125 million (Witzig and Pugh, 2004).

Potatoes, a cool season crop, are planted in the TCAA beginning in late December

when day length is short and temperatures cool. As the season progresses and the potato

progresses through key developmental stages, daylight hours lengthen and temperatures

increase. Winkler (1971) reported that yields may suffer due to extended periods of cool

temperatures (below 18C) as well as higher temperatures (above 20C) for extended

periods. Cooler and higher temperatures reduce net assimilation to the tubers while

higher temperatures may prevent tuber initiation.

'Atlantic' is the most prevalent chip variety in northeast Florida. 'Atlantic' is

noted for its light chip color, relatively high yield and high specific gravity (Fig 2. la).

However, it is susceptible to internal heat necrosis (IHN), a physiological tuber disorder

that causes an unacceptable browning of the tuber tissue (Fig 2.2).























Figure 2-1. Varieties. a.'Atlantic' b.'Harley Blackwell'

'Harley Blackwell', a new variety resistant IHN, was released in 2003 by the US

Department of Agriculture (USDA, Beltsville Md., 2004) (Fig 2. lb). Yield and specific

gravity of 'Harley Blackwell' are lower than 'Atlantic' but are acceptable according to

chipping standards (United States Standards for Grades of Potatoes for Chipping, 1978).

Both 'Atlantic' and 'Harley Blackwell' were planted in this study.

Growing Degree Days

Growing Degree Days (GDD) are a useful tool to determine harvest dates and yield

in crops such as broccoli (Brassica oleracea L.) (Dufault, 1997), peas (Pisum sativum L.)

(Hoover, 1955); corn (Zea mays L.); cucumber (Cucumis sativus L.) (Perry et al., 1986)

and taro (Colocasia esculenta L. 'Schott') (Lu et al., 2001). Sterrett et al. (1991)

evaluated a revised accumulated heat unit system (Lee et al., 1992) to predict when

potato tubers would go off-grade. With this system, growers could determine when to

harvest to avoid economic losses due to tuber quality issues.

Historically, growers in the TCAA have used calendar days and experience to

predict key potato developmental stages e.g. emergence, full flower and full senescence.

Developing and utilizing the growing degree day system may be a more accurate









predictor of these stages throughout the season to determine optimal planting dates and

yields compared with calendar days. It would also facilitate a more efficient fertilizer

and pesticide application schedule.

This experiment was designed to evaluate and quantify the effects of multiple

planting dates on the occurrence of IHN based upon environmental stressors (rainfall and

temperature) as well as determine the influence of growing degree day accumulation on

the timing of key developmental stages and production of optimal yields over multiple

planting dates typically experienced in the TCAA.

The objectives of this study were to 1) determine the effects of multiple planting

dates and N rates on yield and quality of potato in Northeast Florida 2) determine when

and what climatic factors influence yield and quality of potato in Northeast Florida 3)

develop a model based on GDD to determine key developmental stages of potato.

Materials and Methods

Site Description

The experiment was conducted during production years 2004 and 2005 at the

University of Florida, Plant Science Research and Education Unit, Hastings, Florida on

an Ellzey fine sand (sandy, siliceous, hyperthermic Arenic Ochraqualf; sand 90% to 95%,

<2.5% clay, <5% silt). The soil profile is described as poorly drained although the top 94

cm have a very high permeability rate (5-10 cm hr-1). A restricting clayey layer lies below

the sandy loam top layer of the profile. The water table is within 25 cm of the surface for

one to six months of the year (Soil Survey, St Johns County, 1983)

Experimental Design

The experiment was arranged as a randomized complete block with a split-split

design with four blocks in bed 16 NL at the PSREU Hastings Farm. Planting dates (1-









6) were assigned to main plots. Each main plot (planting date) was 46.3 m by 6.0 m (6

rows) with a 12.1 m buffer between the north and south end of the main plots. The first

split was the N rate at 168 and 224 kg ha-1. N rate plots were 4.8 m by 6.0 m (6 rows).

The second split was potato variety, 'Atlantic' and 'Harley Blackwell' (Maine Farmer's

Exchange-MFX, Presque Isle, Maine). Potato variety plots were 4.8 m by 3.0 m (3 rows)

Crop Production Practices

Tuber Planting

Potatoes were cut at planting to an approximate 71 g seed piece and dusted with

fungicide [1.13 g a.i. fludioxonil and 21.82 g a.i. mancozeb per 45.4 kg seed pieces

(Maxim MZ; Syngenta Crop Protection, Inc., Greensboro, N.C.)]. Azoxystrobin [0.1 L

ha-1 a.i. (a.i., Amistar; Syngenta, Crop Protection, Greensboro, N.C.)] and aldicarb [3.36

kg ha-1 a.i (a.i., Temik, Bayer Corp., Kansas City, Mo.)] was applied in-row at planting.

All other pesticide applications during the growing season followed recommendations for

Florida potato production (Hutchinson et al., 2004).

Irrigation

Plots were irrigated with seepage irrigation throughout the growing season except

during periods of sufficient rainfall. The seepage irrigation system is a semi-closed

system. Water withdrawn from the confined aquifer is pumped through PVC (polyvinyl

chloride) pipe to each V-shaped open water furrow in the field. Each water furrow is

situated 18.2 m apart. Water seeps from the water furrow laterally, underground, across

the bed and through capillarity reaches the rooting system of the potato plant (Singleton,

1990). Water is controlled at each water furrow by a valve that can be turned on or off

when necessary. Current research at the farm as estimated that each valve can deliver

approximately (8.3 L min-1).









Nutrient Management

Fertilizer application was based on 100 and 75% of the best management practice

(BMP) recommendations for Florida potato production [224 and 168 kg ha-1 N,

respectively] (Hutchinson et al., 2004). In both seasons, pre-plant fertilizer (1 day before

planting) was applied with a two-row hydraulic fertilizer applicator (Kennco Mfg.,

Ruskin Fl, 33570) banded on top of the row at 112 kg N ha-1 as 14N-6.0 P205-12.0 K20.

Total P requirement 44.8 kg P205 ha-1 was applied in a single pre-plant application.

Fertilizer was chopped and incorporated with a four-row chopper then each row was

bedded prior to planting. One sidedress of remaining N [112 and 56 kg N ha-1,

34N-0P205-0 K20] and K [60.4 kg K20 ha- ON-0P205-50K20] was applied

approximately 30 d after each planting date when plants were 10 to 15 cm tall with a two-

row, ground driven, belted fertilizer applicator that banded the fertilizer on each side of

the plant. Rows were then single disked to cover the fertilizer on the shoulder of the row.

Tuber Production Analysis

At harvest potatoes were graded and sized into the following class sizes; B = 3.8 to

4.4 cm, Al = 4.4 to 6.4 cm, A2 = 6.4 to 8.3 cm, A4 = > 10.2 cm. Culls (growth cracks,

misshapen, sunburned and rotten tubers) were removed and weighed before "A" size

classes were separated. Marketable yield is defined as no. 1 tubers with diameters

between 4.4 and 10.2 cm (USDA, 1978) and without visible blemishes (rotten, green,

misshapen, or containing growth cracks).

One row of potato plants (5.8 meters) from each fertilizer rate by variety plot

within each block and planting date were harvested at least 100 DAP as required by

aldicarb labeling. A late season harvest, approximately 128 DAP, of one row of potato

plants (5.8 m) from each fertilizer rate by variety plot within each block and planting date









were also harvested. At both harvests, tubers were washed, graded and sized into five

classes as described above.

Tuber Specific Gravity

Specific gravity was calculated from a sub-sample of marketable tubers from each

fertilizer by variety plot within each block and planting date using weight in air/ weight

in water method (Burton, 1989c). 'Atlantic' potatoes are the standard for chipping in

Florida, therefore, high tuber specific gravity is desired. Specific gravities of at least

1.078 are considered good for production at the PSREU research farm in Hastings, FL

(Hutchinson et al., 2002).

External Quality

Culls (green, growth cracks, misshapen, and rotten tubers) were removed and

weighed at the grading line. External quality (green, growth cracks, misshaped and rot)

were reported as a percentage of total yield.

Internal Quality

A 20 tuber sub-sample from each fertilizer by variety plot within each block and

planting date were cut into quarters and rated for internal quality. Rated physiological

disorders included hollow heart (HH), internal heat necrosis (IHN) and brown center

(BC). Disease induced disorders included corky ring spot (CRS) and brown rot (BR). A

twenty tuber sample from each plot was scored for percent hollow heart, IHN, and BC.

IHN severity was scored on a one to six scale with a score of one to four relating to the

number of quarters with IHN. A score of five or six indicated that all quarters had the

disorder and up to 75 to 100% of all quarters were showed visual symptoms, respectively

(Figure 2- 3).









Growing Degree Days

Growing degree days (GDD) were calculated throughout the season for each

planting date for the 2004 and 2005 production season with the following formula (Sands

et al., 1979):



GDD = [(minT + maxT)/2)-7C].



where minT and maxT are the minimum and maximum daily temperatures and the base is

7C.

GDD totals were recorded for key growth and developmental stages (emergence,

tuber initiation and full flower). Emergence was determined when the plantlets were just

emerging from the soil. Tuber initiation was determined by the visual observance of the

radial growth of the stolon tip and full flower was determined when approximately 90-

95% of the peduncals on plants in each plot had open flowers.

Statistical Analysis

Tuber production. A general linear model was used to determine yield, internal

and external quality responses of 'Atlantic' and 'Harley Blackwell' potato varieties as a

result of multiple planting dates and two N rates for the 2004 and 2005 production

seasons. Normality for each potato class size was checked by residual analysis using the

Shapiro-Wilk test as implemented in the PROC CAPABILITY procedure of SAS (SAS,

Institute, 2004). Means were separated using Tukey adjustment as implemented in SAS

(SAS Institute, 2004) to separate individual factor means and/or interaction means when

significant.









Results And Discussion

This experiment was designed to determine optimal yields over a typical growing

season and the effects of nutrient and environmental stressors (rainfall, temperature)

would have on yields and quality in the TCAA. Additionally, GDD were also calculated

for each planting date to determine optimal yields and key developmental stages and

throughout the 2004 and 2005 growing season.

Tuber Yield for 2004

Planting date main effect

Planting date main effect significantly influenced total and marketable yields for

2004 and 2005 (Table 2-1). Plants in planting dates 5 and 6 (planted 9 Mar. and 24 Mar.)

produced significantly lower total and marketable yields compared with plants in planting

dates 3 and 4 (planted 9 Feb. and 23 Feb.), respectively, in 2004. Tubers in planting

dates 5 and 6 were bulking under high temperatures, 25.9 and 30.3C, respectively that

increased respiration and decreased dry matter accumulation compared with early

plantings (Burton, 1989c).

Tubers in planting dates 3 through 6 (9 and 23 Feb; 9 and 24 Mar), respectively,

had significantly lower specific gravities compared with planting date 2 (planted 26 Jan.).

Tubers from planting dates 3 and 4 (9 and 23 Feb), had (received) a higher percentage

(amount) of water (rainfall) that contributed to their higher tuber yields. Rainfall

accumulation from tuber initiation through harvest for planting dates 3 through 6 was

three times higher compared with planting date 2 (planted 26 Jan.) for the same

developmental stages. Tubers in the size class distribution range Al to A2 in planting

dates 2 and 5 and A2 to A3 in planting dates 5 were significantly lower compared with

planting date 4 (Table 2-4). This result was due to the cooler and warmer temperatures









early and later in the growing season which decreased tuber development caused by

reduced net assimilation to the tubers.

Nitrogen rate main effect

Fertilizer main effect significantly influenced marketable tuber yields in 2004.

Plants in the 224 kg N ha-1 treatment had significantly higher marketable yields compared

with plants in the 168 kg N ha-1 treatment at 23.2 and 20.5 t ha-1, respectively (Table 2-1).

Variety main effect

Variety main effect significantly influenced total and marketable yields in 2004.

Total and marketable yields for 'Atlantic' were 8% and 20% higher compared with

'Harley Blackwell', respectively, over all planting dates and nitrogen rates. 'Atlantic'

had higher specific gravity compared with 'Harley Blackwell' (1.078 and 1.075),

respectively, as well (Table 2-1). Varieties that are resistant to IHN typically have lower

specific gravities than varieties prone to IHN e.g. 'Atlantic' (Sterrett and Henninger who

in 1991). Although 'Harley Blackwell' had lower specific gravity, chipping companies

will still accept them due to their internal quality.

Main effect interaction

The two-way interaction between planting date and fertilizer rate main effects was

significant for the total and marketable tuber yields in 2004. A two-way interaction was

also significant for the planting date by variety main effects. The two-way interaction

term was calculated using LSMeans with the slice option (planting date) (SAS 2004).

This option enabled the comparison of the fertilizer rates within each of the planting dates

as well as the comparison of the varieties within each planting date.

The 224 kg ha-1 N rate had significantly higher total and marketable yields in

planting dates 3, 5 and 6 (planted 9 Feb and 9 and 24 Mar, respectively) compared with









the 168 kg ha-1 N rate within each of the respective planting dates. These results

indicated that planting late in the season (March) led to tuber bulking in warmer and

wetter weather conditions that negatively impacted total and marketable yields (Table 2-

2).

The interaction term for planting date by variety main effects was significant in

2004. 'Atlantic' had significantly higher total tuber yields in planting dates 1, 3, 5 and 6

compared with 'Harley Blackwell'. Although 'Atlantic' had significantly higher total

yields compared with 'Harley Blackwell' in the later planting dates (planting dates 5 and

6), 'Atlantic' had a significantly higher incidence of rots compared with 'Harley

Blackwell' that would explain the non significant planting date by variety interaction for

marketable yield (Table 2-3 and Table 2-7). There were no other main effect interactions

for yield.

Tuber Yield for 2005

Planting date main effect

Planting date main effect significantly influenced total and marketable yields in

2005. Planting dates 1, 2, 5 and 6 had significantly lower marketable yields compared

with planting dates 3 and 4 (planted 8 and 22 Feb) (Table 2-1). A leaching rainfall event

occurred early in the season for planting date 6 (1 June) that delayed plant emergence

(Figure 2-4). The significantly lower marketable yields in planting dates 1 and 2 may be

due to the lower temperatures early in the season, with average low temperatures of

11.4C which reduced net assimilation to the developing tubers and negatively impacted

yield. Higher temperatures in planting dates 5 and 6 later in the season increased tuber

respiration and decreased dry matter accumulation during the bulking period with

average high temperatures of 29C between full flower and harvest (Figure 2-4). Size









class distribution was also significantly influenced by planting dates. Planting date 1 and

6 had the highest weight of B size tubers compared with all other planting dates.

Additionally, planting dates 1 and 6 also had the lowest percentages of tubers in size class

ranges Al to A2 and A2 to A3 (Table 2-4) which are the marketable tuber size class

range. Cooler temperatures early in the season as well as the higher temperatures late in

the season also decreased and/or prevented tuber initiation and development (Burton,

1989c).

Nitrogen rate main effect

Nitrogen rate main effect did not significantly influence total or marketable tuber

yields in 2005. Plants in the 224 kg N ha-1 had slightly higher tuber total yields compared

with the 168 kg N ha-1 rate at 25.2 and 24.5 t ha-1, respectively. Total and marketable

tuber yields were not significantly different in the 224 kg N ha-1 treatment compared with

plants in the 168 kg N ha-' treatment at 19.4 and 19.1 t ha-1, respectively (Table 2-1).

Three leaching rainfall events occurred during the 2005 season compared with one in the

2004. This may explain the similarities in the total and marketable yields between

fertilizer treatments in 2005 (Figure 2-4a and 2.4b). There were no significant nitrogen

rate main effects interaction for tuber total and marketable yields in 2005.

Variety main effect

The variety main effects significantly influenced total and marketable yields in

2005. 'Harley Blackwell' had significantly higher total and marketable yields 26.1 and

20.0 t ha-1 compared with 'Atlantic' at 23.6 and 18.6 t ha-1, respectively. This result was

most likely due to a higher tuber set per plant in 'Harley Blackwell' compared with

'Atlantic'. 'Atlantic' may also be more sensitive to colder temperatures early in the

season and warmer temperatures later in the season, both of which would reduce net









assimilation to developing tubers. 'Atlantic' had significantly higher specific gravity

compared with 'Harley Blackwell' at 1.078 and 1.076, respectively. Plants in planting

dates 5 and 6 in 2004 and 2005 were bulking under high temperatures that increased

respiration and decreased dry matter accumulation compared with early plantings that

resulted in lower yields (Burton, 1989c). Optimum planting dates to obtain highest yields

in the TCAA, based on the results of this research, encompassed a 4-week period in the

middle of the traditional 12-week planting window. These dates corresponded to planting

dates 3 and 4 and extended from early February through the last week of February (Table

2-1).

Main effect interactions

The two-way interaction between planting date and variety main effects were

significant for the total tuber yields in 2005. 'Harley Blackwell' had significantly higher

total yields in planting dates 2, 3, and 6 compared with 'Atlantic' (Table 2-3). As

discussed in the variety main effects, "Harley Blackwell' appears to tolerate

environmental stress better compared with 'Atlantic' early and later in the season.

Tuber External Quality for 2004

Planting date main effect

Planting date main effect significantly influenced the number of total culls in 2004.

Tubers in planting dates 5 and 6 (planted 9 and 24 Mar) produced significantly higher

total culls, 14.5 and 10.4%, respectively, compared with all other planting dates (Table 2-

7). Since potatoes are a cool season crop, this was due to the warmer day and night

temperatures with an average of 4 and 6 degrees warmer, respectively, as well as wetter

weather conditions with an average additional rainfall amount of 5.3 cm.









Nitrogen main effect

Nitrogen rate main effect did not significantly influence the occurrence of external

defects. Percentages of total culls for the 168 and 224 kg ha-1 N rate treatments were 3.2

and 2.4%, respectively (Table 2-7).

Variety main effect

Variety main effect significantly influenced the incidence of total culls. 'Atlantic'

had a significantly higher percentage of total culls (2.9%) compared with 'Harley

Blackwell' (2.8%) (Table 2-7). The interaction term for the planning date and variety

main effects were significant for total culls. 'Atlantic' had a significantly higher

percentage of total culls compared with 'Harley Blackwell' in planting date 2 at 3.1 and

0.3%, respectively. There were no other interaction effects for the 2004 production

season.

Tuber External Quality for 2005

Planting date main effect

Planting date main effect in 2005 significantly influenced total cull production

Tubers in planting dates 5 and 6 had significantly higher percentages of total culls (21.1

and 30.1% of total yields) compared with tubers from all other planting dates. A leaching

rainfall event (17.0 cm) between 31 May and 1 June, 2005 (early to mid bulking) during

planting dates 5 and 6 combined with higher temperatures during these planting dates

(average of 8 degrees) explained the significantly higher total culls, primarily rots, for

both planting dates 5 and 6 (Table 2-7; Fig 2.5).

Nitrogen rate main effect

Nitrogen main effect did not significantly influence external defects in 2005.









Variety main effect

Variety main effect significantly influenced total culls. 'Harley Blackwell' had

significantly lower total culls compared with 'Atlantic' (4.0 and 8.1%), respectively

(Table 2-7). As mentioned previously, 'Atlantic' may be more sensitive to the warmer

temperatures late in the season. 'Atlantic' should be planted for early chipping contracts

and 'Harley Blackwell' should be planted to fill late season contracts when 'Atlantic'

quality can be suspect.

Tuber Internal Quality for 2004

Planting date main effect

Internal tuber defects are an important class of defects. Unlike external tuber

defects, internal defects cannot be seen on the grading table. Therefore, they cannot be

'picked-out' before loading on the truck. The only recourse a grower has for a field of

potatoes with high levels of internal defects is to blend the load with tubers that do not

have a high percentage of defects. According to the Department of Agriculture, 1978,

USDA no. 1 potatoes may not exceed 10 and 5% external and internal defects by weight,

respectively.

Planting date main effect significantly influenced the occurrence of IHN in tubers

in 2004. Tubers from planting date 4 (planted 23 Feb) had significantly higher incidence

of IHN compared with tubers from planting dates 1, 5 and 6 (planted 13 Jan., 9 and 24

Mar.) in 2004 (Table 2-8). IHN severity ranged from a high of 1.5 in planting date 4 to a

low of none in planting date 6. The significantly higher incidence of IHN in tubers

during planting date 4 could be explained in part to a leaching rainfall event in the first 30

DAP, between 200 and 400 GDD, which most likely leached a majority of the preplant

fertilizer (112 kg N ha-1) below the root zone. Although preplant N was applied in









planting dates 1-4, planting date 4 had the shortest amount of time before a leaching

rainfall event occurred after planting, approximately 21 DAP. Plants were in their early

vegetative stage, which required less nitrogen (approximately 15% of total N applied)

(Ojala et al., 1990). N applied preplant may have gone through nitrification and

subsequently leached below the root zone, therefore, leaving only the N applied at the

second sidedress for growth and development the remainder of the season.

Nitrogen rate main effect

Nitrogen main effect did not significantly influence the occurrence of tubers with

IHN in 2004 (Table 2-8).

Variety main effect

Variety main effect significantly influenced the incidence IHN in tubers in 2004.

'Atlantic' had a significant higher percentage of tubers with IHN compared with 'Harley

Blackwell', 1.7 and 0.0% of total yield, respectively (Table 2-8).

Tuber Internal Quality for 2005

Planting date main effect

Planting date main effect significantly influenced the percentage of tubers with

IHN in the 2005 production season. Similarly in 2004, tubers in planting date 4 (planted

22 Feb) had a significantly higher incidence of IHN (3.9%) compared with all other

planting dates. Tubers in planting date 5 also had a higher incidence of IHN (3.1%)

compared with planting dates 1, 2, 3, and 6. Severity was highest in planting dates 4 and

5, each having an IHN severity rating of 1.5.

A leaching rainfall event (Potatoes horticulturally and environmentally sound

fertilization of Hastings area potatoes, brochure) occurred between emergence and tuber

initiation (between 200 and 400 GDD for planting dates 4 and 5). NO3-N was most









likely leached below the root zone leaving the sidedress application as the primary N

supply for the remainder of the season. A second and third leaching rainfall, 55-60 DAP;

10.26 cm and 85 DAP; 9.69 cm, respectively, occurred during the early to mid and late

bulking periods for planting date 5 (Fig 2.5). The two late seasons leaching rainfall events

occurred during the period of highest N demand by the plant explaining the 15 fold

increase in tuber IHN levels compared with the 2004 season (Table 2-4). Ojala et al.

(1991) reported plants during tuber initiation and bulking use approximately 30 and 58

to71%, respectively, of the total N applied.

Nitrogen rate main effect

Nitrogen rate main effect did not significantly influence IHN in tubers, with similar

nitrogen rate main effect results in 2004, it would suggest that N rate alone is not the

single cause of IHN development in tubers

Variety main effect

Variety main effect significantly influenced the incidence of IHN in tubers.

'Atlantic' had a significantly higher incidence of IHN compared with 'Harley Blackwell'

at 2.3 and 0.0%, respectively. 'Atlantic' also had a higher severity rating (1.3) compared

with 'Harley Blackwell' (0.0) (Table 2-8).

The percentage of tubers with IHN was highest in planting date 4 in 2004 and

2005. The highest mean maximum temperatures during the first 30 DAP and mean

minimum temperatures up to 90 DAP were observed starting in planting date 4. This

supports the findings by Lee et al. (1992) that IHN in 'Atlantic' is highly correlated with

high maximum temperatures in the first 30 DAP and high minimum temperatures for the

remainder of the season up to 90 DAP (Table 2-9). Additionally, leaching rainfall events

early in the season for planting date 4 in 2004 and 2005 as well as planting date 5 in 2005









predisposed these tubers to IHN due to a combination of nutritional and environmental

stress during early tuber development (Fig 2.4).

Growing Degree Day Model

Growing Degree Day Model and Potato Plant Development

The key developmental stages evaluated for this study were emergence and full

flower. Emergence and full flower occurred on average across planting dates at 213 and

804 accumulated GDD, respectively for the 2004 production season. In 2005, the

average across planting dates for emergence and full flower were 210 and 813

accumulated GDD, respectively. GDD is a more predictive model compared with

calendar days for determining key developmental stages for the potato plant. For

instance, full flower occurred from 68 to 40 d after planting for 2004 and 71 to 42 DAP

in 2005 over all planting dates. As planting dates progressed during the season, periods

between developmental stages compressed (Table 2-10). This result would be an

important concept to communicate to growers. Fertilizer and pesticide applications, as

well as, harvest dates should be timed by accumulated GDD and not calendar days as

commonly done.

Growing Degree Day Model and Tuber Yield

During the 2004 production season, planting date 4 had the highest total and

marketable yields, with accumulated GDD 2374. Marketable tuber yields were similar

for planting date 1 through 3 (Table 2-1). Planting in January and March resulted in an

average reduction in yield of 16 and 25%, respectively (Table 2-11).

The 2005 production season also had the highest yields in planting dates 3 and 4,

with accumulated GDD of 1894 an 2160, respectively. Optimum planting dates to obtain

highest yields in the TCAA, based on the results of this research, encompassed a 4-week









period in the middle of the traditional 12-week planting window. Optimum period for

highest yield extended from early to late February, 2004, which corresponded to 1951 to

2374 accumulated GDD for a 100 d season when planted during this part of the season.

Planting before and after this 4 week period resulted in an average decline in yield of 16

and 25% compared with planting date 4 respectively (Table 2-11).

The optimum period for highest yields in 2005 extended from early February

through the first week of March, 2005, which corresponded to 1894 to 2385 accumulated

GDD for a 100 d season. Planting date 4 had the highest yields in 2005, as well.

Planting before this date resulted in a reduction in yields from 48 to 55%. Planting later

resulted in a decrease in yields from 36 to 73% (Table 2-11).

Optimum planting dates for both the 2004 and 2005 season were planting dates 3

and 4. Planting before and after this 4-week period resulted in decreased yields for both

'Atlantic' and 'Harley Blackwell' for the 2004 and 2005 production seasons due to colder

temperatures early in the season and warmer and wetter weather later in the season

(Figure 2-4).

In this experiment (and on many private farms), harvest was not determined by

accumulated GDD but determined by calendar days. Aldicarb, a common soil applied

insecticide/nematicide used in the area has a 100-d harvest interval. Growers time their

harvest according to this required harvest interval. The calendar method works better for

the mid-season planting because 'Atlantic' and 'Harley Blackwell' both have about a

100-d season. Timing harvest by calendar days does not work late in the season because

as the season compresses, harvest should be accelerated. This concept would be

important in later plantings because hot and wet weather in June increases rots in mature









tubers as was demonstrated in this research. A grower that had late season contracts to

fill, could theoretically harvest their crop from 92 to 83 DAP rather than the 100 day

interval based upon aldicarb labeling requirements if an alternative to aldicarb could be

identified (Table 2-11).

Growing Degree Day Model and Internal Tuber Quality

The highest incidence of tubers with IHN in 2004 was during planting dates 3 and 4

with IHN values of 1.8 and 5.6% of total yield, respectively (Table 2-8). A leaching

rainfall event occurred between 200 and 400 GDD for planting dates 3 and 4 in 2004

(emergence and tuber initiation) (Figure 2-4). Accumulated GDD for planting dates 3

and 4 at harvest were 1951 and 2374, respectively (Table 2-11). The GDD accumulated

by harvest should not be used to predict the incidence of IHN in tubers. IHN most likely

is a combination of plants stresses that occur throughout the season and cannot be tied to

a single GDD number at the end of the season. It would be useful to relate the

accumulated GDD to the development stage of the potato plant and the timing of a

perceived plant stress. This may provide insight to the development of IHN in tubers.

The highest percentage of tubers with IHN in 2005 occurred in planting dates 4 and

5, with IHN values of 3.9 and 3.1% of total yield, respectively (Table 2-8). As is 2004, a

leaching rainfall event occurred between 200 and 400 accumulated GDD during planting

dates 4 and 5 in 2005 (Figure 2-4).

Lee et al. (1992) reported that IHN in 'Atlantic' developed early in the plant season

and correlated with the highest mean maximum temperature from 0-30 DAP and the

highest mean minimum temperature during the remainder of the growing season up to 90

DAP. The results of this research indicated that a leaching event early in the season,









between emergence and tuber initiation (200 to 400 GDD) also contributed to the

occurrence of IHN in tubers.

Conclusion

This experiment was designed to determine seasonal environmental (rainfall,

temperature) and nutrient constraints that impact plant stress and, in turn, tuber quality as

well as determining optimal yields over a typical growing season in the TCAA.

Optimal yields for the TCAA occur over a 4 week period in a twelve week planting

window from late January to late February. The results from this research suggest a

couple of options for growers who need to meet late season contracts. First, 'Harley

Blackwell' has demonstrated its effectiveness to produce quality tubers under conditions

when air temperatures and leaching rainfall events stress plants. Second, if an alternative

to the pesticide aldicarb is identified, a grower could harvest at 79 to 90 DAP based on

the GDD model. This alternative would reduce the incidence of rots due to the warmer

and wetter weather conditions typically experienced later in the season.

This research has also demonstrated that the internal physiological disorder, IHN is

triggered by rainfall and nutritional conditions that stress the plant early in the season

combined with increasing minimum daily temperatures later in the season. Leaching

rainfall events between 200 and 400 GDD after planting stressed the plants nutritionally

by potentially leaching nutrients from the root zone when potato plants are at a stage of

rapid growth and development as discussed in chapter 3.









Table 2-1. Total and marketable yield and specific gravity production statistics for 2004 and 2005
Total Marketable Specific Total Marketable Specific
yield yield gravity yield yield gravity
2004 2005


Main Effect


t ha-


t ha1


Planting Date2 (PD)


28.0 bcy
28.0 bc
30.8 ab
33.0 a
25.5 c
24.5 c


Nitrogen Rate (NR)

168 kg N ha-1
224 kg N ha-1
Variety (V)

Atlantic
Harley Blackwell


29.4 a
27.1 b


29.3 a
27.1 b


24.0 ab
21.2 bc
23.7 ab
26.4 a
17.0 d
19.4 cd


20.5 b
23.2 a


24.2 a
19.6 b


1.083
1.085
1.079
1.076
1.068
1.066


1.076
1.076


1.078
1.075


19.3 c
19.6 c
29.7 b
35.3 a
30.5 b
17.4 c


25.2
24.5


23.6 b
26.1 a


14.9 d
16.9 d
26.2 b
32.4 a
20.9 c
9.0 e


19.1
19.4


18.6 b
20.0 a


1.081 a
1.076 b
1.080 a
1.081 a
1.076 b
1.069 c


1.077
1.077


1.078 a
1.076 b









Table 2-1. Continued
Total Marketable Specific Total Marketable Specific
yield yield gravity yield yield gravity
2004 2005

t ha t ha-


Interaction effects
PD*NR ** ** ns ns ns ns
PD*V ns *** ** ns *
NR*V ns ns ns ns ns ns
PD*NR*V ns ns ** ns ns ns
zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004
and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005).
YMeans are separated with column and main effect using Tukey's studentized range test. Means followed
by different letters are significantly different at p< 0.05. Means with no letters are not significantly
different.
Xns, *, **, *** non-significant or significant at p< 0.05, 0.01, 0.001 using ANOVA









Table 2-2. Two-way interaction between planting date and nitrogen rate main effects for
total and marketable tuber yields in 2004
Total Marketable
yield yield
2004

PDZ*NR t ha'
Slicedy by PD

1 168 27.8 23.8
1 224 28.2 24.0
2 168 27.0 20.7
2224 28.9 21.7
3 168 28.0 bx 20.3 b
3224 33.7 a 27.4 a
4 168 33.4 26.8
4224 32.5 26.1
5 168 24.4 b 15.7 b
5224 26.7 a 18.5 a
6 168 22.5 b 17.1 b
6224 26.6 a 21.8 a
zPlanting dates 1 through 6 for 2004 and 2005
were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24
Mar, 2004)
'Sliced by PD This option enabled the
comparison of the fertilizer rates among each of
the planting date treatments
xMeans of the interaction effects followed by
different letters within each planting date and
column are significantly different at p< 0.05.
Means with no letters are not significantly
different.









Table 2-3. Two-way interaction between planting date and variety main effects for total
tuber yields in 2004 and 2005


PDz*V
Slicedy by PD


1 Atlantic
1 Harley Blackwell
2 Atlantic
2 Harley Blackwell
3 Atlantic
3 Harley Blackwell
4 Atlantic
4 Harley Blackwell
5 Atlantic
5 Harley Blackwell
6 Atlantic
6 Harley Blackwell


Total
yield
2004

t ha


29.3 ax
26.8 b
27.5
28.4
32.1 a
29.4 b
33.8
32.1
29.0 a
22.2 b
24.5
24.5


Total
yield
2005

t ha1


19.2
19.4
16.8 b
22.7 a
26.9 b
32.6 a
35.1
35.5
32.5 a
28.5 b
14.9 b
20.0 a


zPlanting dates 1 through 6 for 2004 and 2005 were
(13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004
and 11 Jan, 25 Jan, 8 Feb, 22 Feb, 7 Mar 22
Mar,2005).
'Sliced by PD This option enabled the comparison
of the varieties among each of the planting date
treatments
XMeans of the interaction effects followed by
different letters within each planting date and
column are significantly different at p< 0.05.
Means with no letters are not significantly different.










Table 2-4. Size class distribution and range (%) production statistics 2004 and 2005


Size
Distribution by class (%)z
B Al A2


Size Class
Range (%)


Al to
A2


A2 to
A3


Size
Distribution by class (%)z
B Al A2


2004


Main
effects
Planting
Datez
(PD)
1
2
3
4
5
6
Nitrogen
Rate (NR)
(kg ha-)
224
168

Variety
(V)
Atlantic
Harley
Blackwell


5.4 b
10.8 a


68.5 a
61.4 b
62.0 b
63.9 ab
66.4 ab
65.5 ab


15.3 a
13.9 ab
15.5 a
18.6 a
9.1 b
18.6 a


Size Class
Range (%)
Al to A2 to
A2 A3


2005


1.0 ab
0.7 ab
0.Ob
1.1 ab
0.0 ab
1.6 a


64.1 16.3 0.9
65.2 13.7 0.5


84.4 a
76.1 c
78.8 bc
83.3 ab
77.5 c
86.4 a



81.8
80.6


17.1 ab
15.6 bc
15.7 bc
15.6 ab
10.5 c
21.7 a



18.4
15.2


64.9 20.3 a 1.5 a 86.1 a 23.3 a
64.3 10.4 b 0.2 b 75.0 b 11.2 b


19.2 a
10.1 b
8.8 bc
6.1 c
9.8 b
22.3 a


71.2 ab
73.6 a
62.5 c
52.8 d
71.7 ab
68.2 b


5.9 d
13.0 c
22.4 b
38.8 a
15.4 c
2.8 d


0.Ob
0.2 b
3.6 a
3.9 a
0.Ob
0.Ob


13.0 a 66.4 13.7 0.6
11.3 b 67.2 14.4 0.7


9.6 b
15.0 a


66.7 17.6 a 0.9
66.9 10.8 b 0.4


78.3 b
87.3 a
85.2 a
87.5 a
88.1 a
75.1 b


6.3 d
13.9 c
27.1 b
39.9 a
15.8 c
3.6 d


7.5 aby
9.7 a
9.2 a
6.1 b
9.2 a
5.8 b



7.4
8.3


84.7 a 15.3
83.1 b 16.6


86.4 a 19.9 a
81.1b 12.4b









Table 2-4. Continued
Size Size Class Size Size Class
Distribution by class (%)z Range (%) Distribution by class (%)z Range (%)
B Al A2 A3 Al to A2 to B Al A2 A3 Al to A2 to
A2 A3 A2 A3
Interaction 2004 2005
effects
PD*NR ns ns ns ns ns ns ns ns ns
PD*V ns *** ** ns *** ** ns *** ns
NR*V ns ns ns ns ns ns ns ns ns ns
PD*NR*V ns ns ns ns ns ns ns ns ns ns ns ns
zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22
Feb, 7 Mar 22 Mar,2005).
YMeans are separated with column and main effect using Tukey's studentized range test. Means followed by different letters are
significantly different at p< 0.05. Means with no letters are not significantly different.
Xns, *, **, *** non-significant or significant at p< 0.05, 0.01, 0.001 using ANOVA.









Table 2-5. Two-way interaction between planting date and nitrogen rate main effects for
size class range (%) for Al in 2004 and A3 and size class distribution for Al
to A2 in 2005
Al A3 Al to A2

2004 2005

PDZ*NR % %
Sliced' by PD
1 168 84.1 ax 0.0 79.6
1 224 77.4 b 0.0 76.1
2 168 71.9 0.5 88.8
2224 72.9 0.0 85.4
3 168 71.1 2.0 b 86.1
3224 74.2 5.2 a 84.0
4 168 76.5 5.9 a 85.4 b
4 224 74.7 2.4 b 88.8 a
5 168 76.1 0.0 88.1
5224 81.3 0.0 87.5
6 168 80.8 0.2 76.9 a
6224 73.6 0.0 72.6 b
zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan,
9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25 Jan, 8 Feb, 22
Feb, 7 Mar 22 Mar,2005)
'Sliced by PD This option enabled the comparison of the fertilizer
rates among each of the planting date treatments
xMeans of the interaction effects followed by different letters within
each planting date and column are significantly different at p< 0.05.
Means with no letters are not significantly different.









Table 2-6. Two-way interaction between planting date and variety main effects for size class range (%) for Al, A2, A3 and A2 to A3
in 2004 and B, Al, A3 and Al to A2 in 2005
Al A2 A3 A2 to B Al A3 Al to
A3 A2
2004 2005
PDZ*V % %
Sliced' by PD
1 Atlantic 69.4 18.1 1.1 20.1 16.9 b 71.7 0.0 80.8 a
1 Harley Blackwell 67.6 12.4 0.9 14.3 21.7 a 69.8 0.0 75.2 b
2 Atlantic 64.7 ax 16.7 0.7 18.6 9.1 73.8 0.3 88.1
2 Harley Blackwell 58.0 b 11.3 0.8 12.8 11.1 73.4 0.1 86.1
3 Atlantic 62.4 20.8 a 0.0 21.2 a 6.6 b 60.7 6.4 a 84.7
3 Harley Blackwell 61.5 10.9 b 0.0 10.9 b 11.2 a 64.1 1.5 b 85.1
4 Atlantic 64.1 22.8 2.8 a 26.8 a 4.2 b 50.6 5.6 a 88.1
4 Harley Blackwell 63.7 14.6 0.2 b 15.6 b 8.3 a 55.0 1.6 b 86.1
5 Atlantic 70.8 a 12.9 a 1.9 a 16.5 a 7.7 b 67.9 b 0.0 90.6 a
5 Harley Blackwell 61.1 b 5.7 b 0.0 b 5.7 b 12.0 a 75.3 a 0.0 84.7 b
6 Atlantic 57.2 b 31.7 a 4.5 a 38.1 a 15.6 b 73.3 a 0.0 83.3 a
6 Harley Blackwell 72.6 a 8.3 b 0.1 b 9.0 b 29.7 a 62.9 b 0.2 65.7 b
zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan,
25 Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005)
'Sliced by PD This option enabled the comparison of the varieties among each of the planting date treatments
xMeans of the interaction effects followed by different letters within each planting date and column are significantly
different at p< 0.05. Means with no letters are not significantly different.









Table 2-7. External quality (green, growth cracks, mis-shaped, rot and total culls) % of total yield 2004 and 2005


Main effects

Planting Date
(PD)
1
2
3
4
5
6
Nitrogen Rate
(NR) kg ha1
224
168

Variety (V)
Atlantic
Harley
Blackwell


Green Growth Mis-
crack shaped
2004


0.0 c
0.0 bc
0.1 ab
0.5 a
0.0 bc
0.0 c


0.0
0.3 a
0.0
0.0
0.0
0.0


0.20 0.0
0.39 0.0


0.0b
0.2 a
0.1 ab
0.0b
0.0 ab
0.0 ab


0.0
0.0


Rot


0.0 c
0.0 c
0.4 c
4.6 b
13.8 a
10.4 a


2.4
3.2


0.1 a 2.9
0.0b 2.8


External tuber
Total
cull2


0.0 c
0.0 c
0.4 c
4.6 b
14.5 a
10.4 a


2.4
3.2


2.9 a
2.8 b


* defects (%)
Green Growth
crack


0.5 a
0.3 a
0.5 ab
0.3 b
0.5 ab
0.0 a


0.3
0.3


0.1 a
0.1 a
0.0 ab
0.0b
0.0 ab
0.0b


0.0
0.0


0.0 a
0.0b


Mis-
shaped
2005


Rot


0.0
0.1
0.0
0.0
19.9
29.9


8.20
9.18


0.1 a 9.87
0.0 b 7.52


Total
cull2


0.9 c
1.5 c
1.4 c
0.5 c
21.1 b
30.1 a


8.1 a
4.0 b









Table 2-7. Continued
Green Growth Mis- Rot Total Green Growth Mis- Rot Total
crack shaped cullz crack shaped cullz
Interaction 2004 2005
effects
PD*NR ns ns ns ns ns ns ns ns ns *
PD*V ns ns ns ns ns ns ns ns ns
PD*F ns ns ns ns ns ns ns ns ns
PD*NR*V ns ns ns ns ns ns ns ns ns ns
zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25
Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005).
YMeans are separated with column and main effect using Tukey's studentized range test. Means followed by different
letters are significantly different at p< 0.05. Means with no letters are not significantly different.
Xns, *, **, *** non-significant or significant at p< 0.05, 0.01, 0.001, respectively using ANOVA.









Table 2-8. Internal quality (%) of total yield 2004 and 2005
Internal Quality (%)


Main effects

Planting Date
(PD)
1
2
3
4
5
6
Nitrogen Rate
(NR) kg ha1
224
168

Variety (V)
Atlantic
Harley
Blackwell


HH IHN IHN CRS BCL
severity
2004


0.9 b
3.8 a
0.0 c
0.0 c
0.0 c
0.0 be


0.3
0.2


0.0b
1.2 ab
1.8 ab
5.6 a
0.2 b
0.8 b


1.0
1.1


14.3 a
0.7 b
3.9 ab
0.4 b
0.0b
0.0b


0.8 b
2.6 a


1.0 a 3.2 a
0.0b 0.0b


0.0b
1.2 a
0.0b
1.4 a
0.0b
0.0b


0.4 a
0.1 b


0.0b
0.0b
0.0b
3.9 a
3.1 a
0.2 b


0.4
0.8


2.3 a 1.3 a
0.0b 0.0b


HH IHN IHN CRS BCL
severity
2005


0.3 a
0.0b
0.0b
0.0b
0.0b
0.0b









Table 2-8. Continued
HH IHN IHN CRS BCL HH IHN IHN CRS BCL
severity severity
Interaction 2004 2005
effects
PD*NR ns ns ns ns ns ns ns ns ns
PD*V ns ns ns ns ns *** ns ns **
PD*F ns ns ns ns ns ns ns ns ns
PD*NR*V ns ns ns ns ns ns ns ns ns ns
zPlanting dates 1 through 6 for 2004 and 2005 were (13 Jan, 27 Jan, 9 Feb, 23 Feb, 9 Mar, 24 Mar, 2004 and 11 Jan, 25
Jan, 8 Feb, 22 Feb, 7 Mar 22 Mar,2005).
YMeans are separated with column and main effect using Tukey's studentized range test. Means followed by different
letters are significantly different at p< 0.05. Means with no letters are not significantly different.
Xns, *, **, *** non-significant or significant at p< 0.05, 0.01, 0.001, respectively using ANOVA.










Table 2-9. Mean maximum and minimum temperature (C)
0-30 DAP
2004 Mean
Planting Date of Max Min


Order
1
2
3
4
5
6


2005
Planting
Order
1
2
3
4
5
6


Planting
13 Jan
27 Jan
9 Feb
23 Feb
9 Mar
24 Mar


Date of
Planting
11 Jan
25 Jan
8 Feb
22 Feb
7 Mar
22 Mar


18.8
18.3
19.4
21.1
22.2
23.8


Max

17.2
19.4
20.0
20.0
22.2
24.4


7.2
7.7
8.8
10.5
9.4
10.5


0-30 DAP
Mean
Min


6.1
7.2
7.7
9.4
11.1
11.6


for planting dates 1-6, 2004 and 2005
30-60 DAP
Mean
Max Min Ma


19.4
22.2
22.7
23.8
25.5
27.2


8.3
10.0
9.4
11.1
12.2
15.0


23.3
24.4
25.5
27.2
30.0
31.6


30-60 DAP
Mean
Max Min


20.0
20.0
23.3
24.4
23.8
26.1


7.2
8.8
11.6
11.6
11.1
13.3


Max

23.3
24.4
23.8
26.1
28.8
29.4


60-90 DAP
Mean
Min

10.5
11.1
12.2
16.1
17.7
20.0

60-90 DAP
Mean
Min

11.6
10.5
10.5
13.3
16.1
19.4


x









Table 2-10. Accumulated GDD and calendar days to obtain emergence and full flower 2004 and 2005


2004
Planting
Order

1
2
3
4
5
6
Average
2005
Planting
Order

1
2
3
4
5
6
Average


Days to
emergence


GDDy to
emergence


Calendar
days to FF


240
226
178
218
202
211
213


Date of
Planting

13 Jan
27 Jan
9 Feb
23 Feb
9 Mar
24 Mar


Date of
Planting

11 Jan
25 Jan
8 Feb
22 Feb
7 Mar
22 Mar


GDD to FF


841
806
749
820
816
792
804


Date of
emergence

6 Feb
16 Feb
25 Feb
7 Mar
22 Mar
5 Apr


Date of
emergence

8 Feb
15 Feb
23 Feb
12 Mar
22 Mar
31 Mar


244
213
199
211
197
198
210


Calendar
days to
FFx


GDD to FF


814
794
837
801
811
826
813


Days to
emergence


GDD to
emergence


Calendar
days to
harvest
104
104
106
106
104
104


Calendar
days to
harvest
104
106
105
106
105
105


GDD to
harvest

1493
1676
1951
2374
2490
2840
2137

GDD to
harvest

1442
1677
1894
2160
2385
2719
2046









Table 2-11. Early and late season yield reduction and harvest date at 2000 GDD for 2004
and 2005


2004
Planting
Order

1
2
3
4
5
6
2005
Planting
Order

1
2
3
4
5
6


Yield Calendar
reduction days to
2000 GDD
-15 130
-16 115
-7 104
0 97
-23 89
-26 81


Date of
Planting

13 Jan
27 Jan
9 Feb
23 Feb
9 Mar
24 Mar

Date of
Planting

11 Jan
25 Jan
8 Feb
22 Feb
7 Mar
22 Mar


Date of
emergence

6 Feb
16 Feb
25 Feb
7 Mar
22 Mar
5 Apr

Date of
emergence

8 Feb
15 Feb
23 Feb
12 Mar
22 Mar
31 Mar


Harvest date
at 2000 GDD

17 May
21 May
25 May
30 May
6 June
13 June

Harvest date
at 2000 GDD

21 May
23 May
29 May
3 June
9 June
14 June


Yield
reduction

-55
-48
-20
0
-36
-73


Calendar
days to
2000 GDD
130
118
110
101
94
84








47




a. Daily rainfall and average daily temperature 2004


10.00-


253


20 E


15

1 1
10

5


0


Date
Rainfall events Average daily temperature





b. Daily rainfall and average daily temperature 2005


30

25
0.
E
20 2

15

10


LO o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
N C! (0 5N CD ( C2 0 g, (0 oi 0 P_ O C 0 1 : 7 C O 7 CO I (, I
(N (N'M C' c Ci) (0(0^ 'C'i ^ O S S '
- (N4 (N 0 0) Q0 Q0 'I Q Q O (0 6 (0 (0


Date
Rainfall events -Average daily temperature


Figure 2-2. Daily rainfall (cm) for a. 2004 and b. 2005 production season. Grouping of
red bars denote a leaching rainfall event (7.6 cm in 3 days or 10.1 cm in 4
days). The yellow, pink, blue, green, orange and black lines denote planting
dates 1-6, respectively, from emergence to tuber initiation








48








40.00 3000

35.00
2500
30.00
2000 0
25.00 -

20.00 1500
.- E
>- 15.00
100010.00
10.00
500
5.00

0.00 0
Atl Atl Atl Atl Atl Atl HB HB HB HB HB HB

1 2 3 4 5 6 1 2 3 4 5 6

Planting Date x Variety

l Total yield m Marketable yield Accumulated GDD







40.00 3000

35.00
2500
30.00
2000 a
25.00

20.00 1500 _0
.-D E
>- 15.00









5 6 1 2

5.00GDD at harvest, a. 2004 b. 2005








GDD at harvest. a. 2004 b. 2005














CHAPTER 3
YIELD AND QUALITY OF 'ATLANTIC' POTATO (SOLANUM TUBEROSUML.)
TUBERS AND OFF-FIELD NUTRIENT MOVEMENT UNDER VARYING
NITROGEN SOURCES AND STAGED LEACHING IRRIGATION EVENTS

Introduction

The St. Johns River has been identified by the state of Florida as a priority water

body in need of restoration under the auspices of the Surface Water Improvement and

Management Act implemented by the Florida legislature in 1987. Personnel from the St.

Johns River Water Management District (SJRWMD), University of Florida, multiple

state government agencies, and the North Florida Grower's Exchange have developed

"Best Management Practices" (BMP) for potato production in the Tri-County

Agricultural Area (St. John's, Putnam, and Flagler Counties, TCAA). The purpose of

implementing BMPs is to reduce nitrate run-off from the approximately 7,300 ha of land

in potato production in the St. John's River watershed.

The SJRWMD has estimated that as much as 36% of the pollutant load entering the

river basin today is related to human activities that include agricultural production. Algal

blooms in the St. Johns River have coincided with peak runoff associated with the TCAA

potato season (SJRWMD, 1996).

Bailey and Wadell (1979) reported non-point source pollution from agricultural

runoff contributes approximately 9.5 million tons of N and P to U.S. surface waters

annually. The EPA reports that non-point source pollution from agriculture has impaired

60% of the river miles and half of the lake acreage surveyed by states, territories and

tribes (EPA website).
























Figure 3-1. Aerial photograph of potato production fields along the St. Johns River, St.
Johns County, Florida. Courtesy of Pam Livingston-Way, SJRWMD

Growers in Northeast Florida typically apply approximately 308 kg N ha-1 for

commercial potato production (Hochmuth, et al., 1993). Growers participating in the

BMP program are encouraged to apply the IFAS recommended nitrogen rate of 224 kg N

ha-1. In the event of a leaching rain, growers are allowed, under the provisions of the

program, to apply an additional 34 kg N ha-1 (Hutchinson et al., 2002).

It has generally been accepted that leaching rains are responsible for the majority of

nitrate movement out of potato production ground. IFAS research defines a leaching rain

as 7.6 cm of rain in three days or 10 cm of rain over seven days. After a leaching event,

growers are encouraged to apply an additional 34 kg N ha-1 (Kidder et al., 1992)

Potatoes are typically grown in sandy, course textured soils that have a low water

holding capacity, which exacerbates the potential of NO3-N leaching below the root

system of the potato plant. Potato plants have a relatively shallow root system with

greater than 90% of the total root area located in the upper 25 cm of the soil profile

(Munoz, 2004; Rosen, 2001). Heavy rain washes fertilizer out of the potato row and

either into the furrow or into the perched water table. Fertilizer washed into the furrow









moves in surface water off the potato beds and into tail-water or drainage canals. The

amount of fertilizer that potentially could be leached from the row is dependent on the

type and amount of fertilizer applied within the row, as well as the time between fertilizer

application and a leaching event occurs.

Controlling NO3-N leaching can be difficult under the best management practices

due to unforeseen leaching rainfall events. Wang and Alva (1996), evaluated soil

columns with a Wabasso sand and reported approximately 88 to 100% of ammonium

nitrate was lost due to leaching compared to 11.5 to 11.7% of a polymer-coated

controlled release fertilizer (CRF). Maynard and Lorenz, (1979); Elkashif and Locascio,

(1983) reported the release of N from sulfur coated urea (SCU, slow release fertilizer)

was too slow to sufficiently meet the demands of the potato crop. Waddell et al. (1999)

reported the tuber N uptake in SCU treatments was the lowest compared with other

fertilizer treatments and attributed this to the lack of release of the coated urea when the

plant N demand was high. While CRFs have been on the market for several years

(Trenkel, 1997), vegetable growers require a CRF with a more predictable release

pattern, one that is customized for individual crop growth and development stages.

Fertilizer manufacturers addressed this with the release of a polymer-coated urea (PCU).

Unlike SCU that is affected by soil properties (moisture or microbial activity), PCUs are

dependent upon temperature and moisture permeability of the resin coating, therefore,

making the release rate more predictable or controlled (Shoji and Gandeza, 1992).

Studies have reported the benefits of polymer-coated CRFs in potato production

systems. CRFs maintained quality and yield while reducing nutrient leaching.

Hutchinson et al. (2003), reported that yield and quality of 'Atlantic' on an Ellzey fine









sand in FL was not adversely affected, although, two leaching rainfall events occurred

during the production season (7-13 DAP and 92-98 DAP).

Hutchinson (2005) reported a 69% reduction in tubers with IHN with the use of a

blended polymer coated urea product (168 kg N ha-1) with an approximate release rate of

45, 75 and 120 DAP, compared with ammonium nitrate (AN) at the BMP rate (224 kg N

ha-1). Similar results were also reported by Pack (2004), in which the average reduction

of tubers with IHN was68% with CRF (168 kg N ha-1) treatments compared with the

BMP rate of AN (224 ha N ha-1). Zvomuya and Rosen (2001) reported in 1996 and 1997,

PCU treatments produced significantly higher total and marketable tuber yields of

'Russet Burbank' on a Hubbard loamy sand in MN when compared with AN fertilizer.

Leaching events (> 5cm within a 48 hr period) were recorded in 1996 (20 and 50 DAP)

and 1997, (40, 50 and 75 DAP). IHN was not reported, although the incidence of HH

remained the same over both production seasons for the CRF treatment and decreased in

1997 in the AN fertilizer treatment.

Zvomuya et al. (2003) reported a decrease in NO3-N leaching of 34-49% after

leaching irrigation events in CRF plots. Total and marketable tuber yields of 'Russet

Burbank' were 12 to 19% higher with CRFs compared with multiple applications of urea

on a Hubbard loamy sand in Becker, MN.

CRF could be the N management tool for Northeast Florida potato production that

reduces NO3-N leaching while, at the same time, maintaining acceptable yields.

However, the relationships between fertilizer source, leaching irrigation timing, and tuber

quality and yield are not well understood.









The objectives of this study were to 1) determine the influence of fertilizer source

(soluble and controlled release) and timing of leaching irrigation on yield and quality of

'Atlantic' 2) determine the influence of fertilizer source (soluble and controlled release)

and timing of leaching irrigation on nutrient leaching and nutrients in surface water

runoff during a leaching event.

Materials and Methods

Site Description

The experiment was conducted during the 2004 and 2005 production years at the

University of Florida, Plant Science Research and Education Unit (PSREU), Hastings,

Florida on an Ellzey fine sand (sandy, siliceous, hyperthermic Arenic Ochraqualf; sand

90% to 95%, <2.5% clay, <5% silt). The soil profile is described as poorly drained

although the top 94 cm have a very high permeability rate (5-10 cm/hr). A restricting

clayey layer lies below the sandy loam top layer of the profile. The water table is within

25 cm of the surface for one to six months of the year (Soil Survey, St Johns County,

1983)

Experimental Design

The experiment was arranged as a factorial randomized complete block as a split-

split design with four blocks. Each of the four blocks were located in a single bed at the

PSREU (beds 12-15 NL). The study was conducted at the same location for the 2004 and

2005 production years. The main effects were irrigation event, nitrogen source, and side-

dress fertilizer application.

Main plots were 16 rows wide (102 cm centers) by 18.3 m (60 ft) long running

south to north with a 6.1 m (20 ft) buffer between main plots. Irrigation treatments were

applied to main plots at 0, 2, 4, 8, and 12 WAP (weeks after planting). Nitrogen source









was applied to eight row sub-plots in each main plot. Ammonium nitrate (AN) and

polymer coated urea (controlled release fertilizer; CRF) were the fertilizer sources. The

last main effect, side-dress fertilizer application, was applied to four of the eight rows in

each sub-plot. Ammonium nitrate (34-0-0) was applied with a hydraulic fertilizer

applicator as a band on either side of the potato plant after each leaching irrigation date

event (Table 3-1 and Fig 3.1).

Crop Production Practices

Tuber Planting

Potatoes were cut at planting to an approximate 71 g seed piece and dusted with

fungicide [1.13 g a.i., fludioxonil and 21.8 g a.i. mancozeb per 45.4 kg seed pieces]

(Maxim MZ; Syngenta Crop Protection, Inc., Greensboro, N.C.)]. Azoxystrobin, a.i.[0.1

L ha-1 (Amistar; Syngenta, Crop Protection, Greensboro, N.C.)] and aldicarb a.i. [3.4 kg

ha-1 (Temik, Bayer Corp., Kansas City, Mo.)] was applied in-row at planting. All other

pesticide applications during the growing season followed recommendations for Florida

potato production (Hutchinson et al., 2004).

Potatoes were planted 19 and 22 Feb 2004 and 2005 and harvested 1 and 8 June

2004 and 2005 (106 and 108 DAP), respectively. Between and within row spacing was

102 and 20 cm (40 and 8 inches), respectively. This resulted in a plant density of

approximately 48,400 plants ha-1.

Irrigation

Overhead solid set sprinkler irrigation system with #4 mini-wobblers (127 L hr-1 or

0.6 gpm at 25 psi; Senninger Irrigation, Inc., Clermont, FL) was installed to apply each

leaching irrigation event (2, 4, 8 and 12 WAP) 7.6 cm of simulated rainfall to main plots.









Irrigation was collected in U. S. Weather Bureau approved rain gauges (Forestry

Suppliers, Inc., Jackson, MS) placed in each irrigation main plot.

Plots were irrigated with seepage irrigation throughout the growing season except

during leaching irrigation events and periods of sufficient rainfall. The seepage

irrigation system is a semi-closed system. Water withdrawn from the confined aquifer is

pumped through PVC (polyvinyl chloride) pipe to each V-shaped open water furrow in

the field. Each water furrow is situated 18.2 m apart. Water seeps from the water furrow

laterally, underground, across the bed and through capillarity reaches the root system of

the potato plant (Singleton, 1990). A perched water table was maintained at

approximately 45-60 cm from the top of the potato row.

Nutrient Management

Ammonium Nitrate Nitrogen

Fertilizer application was based on best management practice (BMP)

recommendations for Florida potato production (224 kg N ha-1; Hutchinson et al., 2004).

Pre-plant fertilizer was applied as a 15 cm wide band on top of the row at a rate of 112 kg

N ha-1 as 14N-6P205-12K20 with a John Deere 6615 and a two-row hydraulic fertilizer

applicator (Kennco Mfg., Ruskin FL,). Fertilizer was incorporated into each row with a

four-row chopper then rows were bedded prior to planting. Two additional sidedress

applications of 56 kg N ha-1 as 30-0-0 were banded on either side of the potato plants

with a two row hydraulic fertilizer applicator at 34 and 43 DAP in 2004 and 37 and 43

DAP in 2005 to AN plots to achieve the BMP rate of 224 kg ha-1. Following each

sidedress application, a four row covering disk was used to cover the fertilizer banded

along side the potato plants in each row. This is not the side dress nitrogen main effect.









After a leaching irrigation event, a third side dress nitrogen application of 34 kg N

ha-1 (30-0-0 NPK) was mechanically applied to four of the eight row main fertilizer

treatments (treatments 2 and 4) following the BMP recommendation for fertilizer

application after a leaching rain. (Table 3-1, Fig 3.1). This is the sidedress nitrogen

application main effect.

Controlled Release Fertilizer

All CRF fertilizer was applied in a single preplant application at 196 kg N ha-1 (38-

0-0, The Scotts Company, Marysville, OH) on 12 and 21 Feb 2004 and 2005,

respectively (Fig 3.1). CRF is a polymer-sulfur coated urea product designed to release

75% of the nitrogen by 75 DAP. All CRF treatments received 78 kg ha-1 P205 as 0-20-0

and 202 kg ha-1 K20 as 0-0-50 preplant.

Tuber Production Analysis.

At harvest, two rows (6.1 meters each) from each fertilizer source by additional

sidedress application plot were harvested, washed, and mechanically graded and sized

into the following class sizes; B = 3.8 to 4.4 cm, Al = 4.4 to 6.4 cm, A2 = 6.4 to 8.3 cm,

A3=8.3 cm to 10.2 cm, A4 = > 10.2 cm at the PSREU. Marketable yield is defined as

no. 1 tubers with diameters between 4.4 and 10.2 cm (USDA, 1978) and without visible

blemishes (rotten, green, misshapen, or growth cracks).









Tuber Specific Gravity.

Specific gravity was calculated on a sub-sample of marketable tubers from each

fertilizer source by additional sidedress application plot using the weight in air/weight in

air-weight in water method (Burton, 1989a). 'Atlantic' potatoes are the standard chip

variety. High specific gravity is desired. Specific gravities of at least 1.078 are

considered good for production at the PSREU research farm in Hastings, FL (Hutchinson

et al., 2002).

External Quality.

Culls (green, growth cracks, misshapen, and rotten tubers) were removed and

weighed at the grading line. External quality (green, growth cracks, misshaped and rot)

were reported as a percentage of total yield.

Internal Quality.

A 20 tuber sub-sample from each fertilizer source by additional sidedress

application plot was cut into quarters and rated for internal quality. Rated physiological

disorders included hollow heart (HH), internal heat necrosis (IHN) and brown center

(BC). Disease induced disorders included corky ring spot (CRS) and brown rot (BR).

IHN severity was scored on a one to six scale with a score of one to four relating to the

number of quarters with IHN. A score of five or six indicated that all quarters had the

disorder and up to 75 to 100% of all quarters were covered, respectively.

Water Sample Collection and Nutrient Load

Surface Run-Off Volume

Surface run-off volume was collected from a fertilizer source main plot during each

irrigation event. A 7.1 cm (18 in) PVC pipe was placed perpendicular to each of the









eight plots at the water furrow to route surface water flow. Water volume was collected

every ten minutes from the pipe for ten seconds and the water volume was recorded.

Nutrient Load

A 20 mL water sample was collected every 10 min as runoff started from each

fertilizer source main plot, (8 total) at each 10 minute sample interval using the system

described for surface water volume. Sample collection stopped once irrigation was

turned off and runoff ceased from each of the fertilizer plots. Water samples were stored

in a freezer at -15C until analyzed. Samples were analyzed for NO3-N and NH4-N (EPA

method 353.2), P, K (EPA method 200.7), and EC at the University of Florida/IFAS

Analytical Research Laboratory, Gainesville, FL (Mylavarapu and Kennelley, 2002).

Wells

Observation wells (10 cm diameter by 0.9 m long) were installed (10 and 8 Mar,

2004 and 2005 (23 and 15 DAP), respectively in each fertilizer source by sidedress

application plot (80 total) so that the top of the wells were flush with the top of the row.

This allowed access to the perched water table for water samples during the growing

season. A 20 mL water sample was collected biweekly and at 24 hours post irrigation

event. Water samples were processed and stored as described previously.

Lysimeters

Porous cup suction lysimeters (model 1900 Soil Water Samplers) (SoilMoisture

Equipment Corp., Santa Barbara, CA) were installed (10 and 9 Mar, 2004 and 2005; 23

and 16 DAP, respectively) in each fertilizer source by sidedress application plot (80 total)

to a depth of 30 cm. At sampling, a vacuum (50-60 kPa) was drawn on each lysimeter. A

46 cm plastic tube attached to a 50cc syringe was used to extract the water from each

lysimeter. Samples (20 mL) were taken biweekly and at 24 hours post leaching irrigation









event from each fertilizer source plot. Water samples were processed and stored as

described previously.

Growing Degree Day Model

Growing degree days (GDD) were calculated throughout the season in 2004 and

2005 with the following formula (Sands et al., 1979):

GDD = [(minT + maxT)/2)-7C].

where minT and maxT are the minimum and maximum daily temperatures and the base is

7C or 450F.

GDD totals were recorded for key growth and developmental stages (emergence,

and full flower). Emergence was determined when the plantlets were just emerging from

the soil. Full flower was determined when approximately 90-95% of the peduncals on

plants in each plot had open flowers.

Statistical Analysis

Tuber production. A general linear model was used to determine yield and

internal and external quality responses of potato as a result of fertilizer source and

leaching irrigation events for the 2004 and 2005 production seasons. Normality for each

potato class size was checked by residual analysis using the Shapiro-Wilk test as

implemented in the PROC CAPABILITY procedure of SAS (SAS Institute, 2004).

Means were separated using Tukey adjustment as implemented in SAS (SAS Institute,

2004) to separate individual factor means and/or interaction means when significant.

Interactions were calculated using LSMeans with the slice option (SAS 2004).

Water analysis. A general linear model was used to determine water nutrient

concentrations in the water table (wells and lysimeters) as well as nutrient load from each

irrigation date treatment for 2004 and 2005 production years. Normality for each water









nutrient analyzed was checked by residual analysis using the Shapiro-Wilk test as

implemented in the PROC CAPABILITY procedure of SAS (SAS, Institute, 2004).

Concentrations of nutrients were log transformed and checked for normality then back

transformed. Means were separated using Tukey adjustment as implemented in SAS

(SAS Institute, 2004) to separate individual factor means and/or interaction means when

significant.

Results And Discussion

Tuber Yield for 2004

Irrigation date main effect

Irrigation date main effect significantly influenced total and marketable tuber yields

for the 2004 season (Table 3-2). The later in the season a leaching event occurred, total

and marketable tuber yields and specific gravity were more negatively impacted. Total

and marketable tuber yields for the 8 and 12 WAP irrigation date were 10 and 11 %

lower, respectively, than the 0 WAP irrigation date. Ojala et al. (1990), reported

nutritional and/or environmental stress at or near full flower can negatively impact total

and marketable tuber yields as well as specific gravity. This is due to the high nitrogen

requirement during the tuber bulking stage. Approximately, 58 to 71% of total nitrogen

uptake by the potato crop occurs from early to mid tuber bulking.

Optimal yield for this study should be in 0 WAP irrigation plots since no

supplemental irrigation was applied. The 4 WAP irrigation date was not applied due to a

naturally occurring leaching rainfall at the scheduled irrigation event in 2004. It received

the same rainfall and irrigation schedule as the 0 WAP plot. Total and marketable tuber

yields for plants in the 0 WAP treatment were a respectable 29.5 and 25.0 t ha-1,

respectively in 2004.









Tubers from plants in the 8 and 12 WAP irrigation treatment had significantly

lower specific gravities compared with tubers in the 0, 2 and 4 WAP irrigation treatments

in 2004 (Table 3-2). The percent of tuber weight in the A2 to A3 size class range was

also negatively impacted in the 8 and 12 WAP irrigation date treatments. A 45%

decrease in this tuber classification was observed compared with the 0 WAP date (Table

3-4). The scheduled leaching rainfall in combination with frequent rainfall events after

the 8 and 12 WAP irrigation treatments negatively influenced tuber specific gravity.

Fertilizer main effect

The fertilizer source main effect demonstrated the effectiveness of the CRF in

potato production. Total and marketable tuber yields for plants in the CRF fertilizer

treatments were 8 and 10 % higher, respectively, compared with plants in the

conventional AN treatment for the 2004 production season (Table 3-2). The sidedress

main effect treatment did not significantly influence total and marketable tuber yields nor

tuber size and specific gravity (Table 3-2).

Main effect interactions

The three-way interaction between irrigation date, fertilizer source, and side dress

application main effects was significant for total and marketable tuber yields. The three-

way interaction term was calculated using LSMeans with the slice option (irrigation

treatment*side) (SAS 2004). This option enabled the comparison of the fertilizer source

with or without the extra sidedress treatment among each of the irrigation date treatments

Plants in the CRF 2 WAP irrigation date treatment with the 34 kg N ha-1 sidedress

application had significantly higher marketable tuber yields (28%) compared with plants

in the AN fertilizer plots with the same sidedress amount (Table 3-3). Lower yield from

plants in the AN fertilizer--extra sidedress application plots may be explained by a large









amount of AN leached from the plot (Table 3-9) at the 2 WAP irrigation date. Potato

plants were just starting to emerge and the root system of the plant was not large enough

to utilize the applied fertilizer. The CRF plots did not leach as much nitrogen (data to

follow). Therefore, the sidedress nitrogen added to the overall nitrogen load instead of

replacing lost nitrogen as in the AN plots. All other irrigation treatments with or without

the extra sidedress were not significantly different among each irrigation treatment.

Tuber Yield for 2005

Irrigation date main effect

Irrigation date main effect significantly influenced total and marketable tuber yields

during the 2005 season. Plants in the 12 WAP irrigation date treatment had the lowest

marketable yield followed by plants in irrigation treatments 4 and 8 WAP plots (Table 3-

2). The leaching rainfall event that occurred at the scheduled 4 WAP irrigation date

treatment, negatively affected marketable tuber yields, since tubers are usually initiated at

this time (Figure 3-12). Plants in the 8 and 12 WAP irrigation treatments also produced

the lowest percentage of tubers in the size class range A2 to A3 compared with the 0

WAP treatment (Table 3-4). The additional plant stress (too much water) in plants in

irrigation treatments 4, 8 and 12 WAP resulted in an average decline of marketable tubers

weight by 18% compared with the 0 WAP irrigation date treatment.

Specific gravities for tubers from plants in the 4 and 12 WAP irrigation treatments

(1.080) were significantly lower than in tubers from plants in the 0 WAP irrigation date

treatment (1.082). A leaching rainfall event occurred within 7 to 10 days of the 4 and 12

WAP scheduled leaching irrigation events (Figure 3-13). As in 2004, the additional

leaching irrigation events in conjunction with the wetter weather conditions later in the

season reduced tuber specific gravity.









Fertilizer main effect

Fertilizer main effect demonstrated the effectiveness of CRF in potato production

in 2005. Plants in the CRF treatment produced 10.0 and 13.0% more total and

marketable tuber yields than plants in the standard ammonium nitrate treatment (Table 3-

2). A 16% increase in the percent of tubers in size class range A2 to A3 was also

observed for the CRF treatments compared with the AN fertilizer treatment in 2005

(Table 3-4).

Specific gravity was also influenced by the fertilizer main effect treatments.

Tubers from plants in the AN fertilizer treatment had significantly higher specific gravity,

1.079 compared with tubers from plants in the CRF fertilizer treatment, 1.077 (Table 3-

2).

Sidedress main effect

The sidedress main effect did not significantly influence total and marketable tuber

yield, specific gravity or size class distribution (Table 3-2 and 3.4).

Main effect interactions

The three-way interaction between irrigation date, fertilizer source and side dress

application main effect was significant for the total and marketable tuber yields in 2005.

In 2005, plants in the CRF additional 34 kg-N ha-1 treatment had higher total and

marketable tuber yields, 28 and 26%, respectively compared with yield from plants in the

AN additional 34 kg N ha-1 (Table 3-3) in the 2 WAP irrigation date treatment. This is

a similar result to 2004. Nitrogen in the CRF is protected early in the season compared

with AN. The sidedress N application adds positively to the CRF treatment but does not

make up for that which is leached in the AN treatment. As the season progressed, the









ability for the sidedress N to add positively to yield decreased. The extra side dress

application should be examined further.

Tuber External Quality for 2004

Irrigation date main effect

Irrigation treatment main effect had limited influence on external tuber quality such

as green, growth cracks, misshapes, and total culls. Green tubers were reduced in the 8

and 12 WAP irrigation treatments in 2004 (Table 3-5). This is because the irrigation

treatment plots were middle busted and hilled later in the season compared with the 0

WAP irrigation date plots resulting in better soil coverage of the tubers.

Fertilizer main effect

Fertilizer main effect did not significantly influence external tuber quality in 2004.

Sidedress main effect

Sidedress main effect had no influence on external tuber quality. There were no

interaction effects for external tuber defects for the 2004 production season.

Tuber External Quality for 2005

Irrigation date main effect

Irrigation date main effect significantly influenced all external tuber defects in

2005. The 12 WAP irrigation date in 2005 resulted in significantly higher percentages of

green, rotten and total culled tubers compared with the 0 WAP irrigation date (Table 3-5).

Late in the season, the 12 WAP irrigation date washed soil from the potato row exposing

tubers and resulting in green tubers. The combination of late season irrigation and heat

resulted in a high number of rots in the 12 WAP irrigation date. Tubers in the 12 WAP

irrigation date had significantly higher total culls 16.6% compared with the 0, 2, 4 and 8

WAP irrigation treatments at 4.8, 5.9, 7.5 and 7.5%, respectively (Table 3-5).









Fertilizer main effect

Fertilizer main effect significantly influenced external tuber defects in 2005. Plants

in CRF plots had a higher percentage of tuber rots compared with plants in the AN

fertilizer plots (3.4 and 2.7 % respectively; Table 3-5). The additional water applied at

the 12 WAP irrigation date combined with a leaching rainfall event 7 to 10 days prior to

harvest (Figure 3-13) and warmer temperatures negatively impacted tuber quality late in

the season.

Sidedress main effect

Sidedress main effect did not significantly influence tuber external quality. There

were no interaction effects for external tuber defects for the 2005 production season

(Table 3-5).

Tuber Internal Quality for 2004

Irrigation date main effect

Internal defects include physiological disorders which are hollow heart (HH),

internal heat necrosis (IHN) and brown center (BC). Disease induced disorders include

corky ring spot (CRS) and brown rot (BR).

BC and HH occur when sudden growing conditions change during the growing

season. This occurs when the potato plant recovers too quickly after an environmental or

nutritional stress during the growing season. As the tubers start to grow and expand the

pith tissue in the center of the tuber turns necrotic or can split open leaving a void in the

center of the potato. IHN is characterized by necrotic areas mostly in and around the

vascular ring usually coalescing and radiating to the center (pith) at the bud (apical) end

of the tuber and not the stem end. IHN is thought to occur late in the growing season due

to elevated temperatures and hot dry weather conditions, but may be initiated earlier in









the growing season as discussed in chapter 2. BC, HH, nor IHN affects the potato

nutritionally, but can negatively impact the chip processing potatoes.

CRS is a viral disease (tobacco rattle virus; TRV) transmitted by the stubby-root

nematode (Paratrichodorus minor). As the nematode feeds on the tuber the virus

transmitted causes concentric brown necrotic arcs in the tuber flesh. Brown rot also

known as bacterial wilt is caused by a soil borne pathogen (Ralstonia solanacearum).

The pathogen infects the potato roots through wounds and at emergence of lateral roots.

In this study, both percent affected and severity were calculated for IHN. Severity is

based upon a score on a scale of one to six. A score of one to four indicates that 0 to 25%

of all four quarters had the disorder. A score of five or six indicated that all quarters had

the disorder and up to 75 to 100% of all quarters were covered, respectively.

Irrigation date main effect treatments significantly influenced the development of

internal heat necrosis in tubers (IHN) in 2004. IHN appears to be initiated by early

season plant stress (too much water and poor nutrition) and is exacerbated by increased

temperatures later in the season as discussed in chapter 2. Plants in the 8 and 12 WAP

irrigation treatments produced tubers with significantly lower percentages of IHN, 3.3

and 4.3% of total tuber yield, respectively, compared with the 2WAP irrigation date at

16.3%. The 2 WAP irrigation event occurred at emergence and was followed by another

natural leaching rainfall event that occurred approximately 2 weeks later around tuber

initiation. This corresponded to approximately 200 to 400 GDD, respectively. This is

supported by the findings in chapter 2. The plots with the highest incidence of tubers

with IHN experienced a leaching rainfall event between 200 and 400 GDD. Plant stress

(too much water) in conjunction with a nutritional loss (nutrient leaching) early in the









season, between 200 and 400 GDD, may predispose the tubers to IHN. IHN severity was

highest as well in tubers from the 2 WAP irrigation treatment at 2.3. IHN severity in

tubers in the 2 WAP irrigation treatment was significantly different from levels in tubers

at 8 and 12 WAP (1.3 and 1.7), respectively, but the same as 0 and 4 WAP irrigation

treatments (Table 3-6).

The natural rainfall event described above that was devastating to plants in the 2

WAP irrigation treatment occurred at the 4 WAP irrigation date. Therefore, the irrigation

treatment was not applied at 4 WAP. Interestingly, the percentages of tubers with IHN

and their IHN severity were similar in the 0 WAP and 4 WAP irrigation treatments.

Therefore, this provides evidence that the 2 WAP irrigation event "stressed" (too much

water) plants causing the increase in the percentage of tubers with IHN and the severity

of IHN.

Although this early "plant stress" at 2 WAP was necessary for the development of

IHN, it may have only been part of the necessary events for the development of IHN by

the end of the season. In other words, creating potato plant stress by excessive irrigation

and the resulting reduced nutrition early in the season (emergence to tuber initiation) may

predispose the developing tubers to the occurrence of IHN. However, a late season stress

may be necessary to exacerbate the symptoms.

Fertilizer main effect

Fertilizer main effect significantly influenced the incidence of tubers with IHN.

CRF treatment had a significantly higher incidence of tubers with IHN compared with the

AN fertilizer treatment, 11.0 and 5.6% of total tuber yield, respectively. IHN severity

was not significantly different among fertilizer treatments (Table 3-6). The higher

incidence of IHN may be caused by the time needed for the CRF treatments to 'recharge'









the nutrient levels in the soil after a leaching event. CRF with a faster release rate will

recharge sooner than one that has a slower release rate. A slow recharge rate would

result in sub-optimal soil nutrient conditions resulting in plant nutrient stress. Studies

have related IHN development in tubers to nitrogen stress as reported by (Sterrett and

Henninger, 1997; Sterrett and Henninger, 1991 and Clough, 1994).

Sidedress main effect

Interestingly, the sidedress main effect did not significantly reduce the occurrence

of tubers with IHN in 2004. Tubers with IHN and the IHN severity rating for the CRF

treatment was 9.8% and 1.9 respectively compared with the AN fertilizer treatment at

7.1% and 1.8, respectively. If nutrient stress does relate to IHN, then additional nitrogen

should reduce the occurrence and severity of IHN. Three items relating to the application

of additional nitrogen in this study may have prevented the optimal use of the sidedress

application. First, the application method applied a "dry" soluble fertilizer to the row

shoulders. However, this application method places the fertilizer in the dry area of the

bed above the capillary zone of the seepage irrigation and where few potato roots are

located (Munoz, 2004). This means that rainfall is necessary to push the fertilizer into

the root zone of the crop. If the rainfall is too heavy, fertilizer will move in surface water

runoff into the drainage canals.

Secondly, in order for fertilizer to be used by the plant, it needs to be available

prior to full flower (30 to 50 DAP). Certainly, the 8 and 12 WAP application treatments

are well past full flower and not expected to be beneficial to the crop. And as noted, the

0, 2, and 4 WAP sidedress applications could only be beneficial if natural rainfall pushed

the fertilizer into the row and not off the row in surface water movement. The leaching









rainfall event that occurred at 4 WAP washed the soil away from the hill exposing the

potato roots as well as washing the fertilizer away from the hill and into the alley.

Lastly, the BMP recommendation of 34 kg N ha-1 may not be enough N to make a

difference in yield or quality. The functionality of the application is related to placement

and rate. For instance, if it were placed properly, less N would be needed to impact

quality and/or yield. However, this study did not examine rate; therefore, a conclusion on

the influence of rate and placement on the effectiveness of the sidedress application can

only be presumed. There were no significant main effect interactions in 2004 (Table 3-

6).

Tuber Internal Quality for 2005

Irrigation date main effect

Irrigation date main effect treatments did not significantly influence the internal

tuber quality in 2005. Occurrence of IHN in tubers for the 2005 season was 71% higher

compared with the 2004 production season (Table 3-6). There was no significant

differences among the irrigation date treatments for the incidence or severity of tubers

with IHN. Tubers with IHN ranged from a high of 35.5% in the 2 WAP irrigation date

treatment to a low of 24.9 in the 0 WAP irrigation treatment. Plants in the 2 WAP

irrigation treatment received water/nutrient stress early in the season with the staged

leaching irrigation event followed by an additional leaching rainfall event near 4 WAP

(Figure 3-13); (Table 3-6). IHN severity among irrigation treatments was not

significantly different. IHN severity rating ranged from 3.4 in the 2 WAP irrigation date

treatment down to 3.0 in the 12 WAP irrigation date treatment.









Fertilizer source main effect

Fertilizer source main effect significantly influenced the development of tubers

with IHN. The incidence of IHN was 24% higher in tubers in the CRF treatments

compared with tubers in the AN fertilizer treatment (Table 3-6). IHN severity was not

significantly different between the CRF and AN treatment at 3.3 and 3.1, respectively.

Although CRF had significantly more tubers with IHN, the severity rating was similar.

As in 2004, this was most likely caused by the CRF treatments to 'recharge' the nutrient

levels in the soil that is related to CRF type and release rate.

CRF treatments had significantly higher incidences of tubers with IHN in 2004 and

2005 compared with the AN fertilizer treatments that contradicts the results reported by

Hutchinson, 2005 and Pack, 2004. The difference in results may be due to the timing of

the leaching event and its relation to the growth stage of the potato plant.

In 2004, the highest incidence of tubers with IHN was in the 2 WAP irrigation

treatment while the lowest incidence of tubers with IHN were the late season irrigation

events, 8 and 12 WAP. Similarly, in 2005, the 2 WAP irrigation treatment also had the

highest incidence of tubers with IHN compared with the other irrigation treatments.

Although leaching rainfall events occurred during both seasons, the time when leaching

rainfall events occurred in conjunction with the growth stage of the potato crop may

determine when IHN in tubers is initiated due to nutritional and environmental stressors.

Sidedress main effect

Sidedress main effect treatment did not significantly influence the occurrence of

tubers exhibiting IHN. The IHN severity rating for the sidedress treatments were

identical at 3.2. Quality (particularly IHN) did not improve with the BMP recommended









side dress application. The BMP should be reexamined to make sure the side dress

methodology is beneficial to potato crop in the production system (Table 3-6).

Nitrate Nitrogen Concentration in Wells for 2004

Irrigation main effect

Irrigation treatment main effect significantly influenced NO3-N concentrations in

well water samples in 2004. During the 2004 production season, well water NO3-N

concentrations were highest at the 29 DAP sample date and decreased exponentially over

time. A leaching rainfall event occurred the night before that would explain the high

NO3-N values.

The 4 WAP irrigation treatment had the highest well NO3-N value at the 29 DAP

sample date at 30.2 mg L-1. All other irrigation treatments had well NO3-N

concentrations between 17.1 and 29.5 mg L-1. Well water NO3-N concentrations at 72

DAP were significantly higher at the 8 WAP irrigation date compared with the 0 and 2

WAP irrigation date. All sample dates except at 29 DAP had well NO3-N levels < 8.2

mg L-1 (Table 3-7). The relatively low NO3-N concentrations in the observation wells

may be due to a couple of factors. First, most of the nutrients were most likely moved

out of the bed due to surface water flow. Second, the amount of water applied at the

leaching events may not have been enough and/or had been diluted by the time the

nutrients reached the depth of the observation wells as it moved down through the soil

profile.

Fertilizer main effect

The fertilizer main effect significantly influenced well water NO3-N concentrations

in 2004. The 89 DAP well water NO3-N concentrations were significantly higher in the

CRF compared with the AN fertilizer treatment, 0.5 and 0.2 mg L-1, respectively. This









may indicate that the CRF was still releasing N late in the season. Similarly to the

irrigation treatments, well water NO3-N concentrations were highest at the 29 DAP

sample date and decreased exponentially over time.

Sidedress main effect

The sidedress main effect did not significantly influence well water NO3-N

concentrations at any of the sampling dates. There were no significant interaction effects

for the 2004 production season (Table 3-7).

Nitrate Nitrogen Concentration in Wells for 2005

Irrigation main effect

The irrigation treatment main effects did not significantly influence well water

NO3-N concentrations in 2005. At the 17 DAP sample date, well water NO3-N

concentration ranged from a high of 7.4 mg L-1 in the 2 WAP irrigation treatment,

followed by 12, 4, 8 and 0 WAP irrigation treatments at 7.3, 6.4, 5.2 and 4.1 mg L-1,

respectively. This result was due to the 2 WAP irrigation treatment that was applied 24 h

prior to the 17 DAP sample acquisition. Well water NO3-N concentrations increased up

to 45 DAP. Since no irrigation treatment was applied before this sample date, the

increase in NO3-N concentration in the wells was the result of a 2.8 cm rainfall event at

44 DAP. Well water NO3-N concentrations ranged from a high of 3.4 mg L-in the 8

WAP irrigation date treatment to a low of 1.4 mg L-1 in the 0 WAP irrigation treatment at

the 59 DAP sample event. This result was due to the 8 WAP irrigation treatment applied

24 h previous to the 59 DAP well sample (Table 3-7). This shows that leaching events do

have an impact on the movement of nutrients down through the soil profile into the water

table.









Fertilizer main effect

Fertilizer main effect did not significantly influence well NO3-N concentrations in

2005. CRF treatments consistently had lower NO3-N levels throughout each of the

sampling dates compared with the AN fertilizer treatments. Overall sample dates, the

average reduction of well NO3-N in the CRF treatments was approximately 19% lower

compared with the AN fertilizer treatment.

Sidedress main effect

The sidedress main effect did not significantly influence well NO3-N

concentrations in 2005. The 0 and 34 kg N ha-1 sidedress treatments were similar

throughout all sample dates (Table 3-7).

A decreasing trend in lysimeter NO3-N concentration was noted after the 29 and 45

DAP sampling dates for 2004 and 2005, respectively. This may be due to the

combination of the scheduled leaching irrigation events and the leaching rainfall events

during the latter part of the season in 2005 (Figure 3-13).

Nitrate Nitrogen Concentration in Lysimeters for 2004

Irrigation main effect

Irrigation date main effects significantly influenced lysimeter NO3-N

concentrations in 2004. The highest values observed during the 2004 production season

were at the 30 DAP sampling event with an average value of 216.4 mg L-1. The flush of

NO3-N was most likely due to the leaching rainfall received the previous night (11 cm)

(29 DAP). At the 45 DAP sample date the 8 WAP irrigation treatment had the highest

lysimeter NO3-N concentration at 41.9 mg L-1 followed by irrigation treatments, 12, 2, 0

and 4 WAP with NO3-N values of 34.4, 26.1, 25.2, and 22.1 mg L1, respectively. A

sharp decline in lysimeter NO3-N concentrations were observed at the 90 DAP sample









date in all irrigation treatments with the exception of the 12 WAP irrigation treatment had

lysimeters NO3-N concentrations below 1.1 mg L-1. The 12 WAP irrigation date at the

90 DAP sample date had significantly higher lysimeter NO3-N concentration, 9.3 mg L-1

that was most likely due to the 12 WAP irrigation treatment applied 24 h before the 90

DAP sample acquisition (Table 3-8).

Fertilizer main effect

Fertilizer main effect did not significantly influence lysimeter NO3-N

concentrations. CRF treatment consistently had lower NO3-N nutrient concentrations

throughout all sampling dates compared with the AN fertilizer treatment for the 2004

production season. CRF treatments had an average 30% lower lysimeter NO3-N

concentration compared with AN fertilizer treatment over all lysimeter sampling dates in

2004 (Table 3-8). A decreasing trend was noted over the season until the last sample date

(90 DAP) when lysimeter NO3-N concentrations increased. This may be due to the flush

of nutrients from the potato crop late in the season due to the lack of nutrient uptake by

the senesced plants.

Sidedress main effect

Sidedress main effect did not significantly influence lysimeters NO3-N

concentrations. Similarly to the fertilizer main effects, a downward trend was also noted

over the season until the last sample date 90 DAP when lysimeter NO3-N concentrations

increased. There were no other significant interaction effects for 2004 (Table 3-8).

Nitrate Nitrogen Concentration in Lysimeters for 2005

Irrigation main effect

Irrigation date main effect significantly influenced NO3-N concentrations in

lysimeter water samples in treatment plots in 2005. Although not significant, at the 18









DAP sample date, the 2 WAP irrigation treatment had higher lysimeter NO3-N

concentration (39.6 mg L-1) compared with all other irrigation treatments at 18 DAP. The

lysimeter water sample at 18 DAP was within 24 h of the 2 WAP irrigation treatment that

would explain the higher lysimeter NO3-N concentration. NO3-N concentrations in

lysimeter water samples continued to rise until the 45 DAP sample date, then again

lysimeter NO3-N concentrations began to decline and were lowest at the 89 DAP sample

date. Similarly to the discussion above, at the 34 DAP which was within 24 h of the 4

WAP irrigation treatment, lysimeter NO3-N concentrations were higher (60.8 mg L1)

compared with all other irrigation treatments. Again, lysimeter NO3-N concentrations

peaked at 45 DAP followed by a decreasing trend to a low at the 89 DAP sample date in

which all lysimeter NO3-N concentrations were < 3.6 mg L-1. This indicated that a

majority of the N applied was either taken up by the plant or leached below the root zone

(Table 3-8).

Fertilizer main effect

Fertilizer main effect significantly influenced again lysimeter NO3-N

concentrations in 2005. CRY had again, significantly lower lysimeter NO3-N

concentrations for the 18, 34 45 and 60 DAP sampling dates. After the 45 DAP sample

date again lysimeter NO3-N concentrations in the CRF and AN fertilizer treatments

declined to a low of 2.8 and 3.3 mg L-1, respectively. Overall, the CRF decreased

lysimeter water NO3-N by 32% compared with the AN fertilizer treatment. This shows

the benefits of the CRF throughout the season, but especially early in the season when the

risks of nutrient leaching is at its highest.









Sidedress main effect

Sidedress main effect did not significantly influence again, lysimeter NO3-N

concentrations for any of the lysimeter sample dates in 2005. There were no significant

main effects interactions in 2005 (Table 3-8). Therefore, this is another argument that the

placement of a dry soluble fertilizer on the shoulder of the row is not the proper

application method. The production BMPs for potato production may need to be revised

to create an effective sidedress treatment after a leaching rain.

Overall, the lysimeter NO3-N nutrient concentrations in 2004 and 2005 again for

CRF treatments was 29 and 25% less, respectively, compared with the AN fertilizer

treatments. Theoretically, if growers in the TCAA used a CRF, based upon this research,

reduction of N into the St. Johns River could be 56,000 kg N per year.

Nutrient Load Concentration in Surface Water

Water volume: 2004

The volume of water flow from the field varied with irrigation treatments in 2004.

Surface water flow during the 2 WAP irrigation treatment was highest peaking between

300 and 350 L compared with the 8 and 12 WAP irrigation treatments. High surface

flow from the plot was most likely due to the wetter weather conditions prior to the

irrigation event as well as the lack of crop cover since potato plants were just starting to

emerge at 2 WAP. Additionally, at this stage of growth and development of the potato

plant, high surface water flow from the plots would have carried fertilizer out of the bed

into the drainage canals creating a nutrient and water stress early in the season. This can

be seen due to the higher incidence of tubers with IHN in the 2 WAP irrigation treatment

and would also support the theory that IHN may be initiated early in the season due to a

combination of plant stress caused by too much water and too low nutritent concentration









followed by hot dry weather late in the season. At the 12 WAP irrigation treatment,

surface water flow was lowest because of hot dry weather conditions (Figure 3-3a).

Although IHN has been reported to be caused by hot dry weather conditions late in the

season and when tubers are near maturity (Stevenson et al., 1987; Sterrett and Henninger,

1991), tubers from the 12 WAP irrigation treatment had the lowest incidence of IHN.

Water volume: 2005

The volume of water flow also varied with irrigation treatments in 2005. The

surface water runoff was the highest during the 4 WAP irrigation date, peaking around

375 L that may be attributed to the wetter weather conditions two days prior to the

irrigation event. The 12 WAP irrigation date surface water flow was the lowest due to

drier conditions prior to the irrigation event and (Figure 3-3b).

Nutrient load: 2004

CRF treatments had consistently lower NO3-N nutrient loads (kg ha-1) compared

with the AN fertilizer treatments at the 2, 8 and 12 WAP irrigation treatments in 2004.

NO3-N nutrient loading from surface water runoff in the CRF treatments were reduced by

35, 28 and 32% compared with the AN fertilizer treatments at 2, 8 and 12 WAP,

respectively in 2004. Overall, the average reduction in NO3-N loading from the CRF

treatments was 31% less compared with AN fertilizer treatments (Table 3-9; Figure 3-

11).

Nutrient load: 2005

As in 2004, the CRF had consistently lower NO3-N nutrient loads (kg ha-1) over

time compared with the AN fertilizer treatment in 2005. The CRF treatment during the

2005 production season also decreased NO3-N nutrient loads from surface water runoff

by 55, 22, 63 and 79% for the 2, 4, 8 and 12 WAP irrigation treatments, respectively









(Table 3-10; Figure 3-12). Nutrient runoff over time in each leaching irrigation event in

2004 and 2005 was variable within replications, but overall, the CRF treatment had less

NO3-N runoff (Figure 3.4-3.6; Appendix E-24 pg 189) and (Figure 3-7-3.10; Appendix

E-25 pg. 190).

Overall the average reduction in NO3-N nutrient loading from the CRF treatment

was 54% compared with AN fertilizer treatment (Table 3-10). This data has shown the

benefits using a CRF that can significantly reduce the amount of nutrient loading into the

watersheds and reduce the negative impacts that nutrient loading would have on sensitive

environmental areas in the TCAA. Based upon this research, if growers in the TCAA

used a CRF in their production practices, N into the St. Johns River could be reduced by

56,000 kg per year, a substantial savings of pollutant into the river. This was determined

by the average NO3-N load (kg ha-1) for AN and CRF treatments in 2004 and 2005 (Table

3.9 and 3.10) multiplied by the total potato production area in the TCAA (8,000)

hectares.

Growing Degree Days

Potato plant emergence in 2004 and 2005 occurred at 18 and 19 DAP, respectively.

The accumulated GDD to reach emergence in 2004 and 2005 was 225 and 228,

respectively. Full flower in 2004 and 2005 occurred 53 and 49 DAP, respectively that

corresponded to 807 and 798, respectively (Table 3-11). The accumulated GDD to reach

emergence and full flower are in agreement with the findings discussed in chapter two.

The highest incidence of tubers with IHN in 2004 and 2005 occurred in the 2 WAP

irrigation treatment. The 2 WAP irrigation event occurred at 193 accumulated GDD. As

in chapter two, the higher incidence of tubers with IHN experienced a leaching event

between 200 and 400 accumulated GDD for both 2004 and 2005.









Conclusions

This research has demonstrated the effectiveness of a CRF in potato production

compared with a soluble N fertilizer. Marketable yields in the CRF treatments were an

average of 12% higher compared with the AN fertilizer treatment. Additionally, 13%

less N fertilizer was applied in the CRF treatment compared with the AN fertilizer

treatment.

Overall, the sidedress main effect of the additional 34 kg N ha-1 after a leaching

rainfall event did not significantly influence total or marketable yields in 2004 or 2005.

Although, the three-way interaction between irrigation date, fertilizer source and side

dress application main effect was significant for the total and marketable tuber yields in

2004 and 2005 in the CRF treatment at the 2 WAP irrigation treatment date. Internal and

external quality were unaffected with the additional N application after a leaching event,

therefore, the BMP rate was not adequate to prevent IHN.

The CRF treatments had a significantly higher incidence of tubers with IHN

compared with the AN fertilizer treatment at 22.3 and 15.6%, respectively. The CRF

treatment had a 31% higher incidence of tubers with IHN compared with the AN

fertilizer treatment. This also supports the hypothesis that the CRF needed to have a

faster release rate earlier in the season.

NO3-N loading from surface water runoff from potato production was decreased by

an average of 43% with the use of the CRF compared with the AN fertilizer treatment.

Therefore, if growers in the TCAA used a CRF in potato production, rather than a soluble

N fertilizer at the BMP rate of 224 kg N ha-1, NO3-N loads into the St. Johns River

watershed could be reduced by 56,000 kg N per year.









Table 3-1. Irrigation treatment (WAP),
2005 production seasons


fertilizer treatment, fertilizer source and additional sidedress application (DAP) for 2004 and


8 1 AN 59 58
8 2 AN 59 58
8 3 CRF 59 58
8 4 CRF 59 58
12 1 AN 91 88
12 2 AN 91 88
12 3 CRF 91 88
12 4 CRF 91 88
zWAP Weeks after planting
YAN Ammonium nitrate; CRF Controlled release fertilizer
XDAP Days after planting
WAdditional sidedress applied as 30-0-0.


67

67

N/A

N/A


64

N/A

N/A


Irrigation Fertilizer Fertilizer Irrigation date Additional N Additional
treatment treatment sourcey Timing side dress sidedress DAP
WAPz DAPx kg N ha-1
2004 2005 2004 2005
0 1 ANy 0 0 0 -
0 2 AN 0 0 34 43 43
0 3 CRF 0 0 0 -
0 4 CRF 0 0 34 43 43
2 1 AN 17 16 0 -
2 2 AN 17 16 34 43 43
2 3 CRF 17 16 0 -
2 4 CRF 17 16 34 43 43
4 1 AN 28 30 0 -
4 2 AN 28 30 34 43 43
4 3 CRF 28 30 0 -
4 4 CRF 28 30 34 43 43















Rep 1


Rep 2


Rep 3


3 14 11 1 2 1 2 13 14 1 14 13 12 11


1 12 13 14


4 3 2 1




B




3 4 1 2


3 11 1 2 14 13 12 11


2 1 4 3




B




1 2 3 4


3 4 2 1




B




1 2 3 4


Rep 4


2 11 14 13


3 14 11 1 2


1 2 3 4


4 13 1 2


Irrigation treatment
(WAP)


A No irrigation

B-2

C-4

D-8


E -12


N source and additional
N treatment


1 AN No additional N
2 AN 30-0-0

3 CRF No additional N
4 -CRF 30-0-0


2 11 14 13 12 11 13 14 13 14 11 12 12 11 14 13


Figure 3-2. Plot map leaching irrigation project