Citation
Incorporation of Controlled-Release Fertilizer in a Seepage Irrigated Tomato Fertility Program in Florida

Material Information

Title:
Incorporation of Controlled-Release Fertilizer in a Seepage Irrigated Tomato Fertility Program in Florida
Creator:
Carson, Luther C
Place of Publication:
[Gainesville, Fla.]
Florida
Publisher:
University of Florida
Publication Date:
Language:
english
Physical Description:
1 online resource (180 p.)

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Horticultural Sciences
Committee Chair:
OZORES-HAMPTON,MONICA
Committee Co-Chair:
OBREZA,THOMAS ANTHONY
Committee Members:
SARGENT,STEVEN ALONZO
MORGAN,KELLY T
SARTAIN,JERRY B
Graduation Date:
5/3/2014

Subjects

Subjects / Keywords:
Controlled release ( jstor )
Fertilizers ( jstor )
Fruits ( jstor )
Nitrogen ( jstor )
Nutrients ( jstor )
Polymers ( jstor )
Pouches ( jstor )
Soil science ( jstor )
Soil temperature regimes ( jstor )
Tomatoes ( jstor )
Horticultural Sciences -- Dissertations, Academic -- UF
bmp -- crf -- eef -- solanum -- srf
Miami metropolitan area ( local )
Genre:
bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Horticultural Sciences thesis, Ph.D.

Notes

Abstract:
Controlled-release fertilizers (CRF) are soluble fertilizers (SFs) coated with a polymer, resin, or a hybrid of polymer coating sulfur coated urea and a vegetable production best management practice in Florida { TC ABSTRACT }. The goal with CRF will be that nitrogen (N) release matches tomato (Solanum lycopersicum) N uptake, which may increase N use efficiency resulting in higher marketable yields and fruit quality with reduced N rates and environmental impacts. Therefore, the purposes of this dissertation were to: evaluate N release from CRFs buried in pouches in seepage-irrigated tomato beds, and correlate the N release with accelerated temperature controlled incubation method (ATCIM) extraction values. Also, a hybrid fertilizer system combining individual 120 and 180 d release (DR) CRFs or CRF mixes of 100, 140, and 180 DR with SFs was evaluated on fall season marketable fruit yield, postharvest quality, leaf tissue N content (LTNC), and post season soil N content. The high bed temperatures compared to the temperatures at which manufacturers measure CRF N release (20.0 to 25.0 C), shortened N release duration by 23% to 88% and 23% to 79% in 2011 and 2013, respectively. Correlations of the ATCIM and pouch method predicted N curves of individual CRFs with a R2 of 0.90 and grouped CRF with a R2 of -0.64 to 0.99. The CRF mixes at 112/56 (CRF/SF) and 168/56 kg/ha N in the hybrid fertilizer system and individual CRF containing N, phosphorus, and potassium at 190 to 224 kg/ha N pre-plant incorporated in the bottom mix can be recommended for fall tomato production. No negative impacts of CRFs were found on postharvest fruit quality or LTNC during the seasons. Therefore, CRFs can supply 65% to 80% of a fall tomato fertility program and maintain marketable yields and fruit quality at reduced N rates and low residual soil N. ( en )
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis:
Thesis (Ph.D.)--University of Florida, 2014.
Local:
Adviser: OZORES-HAMPTON,MONICA.
Local:
Co-adviser: OBREZA,THOMAS ANTHONY.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2015-05-31
Statement of Responsibility:
by Luther C Carson.

Record Information

Source Institution:
UFRGP
Rights Management:
Applicable rights reserved.
Embargo Date:
5/31/2015
Resource Identifier:
907379239 ( OCLC )
Classification:
LD1780 2014 ( lcc )

Downloads

This item has the following downloads:


Full Text
xml version 1.0 encoding UTF-8
REPORT xmlns http:www.fcla.edudlsmddaitss xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.fcla.edudlsmddaitssdaitssReport.xsd
INGEST IEID EGCXH3SBT_MGFKED INGEST_TIME 2014-10-03T22:00:20Z PACKAGE UFE0046445_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC
FILES



PAGE 1

1 INCORPORATION OF CONTROLLED RELEASE FERT I LIZER IN A SEEPAGE IRRIGAT ED TOMATO FERTILITY PROGRAM IN FLORIDA By LUTHER C. CARSON 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 201 4

PAGE 2

2 201 4 Luther C. Carson

PAGE 3

3 To m y parents and my family

PAGE 4

4 ACKNOWLEDGMENTS I thank my advisor, Dr. Monica Ozores Hampton for her guidance and support throughout my doctoral program I am also thankful to m y supervisory committee Dr. Sartain, Dr. Obreza, Dr. Morgan, and Dr. Sargent who provided time, comments on my project, and laboratory space and supplies in which to conduct research. A special thanks goes Vegetable Horticulture Laboratory (Kiran, Aline, Joel, Ozzy, Dago, and Stacy) and the staff of the Soil Fertility and Turf Grass Nut rition Laboratory (Dolly, Nahid, and Dawn) for their assistance during my laboratory research. I am grateful to Garguilo Farms for their invaluable contributions to my research. Finally, I thank my family and friends for the love and support that they ha ve given during my PhD, which has given me the inspiration to complete this degree

PAGE 5

5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF FIGURES ................................ ................................ ................................ ........ 11 LIST OF ABBREVIATIONS ................................ ................................ ........................... 12 ABSTRACT ................................ ................................ ................................ ................... 16 CHAPTER 1 BACKGROUND AND LITERATURE REVIEW ................................ ....................... 18 Background ................................ ................................ ................................ ............. 18 Literature Review ................................ ................................ ................................ .... 22 Tomato Nitrogen Uptake ................................ ................................ .................. 22 Florida Fertilization Practices in Seepage Irrigated Crops ................................ 25 What are Enhanced Efficiency Fertilizer and Controlled Release Fertilizer? .... 26 Factors Affecting Controlled Release Fertilizer Nutrient Release for Vegetable Production in Florida using Seepage Irrigation ............................ 28 Temperature ................................ ................................ .............................. 28 Soil moisture ................................ ................................ .............................. 30 Osmotic potential ................................ ................................ ....................... 30 Soil pH ................................ ................................ ................................ ....... 31 Soil microbial populatio ns ................................ ................................ .......... 31 Soil texture ................................ ................................ ................................ 32 Controlled release fertilizer composition ................................ .................... 32 Coating thickness, type, and prill diameter ................................ ................. 33 Cultural Practices Affecting CRF Release Duration ................................ ......... 34 CRF field placement ................................ ................................ .................. 34 Nitrogen rate supplied from CRFs ................................ .............................. 36 CRF application timing ................................ ................................ ............... 37 Fumigation and staged planting ................................ ................................ 38 Methods for Determining Nitrogen Release from Controlled Release Fertilizers used for Vegetable Production ................................ ..................... 39 Laboratory methods for determining controlled release fertilizer nutrient release duration ................................ ................................ ...................... 39 Field methods for determining nitrogen release from controlled release fertilizers ................................ ................................ ................................ 41 Correlations between methods ................................ ................................ .. 43 Procedure to measure N ................................ ................................ ............ 43 Fresh Market Tomato Harvest, Ripening, and Quality ................................ ..... 46 Fruit quality aspects of ripe, round tomatoes ................................ ............. 46 Tomato maturity ................................ ................................ ......................... 48

PAGE 6

6 Determining when to harvest; Problems with green harvest ...................... 49 Stages of commercial harvest (6 USDA ripeness stages): W hy pick green? ................................ ................................ ................................ .... 49 Pre harvest nutritional program effects on fruit quality ............................... 51 Packinghouse operations: washing, sorting, sizing, packing, and ripening ................................ ................................ ................................ ... 52 Temperature and ethylene management ................................ ................... 53 Shipping ................................ ................................ ................................ ..... 54 Hypotheses ................................ ................................ ................................ ............. 54 2 NITROGEN RELEASE PROPERTIES OF CONTROLLED RELEASE FERTILIZERS IN TOMATO PRODUCTION OF SOUTH FLORIDA ....................... 67 Introduction ................................ ................................ ................................ ............. 67 Material and Methods ................................ ................................ ............................. 69 Results and Discussion ................................ ................................ ........................... 72 Weather Conditions ................................ ................................ .......................... 72 Soil Temperatu re ................................ ................................ .............................. 72 Measured Nitrogen Release from Field Incubated Pouches ............................ 73 Non Linear Regression Analysis of Nitrogen Release ................................ ...... 75 Days to 75% Nitrogen Release ................................ ................................ ........ 77 3 PR EDICTION OF CONTROLLED RELEASE FERTILIZER NITROGEN RELEASE IN TOMATO PRODUCTION USING ON FARM POUCH AND ACCELERATED TEMPERATURE CONTROLLED INCUBATION LABORATORY METHODS ................................ ................................ .................... 89 Introduction ................................ ................................ ................................ ............. 89 Material and Methods ................................ ................................ ............................. 91 Accelerated Temperature Controlled Incubation Method ................................ 91 Pouch Method Field Study ................................ ................................ ............... 92 Correlation of the ATCIM with the Pouch Method Using a Two Step Process ................................ ................................ ................................ ......... 94 Results and Discussion ................................ ................................ ........................... 95 Accelerated Temperature Controlled Incubation Method ................................ 95 Prediction Model: Correlation of ATCIM and Pouch N Release ....................... 96 Prediction Model: Correlation of the ATCIM and the Pouch N Release Grouped by CRF Release Duration ................................ .............................. 98 4 EFFECT OF CONTROLLED RELEASE AND SOLUBLE FERTILIZER ON TOMATO PRODUCTION AN D POSTHARVEST QUALIT Y IN SEEPAGE IRRIGATION ................................ ................................ ................................ ......... 109 Introduc tion ................................ ................................ ................................ ........... 109 Material and Methods ................................ ................................ ........................... 112 Results and Discussion ................................ ................................ ......................... 115 Weather Conditions ................................ ................................ ........................ 115

PAGE 7

7 Soil Temperatures ................................ ................................ .......................... 116 Water Table De pth ................................ ................................ ......................... 117 Plant Nutritional Status ................................ ................................ ................... 117 Yield Responses to CRF N Rates ................................ ................................ .. 118 Post Season Soil Samples ................................ ................................ ............. 121 Postharvest Quality ................................ ................................ ........................ 123 5 EFFECT OFC ONTROLLED RELEASE FERTILIZER N ITROGEN RATE, PLACEMENT, SOURCE, A ND RELEASE DURATION ON TOMATO GROWN WITH SEEPAGE IRRIGAT ION IN FLORIDA SANDY SOILS ............................... 133 Introduction ................................ ................................ ................................ ........... 133 Material and Methods ................................ ................................ ........................... 136 Results and Discussion ................................ ................................ ......................... 1 39 Weather Conditions ................................ ................................ ........................ 139 Soil Temperature ................................ ................................ ............................ 140 Water Table Depth ................................ ................................ ......................... 141 Mortality ................................ ................................ ................................ .......... 141 Plant Nutritional Stat us ................................ ................................ ................... 142 Yield Responses to CRF N Rates ................................ ................................ .. 143 Post Season Soil Test ................................ ................................ .................... 146 Postharvest Quality ................................ ................................ ........................ 148 6 CONCLUSIONS ................................ ................................ ................................ ... 160 Proposed IFAS Reco mmendations ................................ ................................ ....... 162 Future Research ................................ ................................ ................................ ... 164 LIST OF REFERENCES ................................ ................................ ............................. 166 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 180

PAGE 8

8 LIST OF TABLES Table page 1 1 Summary of fresh market tomato field trials using enhanced efficiency fertilizers and seepage irrigation ................................ ................................ ......... 56 1 2 Summary of fresh market bell pepper field trials using controlled release fertilizers and seepage irrigation ................................ ................................ ......... 58 1 3 Summary of chip stock potato field trials using enhanced efficiency fertilizers and seepage irrigation in an open bed system ................................ ................... 59 1 4 Nitrogen determination method to use with different incubation methods, N species, and controlled release fertilizer N source. ................................ ............ 61 1 5 Cost of laboratory analysis for nitrogen content remaining in controlled release fertilizer prills in a field trial consisting of 6 replications, 5 t reatmen ts and 11 sampling dates ................................ ................................ ....................... 62 1 6 Official USDA color descriptions for mature tomatoes. ................................ ....... 63 1 7 Green tomato maturity defined by internal appearance from an equatorial cross section ................................ ................................ ................................ ...... 64 2 1 Collection dates and days after placement for pouches containing controlled release fertilizer, incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 ................................ ............................. 80 2 2 Controlled release fertilizers placed in pouches and incubated in white polyethylene mulch cov ered raised tomato beds during Fall 2011 and 2013 ..... 81 2 3 Minimum mean, and maximum soil temperatures at 10 cm below the bed surface during Fall 2011 and 2013 ................................ ................................ ..... 82 2 4 Main and interaction effects of 12 controlled release fertilizers by collection dates from pouches incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 ................................ ............................. 83 2 5 Percentage nitrogen rele ase from controlled release fertilizers incubated in pouches 10 cm below the surface of a white polyethylene mulch covered raised bed during Fall 2011 and 2013 ................................ ................................ 84 2 6 Contrasts of controlled release fertilizers by collection date and coating technology from pouches incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 ................................ .................. 85

PAGE 9

9 2 7 Nonlinear regression analysis of N release from controlled release fertilizers incubated in pouches 10 cm below the surface of a white polyethylene mulch covered raised tomato bed during Fall 2011 and 2013 ................................ ....... 86 3 1 Controlled release fertilizers used in the accelerated temperature contr olled incubation and the on farm pouch methods incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 ........................ 100 3 2 Collection dates and days after placement for controlled release fertilizer in on farm pouch field study incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 ................................ ................ 101 3 3 Nitrogen extracted from controlled release fertilizers during the accelerated temperature controlled incubation method ................................ ....................... 102 3 4 Regression coefficients and coefficient of determination for predicted controlled release fertilizer nitrogen release curve based on the two step process ................................ ................................ ................................ ............. 103 3 5 Regression coefficients and coefficient of determination for predicted nitrogen release based on controlled release fertilizer coefficient groupings in the two step process ................................ ................................ ........................ 104 4 1 Nutrient rates and bed placement used in testing controlled release fertilizer fall mixes in Immokalee, FL during Fall 2011 and Fall 2012. ............................ 125 4 2 Summary of minimum average, and maximum air tempera ture and total rainfall in Immokalee, FL during Fall 2011 and 2012 growing seasons. ........... 126 4 3 Summary of minimum, average and maximum soil temperature at 10 cm below the bed surface in Immokalee, FL during Fall 2011 and 2012 ................ 127 4 4 Fruit yield by size categories for first harvest, first and second harvest combined, and season total harvest for five controlled release fertilizer /solubl e nitrogen fertilizer programs ................................ ................................ .. 128 4 5 1 as ammonium N nitrate N and urea N in the soil an d controlled release fertilizer prills from five CRF/soluble nitrogen fertilizer programs ................................ ................................ ............... 129 4 6 Postharvest firmness and color at red ripe stage for tomato grown using fiv e controlled release fertilizer /soluble nitrogen fertilizer programs ........................ 130 5 1 Nutr ient rates and bed placement use d in testing soluble fertilizer/ controlled release fertilizer fertility programs on tomato in southwest Florida during Fall 2011 and Fall 2012. ................................ ................................ .......................... 150

PAGE 10

10 5 2 Summary of minimum, mean, and maximum air temperature and total rainfall in Immokalee, FL during Fall 2011 and 2012. ................................ .................. 151 5 3 Summary of minimum, mean, and maximum soil temperatures at 10 cm below the bed surface in Immokalee, FL during Fall 2011 and 2012. ............... 152 5 4 Fruit yield by size categories for first harvest, first and second harvest combined, and season total harvest for two soluble fertilizer and six con trolled release fertilizer tomato fertility programs ................................ ........ 153 5 5 Fruit yield by size categories for first harvest, first and second harvest combined, and season total harvest for two soluble fertilizer and seven controlled release fertilizer tomato fertility programs ................................ ........ 154 5 6 Residual soil ammonium nitrogen, nitrate N, urea N, and total N from two soluble fertilizer and six controlled release fertilizer programs ......................... 155 5 7 Res idual soil ammonium nitrogen, nitrate N urea N, and total N f rom two soluble fertilizer and six controlled release fertilizer programs ......................... 156

PAGE 11

11 LIST OF FIGURES Figure page 1 1 Accumulation of N by tomato plants ................................ ................................ ... 65 1 2 Nitrogen accumulation of tomatoes grown using drip irrigation .......................... 66 2 1 A tomato nitrogen uptake curve charted with fitted N release curves from a 120 d release polymer coated compound nitrogen, phosphorus, and potassium controlled release fertilizer ................................ ................................ 88 3 1 Field release points for CRFs incubated 10 cm below the surface of a white polyethylene mulched raised bed during Fall 2011 and 2013 in Immokalee, FL and fi tted and predicted release curves from the two step correlation ........ 105 3 2 Field release points for CRFs incubated 10 cm below the surf ace of a white polyethylene mulched raised bed during Fall 2011 and 2013 in Immokalee, FL and fitted and predicted release curves from the two step correlation ........ 106 3 3 Fitted and predicted nitrogen release curve of controlled release fertilizers grouped based on release duration in the two step correlation ........................ 107 3 4 Fitted and predicted N release curves for controlled release fertilizers grouped based on release duration in the two step correlation ........................ 108 4 1 Water table levels for tomato grown with seepage irrigation in Immokalee, FL during Fall 2011 and 2012. ................................ ................................ ............... 131 4 2 Leaf tissue nitrogen concentration for tomatoes grown with fiv e controlled release fertilizer /soluble nitrogen fertilizer (S NF) programs in Immokalee, FL 132 5 1 Water table levels for tomato grown with seepage irrigation in Immokalee, FL during Fall 2011 and 2012. ................................ ................................ ............... 157 5 2 Plant mortality by treatment for tomato grown with soluble fertilizer and different CRF rates and sources in Immokalee, FL. during Fall 2011 ............... 158 5 3 Changes in leaf tissue nitrogen concentration for tomato grown with soluble fertilizer and c ontrolled release fertilizer programs in Immokalee, FL ............... 159

PAGE 12

12 LIST OF ABBREVIATIONS AN Ammonium nitrate ATCIM Accelerated temperature controlled incubation BMP Best management practice Ca 2+ Calcium CRF Controlled release fertilizer CRF NPK Controlled release fertilizer containing a compound fertilizer composed of nitrogen, phosphorus, and potassium CRKN Controlled release potassium nitrate CRN Controlled release nitrogen CRU Controlled release urea Cu 2+ Copper d day DAP Days after placement DAT Days after transplant DI De ionized DBP Days before planting EEF Enhanced efficiency fertilizer FAWN Florida Automated Weather Network FDACS Florida Department of Agricult ure and Consumer Services FH First harvest FL100 Polymer coated nitrogen, 100 day release FL140 Polymer coated nitrogen, 140 day release FL180 Polymer coated potassium nitrate, 180 day release

PAGE 13

13 FLmix Fall mix containing FL100, FL140, and FL180 without soluble fertilizer FSHC First and second harvest combined H + Hydrogen H 2 PO 4 Orthophosphate IBDU I sobutydine diurea ISE Ion selective electrode K Potassium K + Potassium in the ionic form KCl Potassium chloride KNO 3 Potassium nitrate LTN C Leaf tissue nitrogen concentration M112 1 N when applied at 1 1 M168 1 N when applied at 1 1 M224 1 N when applied at 1 1 Max Maximum Mg 2+ Magnesium Min Minimum MU Methylene urea N Nitrogen N 2 O Nitrous oxide NFT Nutrient film technique NH 3 Ammonia NH 4 + Ammo nium NH 4 + N Ammonium nitrogen NH 4 NO 3 Ammonium nitrate

PAGE 14

14 NO 3 Nitrate NO 3 N Nitrate nitrogen NRC Nitrogen release curve NUE Nitrogen use efficiency OH Hydroxide OX Oxamide P Probability value P Phosphorus PCF Polymer coated fertilizer PCKN Polymer coated potassium nitrate PCM Polymer coated mix containing FL100, FL140, and FL180 PCNPK Polymer coated fertilizer containing nitrogen, phosphorus and potassium PCU Polymer coated urea PNR Percentage nitrogen release PSCU Polymer sulfur coated urea PVC Polyvinyl chloride r Coefficient R 2 Coefficient of determination RCF Resin coated fertilizer RCK Resin coated potassi um RCNPK Resin coated fertilizer containing nitrogen phosphorus and potassium RCU Resin coated urea RD Release duration SCU Sulfur coated urea

PAGE 15

15 SF Soluble fertilizer SNF Soluble nitrogen fertilizer SRF Slow release fertilizer SW South west SWFREC Southwest Florida Research and Education Center T# Treatment #, where # = a number between 1 and 9. TCIM Temperature controlled incubation method TKN Total K j elda h l nitrogen TN Total nitrogen TMDL Total maximum daily load UF Urea formaldehyde UF/IFAS University of F lorida/Institute of Food and Agriculture Science s U.S. United States USA United States of America USDA United States Department of Agriculture VegLa b Vegetable Horticulture Lab Vs. Versus

PAGE 16

16 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 INCORPORATION OF CONTROLLED RELEASE FERT I LIZER IN A SEEPAGE IRRIGAT ED TOMATO FERTILITY PROGRAM IN FLORIDA By Luther C. Carson May 201 4 Chair: Monica Ozores Hampton Major: Horticultural Sciences Controlled release fertilizers (CRF) are soluble fertilizers (SFs) coated with a polymer, resin, or a hybrid of polymer coating sulfur coated urea and a vegetable production best management practice in Florida { TC ABSTRACT } The goal with CRF will be that nitrogen (N) release matches tomato ( Solanum lycopersicum ) N uptake, which may increase N use efficiency result ing in higher market able yields and fruit quality with reduced N rates and environmental impacts. Therefore, the purposes of this disserta tion were to: evaluate N release from CRFs buried in pouches in seepage irrigated tomato bed s and correlate the N release with accelerate d temperature controlled incubation method (ATCIM) extraction values fertilizer system or CRF mixes of 100, 140, and 180 DR with SF s w as evaluated on fall season marketable fruit yield postharvest quality, leaf tissue N content (LTNC), and post season soil N content. The high bed temperatures compared to the temperatures at which manufacturers measure CRF N release ( 20.0 to 25.0 C), shorten ed N release duration by 23% to 88% and 23% to 79% in 2011 and 2013, respectively Correlations of the ATCIM and pouch method predicted N curves of individual CRFs with a R 2 of 0.90 and grouped CRF with a R 2 of

PAGE 17

17 0.64 to 0.99 1 N in the hybrid ferti lizer system and individual CRF containing N, phosphorus, and potassium at 190 to 1 N pre plant incorporated in the bottom mix can be recommended for fall tomato production. No negative impacts of CRFs were found on postharvest fruit quality or L TNC during the seasons. Therefore, CRFs can supply 6 5% to 80% of a fall tomato fertility program and maintain marketable yields and fruit quality at reduced N rates and low residual soil N.

PAGE 18

18 CHAPTER 1 BACKGROUND AND LITERATURE REVIEW B ackground Florida ranks first in the U nited States in fresh market tomato ( Solanum lycopersicum L.) production value at $ 268 million and 11,700 ha harvested (U.S. Department of Agriculture, 201 3 ) The U S Environmental Protection Agency and Florida Department of Environmental Protection have recognized the importan ce of water quality through implementation of the Federal Clean Water Act of 1972 and the Florida Res toration Act of 1999 (Bartnick et al., 2005) The Federal Clean Water Act Section 303(d) requires identification of impaired water bodies and establishment of total maximum daily loads (TMDLs) for pollutants that may enter these water bodies while maintain ing the designated use (Environmental Protection Agency, 2009) Florida best management practices (BMPs) are a voluntary series of production practices that help the vegetable industry meet TMDLs by minimizing nutrient and sediment runoff (Bartnick et al. 2005) Furthermore, BMPs may be implemented individually or as a group but they must (Bartnick et al., 2005) Traditionally, split applied soluble fertilizer (SF), fertigation, and enhanced efficiency fertilizers (EEF) are used to increase N use efficiency (NUE) in tomato Reprinted with permission from HortTechnology: Carson, L.C. and M. Ozores Hampton. 2013. Nutrient availability factors of controlled release fertilizers for Florida vegetable pro duction using seepage irrigation. HortTechnology 23:553 562 Carson, L.C. and M. Ozores Hampton. 2012. Methods for determining nitrogen release from controlled release fertilizers used for vegetable production. HortTechnology 22:20 24.

PAGE 19

19 production. Enhanced efficiency fertilizers are a group of fertilizers that reduce the risk of nutrient loss to the environment and subsequently increase NUE (Slater, 2010) Increases in NUE can be accomplished by maintaining nutrients in the root zone through reduced solubility ( isobutydine diurea or IBDU ), retaining nutrients in a less leachab le form (nitrification inhibitors), or physical barriers (e.g., fertilizer coating) (Trenkel, 2010) There are three subgroups of EEFs with different characteristics for horticultural crop production systems: 1) slow release fertilizers (SRFs) contain N i n a less soluble, plant unavailable form that usually needs microbial degradation to become plant available N; 2) stabilized fertilizers are SFs applied concurrently with a chemical inhibitor to slow the bacterial oxidation of ammonium ( NH 4 + ) to nitrate ( N O 3 ) or to slow the enzymatic transformation of urea to NH 4 + (Trenkel, 1997) ; and 3) controlled release fertilizers (CRFs), are usually urea, ammonium nitrate (NH 4 NO 3 ) potassium nitrate (KNO 3 ) or other SF coated with a polymer (polyethylene and ethylene v inyl acetate or thermoplastics), resin (alkyd type resins and polyurethane like coatings), sulfur, or a hybrid of a polymer coating over a sulfur coated urea. These coated materials release nutrients in water at a predictable temperature dependent rate (T renkel, 2010) Slow release fertilizer and CRF are recognized in the Florida Vegetable and Agronomic Crops BMP manual ( www.floridaagwaterpolicy.com ) as a nutrient management BMP. Controlled release fertili zers allow for a single fertilizer application, but are more costly than conventional SFs. Split SF applications require extra trips across the field compared with a single fertilizer application, or the use of fertigation that requires a high initial inv estment for a permanent irrigation system.

PAGE 20

20 The University of Florida, Institute of Food a nd Agricultural Sciences (UF/IFAS) recommended nutrient rates for tomato are 224 ha 1 N for all seasons and types and 0 to 74 1 P and 0 to 209 1 K depending on soil test results (Simmone and Hochmuth, 2010) mix (Simmone and Hochmuth, 2010) (Cold a nd hot indicate the relative salinity that develops in the area of fertilizer placement.) The bottom mix is broadcast in row prior to false bedding, and the top mix is placed in two bands on the bed shoulders after formation (Simmone and Hochmuth, 2010) The bottom mix contains all the P and micronutrients plus 10% to 20% of the N and K, while the hot mix contains the remainder of the N and K. With the exceptions of leaching rain events (76 mm of rainfall in 3 d or 102 mm in 7 d), extended season, and low petiole sap NO 3 test result, SF must be applied at bed formation (pre plant) for plasticulture tomato production using seepage (water table control) irrigation (Cantliffe et al., 2006) After the occurrence of one or several of the exceptions, supplemen tal dry or liquid fertilizer may be applied by punching holes in the polyethylene mulch or by liquid fertilizer injection wheel Seepage irrigation consists of managing a perched water table above a slowly permeable soil layer (a spodic or textural horizo n ) located 6 0 to 90 cm below the soil surface (Ozores Hampton Simmone et al., 2012) Ground or surface water is pumped into canals or ditches, which moves horizontally between parallel adjacent ditches spaced 25 35 m apart. When water from adjacent di tches meets, the so called perched water table is formed ther eby irrigating the crop by capillarity The perched water table may also serve as a frost protection measure by elevating t he water table to near the

PAGE 21

21 soil surface (Ozores Hampton et al., 2011) However, raising the water table solublizes fertilizer nutrients that are subject to loss through leaching upon lowering the water table or drop out by gravitational convection given appropriate conditions, such as a high water table, low soil organic ma tter and high fertilizer rates (Bonczek and McNeal, 1996) Nutrient release from CRF is temperature and moisture dependent (Ahmed et al., 1963; Du et al., 2006; Engelsjord et al., 1996; Huett and Gogel, 2000; Kochba et al., 1990) Manufacturers typically measure CRF nutrient release at 20.0, 21.1, and 25.0 C, but the temperature beneath mulch covered, raised beds used for tomato production in southwest (SW) Florida varies depending of the planting season (Agrium Advanced Technol ogies, 2010; Everris, 2013; Florikan, 2012a and 2012b) Tomato planting in SW Florida begins in August and continues until February (Ozores Hampton et al., 2009; Scholberg, 1996; Simmone and Hochmuth, 2010) Soil temperature under plastic mulch may be as high as 4 0 C during the early fall and as low as 8 C during the winter (Carson Ozores Hampton, and Morgan 2012; M.P. Ozores Hampton, u npublished data ) These seasonal temperature differences may affect CRF release rate. According to Lammel (2005), r elease of N from CRF and crop N uptake during the season should be synchronized ; however, n utrient release rates of CRF under plastic mulch during tomato production seasons in SW Florida have not been published Thus, synchronization of CRF N release with the temporal tomato N requirement is difficult. Sartain et al. ( 2004b) developed an accelerated temperature controlled incubation method ( A TCIM) that can predict nutrient release from some CRFs and

PAGE 22

22 SRFs after column incubation with greater than 90% accuracy. The nonlinear regression model fit to the c olumn incubated CRF nutrient release was : % Nutrient Released = a b e ct Where a = the mean value of percentage N released at time ( t ) = 0, b = the slope of the function or the mean rate of increase in N released, and c = the maximum amount of N released (the asymptote) (Sartain et al., 2004a, 2004b) If an A TCIM could be used to predict CRF field release, then it may assist growers with CRF manag ement decisions in tomato production. Therefore, the purpose of this research is to evaluate N release from various CRFs using the A TCIM and c orrelate this N release with field N release using pouches containing CRF buried in seepage irrigated tomato beds Controlled release fertilizers and mixtures of CRF with different release duration will be combined with SF to create fertilizer mixes that will be evaluated by growing tomato and measuring marketable fruit yield and postharvest quality and petiole sap NO 3 content Literature Review Tomato Nitrogen Uptake Plants utilize and take up several forms of N including NO 3 NH 4 + urea, and amino acids (Kirkby et al., 2009) However, NH 4 + and NO 3 uptake inhibit urea uptake and rapid hydrolysis of urea to NH 4 + in the soil reduces urea concentrations in the soil resulting in reduced urea uptake by crops (Mrigout et al., 2008) Tomatoes are sensitive to high levels of both NH 4 + and NH 3 thus accumulation of NH 4 + and volatilization of NH 3 causes damage to tomat o plants and may become toxic (Barker and Mills, 1980; Britto and Kronzucker, 2002; van der Eerden, 1982)

PAGE 23

23 The preferred N sources for tomato production are NO 3 N and NH 4 + N. Feigin et al. ( 1980) used the nutrient film technique (NFT) to produce tomato a nd reported highest yield with 100% NO 3 N solution; significantly lower yield s were measured for treatments containing greater than 50% NH 4 + N. Another NFT study reported highest tomato plant dry weight in solutions composed of pure NO 3 N and 1:10 NH 4 + N: NO 3 N ratio, and treatments using equal amounts of NH 4 + N and NO 3 N had significantly lower tomato plant dry weight (Errebhi, 1990) The reduced biomass was associated with the incorporat ion of NH 4 + into organic acids at the expense of plant growth. Field production and solution culture differ due to ability of soil to hold NH 4 + on the cation exchange complex and to soil microbial activity. Adsorbed NH 4 + decreases soil solution concentration, ameliorating toxicity (Wilcox et al., 1985) Furthermore, nitrifying soil microorganisms reduce NH 4 + to NO 3 which lowers toxicity. When equal amounts of the NH 4 + and NO 3 sources are applied, plants absorb greater quantities of NO 3 compared with NH 4 + due to nitrification and preferential plant up take (Gweyi Onyango et al., 2009; Kirkby et al., 2009) Guertal and Kemble ( 1998) found no differences in tomato yield between KNO 3 AN and urea as N fertilizer sources in a 2 year field study. However, according to Ivors ( 2010) urea use should be avoi ded in tomato production with fumigated soil. Without microbial populations to transform NH 4 + to NO 3 a buildup of NH 4 + or volatilization may occur. Volatilization of NH 3 increases with high soil pH and low cation exchange capacity soils (Junejo et al., 2011) Crop uptake of NH 4 + and NO 3 affects rhizosphere pH and the uptake of other essential nutrients (Kirkby et al., 2009) Plants must maintain electrical neutrality, thus when taking up NO 3 the plant concurrently takes up a cation such as H + or releases an

PAGE 24

24 anion such as OH Uptake of H + by the plant increases the rhizosphere pH; however, NO 3 may also be taken up with other cations such as K + Mg 2+ Ca 2+ (Kirkby et al., 2009) In three experiments conducted by Errebhi ( 1990) pure NO 3 N t reatment accumulated greater amounts of K + Ca 2+ and Mg 2+ compared with the 50% N O 3 N treatment. Rhizosphere pH decreases with NH 4 + uptake due to H + ion release, which may increase the uptake of H 2 PO 4 and micronutrients such as Cu 2+ However, NH 4 + upt ake competes with uptake of cations such as K + Ca 2+ and Mg 2+ (Kirkby et al., 2009) Feigin et al. ( 1980) found that beyond decreased yield, the pure NH 4 + N treatments grown in solution culture had fewer large or extra large tomatoes compared with the NO 3 N treatment. Furthermore, tomatoes harvested from the pure NH 4 + N and NO 3 N treatments were of lower fruit quality and developed color more slowly (Feigin et al., 1980) Often there is a synergistic increase in plant growth from the application of NH 4 + and NO 3 together (Kirkby et al., 2009). Scholberg ( 1996) measured N accumulation by tomato plants in several locations and years ( Figure 1 1). Less than 10% of the total N was absorbed during the first 30 days after planting (DAP). Beginning 30 days after transplanting (DAT), N accumulation increased linearly until about 80 to 100 DA T where N accumulation slowed or decreased ( Figure 1 1). Accumulation period length depends on factors such as season (e.g., fall or spring), location, and variety. Sin ce, CRF N release data from SW Florida during tomato production has not been published, Figure 1 2 shows N released from CRFs incubated under citrus trees in Immokalee, FL and in a potato ( Solanum tuberosum L.) field in Hastings, FL (Medina et al., 2008; S cholberg, 1996; Simonne and Hutchinson, 2005) The CRFs [3 4 month at 224 kgha 1 Medina et al. (2008); unstated

PAGE 25

25 CRF release duration at 224 kgha 1 Simonne and Hutchinson (2005)] neither provided sufficient N 70 DAT nor released 75% of the N during the equivalent of a tomato growing season. Florida Fertilization Practices in Seepage Irrigated Crops S eepage irrigation systems irrigate crops by capillarity through management of a water table perched on a slowly permeable soil layer. R aising the water table solublizes fertilizer nutrients that are subject to loss through leaching or drop out (Bonczek and McNeal, 1996) Traditionally, when using SFs and seepage irrigation in plasticulture vegetable production, UF/IFAS recommend s placemen t of 10% to 20% of the SF N and K plus remaining N and K fertilizers are placed in bands on top of the bed, which is referred to a placed in one band in the bed center for double row crops such as pepper ( Capsicum annuum ) or in two bands on the shoulders of the bed in single row crops such as tomatoes ( Solanum lycopersicum ) and eggplant [ Solanum melongena (Simmone and Hochmuth, 2010)]. In s eepage irrigated plasticulture vegetable crops, all fertilizer s are applied at bed formation. Extra fertilizer may be applied to the crop after crop establishment as a supplemental dry or liquid SF by hand punching holes in the polyethylene mulch or by l iquid fertilizer injection wheel in several situations However, these application methods are labor intensive and increases production cost. In open bed vegetable production with seepage irrigation [e.g. potatoes ( Solanum tuberosum )], all P and micronu trients are applied at planting. A portion (e.g. 60%) of both N and K are banded in the bed at planting or hypocotyl

PAGE 26

26 emergence (Hochmuth and Hanlon, 2011) Banding or injection of the remaining soluble N and K fertilizer occurs at a later stage of growth (Zotarelli et al., 2012) What are Enhanced Efficiency Fertilizer and Controlled Release Fertilizer ? Although the terms SRF and CRF are often used interchangeably, there are important differences. Slow release fertilizers are long chain molecules with reduced solubility that release nutrients more slowly compared to immediately available soluble fertiliz ers (SF), but the release duration and pattern are often dependent on the soil microbi ology, and thus not as easily controlled compared to CRF (Trenkel, 2010) Examples of SRF include: urea formaldehyde (UF) methylene urea (MU), and IBDU. Stabilized fer tilizers are SFs that have either a nitrification inhibitor or a urease inhibitor included when field applied (Slater, 2010) Nitrification inhibitors are us ed to maintain nitrogen in the NH 4 + form rather than allowing soil microorganisms, such as Nitroso monas sp. and Nitrobacter sp., to transform NH 4 + into NO 3 which may be leached or further reduced to gaseous N 2 O (Trenkel, 1997) The nitrification inhibitors d icyandiamide and 3 amino 1,2,4 triazole reduced nitrification by 28% and 52% in subtropi cal and upland soil conditions (Singh and Verma, 2007) Urease inhibitors slow the urease enzyme that changes urea into ammonia (NH 3 ), which is subject to volatilization and leaching if nitrified. N (n butyl) thiophosphoric triamide, a urease inhibitor, redu ced NH 4 + volatilization by 30% to 75% in fine sandy loam soil compared with an untreat ed control during a 21 d trial (Rawluk et al., 2001) Finally, CRFs are a SF with a coating that consists of a polymer (polyethylene and ethylene vinyl acetate or thermoplastics) resin (alkyd type resins) sulfur, or a hybrid coating of a polymer outer coating over a sulfur coated urea (PSCU). Ideally, coatings are formulated to control the release of nutrients to match differ ent crop nutrient requirements (Lammel 2005)

PAGE 27

27 Single SFs or homogenized N P K fertilizers may be coated; however, fertilizers with rounded granules coat more uniformly and release more predictably compared to angular fertilizer granules (Tzika et al., 2003) Nutrients diffuse throu gh the po lymer or resin coating of the CRF for release (Shaviv et al., 2003a) First, water enters the fertilizer prill, and the resin CRF prill increase s in volume which opens micropores for diffusion (Shaviv et al., 2003b) However, for polymer coatings, nutri ents diffuse through a network of tortuous channels which are created during the coating process by mixing moisture impermeable and moisture permeable materials (Trenkel, 2010) Sulfur coated urea is degraded b y microbes and hydrolysis. These mechanisms create openings in the coating and the fertilizer diffuses out. A lso SCU may lock off or release catastrophically, which is the loss of CRF characteristics due to the non release of a SCU lacking imperfections in a thick coating, or prill breakage, resp ectively (Trenkel, 2010) Nutrient release from CRF may be sigmoidal or linear (Trenkel, 2010) The sigmoidal nutrient release pattern of CRF begins with a lag period during water imbibition into the CRF then shows a constant rate of release at a given temperature, which slows as osmotic potentials inside and outside the fertilizer prill equilibrate During the linear release phase, water enters the CRF prill and nutrient solution exits (Shaviv et al., 2 003b) The phase of reducing release rates after the constant nutrient release period (linear phase) is known as the decay phase. It is during the decay phase where the effects of osmotic potential are greatest.

PAGE 28

28 Factors Affecting Controlled Release Fer tilizer Nutrient Release for Vegetable Production in Florida using Seepage Irrigation Nutrient release from CRF may be affected by soil factors including temperature, moisture, osmotic potential, pH, microbial populations, and texture. Furthermore, facto rs intrinsic to CRF may also affect nutrient release includ ing nutrient composition, coating thickness, and CRF prill shape and diameter. Temperature The rate of nutrient release from CRF increases with increasing soil temperature, which shortens the rel ease duration (Ahmed et al., 1963; Basu et al., 2010 ; Brown et al., 1966; Carson et al., 201 3 ; Dai et al., 2008; Kochba et al., 1990) Gandeza et al. ( 1991) illustrated that after 60 d of incubation in water, a polymer coated fertilizer (PCF) released 20% of the N at 10 C, 48% at 20 C, and 80% at 30 C. Oertli and Lunt ( 1962) on the other hand, showed that after 60 days, a different PCF released approximately 50%, 45%, 25%, and 27% each NO 3 NH 4 + K, and P at 10 C, but at 21 C the PCF released appro ximately 60%, 50%, 48%, and 48% each NO 3 NH 4 + K, and P. Engelsjord et al. ( 1996) found that during a 6 week laboratory incubation at 4 and 21 C, N release of 3% and 12%, and 7% and 15% in two different SCUs respectively. A longer incubation period performed by Lamont et al. ( 1987) measured nutrient release from resin coated fertilizer (RCF) at nine t emperatures (5 to 45 C) for 19 weeks and found that nutrient release was quadratic in both time and temperature. Du et al. ( 2006) tested PCF in free water and saturated sand at 20 and 40 C and found a decreased CRF lag period and an increased nutrient release rate during the linear release phase at the higher temperature.

PAGE 29

29 Diurnal temperature fluctuations cause concomitant increases and decreases in PCF nutrient release (Husby et al., 2003) These diurnal fluctuations may be stabilized to some degree by the use of colored polyethylene mulch. Decoteau et al. ( 1990) found that planting beds mulched with white polyethylene wer e 5C lower at 1800 HR than black polyethylene mulched beds. In two other studies, soils with black colored mulch were 1.3 to 1.8 C, 0.8 to 1.2 C, and 2.2 to 2.4 C warmer than bare soil, silver mulched, and white mulched soils, respectively (Diaz Pere z and Batal, 2002; Diaz Perez et al., 2005) Silver colored mulch had lower temperature fluctuation throughout the day compared to bare soils. Thus, the effect of mulch color is important for understanding the CRF nutrient release, but mulch color is ult imately dependent on the crop grown. produced during the fall (planting July to 15 Oct.), winter (16 Oct. to 15 Dec.), and spring (16 Dec. to March), while potatoes are planted fr om October t o January in Southwest Florida (Olson et al., 2012 b ; Ozores Hampton et al., 2006) Thus, the fall growing season begins with high and ends with lower air temperatures or the spring season begins with low and ends with higher air temperatures ( Ozores Hampton et al., 2006). According to Zheng et al. ( 1993) soil temperature and air temperature are highly correlated (R 2 =0.85 to 0.96) and soil temperature may be predicted using air temperature. Using the above planting dates, a season length of 18 and 16 weeks for fall and spring, and a 6 week harvest, the average air temperatures during planting and harvest for the fall 2011 and spring 201 2 seasons were 26.7 and 20.6 C and 18.2 and 21.9 C ( FAWN 2013 ; Ozores Hampton et al., 2006) The average soil temperatures,

PAGE 30

30 at 10 cm below the bed surface, during the same time periods were 28.0 and 22.5 C, and 19.9 and 23.7 C (FAWN, 201 3 ). Thus, average soil temperatures were between 1.3 C and 1.9 C warmer compared to the average air temperature. The h igh air and soil temperatures during the beginning and throughout the fall season will shorten CRF release duration by decreasing the lag period and increasing rate during the linear release phase; thus a release duration longer than the season may be nece ssary. However, the cooler average air temper atures will extend CRF release duration, and CRF with a release duration of the season length would be more appropriate. Soil moisture Water vapor infiltration into CRF prills is a limiting factor for nutri ent release from CRF (KNO 3 ) at soil moisture of less than 50% field capacity (Kochba et al., 1990). Nutrient release from a different CRF (NH 4 NO 3 ) was not affected by soil moisture levels between field capaci ty and the permanent wilting point (Lunt and Oertli, 1962) Ahmed et al. (1963) indicated that release varies due to soil moisture content and the SF type occluded within the PCF. Nutrient release from PCF (ammonium phosphate) was independent of soil moisture content between field capacity and 25% field capacity. However, PCF (KNO 3 ) released faster at 100% and 75% than 50% and 25% field capacity. At soil water potentials below the permanent wilting point, water vapor movement into CRF prills limits nutrient release. However, under well managed pr oduction systems, soil moisture should be managed for optimal crop production, which keeps soil moisture at ideal levels for nutrient release from CRF. Osmotic potential Several CRF mechanistic nutrient release models incorporate nutrient diffus ion from CRF prills (Basu et al., 2010; Holcomb, 1981; Shaviv et al., 2003a; Shaviv et al.,

PAGE 31

31 2003b) A large nutrient specific concentration gradient (osmotic potential) is present inside the CRF prill as compared to the soil solution (Shaviv et al., 2003a ). Therefore, the rate of nutrient release from CRF is dependent on the osmotic potential difference between the soil solution and CRF prill Shaviv et al. (2003a) explains that during the lag phase of nutrient release water enters the fertilizer prill a nd is followed by a linear release phase with constant release where the osmotic potentials are equilibrating and eventually enters a decay phase where the osmotic potentials become equilibrated. However, Oertli and Lunt (1962) found no effect of osmotic potential on nutrient release, but postulated that different conditions such as low soil moisture concentration would cause solute accumulation around the fertilizer prill, which may elevate salt concentrations around the CRF prill to levels that may slow nutrient release. Soil pH Soil pH has not been shown to have a direct effect on the CRF (PCF and RCF) (Basu et al., 2010; Christianson, 1988; Oertli and Lunt, 1962) However, low soil pH may slow the release of SCU due to t he pH effect on soil microbes (J arrell and Boersma, 1979) Soil microbial populations When exposed to sterilized soil and non sterilized soils, nutrient release from RCF was similar (Oertli and Lunt, 1962). Salman et al. ( 1989) found that microorganisms had no effect on nutrient release from PCF but did affect urea release from SCU. Similarly, soil microbes did not affect N release from reactive layer coated fertilizers, a type of PCF (Christianson, 1988). Speciation of soil N (NH 4 + or NO 3 ) and plant growth will be affected by soil mi crob es once released. In a Florida winter tomato growing season, 29% and 54% plant mortality occurred with two different polymer

PAGE 32

32 coated urea (PCU) fertilizers, applied in fumigated soil under virtually impermeable polyethylene mulch, due to accumulation o f NH 4 + (Ozores Hampton et al., 2009) Soil texture Soil texture alone does not influence nutrient release from CRF. However, soil texture does influence soil moisture holding capacity and to some extent temperature, which do affect CRF nutrient release (Ahmed et al., 1963; Salman et al., 1989). Nutrient release from PCF (urea, KNO 3 and ammonium phosphate) was similar in sandy loam and silt loam soils (Ahmed et al., 1963). Urea release from PCU was similar when incubated in water, sandy soil, or soil from a paddy rice field (Salman et al., 1989) Controlled release fertilizer composition While the nutrient core of some CRF contains a single fertilizer such as urea, many CRFs contain multiple nutrients within the prill that release differently. Du et al. (2006) measured nutrient release from a PCF containing a N P K fertilizer at three moisture levels and found that at each moisture level the nutrient release as a fractional percentage of the total nutrient type was NO 3 > K > P. For instance, a PC F (N P K) incubated in free water for 60 days at 30 C released 82% NO 3 79% K, and 42% P. This relative order remained for all three water levels. Similarly, Huett and Gogel ( 2000) measured nutrient release from PCF in a column study and found release rates were N > K > P at both 30 and 40 C. In two studies, N release from several CRFs was speciated and found that NO 3 4 + > K > P (Broschat, 2005; Broschat and Moore, 2007) The specific soluble fertilizer, i.e. urea, KNO 3 ect., that is coated may influence the water vapor infiltration rate due to variations in salt index among the fertilizers.

PAGE 33

33 Fertilizers with a higher salt index have a higher water vapor pressure lowering capacity compared to fertilizers with a lower salt inde x; thus, a CRF with a higher salt index will have a higher water absorption rate and faster solubilization of the solid fertilizer core (Attoe et al., 1970) Water vapor lowering capacity and solubility increase with increasing temperature; thus, the CRF p rill solution may become saturated at a higher concentration compared to lower temperatures, which will increase the osmotic potential further between the prill and the soil solution. Ahmed et al. ( 1963) reported that CRFs incubated in soil at room temper ature and field capacity had different release rates due to the fertilizer core, such that urea was released from the prill faster than ammonium phosphate, which released faster than KNO 3 ; these release rates relate to the order of solubility and vapor pre ssure lowering capacity. Broschat and Moore (2007) found that PCF micronutrients were released slower than PCF macronutrients, which purportedly was not due to precipitation with P. However, sulfates of magnesium and iron have lower solubility compared t o many macronutrient fertilizers such as NH 4 NO 3 diammonium phosphate, and KNO 3 while manganese sulfate has a lower solubility compared to NH 4 NO 3 and KNO 3. The differences in solubility may help explain the slower release rates of micronutrients. The re lationship of fertilizer solubility and vapor pressure reduction with temperature partially explains the nutrient release rate change with temperature (Attoe et al., 1970). Coating thickness, type, and prill diameter The duration of the nutrient release p eriod of SCU, RCF, PCF, and PSCU may be adjusted by coating thickness T hicker coatings have a longer release duration (Brown et al., 1966; Du et al., 2006; Fan, 2009; Ko et al., 1996; Shaviv et al., 2003a; Trenkel, 2010) Additionally, nutrient release rates of polymer, resin, and hybrid coated

PAGE 34

34 fertilizers may be adjusted by modifying the ratios of coatings. For instance, increasing the percentage of polymer in the polymer to solvent ratio of a polysulfone coating increases the release period (Tomaszews ka and Jarosiewicz, 2002) Similarly, increasing the amount of plasticizer in the plasticizer to ethylcellulose ratio increases the release period (Perez Garcia et al., 2007) Larger diameter CRF prills have a longer nutrient release period (e.g., a 2 mm diameter CRF prill released N more slowly compared to a 1 mm diameter CRF prill) (Perez Garcia et al., 2007; Shaviv, 2001) Cultural P ractices A ffecting CRF R elease D uration CRF field placement In plasticulture vegetable production, when SRFs and CRFs w ere used as a singular N source in the bottom mix [RCF (urea and KNO 3 ), MU and PSCU ] during a spring season, lower or similar extra large and total marketable tomato yield s were found as compared to SF (Csizinszky, 1994) However, when PCU was used with soluble N in the bottom mix during the fall season, marketable tomato yield was similar or greater than yields using SF (Ozores Hampton et al., 2009) But, detrimental effects were found when placing PCU as a bottom mix during the winter production seaso n due to low soil NO 3 concentrations or plant mortality associated with NH 4 + toxicity [Table 1 1 (Csizinszky et al., 1993; Ozores Hampton et al., 2009) ]. Csizinszky ( 1989 ), Csizinszky et al. ( 1992 ), and Ozores Hampton et al. ( 2009) applied EEFs (Oxamide, methylene urea, PCU, IBDU, and SCU) in plasticulture production during the spring, fall, and spring, respectively, as a top mix, and found similar or lower total marketable tomato yields compared with SF at similar N rates. These r esults were due to slow N release from the SRF or CRF, which caused low NH 4 + and NO 3 soil concentration during the season (Csizinszky, 1994; Ozores Hampton et al., 2009). Thus, do not place

PAGE 35

35 CRF as part of the hot mix in seepage irrigated plasticulture pr oduction. To increase NH 4 + and NO 3 bottom mix with the remainder of the N as SF in the top mix (Ozo res Hampton et al., 2009). In a winter season, similar marketable tomato yields were found when comparing SF and the hybrid fertilizer system using CRF (KNO 3 ) at equal and 25% reduced total N rates (Ozores Hampton et al., 2009). Hochmuth et al. ( 1994) ap plied CRF K in the bottom mix to bell peppers and found no increase in earliness or total season yields (Table 1 2). Increased early, fancy bell pepper yields were found using RCF (urea and KNO 3 ) in a hybrid fertilizer system, however treatments had simil ar total marketable yield (Csizinszky, 1994). Controlled release fertilizers placed in a hybrid fertilizer system have shown improved performance compared to CRFs placed as a single N source in the bottom mix or top mix. Furthermore, placement of CRF in a hybrid fertilizer system has the potential to produce equal marketable tomato yield at equal or lower N rates compared to SFs (Carson Ozores Hampton, and Morgan, 2012; Ozores Hampton et al., 2009) In open bed (no polyethylene mulch) production, Hutchin son ( 2005 ) and Pack et al. ( 2006) incorporated PCU into potato hills and found positive results compared SF (Table 1 3). However, Hutchinson ( 2004) found increased yields with incorporated PCU in 2002 but not in 2003, due to environmental and treatment di fferences; there was more rainfall 1 N more in the grower practice in 2003 compared to 2002. When banded in potato hills, CRFs [PSCU, PCU, PCF (NH 4 NO 3 )] produced similar marketable potato yields at equal and total N rates reduced 25% and 50% compared to

PAGE 36

36 SFs (Hutchinson et al., 2002) In a greenhouse soil column study, N recovery was greater from PCF (NH 4 NO 3 ) and PSCU when incorporated compared to surfa ce applied; thus, these CRFs should be incorporated into an open vegetable bed (Sato and Morgan, 2008) In a field incubation study, Simonne and Hutchinson ( 2005) compared 17 RCF, PCU, and PSCU and found that CRFs did not release 80% of the nutrients duri ng a potato production season, thus these CRFs were not recommended as part of a potato fertility program. Nitrogen rate supplied from CRFs In Florida for tomato planted on 1.8 m centers (1 ha = 5,556 linear m of row), the UF/IFAS N recommendation is 22 4 kg ha 1 for all planting seasons, tomato cultivars, soil and irrigation types, with allowances for supplemental N applications (Olson et al., 2012a ) Growers typically follow UF/IFAS irrigation recommendations, but use N fertilizer rates greater than th e UF/IFAS recommendation (Cantliffe et al., 2006) Since EEFs increase nutrient use efficiency by maintaining nutrients in the root zone, growers may potentially reduce N and K fertilizer rates. In plasticulture production, Csizinszky et al. ( 1993) cond ucted a N rate study replacing a portion of the total N (0%, 50%, 75% or 100%) with controlled release urea (CRU) in the bottom mix (Table 1 1). No differences in early extra large or season total marketable tomato yield due to N rate were found; however, season total marketable yield decreased linearly as CRU percent increased. Ozores Hampton (2009) found reduced early extra large tomato yield using PCU at reduced total N rates compared with SF in a winter season, which was due to lower plant biomass and plant mortality with the CRFs. Reduced tomato yields with CRU were probably related to N source rather than N rate.

PAGE 37

37 In an open bed production system using CRF treatments of PCF, PSCU, and PCU at 168 kg ha 1 N equal or greater marketable potato yields r esulted with the CRFs compared to SF treatments at 224 kg ha 1 N [Hutchinson et al., 2002; Hutchinson, 2004 (Table 1 3)]. Hutchinson (2005) reported that of nine CRF treatments at 168 kg ha 1 N, seven treatments produced greater marketable potato yields c ompared to SF N treatments at 168 kg ha 1 N and eight of treatments produced yields equal to SF N at 224 kg ha 1 N a 25% N reduction Chen and Hutchinson ( 2008) found similar marketable potato yields with PSCU (196 kg ha 1 ) applied at planting compared to split applied SF (224 and 280 kg ha 1 ) which resulted in 12.5% to 30% reduction in N application Pack et al. (2006) reported no marketable potato yield difference between two CRF N rates, 146 and 225 kg ha 1 N when compared to SF at 225 kg ha 1 resul ting in a potential 35% N reduction Therefore, it may be concluded that CRFs have the potential to reduce N rates by up to 25% or more and maintain potato yield and quality. CRF application timing Plasticulture vegetable production practices with seepage irrigation include application of all fertilizer (CRF and SF) at bed formation (Table 1 1). The exception (discussed above) would be side dress applications to crops grown with SF. Side dressed ap plications are, ideally, eliminated with the use of CRF (Cantliffe et al., 2006). However, in vegetable production using open beds, SF are typically split applied (Zotarelli et al., 2012) Chen and Hutchinson (2008) applied PSCU and PCU with and without SF N to potatoes as a split application and found that higher yields were obtained when CRFs were applied at or before planting (Table 1 3). Elkashif et al. ( 1983) found a significant increase in total and marketable potato yield in one of two

PAGE 38

38 locations f or two IBDU treatments and a SCU treatment that were banded at planting and side dressed with SF N (NH 4 NO 3 ) compared to treatments where all fertilizer (NH 4 NO 3 SCU, or IBDU) was placed at planting. In the second location, application timing was not signi ficant, but the three split applied treatments had greater yield than the IBDU and SCU treatments where 100% of the fertilizer was applied at planting. In open beds production, CRF should be applied at planting, which may eliminate the need to side dress (depending on environment and N source) and reduces the number of equipment passes across the field, thus reducing production cost (Hutchinson and Simonne, 2003; Shoji et al., 2001) Fumigation and staged planting Plasticulture vegetable production utili zes soil fumigation and staged planting or several planting dates in beds fumigated on the same day. Soil fumigants such as Kpam (AMVAC, Los Angeles, CA), Vapam (AMVAC, Los Angeles, CA), Chloropicirin (Dow AgriScience, Indianapolis, IN), Telon (Dow AgriSc ience, Indianapolis, IN), and DMDS (Arkena, Philadelphia, PA) have a 2 to 3 week lag period between bedding and safe planting. Vegetable beds are formed when soil conditions are appropriate (i.e. moisture content), which may be attained after rainfall o r irrigation; however, vegetables are planted in stages to allow for continual harvests. Thus, up to an additional 3 weeks may be added to the fumigation lag period for the projected planting date. Therefore, CRFs may be selected based on a total season length of 18 to 26 weeks, which includes 2 to 3 weeks for fumigation requirements, 0 to 3 weeks for projected planting date, and 16 to 20 weeks for regular cropping season length.

PAGE 39

39 Incorporation of CRF into a vegetable fertility program for plasticulture and open beds in Florida requires awareness of the expected soil temperature during the growing season, which will help determine the appropriate CRF release period together with optimal crop soil moisture. For plasticulture vegetable production using see page irrigation, best results with CRF have been obtained with 60% to 80% of the N as CRF and the remainder as SF. In an open bed production system, optimal results will be obtained by incorporating CRF into the bed at or before planting. Use of CRF in th ese methods may eliminate the need for side dressed fertilizer applications. Additionally, the use of CRF with recommended production practices will allow for up to a 25% reduction in N application rates. Methods for D etermining N itrogen R elease from C ont rolled Release F ertilizers used for V egetable P roduction Laboratory methods for determining controlled release fertilizer nutrient release duration Laboratory methods allow for CRF incubation in controlled environmental conditions compared with non contro lled field conditions. Laboratory methods, temperature controlled incubation method ( TCIM ) standard, and TCIM accelerated may be used to compare and screen CRFs when an accelerated method is used. These methods may be used to predict laboratory release, but they will not predict field relea se when used alone. Controlled release fertilizer nutrient release differs in free water, water saturated sand, and sand at field capacity (Du et al., 2006) Thus, TCIMs without correlation can offer only restricted practical use for commercial vegetable production because the results will not reflect nutrient release obtained in the field. There are two types of methods based on release time. The so called standard method incubates CRF for specified nutrient releas e time or until a threshold proportion of nutrients (e.g.,

PAGE 40

40 75%) are released (Dai et al., 2008; Du et al., 2006) The accelerated method incubates CRF for a shorter time (e.g., 74 h) at a higher temperature than the standard methods (Dai et al., 2008; Eur opean Committee for Standardization, 2002) There are variations in both TCIMs. Each is designed to test CRF using selected time periods, temperatures, and/or sample collection methods. TCIM standard: The standard TCIM incubates a beaker containing CRF and water (i.e., 1:20, 5:33.3, and 1:50 g CRF: mL water) at a constant temperature of 25 C (Dai et al., 2008; Ko et al., 1996; Shaviv, 2001) Incubation time is based on manufacturer stated release length ( e.g., 4 month release), or based on research ob jectives such as measuring release until 100% of the urea is released (Dai et al., 2008; Ko et al., 1996). Typically, CRF remains static during incubation (Du et al., 2006; Lamont et al., 1987; Perez Garcia et al., 2007) However, the European Standard m ethod incubates CRFs with stirring at 25 C. TCIM accelerated: For commercial applications, the standard TCIM produces reliable results, but it requires extended incubation periods to achieve the 75% nutrient release requirements. Consequently, accelera ted methods have been developed (Dai et al., 2008). Medina et al. ( 2009 ) and Sartain et al. ( 2004a 2004b ) describe a 74 h accelerated TCIM which was correlated to CRF nutrient release from incubated columns. The method of Sartain et al. (2004b) uses jacketed chromatography columns that consisted of hollow glass tubes surrounded by an integrated water jacket where the sample is placed inside the t ube and a water bath controls the temperature. The method uses four separate extractions per sample with temperatures increasing from 25 to 60 C and time to obtain a release curve. Most methods use water as the extracting

PAGE 41

41 solution, while Sartain et al. (2004b) use dilute citric acid (0.2%). Sartain et al. (2004b) and Medina et al. (2009) found that the accelerated method could successfully predict N release from a variety of column incubated SRF and CRF products. Dai et al. (2008) used five separatory funnels to incubate trincote, resin coated CRF between 50 to 90 C and continuously leached (250 mL per 15 min) CRF samples for 6 h. The results of the high temperature incubations were compared with a standard TCIM at 25 C. The researchers found that 80 C was the optimal temperature partially due to reduced coating integrity at 90 C (Dai et al., 2008). Accelerated TCIMs have the advantage of reducing the time and labor cost compared with the standard TCIM, but neither predicted field release well. F ield methods for determining nitrogen release from controlled release fertilizers Field methods can be used to determine how CRFs release under actual field conditions. The field method should subject the CRF to an environment similar to CRFs applied in v egetable production systems (Wilson et al., 2009) Similar environments would include moisture, temperature, and appropriate amount s of fertilizer so that abnormal concentration gradients do not form around the fertilizer prills. Ideally, CRF N release m atches crop N uptake and releases N throughout the entire vegetable production cycle (Lammel, 2005) Nitrogen release should be measured throughout the entire crop cycle, or until 75% of the N is released or recovered (Trenkel, 1997) Pouch method : The p ouch method uses pouches made of fiberglass mesh screen that allows movement of moisture to the CRF prill. For the release curves to accurately reflect environmental conditions, the pouch materials must not interfere with water movement to CRF prills. Po lymer coated urea incubated in polypropylene mesh pouches with 1.2 mm 2 openings had significantly greater N release than pouches

PAGE 42

42 constructed from weed block material with 0.07 mm 2 openings (Wilson et al., 2009). Pouch dimensions ranged from 56 cm to 121 2 cm with CRF sample sizes ranging from 1.3 to 5g N (Gandeza et al., 1991; Haase et al., 2007; Jacobs et al., 2003; Medina, 2006; Zvomuya et al., 2003) Soil may be included in the pouch with the CRF sample (Broschat, 2005; Gandeza et al., 1991) Pouch p lacement in the field should follow standard commercial production practices such as: buried under vegetable beds with plastic mulch or in open potato hills (Broschat, 2005; Medina et al., 2008; Medina et al., 2009; Wilson et al., 2009; Zvomuya et al., 200 3) Pouches can be collected at pre determined times during the vegetable production cycle and the N remaining in the CRF can be determined. Medina et al. (2008) found that CRFs performed differently in citrus groves with different row orientation (north to south vs. east to west) due to the different wetting and drying patterns found in the groves. Differences due to grove row orientation show that the pouch method allows CRF prills to be subjected to real field environments. This method measures N rem aining in CRF prills, thus pouch studies can be used when CRF behavior is monitored (Simonne and Hutchinson, 2005) Pot in pot method: The pot in pot method consists of two 20 cm pots nested together separated by a 2 cm spacer. The interior pot with scre ened drain holes was filled with soil and 4.8 to 6.2 g CRF. Covered pots were buried in a potato hill with 2.5 cm of the bottom pot above the soil surface (Simonne and Hutchinson, 2005). Incubated pots were leached with water at pre arranged dates, and t he following day leachate volumes were collected and measured. The pot in pot method and the column method measure N released from the CRF rather than N remaining in the prills. Measuring released N takes into consideration soil microbial activity, thus it represents

PAGE 43

43 plant available N (Simonne and Hutchinson, 2005). The project research objectives determine the importance of measuring N released in leachate (that requires additional labor), or measuring N remaining in the CRF prill. Important factors to consider are that environmental field conditions can be highly variable, and CRFs are temperature depende nt, therefore field studies must include all growing seasons and multiple years (Fraisse et al., 2010) For vegetable production, both CRF field methods can be viable methods for measuring CRF N successfully. Correlations between methods Controlled releas e fertilizer nutrient release differ s in free water, water saturated sand, and sand at field capacity (Du et al., 2006). Thus, TCIMs without correlation can offer only restricted practical use for commercial vegetable production because the results will n ot reflect nutrient release obtained under field conditions. Sartain et al. ( 2004b) correlated the accelerated TCIM extraction of polymer SCU with a column extraction at room temperature, and found a positive R 2 of 0.90 suggesting that the accelerated TCI M may be able to predict N release from column incubations accurately. A correlation between the TCIM and a field method has not been done. In field conditions there are several factors to consider such as release time, temperature, moisture, placement, rate and cultural practices making the correlation difficult to achieve (Sartain et al., 2004a) These complex effects and their interactions present under field conditions added variability compared to that found with the TCIM methods. Procedure to mea sure N With all CRF research methods (laboratory, growth chamber, greenhouse, and field methods), N concentration in leachate or in the CRF prills needs to be measured after incubation. Methods to measure N include total Kjeldahl N ( TKN ) (Gandeza et al.,

PAGE 44

44 1991; Greenberg et al., 1985; Haase et al., 2007; Zvomuya et al., 2003) prill weight loss (Salman et al., 1989; Savant et al., 1982) combustion (Wilson et al., 2009), colorimetrically with an auto analyzer (Pack et al., 2006) and ion specific electrodes to measure NH 4 + N or NO 3 N (Broschat, 2005) (Table 1 4 ) ] The standard and most popular method, TKN, is a time consuming laboratory procedure, which includes concentrated sulfuric acid and sodium hydroxide. All CRF N sources and research methodologies m ay use TKN. Prill weight loss is a quick procedure where the mass of dried incubated prills is subtracted from the original dry prill mass. Unfortunately, this method may only be used with pouch incubated urea CRF. Each type of nutrient [e.g., NH 4 + NO 3 K + urea, etc.] diffuses out of the CRF prill at a different rate; therefore, it cannot be assumed that the ion ratio inside the incubated CRF prill and the non incubated CRF prill are equal. For example, a KNO 3 fertilizer is composed of 50% K + ions an d 50% NO 3 ions. Nitrate releases more quickly than K + thus K + will represent a larger portion of the nutrients in the prill near the end of a trial (Broschat and Moore, 2007) Combustion and colorimetric N determination with an autoanalyzer use a solut ion, so both methods may be used with any of the CRF research methods or N sources. Ion specific electrodes may be used to measure N in leachate and solublized (homogenized) CRF prills; however, free urea cannot be measured using these electrodes unless t he urease enzyme is added and the solution is incubated (Guilbault et al., 1969) Wilson et al. (2009) compared prill weight loss to combustion methods and found that both were equally reliable methods for measuring N release. Laboratory analysis of N r emaining in CRF prills or in leachate varies in cost. Table 1 5 shows laboratory costs for N analysis from a pouch incubation trial consisting

PAGE 45

45 of six replications, five treatments, and eleven sampling dates (Medina et al., 2008) Prill weight loss costs the least per sample to measure N, but this method can only be used with pouch incubated, urea based CRF. Ion specific electrodes are the next most inexpensive method, but each electrode only measures one N species Thus, more than one electrode must be used to measure total inorganic N. Both organic N and NH 4 + N may be measured using TKN. Total Kjeldahl N costs more to conduct than the prill weight loss or the ion specific electrode method, but is less expensive than the combustion method. Total Kjeda hl N does not measure NO 3 N, but modified methods are available to measure NO 3 N along with NH 4 + N and Organic N (AOAC International, 2000) Selection of a laboratory that uses the modified method will reduce the number of analytical tests required to m easure total fertilizer N. Colorimetric measurements for N O3 N or NH4 + N need separate analyses. Using both colorimetric N analyses would b e m ore expensive than all methods but TKN. The combustion method costs around the s ame amount as TKN; neither method provides N species information like colorimetric a nalysis. Since, the prill weight loss method and the combustion method are equally a cceptable, it would be fiscally responsible to use prill weight loss to determine N r elease, when CRF type allows. Depending on the amount of information needed regarding N species, multiple methods can be used to measure N released for CRF on vegetable production systems. The accelerated TCIM is preferred when compared with the standard TCIM method because of the sav ings on time and labor costs. Column studies can be used to test new CRFs before going to the field from controlled e nvironments, but column studies can be time consuming with associated high cost. Field methods will be the preferred research tools by vege table growers until the

PAGE 46

46 accelerated TCIM has been correlated and calibrated to field studies with a positive crop response, thus determining production in a shorter amount of time. Fresh Market Tomato Harvest, Ripening, a nd Quality Fruit quality aspects of ripe, round tomatoes The USDA quality grade standards emphasize a ppearance (size, color, and freedom from defects) which consumers consider the most important aspect of ripe, round tomato quality (Kader, 2002) The USDA published size grade diameters of small (5.4 to 5.79 cm), medium (5.72 to 6.43 cm), large (6.35 to 7.06 cm), and extra large (7 cm and greater) (USDA 1997) Packinghouse workers sort for defects, and a series of conveyo rs with sized circular ho les sort tomatoes into size categories. Defects include mechanical injury (cuts, punctures, abrasion, compression, and bruising) occurring during the harvest and handling phases, physiological disorder s (freezing, chilling, sunburn, puffiness, graywall, b lossom end rot, and irregular ripening) occurring during the production and marketing cycle, and other defects (scars, catface, growth cracks, and insect injury). To avoid defects associated with mechanical injury, minimal (less than 15 cm ) drop heights s hould be used to avoid bruising when filling field bins, and the bins and field bucks should be wash daily to avoid a buildup of debris that may cause abrasion (McColloch, 1962; Sargent et al., 2005) Packinghouse workers remove these defects when detected ; however, i nternal bruising may not be visible externally until ripening (Thomson and Lopresti, 2008) Color may be measured quantitatively using laboratory instruments or qualitatively by comparison of the fruit to a color chart. Mature green tomatoes, t he most difficult color to measure, are determined by position

PAGE 47

47 on the plant (tomatoes in the crown set and ripen before tomatoes at the top of the plant), size, a waxy shine to the tomatoes, and the presences of brown corky tissue around the stem scar. Fa ctors such as graywall, internal bruising, and low and high temperature (less than 13 C or greater than 27 C) during ripening can cause irregular color development in tomatoes. G rowers and consumers view t omato texture a s an important quality attribute S hipping of tomatoes to distant markets necessitates firm tomatoes and c onsumers desire a tomato with the correct mouthfeel (Kader et al., 1978) Texture in terms of firmness is measured using an instrument such as a penetrometer or texture analyzer. Texture in the mouth is determined using a sensory analysis panel of trained professionals or untrained consumers (Chaib et al., 2007) Tomato flavor is determined by the interaction among organic acids, soluble sugars, and aroma volatiles (Maul, 1999) In the eyes of a grower, f lavor and nutritional quality are secondary characteristics compared to the primary goal of producing a large, round, blemish free tomato that turns red which is free of contaminates and safe to eat. Many factors such as tempe rature management (chilling injury), physiological disorders (graywall) and mechanical injury may affect tomato flavor (Kader, 2002) The tomato fruit is at the highest potential to ripen into a tasty tomato when it is selected and harvest ed from the plan t at greater than mature green stage. After harvesting the tomato, maximum fruit quality is obtained after ripening and may only deteriorate Thus, every bump and bruise a tomato receives, causes the tomato to expend energy due to increased ethylene production. This energy must come from within the tomato fruit since harvested fruit are no longer attached to the plant Flavor volatiles organic sugar

PAGE 48

48 and organic acid s pr ovide a great energy substrate (Kader, 2002) Other energies for the increase d respiration may include carbohydrates, lipids and p roteins within the fruit; thus, the nutritional value of tomato deteriorate s with damage (Kader, 2002) Safety is controlle d by eliminating, to as much of an extent possible, entry of contaminants or human pathogens into the field through the use of proper sanitation facilities in the field, use of clean buckets and bins, sanitation of the f lume water or the dump tank, proper worker training and use of protective gear throughout the chain (Harris et al., 2002) Tomato maturity Tomatoes are divided into four maturity stages (1 4) that are determined after slicing a tomato in half at the equator [Table 1 7, (Kader and Morris, 1976) ]. Maturity group one tomatoes are not considered marketable fruit, while maturity group two tomatoes will ripen to a moderate quality and are often sold to institutions or fast food. Fruit of m aturity groups three and four are considered mature gre en and will ripen to a high quality. Since every tomato may not be cut in the field visual indicators assist in determining tomato maturity. Mature green tomatoes are differentiated from immature green tomatoes by location on the plant, a waxy or glossy appearance to the fruit, and the presence of corky tissue around the stem scar (Sargent et al., 2005). There are two types of maturity for horticultural crops: horticultural maturity and physiological maturity. Mature green stage is defined as the green stage in which the tomato is physiologically mature and will ripen to at least a minimally acceptable eating quality. The mature green tomato is also at horticultural maturity, as it possesses the traits desired by

PAGE 49

49 consumers for use; however, after ripen ing, a tomato will maintain both physiological and horticultural maturity until it is no longer considered edible. Determining when to harvest; Problems with green harvest When determining harvest timing, growers will harvest a representative sample of t omatoes to be harvested and evaluate gel formation in the locules to determine the tomato maturity (Hurst, 2010) Another method to determine harvest timing is to remove a plant from the field remove the fruit and d etermine the percentage and number of fruit that are of harvest maturity (personal communication, Dr. Ozores Hampton). Growers will often harvest when a field has five to ten percent color (Cantwell and Kasmire, 2002) Thus, out of 100 harvestable fruit, five to ten fruit will have progresse d to the breaker stage or beyond, which ensures that fruit are of sufficient maturity to ripen in the ripen room. However, waiting for more color development increases exposure to environmental risk, and decreases yield since growers only pack green fruit Harvesting green fruit in determinate tomatoes results in reduced yie lds since fruits harvested green will weigh less compared to the same fruit allowed to reach the vine ripe maturity, and a portion of the green fruit will be immature or unmarketable (Davis and Gardner, 1994; Kavanagh et al., 1986). Stages of commercial harves t (6 USDA ripeness stages): Why pick green ? The USDA describes six tomato colors ranging from green to red [Table 1 6 (U SDA, 1997) ] Growers choose to harvest fresh market round tomatoes at either the mature green stage of development or later when color has begun to develop. Tomatoes harvested after the mature green stage of development are referred to as vine ripe tomatoes (Sargent et al., 1992) Tomatoes are hand harvested i nto hampers (green tomatoes) or vented plastic trays (vine ripe). Green tomatoes are then emptied

PAGE 50

50 into large fiber reinforced gondolas or into pallet bins, while tomatoes with color are loaded onto trucks in the harvest container and transported to a pack inghouse. Green tomatoes are firm and able to support the weight of each other, remain ing marketable through the handling steps of the harvest process including harvest into hampers, transfer into larger bins or gondolas, and transport to a packing house. A drop of 15 cm or greater may cause internal damag e to both mature green and vine ripe tomato (McColloch, 1962) ; however, the amount of damage sustained varies with cultivar. Therefore, it is important to keep the dump height to a minimum for all tomato es. V ine ripe tomatoes are softer and more susceptible to compression damage (McColloch, 1962) ; t hus vine ripe tomatoes must be harvested into smaller containers. A harvester applying too much pressure to a tomato fruit beyond breaker stage of developme nt may cause damage, but mature green tomatoes may withstand more force without internal damage (Fluck and Gull, 1972) Vine ripe tomatoes must be harvested every 2 to 3 d, but green tomatoes may be harvested ever y 10 to 15 d, whic h reduces harvest co sts. The additional time in the field required by vine ripe tomatoes compared to green tomatoes, exposes vine ripe tomatoes to an addition risk of loss, environmental hazards and reduces yield in terms of fruit number compared to green tomatoes H oweve r individual vine ripe tomato fruit are typically heavier due to maximized fruit growth before harvest (Davis and Gardner, 1994). Thus, m any growers choose to harvest green tomatoes over vine ripe tomatoes due to the reduced harvest costs and reduced risk of environmental hazards at the expense of maximizing average tomato size

PAGE 51

51 Pre harvest nutritional program effects on fruit quality Calcium is a component in cell walls and is not remobilized in the plant thus calcium deficiency in tomato is manife st as blossom end rot due to the loss of cell wall integrity (Sams and Conway, 2003) Blossom end rot may be due to insufficient calcium supply or due to water stress. Fruit transpire at a lower rate compared to leaves; therefore, transpiration waters an d nutrients go to the leaves preferentially in a stressed situation leaving a calcium deficiency in the fruit (Taylor et al., 2004) Potassium regulates stomatal conductance along with chlorine and other ions (Havlin et al., 2005) It is important as a cha rge carrier and as an enzyme cofactor (Sams and Conway, 2003). However, plants do not incorporate K into tissue. F ertilization with K is associated with increased tomato yields, reduced white tissue inside the tomato, and increased fruit size. However, excess K may compete with uptake of other cati ons and cause blossom end rot ( Sams and Conway 2003) Increased soil K applications were shown to decrease ripening disorders such as yellow shoulder and blotchy ripening (Mikkelsen, 2005) In a study under the presumption that increasing N and K fertilizer rates decrease flavor, titratable acidity and soluble solids content increased with increasing fertilizer rates; thus it was concluded that flavor loss with high fertilizer rates was due to loss of other f actors such as loss of volatile compounds (Wright and Harris, 1985). In hydroponics, increasing K concentration (200, 300, and 400 ppm) increased soluble solids, ascorbic acid, and yield (Almeselmani et al., 2012) Errebhi ( 1990) found that tomato grown with pure NO 3 N accumulated greater amounts of K + Ca 2+ and Mg 2+ compared with tomato grown using 50% N O 3 N using

PAGE 52

52 NFT Feigin et al. ( 1980) found decreased yield and fewer large and extra large tomatoes when grown with the pure NH 4 + N in s olution culture compared to NO 3 N. Furthermore, tomatoes harvested from the pure NH 4 + N and NO 3 N treatments were of lower fruit quality and developed color more slowly (Feigin et al., 1980) Often a synergis m in plant growth and yield is found when NH 4 + and NO 3 supply total N (Kirkby et al., 2009) Increased levels of applied N fertilizer delayed crop maturity increase graywall and internal browning and may decrease fruit sugar content (Cristo and Mitchell, 2002 ; Davies and Winsor, 1967 ) Phosph orus fertilization reduced tomato acidity ; however, P fertilizer had no effect on marketable yield, fruit size, soluble solids content, or lycopene content (Davies and Winsor, 1967; Lui et al., 2011) In summary lime soil to a pH 6.5 which will supply the m ost plant available nutrients. Liming should supply enough calcium to reduce blossom end rot. I ncreases in fruit quality (soluble solids and titratable acidity) and yield while decreas es in ripening and color disorders are associated with appropriat e K rates thus apply K However, K in great quantities may upset the cation balance in the soil and cause blossom end rot. Excessive N can cause delayed harvest, which may cause economic loss to Florida growers where earliness to market is important. F urthermore, excess N may c ause a decrease in fruit flavor Little information regarding P fertilization and fruit quality is available; thus, a pply enough P to grow the crop profitably, but avoid over application of P due to environmental quality issues. P ackinghouse operations: washing, sorting, sizing, packing, and ripening When green tomatoes arrive at the packinghouse, bins are dumped or gondolas are flumed into a dump tank, and tomatoes are washed with chlorinated water, pre

PAGE 53

53 sized and sorted to re move small and defective fruit sized, packed into 11.4 kg cartons, palletized, and ripened (Cantwell and Kasmire, 2002) Packinghouse processes are necessary to remove diseased and damaged fruit that may cause postharvest decay and disease proliferat ion in a box during the warm, humid ripening en vironment and to remove unmarketable fruit Tomatoes may be sprayed with wax, which may contain fungicide to help minimize wa ter loss and postharvest decay (Cantwell and Kasmire, 2002; Sargent et al., 2005) Tempera ture and ethylene management Accelerated r ipening of mature green harvested tomato fruit occurs with greater uniformity upon application of e xogenous ethylene gas. However, t omatoes taking more than five days to reach breaker stage with the addition of et hylene gas are considered immature and not marketable (Kavanagh, 1986). For tomatoes at breaker stage of development or later, the add ition of exogenous ethylene will no t enhance ripening (Cantwell and Kasmire, 2002) Ripening of mature green, round tomato fruit is conducted as the last process (unless repacked) before transporting to markets. Tomatoes are ripened at 90% humidity and 20 to 21 C for 24 to 72 h depending on the tomato maturity (Sargent et al., 2005). Tomatoes are sensitive to ethylen e gas and as little as 0.5 LL 1 may trigger ripening; however, UF/IFAS recommends growers use 150 LL 1 (Abeles et al., 1992; Sargent et al., 2005) Ethylene gas may be used by introducing a known quantity of ethylene into a room to supply 1 5 0 LL 1 e thylene, trickling ethylene gas into a room at specific rate to keep a room at 1 5 0 LL 1 ethylene, using ethephon or an ethylene generator (Reid, 2002) Ripening rooms must be cooled to remove field heat and the heat of respiration and must have control led humidity. The size of the cooling coils should be properly sized to the cooling room to maintain cool

PAGE 54

54 room temperatures while maintaining as low of a temperature differential as possible. Thus, the coil will remove a minimal amount of humidity from t he air which will minimize moisture loss from the fruit (Thompson et al., 2002) Temperatures above 29 C inhibit s red color formation in tomato, while temperatures below 13 C cause s chilling injury that result s in tomato flavor loss (Sargent et al., 20 05). Shipping When transporting tomatoes from the field to the packinghouse, farm roads should be graded to minimize ruts and potholes which may cause vibration al a brasion to the tomato fruit Air suspensions reduce vibration al damage to tomato fruit (Thompson, 2002) Tomatoes should be shipped at or above 1 2 C to minimize chilling injury, but ripening rate is controlled by temperature; therefore maintaining temperatures near 10 C will slow tomato ripen ing When mixing tomatoes with other commodities in trailers or storage rooms, tomatoes should be stored with other chilling sensitive crops that tolera te ethylene and do not impart off smells or flavors such as onions or garlic (Thompson, 2002) Hypotheses 1. High soil temperatures in polyethylene mulched tomato beds during the fall tomato production season will shorten CRF N release duration compared to the manufacturer stated release duration at 20 to 25C. 2. The ATCIM will predict N release from individual CRF s incubated in pouches place in polyethylene mulched, raised tomato beds. 3. The hybrid fertilizer system containing 67% to 80% of the total N as CRF in the bottom mix will maintain yields and allow for a 25% N rate reduction compared to a SF N program at UF/ IFAS rates. 4. Ammonium toxicity in tomato production is well documented in the literature. High soil temperatures in polyethylene mulched beds during the fall season will accelerate detoxification of NH4 + from urea encapsulated in polymer material (CRF ur ea) by soil microbes, resulting in production of tomatoes with similar fruit

PAGE 55

55 yields and quality at reduced N rates compared to UF/IFAS recommended SF N rates.

PAGE 56

56 Table 1 1. Summary of fresh market tomato (Solanum lycopersicum) field trials using en hanced efficiency fertilizers (EEFs) and seepage irrigation in plasticulture production conducted in Florida from 1978 to 2009. Fertilizer rate Variety Season z Fertilizers y EEF Total CRF placement Application time x Conclusion Reference -------(kg ha 1 ) ------BHN 726 F PCF, SF 112, 168, 224 168, 224, 258, 280 Hybrid system 27 DBP CRF/SF in the hybrid system (168 kg ha 1 total N) produced greater marketable yields than SF (280 kg ha 1 total N) and equal to SF (224 kg ha 1 total N). Carson Ozores Hampton, and Morgan (2012) Solar Set S OX, MU, IBDU, SCU mixes, SF 342 342 Top mix 14 DBP SCU/MU produced similar or lower yields than SF. Csizinszky (1989) Solar Set F MU:SF at 5 ratios 195, 292 195, 292 Top mix 14 DBP Early season extra large and total early yield had a quadratic response with up to 50% MU. Although, total extra large yield decreased linearly with increasing MU rates, marketable total season yields were not different. Csizinszky et al. (1992) Sunny W/S PCU at 0, 50, 75, and 100% of N rates 97, 195, 292, 390 97, 195, 292, 390 Bottom mix 14 DBP As the percent of PCU increased, the total early extra large fruit yields and total marketable yield decreased among N rates due to lower soil nitrate concentrations. Csizinszky et al. (1993) Sunny S RCU, MU, PSCU, RCK 195, 293 195, 293 Bottom mix 14 DBP EEFs yields were similar or lower than SF. Csizinszky (1994) Hazera 3073 S 1 SF, 1 SRF, 2 PCU 179, 258, 336 224, 302, 381 Top mix Fertilizer applied at bedding. PCU has similar or lower yields than SF. Ozores Hampton et al. (2009)

PAGE 57

57 Table 1 1. Continued. Fertilizer rate Variety Season z Fertilizers y EEF Total CRF placement Application time x Conclusion Reference ------(kg ha 1 ) ------Florida 47 F 1 SF, 3 PCU 112, 168, 224 134, 202, 269 Bottom mix Fertilizer applied at bedding PCU had similar or greater yields than the SF. Ozores Hampton et al. (2009) BHN 832 W 2 SF, 2 PCU 134 CRF: 168 SF: 224, 298 Bottom mix PCU may induce plant mortality due to the risk associated with ammonium toxicity in winter production. Ozores Hampton et al. (2009) BHN 832 W 2 SF, CRKN at three rates 56, 112, 168 CRF: 168, 224, 280 SF: 224, 286 Hybrid system CRKN produced similar yields to SF at equal and lower N rates. Ozores Hampton et al. (2009) z S = spring, F = fall, and W = winter y CRF= controlled release fertilizer, CRKN = controlled release potassium nitrate, CRN = controlled release nitrogen, IBDU = isobutydine diurea, MU = methylene urea, N= nitrogen, OX = oxamide, PCF = polymer coated fertilizer, PCU = polymer coated urea, PSCU = polymer sulfur coated urea, RCK = resin coated potassium, RCU = resin coated urea, SCU = sulfur coated urea, SF = soluble fertilizer, SRF = slow release fertilizer x DBP = days before planting

PAGE 58

58 Table 1 2. Summary of fresh market bell pepper (Capsicum annuum) field trials using controlled release fertilizers (CRFs) and seepage irrigation in plasticulture production conducted in Florida from 1978 to 2009. Fertilizer rate Variety Season z Fertilizers y EEF Total CRF placement Application time x Conclusion Reference -----------(kg ha 1 ) ---------Jupiter F Urea and CRKN 0, 73, 147, 220 N 293 N Bottom mix 14 DBP CRKN had an increase in early fancy yield. No increase in total season yield with CRN. Csizinszky (1994) Super Sweet 860 W CRKN with CRU to equalize the CRN rate 0, 34, 67 K 73, 146, 224 K Bottom mix 27 DBP CRKN did not improve fruit earliness, yield, or quality. Hochmuth et al. (1994) z F = fall, and W = winter y CRKN = controlled release potassium nitrate, CRN = controlled release nitrogen, CRU = controlled release urea, K = potassium, N = nitrogen x DBP = days before planting

PAGE 59

59 Table 1 3. Summary of chip stock potato (Solanum tuberosum) field trials using enhanc ed efficiency fertilizers (EEFs) and seepage irrigation in an open bed system conducted during spring seasons in Florida from 1978 to 2009. Fertilizer rate Variety Fertilizers z EEF Total CRF placement Application time y Conclusion Reference ---------(kg ha 1 ) --------Atlantic SF, IBDU, SCU, SF/EEF mixes 134, 201 134, 201 Banded EEFs placed at planting with split SF application for some treatments. Treatments with 100% SF and SF/EEF mixes had greater total yields compared to 100% IBDU or SCU. Split application increased yield for total and marketable yield in one location. Elkashif et al. (1983) Atlantic 2 NPK CRFs, 1 PCU/PSCU mix, SF 112, 168, 224 112, 168, 224 Banded 14 DAP All treatments at 75% and 100% of IFAS recommended N rates had similar marketable yields. Soluble N was applied in one application. Hutchinson et al. (2002) Atlantic SF and PCU 166 2002: PCU: 166 SF: 207; 2003: PCU: 166 SF: 334 Incorporated PCU was applied at hilling, split SF control applications. 2002: CRF produced greater marketable yields than SF. 2003: There were no significant differences in marketable or total yield. Hutchinson (2004) Atlantic 9 CRFs and 2 SFs 168 0, 168, 224 (SF only) Incorporated 1 DBP Seven of nine CRF treatments had greater marketable yields compared to SFs at equal rates of 168 kg ha 1 Eight of nine CRF treat ments yielded equally to 224 kg ha 1 N SF. Hutchinson (2005) Pot in pot trial 18 CRFs and 5 SFs Incorporated N release was measured CRF treatments failed to release 80% of the nutrient content during a 100 day potato season. Simonne and Hutchinson (2005)

PAGE 60

60 Table 1 3. Continued. Fertilizer rate Variety Fertilizers z EEF Total CRF placement Application time y Conclusion Reference ---------(kg ha 1 ) --------Atlantic 9 CRF and AN at two rates 146, 225 0, 146, 225 Incorporated 1 DBP CRFs and IFAS recommended N rates produced similar marketable yields Pack et al. (2006) Atlantic PSCU, PCU, AN, UF, and PSCU and AN mixed 196 EEF: 196; SF: 0, 224, 280 Undefined 21 DBP, planting, 30 DAP, and multiple timings PCU and PSCUs should be applied at or before planting. PCU and PSCU had greater N recovery rates than the high SF rate. Chen and Hutchinson ( 2008) z AN = ammonium nitrate, CRF = controlled release fertilizer, IBDU = isobutydine diurea, K = potassium, N = nitrogen, P = potassium, PCU = polymer coated urea, PSCU = polymer sulfur coated urea, SCU = sulfur coated urea, SF = soluble fertilizer, UF = urea formaldehyde y DBP = days before planting, DAP = days after planting

PAGE 61

61 Table 1 4 Nitrogen (N) determination method to use with different incubation methods, N species, and controlled release fertilizer (CRF) N source. N determination method CRF incubation methods z N species measured y CRF N source Total Kjeldahl N L,G,F organic N, NH 4 + N, and NO3 N with modification NH 4 + N, NO 3 N and urea Prill weight loss F: pouch None measures change in mass urea only Combustion L,G,F NH 4 + N, NO 3 N, and urea N. NH 4 + N, NO 3 N and urea Colorimetric L,G,F NO 3 N, or NH 4 + N. NH 4 + N, NO 3 N and urea Ion specific electrodes L,G,F NH 4 + N, NO 3 N and urea but it must be transformed with urease. NH 4 + N, NO 3 N and urea z L = Laboratory, G = growth chamber and greenhouse, and F= field methods. y Abbreviations: ammonium N, NH 4 + N; nitrate N, NO 3 N

PAGE 62

62 Table 1 5 Cost of laboratory analysis for nitrogen (N) content remaining in controlled release fertilizer prills in a field trial consisting of 6 replications, 5 treatments and 11 sampling dates (Medina et al., 2008) N determination method z Cost/unit ($) y Total cost ($) x Total Kjedahl N (TKN) 8.25 13.20 2,723 4,356 Prill weight loss 0.17 0.20 5 6 66 Combustion 7.5 11.4 2,475 3,762 Colorimetric (NO 3 N or NH 4 + N) y 6.00 10.00 7.00 10.00 11.6 12.5 1,980 3,300 (NO 3 N) 2,310 3,300 (NH 4 + N) 3,828 4,125 (both) w Ion Specific Electrode 0.25 0.33 83 110 z NO 3 N = nitrate N, NH 4 + N = ammonium N y The laboratory method unit cost for TKN, combustion, and colorimetric are a range of prices given on analytical laboratories websites (University of Minnesota Research Analytical Laboratory, St. Paul, MN; Cornell Nutrient Analysis Laboratory, Ithaca, NY; Univ ersity of California Davis Analytical Laboratory, Davis, CA; and Pennsylvania State University Agricultural Analytical Service Laboratory, University Park ) where the applicable laboratory tests are performed. x Total costs estimates, collected in Jan. 2012, do not include shipping and do not include drying time, which may be necessary for some methods, with inconsequential labor costs to evaluate dryness. w This cost represents the price set by laboratories when both NO 3 N and NH 4 + N are measured.

PAGE 63

63 Table 1 6 Official USDA color descriptions for mature tomatoes. Color Description Green The surface of the tomato is completely green in color. The shade of green color may vary from light to dark Breaker There is a definite break in color from green to tannish yellow, pink or red on not more than 10 percent of the surface Turning More than 10 percent but not more than 30 percent of the surface, in the aggregate, shows a definite change in color from green to tannish yellow, pink, red, or a combination thereof Pink M ore than 30 percent but not more than 60 percent of the surface, in the aggregate, shows pink or red color Light red M ore than 60 percent of the surface, in the aggregate, shows pinkish red or red: p rovided t hat not more than 90 percent of the surface is red color Red More than 90 percent of the surface, in the aggregate, shows red color (Reproduced from USDA, 199 7 )

PAGE 64

64 Table 1 7 Green tomato maturity defined by internal appearance from an equatorial cross section Maturity stage Internal appearance Immature Immature seeds (white) that may be cut when tomato is sliced open; no gel formation in the locules. Fruit is 10 days from breaker stage. Mature green A Seeds fully developed (tan) that are not cut when slicing fruit. Gel formation in at least one locule. Fruit is 6 10 days from breaker stage; minimum harvest maturity. Mature green B Gel formation in all locules but fruit is still completely green. Seeds push aside when cut; Fruit 2 to 5 days from breaker stage. Mature green C Red color is beginning to form in the gel, but color is not visible on the fruit exterior. Fruit is 1 to 2 days from breaker stage. Adapted from Kader and Morris (1976)

PAGE 65

65 Figure 1 1 Accumulation of N by tomato plants for a) Bradenton 1991 and 1992; b) Bradenton 1994; c) Bradenton 1995; d) Immokalee and Quincy 1995; e) Quincy 1995 (fall); and f) Gainesville 1996; (Scholberg, 1996).

PAGE 66

66 Figure 1 2 Nitrogen accumulation of tomatoes grown using drip irrigation in Immokalee, FL in 1995 ( diamonds) (Scholberg, 1996). Controlled release fertilizer (CRF) releases from fertilizer pouches incubated under citrus trees Immokalee, FL (triangles) (Med ina et al., 2008), and from pots placed in a potato f ield Hastings, FL (squares) (Simonne and Hutchison, 2005). 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 N (kg N/ha) Days after planting

PAGE 67

67 CHAPTER 2 NITROGEN RELEASE PROPERTIES OF CONTROLLED RELEASE FERTILIZERS IN TOMATO PRODUCTION OF SOUTH FLORIDA Introduction A series of best man agement practices (BMPs), including use of controlled release fertilizer (CRF), has been implemented for vegetable and agronomic crops by the Florida Department of Agriculture and Consumer Services in response to the Federal Clean Water Act of 1972 and the Florida Restoration Act of 1999 (Bartnick et al., 2005). C ontrolled release fertilizer are soluble fertilizer (SF) coated in polymer, resin, or sulfur coated urea in a polymer coating (Trenkel, 2010 ). Field measure ment of CRF N release may be made by r esearchers using the pot in pot method or the pouch method (Carson and Ozores Hampton, 2012). The pot in pot method consists of an inner pot with drainage that contains soil and CRF nested in a solid outer pot to collect leachate. The pot assemblies are installed in vegetable beds, and leached at predetermined times Then, leachate volume and N content are measured and CRF N release is calculated The pouch method consists of a known mass of CRF (e.g., 3.5 g N) sealed inside fiberglass mesh pouches that may be buried inside a polyethylene mulched or open bed vegetable systems and removed at prearranged dates. After collection, the N content remaining in the CRF prills is measured to determine the amount of N remaining and the N release rate The mesh p ouch allows for soil to CRF prill contact which may affect CRF N release rate. For Portions of this data were published: Carson, L.C., M. Ozores Hampton, and K.T. Morgan. 2013. Nitrogen release from controlled release fertilizers in seepage irrigated tomato production in south Florida. Proc. Fla. State Hort. Soc. 126: In Press

PAGE 68

68 instance pouches with 1.2 mm 2 openings had greater N release compared to a weed block material with 0.07 mm 2 openings (Wilson et al., 2009). Several factors influence n utrient release from CRFs including soil temperature, moisture content, osmotic potential, nutrient composition, coating thickness, and prill diameter. Manufacturers of CRF manipulate the nutrient release duration of resin coated fertilizer polymer coated fertilizer (PCF), and polymer sulfur coated urea (PSCU) by adjusting by coating thickness and composition, with thicker coatings having longer release durations (Carson and Ozores Hampton, 2013). However, in irrigated vegetable production, soil temperatu re may be considered the most influential factor (Carson and Ozores Hampton, 2013). In laboratory conditions, Lamont et al. (1987) measured N release at nine temperatures from 5 to 45 C and found a quadratic release response with temperature and time. I n a similar study, Gandeza et al. (1991) demonstrated a doubling of the percentage N release (PNR) with each 10 C rise in temperature from 10 to 30 C. Thus, a CRF release duration will increase or decrease inversely with soil temperatures that differ fr om CRF manufacturer label specification. Controlled release fertilizer manufacturers such as Agrium Advanced Technologies Inc. (Loveland, CO) Everris Intl. (Dublin, OH) and Chisso Asahi Fertilizer Co. (Tokyo, Japan) and Florikan ESA LLC. (Sarasota, FL) determine nutrient release duration in water at a constant 20.0, 21.1, and 25.0 C respectively (Agrium Advanced Technologies, 2010; Everris, 2013; Florikan, 2012a and 2012b). But, the average daily soil temperatures under a polyethylene mulch covered, raised vegetable bed in south Florida were greater than 23.9 C for eight weeks after bedding and were as high as 40.1 C during the day time in a fall tomato ( Solanum lycopersicum ) season (Carson

PAGE 69

69 Ozores Hampton, and Morgan, 2012; Carson et al., 2013). Thus, high soil temperatures during the fall will affect CRF release duration used in tomato production. Therefore, selection of an incorrect CRF release duration results in slow nutrient release causing plant nutrient deficiencies, low plant growth, and reduced yield, or a high nutrient release rate may result in increased soil electrical conductivity, plant toxicity and injury, and the loss of CRF benefits (Shaviv, 1996). Thus, the purposes of these studies were to evaluate N release duration of CRFs in fall season tomato production in south Florida Material and Methods Two concurrent CRF field studies w ere conducted during Fall 2011 and 2013 on a commercial tomato farm near Immokalee, FL (26 14' 5" N / 81 28' 55" W) The soil at the study location wa s Basinger fine sand (hyperthermic Spodic Psammaquents), which permitted seepage irrigation. The field configuration was a drive road flanked to each side by three beds and an irrigation ditch. The b eds were 76 cm wide and 20 cm high with 1.8 m between r ow centers On the dates listed in Table 2 1, the beds were 1 methyl bromide/chloropicrin (1:1 by weight) (ICL IP, South Charleston, WV), and covered with white virtually impermeable film ( 0.038 mm; Berry Pla stic, Evansville, IN). Fertilizer s applications at bedding that totaled 1 1 1 K were placed as a top mix ( bands on the bed shoulders ) and a bottom mix ( broadcast in row prior to bed formation ) The top mix contained 1 1 K as potassium 1 N from methylene urea and 1 P 1 K from potassium magn esium sulfate plus micronutrients Tomato BHN 726 was

PAGE 70

70 planted on dates provided in Table 2 1 and grown using industry standard cultural practices (Carson Ozores Hampton, and Morgan, 2013 ; Olson et al., 201 2 a ) The t wo concurrent CRF stud ies each conta ined six and seven CRFs in 2011 a nd 2013, respectively (Table 2 2). The CRF fall mixes ( M112, M168, and M224 ) are CRF and SF mixes that when applied at 1 1 1 CRF N ; however, different SF and filler amounts in the pouch may have affected the PNR in 2011. Therefore, FLmix was added in 2013, which contained CRFs equivalent to the fall mixes that were composed of FL100, FL140, and FL180 Fiberglass window screen (18 14 mesh) rectangles (15.2 30.5 cm) were folded in half, and sealed on two sides. C ontrolled release fertilizer samples containing 3.5 g N were placed inside the pouches and the last side was sealed, which resulted in internal dimensions of approximately 12.7 1 4.0 cm (Carson et al., 2013 ) A t bed formation in 2011 and 5 d after bedding in 2013 ( to reduce personal protective equipment requirements ), the p ouches were placed level, 10 cm below the bed surface in the center bed of a three bed 1.5 m long plots. The studies were a randomized complete block design with four replications and eight collection dates P ouches in the e xperimental unit, e.g., a set of six or seven pouches representing each CRF, were placed randomly in the plot After pouches were collected ( Table 2 1) the pouch contents were dried in beakers at ambient temperature and stored until analysis (Carson Ozo res Hampton, and Sartain 2012). In prepar ation for CRFs N analysis, the pouch contents were ground in a blender (Model 36BL23; Waring Commercial, New Hartford, CT) with 300 mL de ionized (DI) water to destroy the CRF coating and dissolve the SF. Samples were diluted to 500 mL using DI water, filtered using Whatman no. 42 filter paper, and frozen until N

PAGE 71

71 analysis. The solution was analyzed for total soluble N by pyrolysis and chemiluminescence using an Antek 9000 N analyzer (Pac. Co., Houston, TX.) in 20 11. In 2013, nitrate N and ammonium N were measured by salicylate hypochlorite, cadmium reduction using a Flow Analyzer (QuikChem 8500, Lachat Co., Loveland, CO) at 660 nm and 520 nm, respectively and u rea N was measured by modified diacetyl monoxime met hods using a DR/4000U Spectrophotometer (Hach Co., Loveland, CO) at 527 nm (Sato and Morgan, 2008; Sato et al., 2009) The results for nitrate N ammonium N and urea N were summed to determ ine total CRF N remaining in the prill The N release results were expressed in cumulative PNR Weather data were obtained through the Florida Automated Weather Network (FAWN) and a Watchdog data logger (model B100; Spectrum Technologies Inc., Plainfiel d IL.) collected soil temperature hourly, 10 cm below the bed surface through the tomato season Analysis of variance and orthogonal contrasts were performed on PNR data by collection date using the general linear model procedure in SAS (version 9.3, SAS Institute Inc., Cary, NC). Year and CRF were considered main effects and year CRF was an interaction effect. The n on linear regression procedure in SAS was used to determine the N release rate by fitting a CRF N release curve, which was also used to c alculate the d to 75% N release (Medina et al., 2008; Sartain et al., 2004a; Sartain et al., 2004b) The non linear regression equation was: PNR = a (a b) e ct Where a = the maximum PNR b = the intercept or value when time ( t ) = 0, and c = the rate of increase (Sartain et al., 2004a; Sartain et al., 2004b) Since t = 0 data

PAGE 72

72 theoretically equals zero, intercept data were not included in the model, but intercept values were determined. An R 2 statistic for the non linear regression was calculated, and a test was used to compare nonlinear regression coefficients betw een years for each CRF Results and Discussion Weather C onditions The minimum, average, and maximum air temperatures from placement until last collection were 6.4, 23.4, and 38.3 C and 1.9 2 1.6 and 3 5.6 C during 2011 and 201 3, respectively The 2011 and 2013 average air temperatures during the incubation period were similar to the 10 year average temperature s, which averaged 23.1 and 21.0 C respectively (FAWN, 2013). T otal rainfall during the incubation period was greater in 20 11 than 2013 with 46.4 and 12.6 cm respectively However, 40.3 cm rainfall accumulated during August and September, which delayed trial initiation in 2013. Both 2011 and 2013 accumulated lower than average rainfall during the incubation period compared to the 10 year average of 49.0 and 31.5 cm. The average daily air temperatures first went lower than Agrium Advanced Technologies Inc. Everris Intl. and Florikan ESA LLC. and Chisso Asahi Fertilizer Co. specification of 20.0, 20.1, and 25.0 after 10, 10, a nd 8 weeks in 2011, and 9, 9, and 1 week in 2013, respectively. Since CRF prills directly contact the soil, they are highly affected by soil temperature; however, since air temperature and soil temperature highly correlate, air temperature may reliably in dicate temperatures effect on CRF (Carson et al., 2014). Soil T emperature The minimum, average, and maximum soil temperature 10 cm below the bed surface decreased during the seasons ranging from 25.7 to 11.9 C, 30.6 to 20.0 C,

PAGE 73

73 and 40.1 to 24.2 C in 20 11, and 25. 2 to 11.1C, 29.3 to 14.8 C, and 34.4 to 20.4 C in 201 3 (Table 2 3 ). The average daily soil temperature s were first recorded below the Agrium Advanced Technologies Inc. Everris Intl. and Florikan ESA LLC. and Chisso Asahi Fertilizer Co. spe cification of 20.0, 21.1, and 25 C on 12 Nov., 5 Nov., and 17 Oct. in 2011 and 28 Nov., 28 Nov., and 24 Oct. in 2013 The average daily soil temperature was greater than the CRF manufacturer specification for more than half the season at all temperatures in 2011 and 20.0 and 21.1 C in 2013. Also, the average air temperature was greater than the 25 C CRF manufacture specification in 2013 for 25% of the season Since, high soil temperature above the CRF manufacture specifications potentially increased N re lease rate during the first 25% to 50% of the season, nutrient release duration may be expected to decrease ( Carson et al., 2013; Carson and Ozores Hampton, 2013; Gandeza et al., 1991; Huett and Gogel, 2000). Measured Nitrogen Release f rom Field Incubated Pouches When data were analyzed without the two treatments added in 201 3 there were interactions between CRF and year s in six of eight collection dates. T he main effects CRF and year s were significant in eight and four collection dates respectively Th erefore, PNR results were presented by year (Table 2 4 ) The PNR at the first collection date ranged from 6.6% to 57.5% in 20 11 and 16.0% to 65.5% in 2013 ( Table 2 5 ). At the end of the season, PNR ranged from 77.6% to 93.8% during 2011 and 58.3 % to 94.3 % in 201 3 In 2011, PCU90 and in 2013, PCU90 and PCNPK120 had the highest season total P N R, while FL180 had the lowest PNR during both seasons. The PNR from PCU120 and PCU180 was not different at any collection date during 2011, but was significantly dif ferent at collection dates one and five through eight in 201 3 (Table 2 6) Similarly, PCNPK120 and PCNPK180 had a different PNR at collection

PAGE 74

74 dates five through eight in 201 3. Perhaps, the high soil temperatures during the early fall accelerated the N re lease rate of 180 d release PCFs for a similar PNR compared to 120 d release PCFs. The PNR from PCU120 and PCNPK120 was similar during collection dates one through four, and three, four, seven and eight in 2011 and 2013, respectively With the exception of collection dates one and three, no PNR differences were found for PCU 180 and PCNPK180 in 2013. At three disconnected and one collection date during the 2011and 2013 seasons, RCNPK and PCNPK120 were significantly different. Nitrogen r elease from PCU90 and FL100 were different in 2011 but not in 201 3 Overall, PNR from the 180 d release CRFs (PSCU, PCU180, and FL180) was significantly different among CRF technologies than within technologies (PCU180 and PCNPK180). T he fall season mixes (M112, M168, and M224) were not linearly related, and PNR from the fall mixes were different than FLmix at four collection dates At six and eight collection dates in 2011 and 2013, respectively, PNR from the components of the fall mix (FL100, FL140, and FL180) were line arly related; thus CRF PNR decreased with increasing release duration in 2011 and 2013 Similarly, PNR from PCU90, PCU120, and PCU180 were linearly related at the five and four collection dates in 2011 and 2013, respectively. The soil temperature during t hese seasons averaged 2.2 C lower in 2013 compared to 2011, which was due to the delayed trial start date in 2013. The lower average soil temperatures in 2013, probably caused the lower PNR found among CRFs when compared to 2011(Carson and Ozores Hampton 2013). Diverse coating technologies released N differently among the 180 d CRF products suggesting that technologies responded differently to increases in temperature during the tomato

PAGE 75

75 season. However, the 120 d release CRFs, especially RCNPK and PCNPK 120, were similar at more collection dates than different; thus, perhaps the increased temperature affected these coating technologies similarly. The resemblance among N r elease from PCU90 and FL100 in 2013 were probably related to underlying variability rather than differences in PNR A numerically greater PNR was found with FLmix than M112 at collections one through seven and one through six in 2011 and 2013, respectively; however, for M168 and M224, FLmix had a greater N release for only collections o ne and two in both years. Perhaps the high levels of SF and fillers reduced the osmotic potential and N release during the early season in M112, with the greatest SF and filer amount s compared to M168 and M224 (Carson and Ozores Hampton, 2013). Similarl y, a CRF study reported that RCNPK and PCNPK release higher N in the first week of laboratory incubation than any subsequent week, and that PNR increased with increasing temperatures from 5 to 45 C (Lamont et al., 1987). However, 70 d release polyolefin CRF, released approximately 20% and 60% N in 50 to 150 d during a potato (Solanum tuberosum) season, which was slower than the current study due to the temperature differences between spring in Minnesota and fall in Florida (Zvomuya et al., 2003). Compara tively, a 70 d release polyolefin CRF released 18% to 20% and 75% to 80% of the N in 30 and 120 d in Japan, which was lower compared to the PNR found at a similar d after placement (DAP) in this study (Gandeza et al., 1991). Non Linear Regression Analysis o f Nitrogen Release Due to interactions between year and CRF, the CRF nonlinear regression models were presented by year and were highly significant for all CRF s (Table 2 4 and 2 7 ). The nonlinear regression model s fit the pouch incubated CRF PNR with R 2 = 0.85 to 0.99 during 2011 and 0. 49 to 0.99 during 201 3

PAGE 76

76 was not different between years for seven of 12 replicated CRFs. T fitted regression model differed from the measured total season PNR less th an 3% for six and four CRFs and lower than 5 % for 10 and six CRFs in 2011 and 2013, respectively. Six of the CRFs that had a 5% or greater PNR difference, which ranged from 8.4 % to 21.8% were bound to 100% N release by the regression model due to a relat ively linear N release as a result of a high initial release or failure to reach the decay stage of release (Table s 2 5 and 2 7) with 10 of ; however, extrapolation to less than seven DAP would be invalid, since t=0 data were not used to % d 1 and 0. 010 to 0. 034 % d 1 during 2011 and 2013 respectively. The N release r ate wa s not different between years for five of 12 CRFs, though numerically 10 of 12 replicated temperature in 2013. Similar to the pouch incubated CRF N release results in th is study, an exponential growth nonlinear regression model fit CRF PNR data with a R 2 when CRFs were incubated in pouches under orange ( Citrus sinensis ) trees (Medina, 2006). Zvomuya et al. (2003) instead used quadratic regression to model N release from pouch incubated PCU placed in a potato field with a DAP model and a growing degree d model and found R 2 of 0.96 and 0.91, respectively. However, Medin a (2006) obtained PNR greater than 90% during the 360 d trial, but Zvomuya et al. (2003) found PNR of 60% during the 150 d trial. The CRF used by Zvomuya et al. (2003) did not reach the decay stage of release, which will be the stage of release where the osmotic potentials

PAGE 77

77 begin to equilibrate and release slows; therefore, linear release results may be expected. Due to the high P N R during the tomato season in the current study the exponential growth nonlinear regression was used to model the data Days to 75% N itrogen R elease Release of 75% N was obtained in 17 to >139 DAP and 26 to >1 21 DAP in 2011 and 201 3, respectively; thus, all CRFs released with a shorter duration in 2011 than 2013 except RNPK, PCNPK120, and M112 (Table 2 7 ). Furthermore, in all c ases 75% N release was accelerated compared to the CRF manufacturers stated release duration. At the manufacturer incubation temperature ( 20.0 C ), PCU180 has a 60 and 90 d longer release duration compared to PCU120 and PCU90 ; although due to higher soil temperatures 75% N release for PCU180 was 1 and 22 d shorter compared to PCU120 and 14 and 18 d longer compared to PCU90 in 2011 and 201 3 respectively. In contrast, PCNPK180 which has a 60 d longer release duration compared to PCNPK120 at CRF manufact urer incubation temperature, had a 58 d longer release duration compared to PCNPK120 in 2013 C ompared to FL100 FL140 ha d a 40 d longer release duration at CRF manufacturer temperatures ; however, in the fall season, FL140 obtained 75% N release 2 d before and 4 d after FL100 in 2011 and 2013, respectively The fall mixes (M112, M160, and M224) obtained 75% N release with a difference of 3 d or lower between years, but a 49 and 44 d differen ce in 75% N release was fo und among the fall mixes and FLmix in 2011 and 201 3 respectively. The CRFs composition in the fall mixes and FLmix were equivalent; thus, the included SF and fillers may have affected the osmotic potential and CRF release duration. An 18 to 26 d lag peri od occurred between bedding and tomato transplanting in these trials due to fumigation requirements During a 26 d lag period FL100 and FL140

PAGE 78

78 in 2011 and FL100 in 2013 released 75% of the N before tomatoes were transplanted. Tomato uptake was 10% and 30 % of the total season N in the first 30 and 46 d after transplant (Scholberg, 1996). Therefore, two and four CRFs in 2011 and one and five CRFs in 2013 release d greater than 75% of the N before tomatoes up take 10% and 30% season total N respectively. F urthermore, greater than 50% of the 2011 season and 3 weeks of the 2013 season included the high rainfall season that ends in mid October in southwest Florida (Rosencrans, 2012). Thus, between 62.8% and 90.3% N in 2011 and 27.1 % and 71.6 % N in 2013 was re leased during the high rainfall season in which N will be subject to leaching due to water table fluctuations (Sato et al., 2009 and 2012). The 90 and 100 d release CRFs released the majority of the N during the rainy season and should not be recommended for tomato production during the fall season. Controlled release fertilizers of 180 d release duration released between 58.3% and 91.5% of the N during the season, but a thicker coating results in a greater cost compared with CRF of lower release duration s. Furthermore, 180 d CRFs did not consistently maintain low early season PNR and high total season PNR compared to CRF of 120 d release. Therefore, CRFs or CRF mixes of 120 to 180 d may be recommended, though the CRFs and mixes must consistently release a high portion of the total N to the intended crop. In conclusion, the P N R from pouch incubated CRFs in the tomato field was accelerated during the fall season compared to the manufacture r s stated release which was due to high soil temperatures that caused coating technolog y dependent N release. A CRF or CRF mixture containing CRFs of 120 to 180 d release duration may be

PAGE 79

79 recommended, but the CRFs must release greater than 75% N during the season, which was not found with all CRFs in this study.

PAGE 80

80 Table 2 1 Collection dates and days after placement (DAP) for pouches containing controlled release fertilizer, incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 in Immokalee, FL. Year/ study Bedding date Planti ng date Pouch p lacement Collection date (DAP) 1 2 3 4 5 6 7 8 2011/ 1 3 Aug. 29 Aug. 3 Aug. 10 Aug. (7) 17 Aug. (14) 30 Aug. (27) 13 Sept. (41) 3 Oct. (61) 1 Nov. (90) 1 Dec. (120) 22 Dec. (139) 2011/ 2 15 Aug. 3 Sept. 15 Aug. 22 Aug. (7) 30 Aug. (15) 13 Sept. (29) 26 Sept. (42) 14 Oct. (60) 14 Nov. (91) 13 Dec. (120) 22 Dec. (129) 2013/ 1 & 2 20 Sept. 8 Oct. 24 Sept. 1 Oct. (7) 8 Oct. (14) 2 1 Oct. (2 7 ) 6 Nov. (4 3 ) 2 1 Nov. (5 8 ) 23 Dec. (90) 2 1 Jan. (1 19 ) 2 3 Jan. (121 )

PAGE 81

81 Table 2 2. Controlled release fertilizers (CRFs) placed in pouches and incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 in Immokalee, FL. Study z CRF y Abbreviation Release duration Grade x Manufacturer w 1 PCU PCU90 90 44 0 0 Agrium Advanced Technology 1 PCU PCU120 120 43 0 0 Agrium Advanced Technology 1 PCNPK PCNPK120 120 19 2.6 10.8 Agrium Advanced Technology 1 PCU PCU180 180 43 0 0 Agrium Advanced Technology 1 PCNPK PCNPK180 180 18 2.6 10 Agrium Advanced Technology 1 PSCU PSCU 180 37 0 0 Everris NA 1 RCNPK RCNPK 120 19 2.6 10 Everris NA 2 PCN FL100 100 28 0 0 Chisso Asahi Fertilizer Co. 2 PCN FL140 140 28 0 0 Chisso Asahi Fertilizer Co. 2 PCKN FL180 180 12 0 33.2 Florikan ESA 2 PCM FLmix 100 to 180 19.2 0 11.3 Florikan ESA 2 Fall Mix 112 M112 100 to 180 7.5 3.6 10.3 Florikan ESA 2 Fall Mix 168 M168 100 to 180 12.3 3.6 10.3 Florikan ESA 2 Fall Mix 224 M224 100 to 180 15 3.6 10.3 Florikan ESA z PCU180NPK and PCM were included in 2013. y PCU, polymer coated urea; PCNPK, polymer coated compound nitrogen (N), phosphorus (P), and potassium (K) fertilizer; PSCU, polymer sulfur coated urea; RCNPK, resin coated compound N, P, and K fertilizer; PCN, polymer coated N, PCNK, polymer coated potassium nitrate; PCM, poly mer coated mix containing FL100, FL140, and FL180; M112, M168, and M224 are mixes of CRF and SF that when applied at 1 1 1 CRF N. x Fertilizer grade = (%N,%P,%K). w Agrium Advnaced Technology, Loveland, CO ; Everris NA, Inc., Dublin, OH; Florikan ESA, LLC., Sarasota, FL; Chisso Asahi Fer tilizer Co. Ltd., Tokyo, Japan.

PAGE 82

82 Table 2 3. Minimum (Min.), mean, and maximum (Max.) soil temperatures at 10 cm below the bed surface during Fall 2011 and 2013 in Immokalee, F L Min. Mean Max. Week ending z 2011 2013 2011 2013 2011 2013 9 Aug. 25.7 30.3 40.1 16 Aug. 25.2 30.3 39.6 23 Aug. 24.7 29.7 40.1 30 Aug. 25.0 29.3 37.6 6 Sept. 24.5 28.5 36.7 13 Sept. 24.7 30.6 39.1 20 Sept. 25.0 30.3 38.1 27 Sept. 24.0 25.2 28.3 28.1 36.0 33.9 4 Oct. 22.5 24.7 28.6 28.4 36.0 34.4 11 Oct. 22.2 23.7 26.4 27.8 32.7 33.2 18 Oct. 23.5 23.4 26.0 27.5 32.7 32.2 25 Oct. 18.2 21.2 23.1 27.3 28.2 33.2 1 Nov. 20.2 20.7 24.0 24.6 28.0 29.4 8 Nov. 17.2 20.2 22.4 24.5 27.7 29.7 15 Nov. 16.5 18.9 21.7 23.6 26.7 26.9 22 Nov. 21.2 21.9 24.3 24.7 28.7 27.4 29 Nov. 19.0 16.9 22.5 22.5 27.7 26.2 6 Dec. 14.7 17.9 20.0 21.5 25.0 24.9 13 Dec. 17.5 18.4 21.3 22.7 26.0 25.4 20 Dec. 15.7 16.7 20.7 20.6 24.2 23.9 27 Dec. 17.2 19.4 20.5 22.0 24.2 24.9 3 Jan. 16.9 21.9 23.7 10 Jan. 14.7 18.6 23.7 17 Jan. 13.2 20.0 24.4 24 Jan. 11.9 16.2 20.4 Average 21.2 19.2 25.7 23.5 32.2 27.7 z Collection dates began on 3 Aug. 2011, and 24 Sept. 2013, and ended on 22 Dec. 2011, and 23 Jan. 2014

PAGE 83

83 Table 2 4. Main and interaction effects of 12 controlled release fertilizers (CRF) by collection dates from pouches incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 in Immokalee, FL. Collection dates Effects 1 2 3 4 5 6 7 8 -----------------------------Significance -----------------------------CRF *** z *** *** *** *** *** *** *** Year NS NS ** NS NS *** *** CRF year ** *** NS *** NS *** *** z NS ,*,** ,*** = Non significant or significance at 0.05 0.01, or 0. 0 01 respectively

PAGE 84

84 Table 2 5 Percentage nitrogen (N) release from controlled release fertilizers (CRFs) incubated in pouches 10 cm below the surface of a white polyethylene mulch covered raised bed during Fall 2011 and 2013 tomato production seasons in Immokalee, FL. Collection d ate CRF z Year 1 2 3 4 5 6 7 8 -----------------------------N Release (%) ------------------------------PCU90 2011 22.9 37.9 64.3 77.8 82.4 89.2 92.6 93.8 2013 16.0 35.7 62.4 65.3 70.3 87.6 94.3 90.0 PCU120 2011 19.5 33.0 48.6 70.6 77.3 84.5 88.3 91.1 2013 41.2 44.5 59.4 55.9 68.6 81.9 79.9 76.0 PCNPK120 2011 27.7 37.0 51.7 71.4 79.2 83.3 86.7 90.2 2013 47.5 61.6 71.1 79.7 85.0 94.8 94.3 94.0 PCU180 2011 23.0 24.4 52.1 69.0 81.8 85.6 88.7 91.5 2013 29.5 38.6 64.4 51.6 73.0 80.6 83.8 82.3 PCNPK180 2011 2013 36.5 34.4 42.6 51.9 61.6 78.3 83.4 85.9 PSCU 2011 31.9 33.6 36.2 45.9 60.6 69.5 77.6 78.2 2013 41.5 40.8 44.6 43.3 35.8 60.8 63.4 64.0 RCNPK 2011 29.3 42.6 52.3 69.3 76.8 85.5 87.6 90.2 2013 50.5 60.3 65.6 70.7 78.7 92.4 93.9 91.6 FL100 2011 57.5 69.4 80.0 88.2 92.0 86.0 87.2 91.5 2013 60.1 65.0 77.3 81.2 87.4 90.1 94.0 92.7 FL140 2011 52.1 68.8 87.0 88.5 94.3 86.9 89.0 91.3 2013 65.5 65.6 75.4 78.0 82.9 86.3 87.4 88.0 FL180 2011 6.6 10.0 63.3 61.3 87.5 62.5 75.1 77.6 2013 19.0 19.1 43.0 44.4 41.1 50.1 59.4 58.3 FLmix 2011 2013 64.3 61.5 66.4 74.5 69.1 79.4 81.9 77.4 M112 2011 14.2 34.5 47.9 54.5 61.1 78.2 81.4 82.5 2013 47.2 49.8 49.8 68.0 64.5 77.1 84.9 80.5 M168 2011 38.4 50.3 68.1 71.1 75.8 81.9 84.5 88.0 2013 57.2 64.3 62.6 72.3 77.3 81.6 88.8 87.6 M224 2011 45.9 57.2 70.8 80.2 80.8 83.2 84.6 86.8 2013 48.5 58.5 69.7 74.9 79.0 87.3 85.9 86.2 z PCU90 = polymer coated (PC) urea, 90 d release (DR); PCU120 = PC urea, 120 DR; PCNPK120 = PC nitrogen, phosphorus and potassium (NPK),120 DR; PCU180 = PC urea, 180 DR; PSCU = polymer sulfur coated urea, 180 DR; RCNPK = resin coated NPK, 120 DR; FL100 = PC urea, ammonium nitrate, 100 DR; FL140 = PC urea and ammonium nitrate, 140 DR; FL180 = PC potassium nitrate, 180 DR; FLmix = mix of FL100, FL140 and FL 180 ; M112, M168 and M224 = mixes of CRF and SF that when applied at 1 1 1 CRF N

PAGE 85

85 Table 2 6 C ontrasts of controlled release fertilizers by collection date and coating technology from pouches incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 in Immokalee, FL. Collection date Contrasts Year 1 2 3 4 5 6 7 8 ------------------------------------P value ------------------------------------PCU120 vs PCU180 2011 0.15 0.56 0.094 0.29 0.29 0.66 0.34 0.13 2013 0.0001 0.09 0.21 0.54 0.01 0.0001 0.0011 0.0001 PCNPK120 vs PCNPK180 2011 2013 0.714 0.84 0.91 0.61 0.03 0.0002 0.008 0.0001 PCU120 vs PCNPK120 2011 0.071 0.057 0.35 0.52 0.0001 0.014 0.0001 0.005 2013 0.0001 0.0003 0.62 0.46 0.049 0.014 0.91 0.57 PCU180 vs PCNPK180 2011 2013 0.027 0.067 0.016 0.38 0.27 0.47 0.49 0.3227 RCNPK vs PCNPK120 2011 0.013 0.079 0.004 0.087 0.15 0.022 0.33 0.94 2013 0.37 0.52 0.65 0.83 0.74 0.0015 0.24 0.16 PCU90 vs FL100 2011 0.045 0.91 0.011 0.27 0.030 0.79 0.0008 0.004 2013 0.13 0.30 0.25 0.40 0.049 0.37 0.07 0.03 PSCU vs PCU180 2011 0.23 0.60 0.0003 0.0003 0.0002 0.025 0.007 0.0001 2013 0.45 0.16 0.43 0.002 0.0001 0.0001 0.0001 0.0001 PCU180 vs FL180 2011 0.063 0.002 0.83 0.055 0.35 0.003 0.002 0.0001 2013 0.007 0.0001 0.31 0.003 0.0001 0.0001 0.0001 0.0001 FL180 vs PSCU 2011 0.004 0.006 0.0006 0.047 0.0001 0.41 0.63 0.82 2013 0.04 0.0005 0.81 0.89 0.21 0.002 0.36 0.052 M112, M168, M224 (regression) 2011 0.61 0.36 0.49 0.82 0.40 0.89 0.84 0.89 2013 0.12 0.35 0.45 0.57 0.29 0.66 0.36 0.03 FLmix vs M112, M168, M224 2011 2013 0.64 0.01 0.0002 0.08 0.0002 0.006 0.46 0.45 FL100, FL140, FL180 (regression) 2011 0.0001 0.0001 0.073 0.001 0.007 0.002 0.77 0.0001 2013 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 PCU90, PCU120, PCU180 (regression) 2011 0.0001 0.0001 0.41 0.45 0.010 0.58 0.0001 0.0009 2013 0.45 0.47 0.004 0.46 0.002 0.001 0.48 0.02 z NS *, **, *** = nonsignificant, or significant at P = 0.05, 0.01, or 0.001. y PCU90 = polymer coated (PC) urea, 90 d release (DR); PCU120 = PC urea, 120 DR; PCNPK120 = PC nitrogen, phosphorus and potassium (NPK),120 DR; PCU180 = PC urea, 180 DR; PSCU = polymer sulfur coated urea, 180 DR; RCNPK = resin coated NPK, 120 D R; FL100 = PC urea, ammonium nitrate, 100 DR; FL140 = PC urea and ammonium nitrate, 140 DR; FL180 = PC potassium nitrate, 180 DR; FLmix = mix of FL100, FL140 and FL 180 ; M112, M168 and M224 = mixes of CRF and SF that when applied at 1 1 supply 1 1 CRF N

PAGE 86

86 Table 2 7 Nonlinear regression analysis of N release from controlled release fertilizers (CRFs) incubated in pouches 10 cm below the surface of a white polyethylene mulch covered raised tomato bed during Fall 2011 and 2013 in Immokalee, FL. a y b c t t est CRF z Year R 2 P value 75% N release x a B c ------(%) ------% 1 -(DAP) --------------( P value) -------------PCU90 2011 93.3 1.4 0.040 0.98 0.0001 42 0.87 0.73 0.28 2013 92.5 1.6 0.031 0.86 0.0001 52 PCU120 2011 92.1 1.7 0.029 0.95 0.0001 57 0.36 0.0001 0.26 2013 84.9 34.3 0.019 0.75 0.0001 92 PCNPK120 2011 90.8 11.1 0.029 0.97 0.0001 56 0.10 0.0001 0.70 2013 95.9 38.1 0.031 0.90 0.0001 32 PCU180 2011 93.5 0.0 0.029 0.97 0.0001 56 0.25 0.018 0.64 2013 86.2 20.6 0.025 0.78 0.0001 70 PCNPK180 2011 2013 100.0 24.6 0.012 0.99 0.0001 90 PSCU 2011 100.0 w 22.7 0.0099 0.99 0.0001 114 v 0.007 0.015 2013 100.0 w 1.6 0.031 0.86 0.0001 >121 v RCNPK 2011 92.4 16.9 0.026 0.97 0.0001 57 0.0008 0.0001 0.008 2013 100.0 w 45.6 0.017 0.99 0.0001 44 FL100 2011 89.4 36.9 0.070 0.92 0.0001 19 0.017 0.017 0.001 2013 94.1 51.7 0.030 0.92 0.0001 26

PAGE 87

87 Table 2 7. Continued. a y b c t test CRF z Year R 2 P value 75% N release x a b c ------(%) ------1 -(DAP) ------------( P value) -----------FL140 2011 90.5 14.4 0.096 0.95 0.0001 17 0.63 0.0001 0.0001 2013 89.5 59.4 0.024 0.88 0.0001 30 FL180 2011 7 2 .2 39.3 0.059 0.85 0.0001 >139 v 0.84 0.002 0.01 2013 68.7 16.9 0.013 0.57 0.0001 >121 v FLmix 2011 2013 87.0 60.3 0.011 0.49 0.0001 68 M112 2011 84.8 6.9 0.024 0.94 0.0001 86 0.0001 0.0001 0.0009 2013 100.0 w 41.6 0.010 0.98 0.0001 83 M168 2011 85.5 26.5 0.036 0.96 0.0001 48 0.0001 0.0001 0.0001 2013 100.0 w 54.8 0.011 0.99 0.0001 51 M224 2011 85.1 31.8 0.045 0.93 0.0001 37 0.34 0.20 0.22 2013 87.2 39.2 0.034 0.89 0.0001 39 z PCU, polymer coated urea; PCNPK, polymer coated compound nitrogen (N), phosphorus (P), and potassium (K) fertilizer; PSCU, polymer sulfur coated urea; RCNPK, resin coated compound N, P, and K fertilizer; PCN, polymer coated N, PCNK, polymer coated potassium nitrate; PCM, polymer coated mix containing FL100, FL140, and FL180; M112, M168, and M224 are mixes of CRF and SF that when applied at 1 1 1 N. y Percent age N release = a (a b) kt where a = maximum N release, b = N release when time ( t ) = 0, and k = rate of N release. x DAP=days after placement w The a regression coefficient was restrained to 100% N release. v Extrapolation beyond the season length is not valid.

PAGE 88

88 Figure 2 1. A tomato nitrogen (N) uptake curve ( ) calculated from Scholberg (1996) charted with fitted N release curves ( and from a 120 d release polymer coated compound nitrogen, phosphorus, and potassium controlled release fertilizer incubat ed in pouches 10 cm below the surface of a white polyethylene mulch covered raised tomato bed in Immokalee, Fl during Fall 2011 and 2013 respectively. 14 28 42 56 70 84 98 112 126 140 154 168 182 196 210 224 0 20 40 60 80 100 120 140 1 ) Days after placement

PAGE 89

89 CHAPTER 3 PREDICTION OF CONTROLLED RELEASE FERTILIZER NITROGEN RELEASE IN TOMATO PRODUCTION USING ON FARM POUCH AND ACCELERATED TEMPERATURE CONTROLLED INCUBATION LABORATORY METHODS Introduction The majority of fresh market tomato in south Florida is grown using subsurface or seepage irrigation due to low costs and simple operation ( E.J. McAvoy, personal communication; Zotarelli et al., 2013). Seepage irrigation consists of managing a perched water table on a slowly permeable agrillic or spodic soil layer (Pitt s et al., 2002). In seepage irrigated fresh market tomato ( Solanum lycoper sicum L. ) production fertilizers are applied broadcast in row prior to false bedding as a bottom mix and in two bands on the bed shoulders after formation as a top mix before plants are transplanted in the field (Liu et al., 2012). The bottom mix will co ntain all the phosphorus (P) and micronutrients plus 10% to 20% of the nitrogen ( N ) and potassium ( K ), while the top mix will contain the remainder of the N and K. Repeated water table fluctuations, resulting from inadequate water table management or inte nse rainfall, may result in N leaching losses from 35% to 43% in tomato production system in south Florida (Sato et al., 2012). Therefore, vegetable growers should maintain a steady water table to reduce N leaching during the crop season. In response to the Federal Clean Water Act of 1972 and the Florida Restoration Act of 1999, a series of agronomic and vegetable best management practices (BMPs) have been adopted by the Florida Department of Agriculture and Consumer Services (Bartnick et al., 2005). On e BMP can be the use of controlled release fertilizers (CRFs), which are soluble fertilizers (SF) encapsulated in a polymer, resin, or a hybrid of sulfur coated urea occluded in a polymer coating (Bartnick et al., 2005;Trenkel, 2010). By

PAGE 90

90 definition, CRFs may increase N use efficiency compared to SF by protecting N against leaching below the root zone and becoming an environmental pollutant (Slater, 2010). Over the past fifty years, several CRF coating technologies have been developed and marketed, but no standard method to evaluate CRF manufacturer claims or performance existed for regulatory purposes in the United States ( Sartain et al., 2004a, 2004b ) Therefore, a taskforce was formed in 1994 to develop an accelerated temperature controlled incubation method (ATCIM) to predict CRF release duration The taskforce developed a correlation between N release from the ATCIM and N release from CRFs incubated in soil filled PVC columns in the laboratory to predict CRF N release (Carson and Ozores Hampton, 2012 ; Medina et al., 2009; Sartain et al., 2004a, 2004b). T he ATCIM predicted PVC column incubated CRF N release with greater than 90% accuracy ( Sartain et al. 2004a, 2004b ; Medina et al. 2009) Medina (2011) tested the robustness of the ATCIM and found th at only variations in temperature and time affected N release from all CRFs tested. However, deviations in extraction solution flow rate and sample size affected N release in some CRF tested. During the PVC column laboratory incubation, CRFs were maintai ned at a constant temperature and moisture content between leaching events; thus, CRFs were subjected to minimal variability compared to CRFs placed in the open field In cont rast s field studies are subject to variations due to diurnal temperature oscilla tion, weather pattern, and water table fluctuations (Medina, 2011). Therefore because of field environment variability correlation for regulatory purposes need to be tested between ATCIM and laboratory based PVC column incubated CRFs (Carson and Ozores Hampton, 2012).

PAGE 91

91 There are two methods to determine CRF N release in the field, the pot in pot and the pouch methods (Carson and Ozores Hampton, 2012). The pot in pot method consists of an inner pot with drainage that contains soil and CRF nested in a soli d outer pot that collects leachate. The pot assemblies may be installed in vegetable beds and leached at predetermined times. The leachate volume and N content are measured and the N release calculated. The pouch method consists of a known mass of CRF ( e.g., 3.5 g N) sealed inside fiberglass mesh pouches, which are buried in a vegetable bed and collected at prearranged dates. After collection, the CRF prills are homogenized in a known volume of water and the N content measured. The mesh allows for cont act between the soil and CRF prills, which may affect CRF N release since pouches with 1.2 mm 2 openings had a greater N release compared to pouches with 0.07 mm 2 openings (Wilson et al., 2009). Although these methods may be effectively used to determine N release rate from CRFs, the pouch and pot in pot methods persist for an entire tomato season and require numerous samples and high analysis costs (Carson and Ozores Hampton, 2012). However, an ATCIM that predicts CRF field release may assist growers with the selection of a CRF with the correct release duration to be use d in tomato production with lower time and costs Therefore, the purpose of this study was to evaluate the correlation of the ATCIM and the pouch field method as a predictor of N release f rom various CRFs in tomato production in south Florida. Material and Methods Accelerated T emperature C ontrolled I ncubation M ethod Fourteen CRFs from Florikan ESA L.L.C. (Sarasota, FL), Agrium Advanced Technologies Inc. (Loveland, CO), Chisso Asahi Fertilzier Co. Ltd. (Tokyo, Japan), and

PAGE 92

92 Everris International B.V. (Dublin, OH) were tested during July 2013 using the ATCIM (Table 3 1) ( Medina et al., 2009). A 30 g CRF sample was exposed to four increasingly aggressive (in length and temperature) extractions, using 0.2% citric acid as a solvent, during the course of 72 h. Extractions were 2 h at 25 C, 2 h at 50 C, 18 h at 55 C, and 5 0 h at 60 C. The extraction device had 16 jacketed chromatography columns; therefore, 14 CRFs and two isobutylidene diurea (31% N) samples as controls were extracted during each incubation cycle, which was replicated three times with CRFs randomized in e ach replicate. Extract N content was measured by pyrolysis and chemiluminescence using an Antek 9000 N analyzer (PAC Co., Houston, TX). The ATCIM N release data were subjected to analysis of variance and orthogonal contrasts using the general linear mode l procedure of SAS (version 9.2; SAS Institute, Cary, NC). Data were presented as cumulative percentage N released (PNR) Pouch M ethod F ield S tudy Twelve and 14 CRFs extracted in the ATCIM were used in the pouch method field study during 2011 and 2013, re spectively in Immokalee, Florida on Basinger fine sand (hyperthermic Spodic Psammaquents) (Carson et al., 2013) The CRFs were divided into two independent studies containing an equal number of CRFs (Table 3 1). The CRF fall mixes (M112, M168, and M224) were CRF and SF mixes that when applied at 1 1 1 CRF N; however, the SF and fillers in the pouch may have affected the N release in 2011. Therefore, FLmix was added in 2013 contain ing CRFs equivalent to the fall mixes that were composed of FL100, FL140, and FL180.

PAGE 93

93 Fiberglass window screen (18 14 mesh) was cut into 15 30 cm rectangles, folded in half, and sealed on two sides. A CRF sample containing 3.5 g N was p laced in the mesh pouch and the last side was sealed giving inside dimensions of 12.7 14 cm. The CRF pouches were buried flat at a 10 cm depth in the center bed of a three bed, 1.5 m long plot. The pouches in the experimental unit, e.g., a set (6 or 7) of pouches representing each CRF, were placed randomly in the plot. The plots were placed in a randomized complete block design with four replications and eight collection dates (Table 3 2). After pouch collection the pouch contents were dried in a beaker at room temperature, placed in plastic bags and stored until N analysis (Carson, Ozores Hamp ton, and Sartain 2012). In preparation of the sample for analysis the pouch contents were ground in 300 mL of deionized water using a blender (Model 36BL23; Waring Commercial, New Hartford, CT) to destroy the prill coating. The CRF samples were diluted t o 500 mL with deionized water, filtered using Whatman no. 42 filter paper, and frozen until analysis. In 2011, the samples were analyzed for total soluble N by pyrolysis and chemiluminescence using an Antek 9000 N analyzer (Pac. Co., Houston, TX.). In 20 13, nitrate N (NO 3 N) and ammonium N (NH 4 + N) were measured by salicylate hypochlorite, cadmium reduction using a Flow Analyzer (QuikChem 8500, Lachat Co., Loveland, CO) at 660 nm and 520 nm, respectively. Urea N was measured by modified diacetyl monoxime methods using a DR/4000U Spectrophotometer (Hach Co., Loveland, CO) at 527 nm (Sato and Morgan, 2008; Sato et al., 2009) The results for NO 3 N, NH 4 + N, and urea N were summed to determine total residual CRF N. The results were ex pressed in cumulative PNR ( Carson et al., 2013 ). The pouch method

PAGE 94

94 P N R data were subjected to analysis of variance and orthogonal contrasts using the general linear model procedure of SAS (version 9.2; SAS Institute, Cary, NC). Correlation o f t he ATCIM w ith t he P ouch M ethod Using a Two Step Process The non linear regression equation PNR = a (a b) e ct in which a = the maximum level of PNR b = the intercept or PNR when time ( t ) = 0, and c = the rate of increase utilized the Gaussian Newton iterative method and was fit to each replicate of the pouch incubated CRF N release data by CRF (Sartain et al., 2004a and 2004b). For each year, replicate one and two, and three and four of the nonlinear regression coefficients from the pouch incubated CRF N release were averaged and paired with replicate one and two of the ACTIM extracted N release values to fit a multiple regression model. The extraction values were the explanatory variable and the nonlinear regression coefficients were the dependent variable as a = a 0 + a 1 E 1 + a 2 E 2 + a 3 E 3 + a 4 E 4 b = b 0 + b 1 E 1 + b 2 E 2 + b 3 E 3 + b 4 E 4 and c = c 0 + c 1 E 1 + c 2 E 2 + c 3 E 3 + c 4 E 4 The ATCIM extraction values were represented by E1, E2, E3, and E4. The fitted multiple linear regression coefficients and the thir d ATCIM replicate were used to create predicted nonlinear regression coefficients and predicted N release curves (NRCs). P rediction models based on CRF release duration rather than CRF specific models, were created by grouping th e nonlinear regression co efficients and ATCIM extraction values from the individual prediction model s to develop a new set of multiple linear regression coefficients (Table 3 1). The new multiple linear regression coefficients and third replicate of the ATCIM were used to create a group predicted NRC for each CRF based on release duration. An R 2 type statistic was developed based on the sum of squares (SS) for the predicted and grouped CRF regression models as (SS1 SS2)/SS1, where SS1 equals

PAGE 95

95 the sum of squared differences betwee n the fitted release curve and the grand mean, and SS2 equals the sum of the squared differences between points on the fitted release curve and points on the individual predicted or group predicted NRC. Thus, the statistic measures agreement between the i ndividual predicted or group predicted NRCs and the fitted release curve compared to a straight horizontal line through the grand mean. Therefore, a value of one indicates that the two lines were the exact same a zero value indicates that the predicted o r group release curves fit will be equivalent to a line through the mean, and a negative value indicates that a line through the mean will agree with the fitted NRC better than the individual or group predicted release curves. Results and D iscussion Accelerated T emperature C ontrolled I ncubation M ethod The PNR from ATCIM extractions one through four ranged between 0.1% to 2.4%, 0.2% to 5.9%, 1.5% to 29 .0 %, and 28.4 % to 72.5%, respectively (Table 3 3) The c omponents of FLmix (FL100, FL140, and FL180) and the PCUs (PCU90, PCU120, and PCU180) had a PNR in order of release duration, i.e., FL100 > FL140 > FL180 and PCU90 > PCU120 > PCU180 during extractions one through four and one through three, respectively Similarly, PCNPK120 had a greater PNR compar ed to PCNPK180 at extractions two, three, and four. The coated SFs impacted CRF PNR with PCU120 having lower PNR compared to PCNPK120 at extractions two and four and PCU180 having higher PNR compared to P CNPK180 at extractions three and four. With only a 10 d difference in release duration, PCU90 had a greater PNR at extractions one through three compared to FL100 but FL100 was greater at extraction 4 However, N release between PCNPK120 and RCNPK were not different at any extraction At extraction on e through three, the PNR from PSCU was greater than the PNR of FL180

PAGE 96

96 and PCU180, which were different at extractions three and four. The extracted N release of the fall mixes were similar in extraction three and four, but there were significant difference s among the CRFs at extraction one and two; thus, the SF and fillers probably affected the extraction Additionally, FLmix had a lower PNR at extractions one, two and three but higher in extraction four compared to the fall mixes. Medina et al. (2009 ) and Medina ( 2011) extracted CRFs in the ATCIM at 2, 2, 20, and 50 h for extractions one through four, respectively, but CRFs in this study were extracted using an 18 h third extraction. According to a ruggedness test conducted by Medina (2011), a 10% re duced time for extractions two and three decreased the second and third N concentration in two of four CRFs, but did not affect the total cumulative PNR T he 180 d release CRFs in the current study had lower and higher cumulative PNR compared to 270 d release polyolefin CRFs (Medina, 2011) indicating that CRF coating technology may impact N extractions Prediction M odel: C orrelation of ATCIM and P ouch N R elease The 2011 and 2013 predicted NRC fit the fitted NRC with R 2 of 0.95 to 0.9 9 and 0.61 to 0.99, respectively (Table 3 regression coefficients were different from the total season PNR by of 0.3% to 19.6% and 0.1% to 18.2% in 2011 and 2013, respectively, with the lowest and high est diff erences in PCNPK120 and PSCU in 2011, and FL140 and M112 in 2013 respectively fitted and predicted PNR were similar to the first PNR points in the majority of the CRFs (Fig 3 1 a nd 3 CRFs except PCNPK120 due to the late trial start date result ing in lower air and soil temperatures.

PAGE 97

97 The high R 2 values indicate that the ATCIM PNR results may predict CRF N release effectively after correlat ion with pouch field method PNR results In several CRFs, such as PCU90, PCU180, and FL100 the NRCs were similar between years suggest ing that soil temperature differences of 2.2 C between seasons did not impact the PNR in the CRF However, variability in PNR results may cause differences in fitted and predicted NRCs in CRFs such as PCU180. Furthermore, the high initial release the initial PNR to differ between the two seasons but NRCs of some CR Fs such as PCU120, RCNPK, M168, and M224 converged 50 to 60 d after placement Sartain et al. (2004a, 2004b) predicted NRCs from CRFs incubated in PVC column with R 2 of 0.90 or greater. Similarly, Medina (2011) used the two step process and to predict CR F NRCs for 180 d CRFs with R 2 se results indicated that the two step process may be used to accurately predict NRCs from CRFs with release duration of 180 d or lower Similarly, studies have used different two step processes and concluded CRF PNR may be predicted by elevating CRF extraction temperatures (Dai et al., 2008; Wang et al., 2011). However, these CRF prediction methods require correlation of PNR from an ATCIM and a long term CRF incubation to determine CRF specific N release coeffici ents. Therefore to predict PNR from a new CRF never tested in tomato production in Florida a pouch or pot in pot method would be required to correlate with an ATCIM Consequently, if a pouch study were conducted an ATCIM would not be needed to predict f ield PNR Th erefore grouping CRFs by release duration may allow for model d evelopment without testi ng CRF in a field pouch study.

PAGE 98

98 Prediction M odel: C orrelation o f the ATCIM a nd the P ouch N Release G rouped b y CRF R elease D uration G roup CRF predicted NRCs fit the fitted NRCs with R 2 of 0.64 to 0.99 and 0.38 to 0.95 for fall 2011 and 2013, respectively (Table 3 5 ). Thus, a line through the grand mean would fit PCU180, PSCU, and M168 in 2011 and M168 in 2013 better than the group predicted NRC. However, s everal g roup predicted NRCs fit the fitted NRCs adequately ( Figures 3 3 and 3 39.1 to 75.3 and 8.6 to 69.8, and o 0.107 and 0.005 to 0.045 respectively The difference between years for the group predicted nonlinear regression coefficients was due to soil temperature differences, which were similarly detected among the individual predicted CRFs. The difference be predicted nonlinear regression coefficients averaged 2.9, 13.8, and 0.01 in 2011 and 4.7, 7.7, and 0.009 in 2013. Compared to the individual predicted NRCs the group predicted NRCs had lower accuracy, w hich might be expected due to the combination of different CRF technologies; although eight CRFs in each year maintained a R 2 predicted NRCs had higher agreement with the fitted NCRs among the 90 to 140 d release CRFs compared to the 180 d release CRFs The lower agreement among the 180 d CRFs were related to the greater variabil ity in response to high soil temperatures among the 180 d release CRF coating technologies that included PSCU and PCF relative to other release durations that i ncluded PCF and RCF, which are more closely related E xcept for the CRFs with a negative R 2 such as PCU180, PSCU, and M168, the group predicted PNR coefficient probably predict ed PNR in the field adequately for a

PAGE 99

99 tomato production system in south Florida The difference between years in the predicted NRCs was likely due to differences in soil temperature. In conclusion, the ATCIM and field pouch method may be correlated to predict field PNR from the individual CRFs in polyethylene mulched tomato production for the majority of the CRFs in the market with an R 2 start dates may have caused differences in predicted PNR among CRFs. Grouping CRFs by release duration to model CRF PNR performed adequately with 90 to 140 d release CRFs in which includes many CRFs recommended for tomato production However, grouping CRFs of 180 d release would not be recommended since coating technologies differ in response to high bed temperatures during the fall tomato season in south Florida With further validation, group ing CRF release durations to model an unknown CRF N release profile in tomato production may allow for use of an ATCIM without performing a pouch study that would negate the usefulness of the ATCIM.

PAGE 100

100 Table 3 1. Controlled release fertilizers (CRFs) used in the accelerated temperature controlled incubation and the on farm pouch methods incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 in Immokalee, FL. CRF z Abbreviation Rel ease d uration y Grade x Manufacturer w Pouch study Group v PCU PCU90 90 44 0 0 Agrium Advanced Technology 1 1 PCU PCU120 120 43 0 0 Agrium Advanced Technology 1 2 PCNPK PCNPK120 120 19 2.6 10.8 Agrium Advanced Technology 1 2 PCU PCU180 180 43 0 0 Agrium Advanced Technology 1 3 PCNPK u PCNPK180 180 18 2.6 10 Agrium Advanced Technology 1 3 PSCU PSCU 180 37 0 0 Everris 1 3 RCNPK RCNPK 120 19 2.6 10 Everris 1 2 PCN FL100 100 28 0 0 Chisso Asahi Fertilizer Co. 2 1 PCN FL140 140 28 0 0 Chisso Asahi Fertilizer Co. 2 2 PCKN FL180 180 12 0 33.2 Florikan ESA 2 3 PCM u FLmix 100 180 19.2 0 11.3 Florikan ESA 2 4 Fall Mix 112 M112 100 180 7.5 3.6 10.3 Florikan ESA 2 4 Fall Mix 168 M168 100 180 12.3 3.6 10.3 Florikan ESA 2 4 Fall Mix 224 M224 100 180 15 3.6 10.3 Florikan ESA 2 4 z PCU, polymer coated urea; PCNPK, polymer coated compound nitrogen (N), phosphorus (P), and potassium (K) fertilizer; PSCU, polymer sulfur coated urea; RCNPK, resin coated compound N, P, and K fertilizer; PCN, polymer coated N, PCNK, polymer coated potassium nitrate; PCM, polymer coated mix containing FL100, FL140, and FL180; M112, M168, and M224 are mixes of CRF and SF that when applied at 1 1 1 CRF N. y Release durations in days x Fertilizer grade=(%N %P %K). w Agrium Advanced Technology, Loveland, CO; Everris NA, Inc., Dublin, OH; Florikan ESA, LLC., Sarasota, FL ; Chisso Asahi Fer tilizer Co. Ltd., Tokyo, Japan. v Groups used in the two step method to predict N release base d on CRF release duration. u PCU180NPK and PCM were included in 2013

PAGE 101

101 Table 3 2. Collection dates and days after placement (DAP) for controlled release fertilizer in on farm pouch field study incubated in white polyethylene mulch covered raised t omato beds during Fall 2011 and 2013 in Immokalee, FL. Collection date (DAP) Year/Study 1 2 3 4 5 6 7 8 2011/1 10 Aug. (7) 17 Aug. (14) 30 Aug. (27) 13 Sept. (41) 3 Oct. (61) 1 Nov. (90) 1 Dec. (120) 22 Dec. (139) 2011/2 22 Aug. (7) 30 Aug. (15) 13 Sept. (29) 26 Sept. (42) 14 Oct. (60) 14 Nov. (91) 13 Dec. (120) 22 Dec. (129) 2013/ 1 & 2 1 Oct. (7) 8 Oct. (14) 21 Oct. (27) 6 Nov. (43) 21 Nov. (58) 23 Dec. (90) 21 Jan. (119) 23 Jan. (121)

PAGE 102

102 Table 3 3. Nitrogen (N) extracted from controlled release fertilizers (CRFs) during the accelerated temperature controlled incubation method (Sartain et al., 2004a, 2004b, and Medina et al., 2009) Extraction number CRF z 1 2 3 4 ----Cumulative N release (%) ----PCU90 1.3 4.4 29.0 48.6 PCU120 0.3 0.6 6.6 36.9 PCNPK120 1.9 3.7 10.5 60.8 PCU180 0.1 0.3 11.8 40.6 PCNPK180 0.5 0.7 1.7 33.0 PSCU 2.4 5.9 21.5 30.7 RCNPK 1.9 4.2 9.7 72.5 FL100 0.2 0.9 17.9 60.5 FL140 0.1 0.6 10.2 43.2 FL180 0.1 0.2 1.5 28.4 FLmix 0.2 0.8 13.5 59.2 M112 1.2 2.8 16.6 55.2 M168 1.1 2.6 14.6 48.0 M224 0.7 2.0 19.1 55.1 P value 0.0001 0.0001 0.0001 0.0001 Significance y *** *** *** *** Single degree of freedom contrast ( P value) PCU90, PCU120, PCU180 x 0.005 0.0004 0.006 0.29 PCNPK120 vs PCNPK180 0.11 0.027 0.018 0.003 PCU120 vs PCNPK120 0.06 0.019 0.07 0.006 PCU180 vs PCNPK180 0.16 0.16 0.02 0.023 RCNPK vs PCNPK120 0.96 0.21 0.07 0.053 PCU90 vs FL100 0.03 0.006 0.038 0.032 PSCU vs PCU180 0.001 0.001 0.036 0.08 PCU180 vs FL180 0.77 0.88 0.031 0.045 FL180 vs PSCU 0.001 0.001 0.003 0.62 M112, M168, M224 x 0.026 0.016 0.21 0.99 FLmix vs M112, M168, M224 0.0001 0.0001 0.0004 0.0001 FL100, FL140, FL180 x 0.027 0.06 0.004 0.013 z PCU90 = polymer coated (PC) urea, 90 d release (DR); PCU120 = PC urea, 120 DR; PCNPK120 = PC nitrogen, phosphorus and potassium (NPK),120 DR; PCU180 = PC urea, 180 DR; PCNPK180 = PC NPK, 180 DR; PSCU = polymer sulfur coated urea, 180 DR; RCNPK = resin coated NPK, 120 DR; FL100 = PC urea, ammonium nitrate, 100 DR; FL140 = PC urea and ammonium nitrate, 140 DR; FL180 = PC potassium nitrate, 180 DR; FLmix = mix of FL100, FL140 and FL 180 ; M112, M168 and M224 = mixes of CRF and SF that when applied at 1 1 1 CRF N y NS ,*,** ,*** = Non significant or significance at 0.05 0.01, or 0. 0 01 respectively x Regression

PAGE 103

103 Table 3 4. Regression coefficients an d coefficient of determination for predicted controlled release fertilizer (CRF) nitrogen (N) release curve based on the two step process from accelerated temperature controlled incubation and on farm pouches incubated in white polyethylene mulch covered r aised tomato beds during Fall 2011 and 2013 in Immokalee, FL. 2011 2013 CRF z a y b c R 2 x a b c R 2 PCU90 92.9 0.7 0.037 0.99 91.2 1.0 0.033 0.99 PCU120 92.2 0.1 0.029 0.99 88.4 29.5 0.027 0.94 PCNPK120 90.5 7.7 0.032 0.99 93.5 28.7 0.051 0.98 PCU180 93.9 1.2 0.036 0.97 86.1 20.4 0.031 0.99 PCNPK180 98.2 28.5 0.007 0.61 PSCU 97.8 20.9 0.009 0.95 80.0 20.9 0.009 0.99 RCNPK 93.4 13.8 0.026 0.99 96.1 50.5 0.013 0.89 FL100 89.6 34.2 0.073 0.99 95.6 51.9 0.028 0.99 FL140 90.8 4.0 0.110 0.99 88.1 63.8 0.024 0.95 FL180 77.3 46.6 0.058 0.99 73.4 12.7 0.022 0.93 FLmix 89.8 57.8 0.019 0.99 M112 85.2 5.2 0.024 0.99 98.7 38.7 0.012 0.99 M168 86.5 21.4 0.036 0.98 91.0 58.1 0.012 0.87 M224 85.4 25.7 0.048 0.99 82.5 34.6 0.044 0.94 z PCU90 = polymer coated (PC) urea, 90 d release (DR); PCU120 = PC urea, 120 DR; PCNPK120 = PC nitrogen, phosphorus and potassium (NPK),120 DR; PCU180 = PC urea, 180 DR; PCNPK180 = PC NPK, 180 DR; PSCU = polymer sulfur coated urea, 180 DR; RCNPK = resin coated NPK, 120 DR; FL100 = PC urea, ammonium nitrate, 100 DR; FL140 = PC urea and ammonium nitrate, 140 DR; FL180 = PC potassium nitrate, 180 DR; FLmix = mix of FL100, FL140 and FL 180 ; M112, M168 and M224 = mixes of CRF and SF that when applied at 1 1 supply 112, 168, and 224 1 CRF N y Percent nitrogen release = a (a b) e ( c t), where a = maximum amount of N released during the season, b = the intercept or value when time eq uals zero, c = the rate of N release and t = time. x The R 2 value (SS1 SS2)/SS1, where SS1 = the sum of the squared differences between points on the fitted release curve and the overall mean and SS2 = the sum of the squared differences between the points on the fitted time release curve and the points on the predicted N release curve points.

PAGE 104

104 Table 3 5. Regression coefficients and coefficient of determination for predicted nitrogen (N) release based on controlled release fertilizer (CRF) coefficient groupings in the two step process from accelerated temperature controlled incubation and on farm pouches incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013 in Immokalee, FL. 2011 2013 CRF z a y b c R 2 x a b c R 2 PCU90 91.9 13.9 0.038 0.96 89.4 8.6 0.045 0.90 PCU120 91.6 4.5 0.058 0.64 89.5 39.6 0.029 0.80 PCNPK120 92.4 13.7 0.039 0.87 96.7 42.1 0.026 0.96 PCU180 105.2 75.3 0.019 0.64 78.8 9.3 0.040 0.94 PCNPK180 106.5 33.7 0.010 0.95 PSCU 90.0 31.8 0.031 0.17 69.7 17.1 0.022 0.61 RCNPK 91.2 15.2 0.048 0.96 102.3 57.3 0.020 0.66 FL100 89.9 27.9 0.080 0.99 96.8 56.1 0.023 0.94 FL140 90.3 2.4 0.107 0.99 92.0 69.8 0.012 0.84 FL180 85.5 39.1 0.038 0.89 70.9 12.3 0.048 0.64 FLmix 91.4 52.3 0.022 0.80 M112 85.4 5.4 0.020 0.96 102.1 47.8 0.005 0.67 M168 85.4 5.5 0.020 0.36 101.6 47.1 0.006 0.38 M224 85.2 45.7 0.038 0.93 78.5 47.8 0.045 0.76 z PCU90 = polymer coated (PC) urea, 90 d release (DR); PCU120 = PC urea, 120 DR; PCNPK120 = PC nitrogen, phosphorus and potassium (NPK),120 DR; PCU180 = PC urea, 180 DR; PCNPK180 = PC NPK, 180 DR; PSCU = polymer sulfur coated urea, 180 DR; RCNPK = resin coat ed NPK, 120 DR; FL100 = PC urea, ammonium nitrate, 100 DR; FL140 = PC urea and ammonium nitrate, 140 DR; FL180 = PC potassium nitrate, 180 DR; FLmix = mix of FL100, FL140 and FL 180 ; M112, M168 and M224 = mixes of CRF and SF that when applied at 1 493 1 supply 112, 168, and 224 1 CRF N y Percent nitrogen release = a (a b) e ( c t), where a = maximum amount of N released during the season, b = the intercept or value when time equals zero, c = the rate of N release and t = time. x The R 2 value (SS1 SS2)/SS1, where SS1 = the sum of the squared differences between points on the fitted release curve and the overall mean and SS2 = the sum of the squared differences between the points on the fitted time release curve and th e points on the predicted N release curve points.

PAGE 105

105 Figure 3 1. Field release points ( diamonds and triangles) for CRFs incubated 10 cm below the surface of a white polyethylene mulched raised bed during Fall 2011 and 2013 in Immokalee, FL and fit ted (dotted and solid lines) and predicted (dash/dotted and dashed lines) release curves from the two step correlation of the accelerated temperature controlled incubation and on farm pouches for 2011 and 2013, respectively (Study one). PCU90 = polymer co ated (PC) urea, 90 d release (DR); PCU120 = PC urea, 120 DR; PCNPK120 = PC nitrogen, phosphorus and potassium (NPK),120 DR; PCU180 = PC urea, 180 DR; PCNPK180 = PC NPK, 180 DR; PSCU = polymer sulfur coated urea, 180 DR; RCNPK = resin coated NPK, 120 DR. 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) PCU90 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) Days after placement PSCU 0 20 40 60 80 100 0 20 40 60 80 100 120 140 Days after placement RCNPK 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) PCNPK180 0 20 40 60 80 100 0 20 40 60 80 100 120 140 PCU120 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) PCU180 0 20 40 60 80 100 0 20 40 60 80 100 120 140 PCNPK120

PAGE 106

106 Figure 3 2. Field release points (diamonds and triangles) for CRFs incubated 10 cm below the surface of a white polyethylene mulched raised bed during Fall 2011 and 2013 in Immokalee, FL and fitted (dotted and solid lines) and predicted (dash/dotted and dashed lines) release curves from the two step correlation of the accelerated temperature controlled incubation and on farm pouches for 2011 and 2013, respectively (Study two). FL100 = PC urea, ammonium nitrate, 100 DR; FL140 = PC urea and ammonium ni trate, 140 DR; FL180 = PC potassium nitrate, 180 DR; FLmix = mix of FL100, FL140 and FL 180; M112, M168 and M224 = mixes of CRF and SF 1 1 CRF N 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) FL180 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) FL100 0 20 40 60 80 100 0 20 40 60 80 100 120 140 FL140 0 20 40 60 80 100 0 20 40 60 80 100 120 140 M112 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) M168 0 20 40 60 80 100 0 20 40 60 80 100 120 140 Days after placement M224 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) Days after placement FLmix

PAGE 107

107 Figure 3 3. Fitted (dotted and so lid lines) and predicted (dotted/dashed and the large dashed lines) nitrogen release curve of controlled release fertilizers (CRFs) grouped based on release duration in the two step correlation of the accelerated temperature controlled incubation and on fa rm pouches incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013, respectively, in Immokalee, FL (Study one). PCU90 = polymer coated (PC) urea, 90 d release (DR); PCU120 = PC urea, 120 DR; PCNPK120 = PC nitrogen, phosp horus and potassium (NPK),120 DR; PCU180 = PC urea, 180 DR; PCNPK180 = PC NPK, 180 DR; PSCU = polymer sulfur coated urea, 180 DR; RCNPK = resin coated NPK, 120 DR. 0 20 40 60 80 100 0 20 40 60 80 100 120 140 PCU120 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) PCU180 0 20 40 60 80 100 0 20 40 60 80 100 120 140 PCNPK120 0 20 40 60 80 100 0 20 40 60 80 100 120 140 Days after placement RCNPK 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) Days after placement PSCU 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) PCU90 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) PCNPK180

PAGE 108

108 Figure 3 4 Fitted (dotted and solid lines) and predicted (dotted/dashed and the large dashed lines) N release curves for controlled release fertilizers (CRFs) grouped based on release duration in the two step correlation of the accelerated temperature controlled inc ubation and on farm pouches incubated in white polyethylene mulch covered raised tomato beds during Fall 2011 and 2013, respectively, in Immokalee, FL (Study two). FL100 = PC urea, ammonium nitrate, 100 DR; FL140 = PC urea and ammonium nitrate, 140 DR; FL1 80 = PC potassium nitrate, 180 DR; FLmix = mix of FL100, FL140 and FL 180; M112, M168 and M224 = mixes of CRF and SF that 1 1 CRF N 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) FL180 0 20 40 60 80 100 0 20 40 60 80 100 120 140 FL140 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) FL100 0 20 40 60 80 100 0 20 40 60 80 100 120 140 M112 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) M168 0 20 40 60 80 100 0 20 40 60 80 100 120 140 Days after placement M224 0 20 40 60 80 100 0 20 40 60 80 100 120 140 N release (%) Days after placement FLmix

PAGE 109

109 CHAPTER 4 EFFECT OF CONTROLLED RELEASE AND SOLUBLE FERTIL IZER ON TOMATO PRODUCTION AND POSTH ARVEST QUALITY IN SE EPAGE IRRIGATION Introduction Florida ranks first in the USA for fresh market tomato production value at $267 million produced on 11,700 ha [ U.S. Department of Agriculture (USDA), 2013 ] The Federal Environmental Protection Agency and Florida Department of Environmental Protection recognize the importance of water quality through the enforcement of both the Federal Clean Water Act of 1972 a nd the Florida Restoration Act of 1999 (Bartnick et al., 2005) T he Florida Vegetable and Agronomic Crops Best Management Practices (BMPs) manual adopted by the Florida Department of Agriculture and Consumer Serv ices contains a series of BMPs to maintain and ameliorate water quality (Bartnick et al., 2005) The majority of the tomato production in southern Florida is seepage irrigated, which involves managing a water table perched on a slowly permeable soil lay er (argillic or spodic) located 0.6 to 0.9 m below the surf ace (Bonczek and McNeal, 1996). Ground or surface water pumped into a ditch that connects a series of parallel ditches spaced 20 to 30 m apart elevates a perched water table. Growers maintain the water table at The first year of this stud y was published: Carson, L.C., M. Ozores Hampton, and K.T. Morgan. 2012. Effect of controlled release fertilizer on tomatoes grown with seepage irrigation in Florida sandy soils. Proc. Fla. State Hort. Soc. 125:164 168. Reprinted with permission from Hort Science: Carson, L.C., M. Ozores Hampton, K.T. Morgan, and S.A. Sargent. 2014. Effect of controlled release and soluble fertilizer on tomato production and postharvest quality in seepage irrigation. HortScience 49:1 7

PAGE 110

110 45 to 60 cm below the bed surface to irrigate the plants by capillarity ( Bonczek and McNeal, 1996 ) In seepage irrigated tomato production, the University of Florida/Institute of Food and Agriculture Sciences (UF/IFAS) recommends applicat ion of all fertilizers at bed row before bed UF/IFAS recommended bottom mix contains all phosphorus ( P) and micronutrients, and 10% to 20% of the nitrogen (N) and potassium (K) (Liu et al., 2012) The remaining N and K are applied as a top mix. During the season, BMPs allow additional fertilizer application in the event of a leaching rainfall, low leaf tissue N concentration ( LTN C) or low petiole sap nitrate concentrat ion or an extended harvest season. A leaching rain is defined as greater than 76 mm of rainfall in 3 d or greater than 102 mm in 7 d (Liu et al., 20 12 ) The additional fertilizer may be applied by punching holes in the polyethylene mulch and hand applying dry granular fertilizer or by a liquid fertilizer injection wheel; however, both methods increase production costs (Liu et al., 2012) The use of enhanced efficiency fertilizer ( EEF ) a Florida vegetable crop BMP, may reduce the risk of nutrient loss to the environment and can subsequently increase N use efficiency in seepage irrigated tomato production (Car son and Ozores Hampton, 2013; Trenkel, 2010). There are three subgroups of EEF: slow release fertilizers (SRF), stabilized fertilizers and controlled release fertilizers (CRFs) (Slater, 2010) Slow release fertilizers are long chain molecules with reduced solubility, such as methylene urea, which typically need microbial degradation to release plant available N. S tabilized fertilizers are soluble ammonium (NH 4 + ) or urea fertilizer applied with a nitrificatio n

PAGE 111

111 inhibitor or urease inhibitor to maintain fertilizers in the original form as NH 4 + or urea. Finally, CRFs are soluble fertilizers ( SFs ) such as urea, ammonium nitrate (NH 4 NO 3 ), or potassium nitrate (KNO 3 ) coated with a polymer, resin, sulfur, or a polym er covering sulfur coated urea (PSCU) (Trenkel, 2010) These coated fertilizers release nutrients by diffusion into water at a predictable, temperature dependent rate ( Carson and Ozores Hampton, 2013 ). In sandy soils with seepage irrigation, when SRF and CRF were used as a singular N source in the bottom mix (resin coated urea, resin coated KNO 3 methylene urea, and PSCU ) or top mix (methylene urea and polymer coated urea ), lower or similar extra large and total marketable tomato yields were found when compared to SF during a spring season (Csizinszky, 1989, 1994; Csizinszky et al., 1992 ; Ozores Hampton et al., 2009) The lower marketable yields were partially due to slow N release from the SRF or CRF and high NH 4 + soil concentration caused by polymer coated urea use (Csizinszky, 1994; Ozores Hampton et al., 2009) Therefore, a was created to increase soluble N concentration in the soil during early tomato developmental stages ( Ozores Hampton et al ., 2009). The hybrid fertilizer system consists of 50% to 75% of the N as CRF in the bottom mix with the remainder of the N as SF in the top mix When the hybrid fert ilizer system was used with KNO 3 CRF at equal and lower N rates similar total marketable tomato yields were obtained compared to SF during a winter season eliminating the high NH 4 + soil concentrations ( Ozores Hampton et al. 2009). Therefore, t he objective of this study was to evaluate the effects of two SF rates and the hybrid fertil izer system with three CRF rates on tomato yields, LTN C post season soil N content, and postharvest fruit quality

PAGE 112

112 Material and Methods The hybrid fertilizer system studies were conducted on a commercial tomato farm near Immokalee, FL (26 14' 5" N / 81 28' 55" W) during Fall 2011 and Fall 2 012 (Carson, Ozores Hampton, and Morgan 2012). T he soil type w as Basinger fine sand (hyperthermic Spodic Psammaquents), which permitted the use of seepage irrigation (Natural Resources Conservation Service, 2012) The field configuration from east to west consisted of an i rrigation ditch three beds, a drive road, three beds, and another irrigation ditch. The beds were 76 cm wi de and 20 cm high with 1.8 m between bed centers. On 2 Aug. 2011 and 17 Aug. 2012, the beds were formed, fumigated with methyl bromide/chloropicrin (50:50 by weight) (ICL IP, South Charleston, WV.) at 84 1 fertilized, and covered with white virtual ly impermeable film (0.038 mm; Berry Plastic, Evansville, IN.). A CRF mix (Florikan Sarasota, FL) composed of coated, homogenized NH 4 NO 3 and urea (28N 0P 0K, 100 and 140 d release) and coated KNO 3 (12N 0P 40K, 180 d release) (1.4:1:1.2, by weight) was applied at three N rates as a bottom mix (Table 4 1). Additional, N as NH 4 NO 3 was applied in the top mix to create treatments CRF112/SNF56, CRF168/SNF56, and CRF224/SNF56 The UF/ IFAS and grower standard treatments contained NH 4 NO 3 in the top mix and 24 1 N from NH 4 NO 3 and 1 N from methylene urea in the bottom mix Following a leaching rainfall event on 28 Oct. 2011 t he UF/ IFAS treatment received 1 N as NH 4 NO 3 fertilize r for a total of 1 N. No additional N was added during the 2012 season. In the bottom mix, P was applied as triple super phosphate and SF K was applied as potassium magnesium sulfate Potassium sulfate applied in the top mix provided the remainder of the K that was not supplied in the bottom mix On 29 Aug.

PAGE 113

113 2011 and 3 Sept. 2012, tomato cultivar BHN 726 (BHNSeed Inc., Immokalee, FL.) was planted in a single row with 51 cm between plants The experimental design was a randomized complete block design with four replications. P lots were 9.1 m long and three beds wide with t he middle 5.1 m of the center row harvested for collection of yield data. The tomato crops were grown using industry standard production practices and UF/IFAS recommend ed pest and disease control (Olson et al., 2012 a ) A Watchdog data logger (model B100; Spectrum Technologies Inc., Plainfield IL.) collected soil temperature at 10 cm below the bed surface The water table depth was recorded 7 and 12 times during 2011 and 2012, respectively, from four m onitoring wells (one in each replicate) installed in the trial, as described by Smajstrla and Muoz Carpena (2011). Beginning at first flower (13 Sept. 2011 and 24 Sept. 2012) six most recently fully mature leaves were collected from each pl day intervals for seven total collections. The leaf tissue was dried at 50 C and ground to pass through a 60 mesh sieve. Leaf tissue N concentration (%) was measured by combustion using a NA2500 C/N Analyzer (Thermo Quest CE Instruments, Walth am, MA). Before first harvest each year, all plots were covered with bird netting to prevent unscheduled harvest by commercial crews. Fruit ranging from marketable mature green to ripe were harvested three times (14 Nov., 1 Dec., and 15 Dec. 2011, and 1 1 Nov., 7 Dec., and 15 Dec. 2012) and graded in the field as extra large (> 7.00 cm) large (6.35 to 7.06 cm) medium (5.72 to 6.43 cm) and unmarketable (cull) fruit according to USDA standards and weighed (USDA, 1997)

PAGE 114

114 In 2011, a subsample of 10 mature green fruit was collected from each plot at first harvest washed with chlorin ated water (150 ppm), dried at room temperature, transported to a commercial packing facility in Immokalee, FL and rip en ed with 150 ppm ethylene at 20 C and 85% to 90% RH for 13 d (Sargent et al., 2005). R ipe tomatoes were transported to the UF/IFAS Southwest Florida Research and Education Center (SWFREC) Vegetable Laboratory in Immokalee, FL, where fruit firmness was me asured as fruit deformation after 5 s using a deformation meter equipped with a 1 kg weight and 16 mm probe (Model C125EB; Mitutoyo Corp., Aurora, IL); fruit were rated for external color using the official USDA grade standards (1 to 6 scale, where 1=green and 6 = red ) ( USDA, 1997) In 2012, to reduce variability due to maturity differences, the subsample size was increased to 20 mature green fruit, which were collected and ripened as described above for 2011. However, the tomato fruit were removed from the ripening room at the first sign of breaker stage (3 d) and transported to the UF/IFAS SWFREC Vegetable Laboratory. Ten fruit from each plot, at breaker stage of development, were selected and ripened at room temperature until full red ripe, which occurred at 10 d after harvest. Fruit firmness and color were measured and rated as described for 2011. Post season soil samples were collected on 19 Dec. 2011 and 2 Jan. 2013 using a soil slicer ( Muoz Arbooleda et a l., 2006) From the middle bed in the center of each plot, an 8.9 cm wide 20 cm deep cross section of the bed was sampled. The cross section was divided into three vertical sections, homogenized, and subsampled. Soil samples were stored at less than 4 C until analysis. Before analysis, soil samples were sieved, weighed. CRF prills were separated from the samples, weighed, crushed,

PAGE 115

115 and analyzed separately Urea N, NH 4 + N, and NO 3 N were extracted from a 4.5 g wet soil sample and CRF prills collected from th e soil sample using 40 mL of 2 M KCl 1 phenyl mercuric acetate (Mulvaney and Bremner, 1979; Sato and Morgan, 2008). Soil and CRF prill extracts were measured for NH 4 + N and NO 3 N by salicylate hypochlorite, cadmium reduction using a Flow Analyzer (QuikChem 8500, Lachat Co., Loveland, CO) at 660 nm and 520 nm, respectively. Urea N in the extracts was measured by modified diacetyl monoxime methods using a DR/4000U Spectrophotometer (Hach Co., Loveland, CO) at 527 nm (Sato and Morgan, 2008; Sato et al., 2009) Yield data LTN C post season soil N contents, and postharvest firmness and color were analyzed using analysis of variance and means were separated using Dunca n level (SAS version 9.3, SAS Institute Inc, Cary, NC, 2011). L inear contrast wa s used to compare the yield post season soil N contents, and postharvest was derived for soil and air temperatures. Results and Discussion Weather C onditions Overall, air temperatures during the 2011 and 2012 seasons were similar compared to the previous 10 year average fall temperature (August through December ) [Florida Automated Weather Network (FAWN), 2013)]. T he minimum, average, and maximum air temperatures during the growing season (planting to third harvest) were 6.4 23.0, and 3 7.4 C in 2011 and 5.5 22.6, and 3 4.2 C in 2012 (Table 4 2) However, the cumulative fall rainfall was 2.5 cm lower and 10.2 cm higher than the 10 year fall

PAGE 116

116 season, moving average during 2011 and 2012, respectively, (FAWN, 2013). Total r ainfall was 33.4 cm during the 2011 growing season with one leaching rain event (7.6 cm of rainfall in 3 d ) on 28 Oct. 2011 1 SNF wa s added to the UF/IFAS treatment following UF/IFAS recommendations (Liu et al., 2012). During 2012, the total r ainfall was 37.4 cm ; however, there were no leaching rain events. Since the manufacturer of t he CRF used in this study determined nutrient release at a constant 25 C, air and soil temperatures differing from 25 C will slow or accelerate nutrient release from CRFs (Engelsjord et al., 1996; Huett and Gogel, 2000). Thus, average weekly air temperatures greater than 25 C from planting to 11 Oct. (2011) and 25 Oct. (2012) may have accelerated nutrient release from the CRFs due to increased soil temperature. Soil T em peratures The mean season minimum, average, and maximum soil temperatures at 10 cm below the bed surface were 21.6, 26.2, and 33.2 C during 2011 and 20.3, 24.7, and 31.1 C during 2012; thus, soil temperatures averaged 1.5 C higher in 2011 compared with 2012 (Table 4 3) When combining soil and air temperature data among 2011 and 2012, soil and air temperature were strongly correlated ( r = 0.95; P =0.0001). As such air temperature can be a strong indicator of soil temperature. Thus, with higher air tem peratures, the rate of release for CRF will increase over what was expected at 25 C. Although no correlation coefficient was developed, Diaz Perez and Batal (2002) found that the soil temperature under black, grey, and silver polyethylene mulch closely fo llowed the air temperature pattern. Similarly, Zheng et al. (1993) reported that air temperature and soil temperature were highly correlated ( r =0.85 to 0.96) in bare soil and sod and that air temperature may be used as a soil temperature prediction tool.

PAGE 117

117 During Fall 2011, bed temperatures, which peaked at 40.6 C and with average daily soil temperatures between 19.7 and 30.3 C, shortened CRF N release duration under nutrient release (Carson et al., 2013) Therefore, a season specific CRF N release duration match ing tomato crop s temporal N uptake will be required for fall winter, and spring seasons due to season temperature differences Water T able D epth Water table depths fluctuated between 0.43 and 0.63 m, and 0.39 and 0.55 m below the bed surface during the 2011 and 2012 seasons, respectively ( Figure 4 1) Water table depths were similar to those reported by Ozores Hampton Simonne, et al. (2012) for s eepage irrigated tomato in Immokalee, FL. Plant N utritional S tatus There were interactions between year and treatment at several sample dates ( P LTN C data were presented by year ( Figure 4 2 A and B). In 2011, CRF168/SNF56 had the great est while CRF112/SNF56 a nd CRF224/SNF56 had the lowest LTN C at 16 d after transplant ( DAT ) ( Figure 4 2 A) A t 78 and 107 DAT t he grower standard treatment had the greatest LTNC while all other treatments were lower and similar. There were no statistical differences in LTN C from 36 to 64 and at 93 DAT. In 2012, at 95 DAT, CRF112/SNF56 had the lowest LTNC and at 67 and 109 DAT, CRF112/SNF56 and CRF168/SNF56 had the lowest LTNC ( Figure 4 2 B) The g rower standard and CRF224/SNF56 treatments were similar with the highest LTN Cs at 67 DAT, but UF/ IFAS was similar to the grower standard and CRF224/SNF56 at 95 DAT, and UF/ IFAS and CRF168/SNF56 were similar to grower standard and CRF224/SNF56 at 109 DAT. T here were no statistical differences in LT N C from 22 to 52 and at 82

PAGE 118

118 DAT. During both years, all LTN Cs (except at 109 DAT in 2012) were higher than the upper sufficiency range. Monitoring of LTN C allows growers to predict yield potential and to diagnose nutrient deficiencies before they might bec ome visible on the plant, which allows for efficient fertilizer management (Hochmuth et al., 20 1 2 ). A ccording to UF/IFAS recommended LTN C guidelines, N was not a limiting factor for any N treatment during 2011 and 2012 since all but one sample were higher than the upper sufficiency range for LTN C ( Figure 4 2 ). The yearly difference in LTN C may be due to the increased rainfall in Sept 2012 compared with 2011 This increased rainfall in the early season may have resulted in nutrient leaching caused by wat er table fluctuations (Sato et al., 2009) Yield R esponses to CRF N R ates There were interactions between year and N treatment; therefore, yield data were presented by year [( P Table 4 4 ]. In 2011, t here were differences ( P among treatments in medium fruit and total marketable tomato (all marketable sizes combined) yield for the first and second harvest combined (FS HC ) season medium fruit, season total marketable tomato yield (all sizes and three harvests combined), and total culls ( all three harvests combined). The UF/ IFAS, CRF1 12 /SNF5 6 and CRF1 68 /SNF5 6 treatments had the highest, while the grower standard treatment had the lowest medium tomato yield for FSHC For FSHC total marketable yield, CRF1 12 /SNF5 6 and CRF1 68 /SNF5 6 had the highest tomato yields, although CRF1 68 /SNF5 6 was not statistically different from CRF2 24 /SNF5 6 or UF/ IFAS Both CRF224/SNF56 and UF/IFAS were not different from the grower standard treatment which had the lowest FSHC total marketable yield The UF/ IFAS treatment had a

PAGE 119

119 greater season medium tomato yield than all other treatments. For season total harvest, all CRF and UF/ IFAS treatments were greater than the grower standard treatment. The gro wer standard CRF1 12 /SNF5 6 and CRF1 68 /SNF5 6 treatments had fewer cull fruit than the UF/ IFAS and CRF2 24 /SNF5 6 treatments. There were no differences for any tomato size or total marketable yield category in the first harvest (FH) or extra large and larg e size categories in the FSHC, and in season total marketable harvests. When linear contrasts were performed among CRF treatments, there wa s no response to N rate [Table 4 4 ( P Thus, yield of the CRF treatments did not increase with increasing rate. In 2012, there were differences in FH extra large and total marketable yield (all size combined) and FSHC extra large yield ( P ) ( Table 4 4 ) The CRF112/SNF56 and CRF168/SNF56 treatments had greater FH and FSHC extra large marketable tomato yields compared with grower standard UF/ IFAS, and CRF224/SNF56 treatments The highest total FH marketable yields were obtained by CRF168/SNF56 and CRF1 12/SNF56 ; however CRF112/SNF56 did not significantly differ from CRF224/SNF56. No differences were found among other sizes and total season marketable and unmarketable (cull) yield A linear response among CRF rate s was significant for large sized fruits in the FSHC, large sized fruits for total season, and total season marketable yields indicating an increase in tomato yield with an increase in CRF N rate. There was no response to CRF N rates among other sizes and harvests. Overall, CRF112 /SNF56 produced similar or higher marketable tomato yields at lower rates compared to both SF and CRF/SNF treatments.

PAGE 120

120 Total marketable yields averaged 28.6% higher in 2012 than 2011 likely due to no leaching rain events during the 2012 season and only a single event during Fall 2011. In spite of high rainfall during 2012, CRF112/SNF56 1 N) and CRF168/SNF56 1 N) produced greater early season extra large and total marketable yields with similar total season marketable yields compared w ith the grower 1 N). Therefore, increasing the N 1 1 Additionally, the fertilizer rate of 280 1 N may have depressed yields as rep orted by Hochmuth and Cordasco (2008). Furthermore, Ozores Hampton Simonne, et al. (2012) showed reduced early season tomato yields at SNF rates of 269 and 336 1 during dry and wet seasons, respectively, which further supports the argument that app 1 may reduce yields. Since all N fertilizer treatments were within or greater than the LTN C sufficiency range throughout the season, N rate was not a limiting factor in production during Fall 2011 and 2012, which may further supp ort CRF112/SNF56 as an acceptable tomato production N rate for this system. However, in 2012, increasing CRF N rates produced higher season total marketable yields indicating that CRF168/SNF56 will be an appropriate N rate. Similarly to 2011, Ozores Ham pton et al. (2009) found no differences in first harvest marketable tomato yield when using the hybrid fertilizer system during a spring season with low rainfall. In contrast, in 2012 with high rainfall, the hybrid fertilizer system treatment CRF224/SNF56 reduced FH extra large and FH total yields which may have been due to increased plant biomass at the expense of crop yield. F or tomatoes produced during the fall season, the earliest fruit harvested tend to provide the

PAGE 121

121 greatest return to the grower (Ozo res Hampton Simonne, et al., 2012). Thus, CRF224/SNF56 is an inappropriate N rate since it lowered early fruit yield. Post S eason S oil S amples There were interactions ( P soil sample data were presented by year and treatment. In 2011, CRF224/SNF56 had a greater NH 4 + N and urea N content remaining in the soil post season compared to the other treatments (Table 4 5 ). The g rower standard, UF/IFAS, and CRF224/SNF56 had the highest NO 3 N content re maining in the soil post season, but CRF224/SNF56 did not significantly differ from CRF112/SNF56 and CRF168/SNF56. There were no differences in NH4 + N, NO 3 N, or urea N content in the fertilizer prills among treatments ha 1 respectively, which indicated that the CRF prills released nearly all the N during the season. There were no differences in total N (TN) 1 among the treatments ; thus, N was likely lost to leaching from the sandy soils with a low CEC The linear contrasts were significant among the CRF N treatments, for NH 4 + N and urea N in the soil, and for TN post season. Therefore, increasing CRF N rates increased NH4 + N, urea N, and TN remaining in t he soil post season samples The CRFs released between 96.4% and 98.7% of their N during the season. In 2012, soil urea N contents from CRF224/SNF56 and CRF168/SNF56 were higher than that of the other treatments (Table 4 5 ). There were no differences a mong treatments in any other N category. Linear contrasts among CRF N treatments were significant for urea N in soil and CRF prills indicating increasing CRF N rates will

PAGE 122

122 increase the amount of urea N remaining post season because of increased urea in the prills The CRFs released between 86.8% and 90.4% of the N during the season. Overall, there was more N remaining in the CRF treatments in 2012 as compared with 2011; though, greater N remained in the soluble treatments in 2011 as compared with 2012. Late season rainfall (64 % in Oct. 2012 vs. 59% in Sept. 2011) and a leaching rain event on 28 Oct. 2011, may explain the lower post season N content in Fall 2011. Higher rainfall would have increased water table depth and caused greater leaching due to d rainage water movement from the field via irrigation ditches. Sato et al. (2009) documented movement of soluble NO 3 with the dropping of water table depth. Potential N losses of 35% to 43% were found for tomato grown with seepage irrigation under similar soil, temperature, and rainfall conditions (Sato et al., 2012). Since, the 1 N after the leaching event to compensate for the loss of N, this additional N may have resulted in higher concentrations of N in the soil. The post season TN remaining in the soil was similar or lower than the values reported by Hendricks and Shukla (2011) and Sato et al. (2012) for seepage irrigated tomatoes with similar rainfall and planting season. There was a similar amount o f time between fertilizer placement and soil sampling dates, but average soil temperature during 2012 was 1.5 C lower compared to that of 2011. Thus, the reduced season average soil temperature may explain the difference in CRF N release between the seasons. In a study by Simonne and Hutchinson (2005), CRFs did not release greater than 80% of the N during the season; thus, they determined that the CRFs were not suitable for use in chip stock potato. In this study, however, all CRFs released greater

PAGE 123

123 than 80% of the N during the season; therefore, using this metric, these CRFs are suitable for use in tomato. The release differences between this study and Simonne and Hutchinson (2005) were likely due to temperature differences between fall and spring seasons. Postharvest Q uality There were interactions between year and N treatment for firmness ( P = 0.002) and color ( P < 0.0001) at the red ripe stage; thus, firmness and color data were presented by year (Table 4 6 ). In 2011, the firmest fruit (i.e., fr uits with the least deformation) were from the grower standard, UF/IFAS, and CRF112/SNF56 treatments, whereas the softest fruit were from CRF224/SNF56. However, no differences were found between UF/IFAS and CRF168/SNF56 treatments. In 2012, there was no N treatment effect on fruit firmness that averaged medium to soft (2.2 mm deformation). When linear contrasts were performed among CRF N treatments there was no response to N rate in 2011 or 2012 [Table 4 6 ( P > 0.05)]. The tomato firmness differences du e to N treatment in 2011 indicated softer fruit with higher CRF N rate; however, this difference was not evident in fall 2012. Similar to 2012, no differences were found in tomato firmness during a spring study using six CRF treatments containing resin co ated urea and KNO 3 methylene urea, and PSCU at two rates (Csizinszky, 1994). In 2011, CRF224/SNF56 and CRF112/SNF56 treatments had the highest while CRF168/SNF56 and grower standard treatments had the lowest color ratings (Table 4 6 ). In 2012, there wer e no differences in color ratings with an average of 5.9 across the treatments; however, there was a significant linear contrast effect among CRF

PAGE 124

124 treatments (P = 0.002), which indicated that color intensity increased with CRF N rate in 2012. Although toma to external color increased with increased CRF N rate in 2012, the UF/IFAS and grower standard treatments did not statistically differ from the CRF treatments. Benard et al. (2009) and Warner et al. (2004) found that tomato color was not affected by N ra te. Thus, the differences in tomato firmness and color were not related to N source or rate, but rather due to differences in tomato maturity, which is difficult to determine through non destructive methods and the reason for different research methods du ring 2011 and 2012 (Maul, 1999) Therefore, the differences noted were not of practical commercial significance, but due to variations found in mature green harvested fruit. In conclusion, the bed temperatures encount ered during both seasons were higher than those recommended by the CRF manufacturer potentially shorten ing the N release duration during the season However, there were no detrimental effects on yield or LTN C due to the possibility of accelerated N rele ase. The hybrid fertility system containing CRF/SNF produce d similar or greater marketable tomato yields with the potential for lower residual soil N post season with CRF112 /SNF5 6 1 ) or 1 ) compared to grower standard rate (280 1 N), CRF224/56SNF (280 1 N), or UF/IFAS (224 1 N), which is a 46% and 25% reduced N rate, respectively. All treatments produced acceptable fruit firmness and color at red ripe stage. The recommended N rate using a h ybrid fertilizer system 1 CRF 1 SNF produced acceptable tomato yield and quality with minimum post season soil N, minimizing the potential losses of N to the environment.

PAGE 125

125 Ta ble 4 1. Nutrient rates and bed placement used in testing controlled release fertilizer (CRF) fall mixes in Immokalee, FL during Fall 2011 and Fall 2012. Treatment Bottom mix z Top mix Total y N P K N K N K SF CRF SF SF CRF SF CRF SF CRF SF CRF T SF CRF T ------------------------------------------------------------( 1 ) --------------------------------------------------------------Grower 24 11 49 37 0 245 0 363 0 269 11 280 400 0 400 UF/ IFAS x 24 11 49 37 0 189 0 363 0 213 11 224 400 0 400 CRF 112 /SNF5 6 0 112 53 33 124 56 0 243 0 56 112 168 276 124 400 CRF168 /SNF5 6 0 168 53 33 124 56 0 243 0 56 168 224 276 124 400 CRF2 24 /SNF5 6 0 224 53 33 124 56 0 243 0 56 224 280 276 124 400 z N=nitrogen, P=phosphorus, K=potassium, SF=soluble fertilizer, and T=total y Bottom mix P is the total P applied x In 2011, the UF/ 1 N after a leaching rain event making the total N applied 1 No additional N was added during 2012.

PAGE 126

126 Table 4 2 Summary of minimum (Min.), average (Avg.), and maximum (Max.) air temperature and total rainfall in Immokalee, FL during F all 2011 and 2012 growing seasons Period Min. z Avg. Max. Total rainfall 2011 2012 2011 2012 2011 2012 2011 y 2012 --------------------(C ) ------------------------(cm) ----Aug ust 23.2 25.4 31.0 0.2 Sep tember 18.4 20.9 26.8 26. 3 37.4 34.2 10.2 22.1 Oct ober 10.2 9.1 23.0 24.3 33.5 34.2 21.3 9. 3 Nov ember 8.6 5.5 20.7 18.5 33.7 28.9 0.3 0.3 Dec ember 6.4 12.5 19.3 21.2 29.2 30.2 1. 4 5.9 Average/Total 13.4 12.0 23. 0 22 .6 3 3.0 3 1.9 33.4 37.4 z Temperature averages and rainfall totals from 29 Aug. to 15 Dec. 2011 and 3 Sept. to 15 Dec. 2012. y A leaching rain even occurred on 28 Oct. 2011.

PAGE 127

127 Table 4 3 Summary of minimum (Min.), average (Avg.), and maximum (Max.) soil temperature at 10 cm below the bed surface in Immokalee, FL during F all 2011 and 2012 growing seasons Period z Min. Avg. Max. 2011 2012 2011 2012 2011 2012 ------------------(C) -----------------9 Aug. 25.7 y 30.1 40.1 16 Aug. 25.2 30.4 39.6 23 Aug. 25.2 25.1 30.3 30.4 39.6 36.6 30 Aug. 25.2 24.6 29.7 28.6 37.6 36.1 6 Sept. 24.7 24.6 28.8 29.4 36.7 36.1 13 Sept. 25.2 24.1 31.2 29.0 39.6 36.6 20 Sept. 25.7 24.6 30.7 28.6 38.6 35.6 27 Sept. 24.2 24.1 28.7 27.5 36.7 34.6 4 Oct. 22.7 24.6 28.9 28.3 36.7 36.1 11 Oct. 22.2 24.1 26.7 28.4 33.7 35.1 18 Oct. 23.7 22.1 26.2 26.6 33.7 33.6 25 Oct. 18.2 21.6 23.3 25.9 29.7 33.6 1 Nov. 20.2 16.6 24.2 22.0 28.7 29.6 8 Nov. 17.7 16.6 22.5 21.3 28.2 27.1 15 Nov. 16.7 14.6 21.8 20.4 27.2 26.6 22 Nov. 21.2 15.1 24.4 19.7 29.7 25.1 29 Nov. 19.2 13.6 22.7 17.9 28.2 22.1 6 Dec. 15.2 16.6 20.2 19.9 25.7 23.1 13 Dec. 17.7 13.6 21.6 19.9 26.7 25.6 20 Dec. 16.2 18.1 21.0 21.2 26.2 25.1 Average/Total 21.6 20.3 26.2 24.7 33.2 31.1 z Temperatures are the average for the week ending on the listed date. y Data collection began on 17 Aug. 2012.

PAGE 128

128 Table 4 4 Fruit yie ld (Mg 1 ) by size categories for first harvest, first and second harvest combined, and season total harvest (three harvests combined) for five controlled release fertilizer (CRF)/soluble nitrogen fertilizer (SNF) programs used to grow tomato in Immokalee, FL during F al l 2011 and Fall 2012 growing seasons Treatments First harvest First and second harvests Season total harvest 1 ) Xlg z Lrg Med Total Xlg Lrg Med Total Xlg Lrg Med Total Cull -------------------------------------------------------------------2011 ---------------------------------------------------------------------Grower standard 9.3 1.7 0.6 11.6 20.2 11.7 9.2c y 41.1c 21.6 15.0 14.6b 51.2b 9.8b UF/IFAS x 10.3 1.8 0.4 12.4 16.6 13.2 13.1a 42.8bc 17.6 16.4 24.7a 58.6a 15.3a CRF112/SNF56 11.2 1.9 0.6 13.6 20.6 15.5 12.0ab 48.1a 22.7 18.9 19.3b 60.9a 10.5b CRF168 /SNF56 7.9 2.3 0.5 10.7 17.6 15.6 11.8ab 45.1ab 19.3 19.5 18.6b 57.4a 11.9b CRF224 /SNF56 8.6 2.2 0.6 11.4 18.4 15.1 11.0b 44.5bc 19.6 18.9 18.9b 57.4a 15.4a P value 0.07 0.79 0.70 0.18 0.21 0.15 0.002 0.006 0.11 0.12 0.001 0.02 0.0002 Significance w NS NS NS NS NS NS ** ** NS NS *** *** Contrast linear (CRF only) 0.58 0.82 0.55 0.63 0.65 0.74 0.40 0.73 0.85 0.71 0.88 0.99 0.12 Significance NS NS NS NS NS NS NS NS NS NS NS NS NS ----------------------------------------------------------------2012 ----------------------------------------------------------------Grower standard 17.1b 2.6 v 19.6cd 25.0b 16.3 5.9 47.2 29.6 28.5 14.8 72.9 7.1 UF/IFAS 13.9b 1.6 15.4d 25.1b 17.0 5.8 47.9 28.5 29.6 14.5 72.5 5.9 CRF112/SNF56 22.0a 2.8 24.8ab 30.1a 14.2 6.1 50.5 31.7 23.9 13.2 68.9 8.2 CRF168/SNF56 22.6a 3.9 26.5a 31.2a 16.3 5.6 53.1 35.3 27.5 12.5 75.3 6.1 CRF224/SNF56 17.6b 3.3 20.8bc 28.1ab 19.0 4.6 51.7 32.4 31.1 12.6 76.1 7.6 P value 0.004 0.06 0.008 0.02 0.09 0.20 0.11 0.06 0.24 0.08 0.30 0.22 Significance ** NS ** NS NS NS NS NS NS NS NS Contrast linear (CRF only) 0.11 0.48 0.20 0.32 0.007 0.08 0.57 0.77 0.04 0.62 0.05 0.63 Significance NS NS NS NS ** NS NS NS NS NS z Xlg= extra large (> 7.00 cm) Lrg=large (6.35 to 7.06 cm) Med=medium (5.72 to 6.43 cm) y Within 5% level. x Total N rate includes 1 N in the top mix and 3 4 1 fertilizer applied following a leaching rain event on 28 Oct. 2011. w NS ,*,**Non significant or significance at 0.05, 0.01, or 0.0 0 1respectively. u No medium size tomatoes were harvested during the first harvest of 2012.

PAGE 129

129 Table 4 5 Total post season soil test nitrogen (N) in 1 as ammonium N ( NH 4 + N ), nitrate N ( NO 3 N ), and urea N in the soil and controlled release fertilizer (CRF) prills from five CRF/soluble nitrogen fertilizer (SNF) programs used to grow tomato in Immokalee, FL during Fall 2011 and Fall 2012 Treatment Soil z CRF prills 1 ) NH 4 + N NO 3 N Urea N NH 4 + N NO 3 N Urea N Total N N release (%) y --------------------------------------------2011 ---------------------------------------------Grower standard 4.8b x 14.3a 0.0b w 19.0 UF/IFAS 2.6b 15.9a 0.1b 18.6 CRF112/SNF56 4.8b 2.7b 0.9b 1.5 2.1 0.4 12.4 96.4 CRF168 /SNF56 4.7b 1.9b 0.4b 1.2 2.0 0.2 10.5 97.8 CRF224 /SNF56 8.5a 8.9ab 2.6a 1.3 1.4 0.2 22.9 98.7 P value 0.006 0.016 0.004 0.78 0.52 0.64 0.12 Significance v ** ** ** NS NS NS NS Contrast linear (CRF only) 0.040 0.10 0.047 0.59 0.31 0.49 0.039 Significance NS NS NS NS --------------------------------------------2012 --------------------------------------------Grower standard 7.5 10.4 0.0b 17.9 UF/IFAS 6.2 3.6 0.0b 9.8 CRF112/SNF56 6.7 3.0 0.0b 1.7 10.1 0.0 21.5 89.5 CRF168 /SNF56 5.2 3.3 0.1a 2.3 13.8 0.0 24.7 90.4 CRF224 /SNF56 4.3 6.4 0.1a 3.0 26.5 0.1 40.4 86.8 P value 0.09 0.20 0.01 0.71 0.32 0.06 0.07 Significance NS NS NS NS NS NS Contrast linear (CRF only) 0.13 0.29 0.037 0.43 0.16 0.027 0.20 Significance NS NS NS NS NS z An 8.9 cm wide 20 cm deep cross section of the tomato bed was taken from each treatment in all four replications. The cross section was divided into three vertical sections, mixed and sampled. Each number is the mean of 12 measurements. y N release = (tot al CRF N applied N remaining in CRF prills)/total CRF N applied. x 5% level. w No CRF were used in the grower standard and University of Florida, Institute of Food and Agriculture Science (UF/IFAS) treatments, thus analysis of variance was carried out on only CRF treatments for these columns. v NS ,*,** = Non significant or significance at 0.05 or 0.01, respectively

PAGE 130

130 Table 4 6 Postharvest firmness and color at red ripe stage for tomato grown using five cont rolled release fertilizer (CRF)/ soluble nitrogen fertilizer (SNF) programs in Immokalee, FL during F all 2011 and Fall 2012 Treatment 1 ) Firmness z Color stag e y 2011 2012 2011 2012 Grower standard 2. 6 c x 2.1 5.0c 5.9 UF/ IFAS w 3.0 bc 2. 2 5.5b 5.9 CRF 112 /SNF5 6 2.6c 2.1 6.0a 5.8 CRF168 /SNF5 6 3.2 ab 2. 2 5.0c 5.8 CRF2 24 /SNF5 6 3.4 a 2. 2 6.0a 6. 0 P value 0.0002 0.89 0.0001 0. 28 Significance v *** NS *** NS Contrast l inear (CRF only) 0. 17 0.85 0.90 0.0 2 2 Significance NS NS NS z Deformation in mm: Very y Color rating on a scale of 1 to 6, with 1=mature green (unripe), 2= breaker, 3=turning 4= pink, 5=light red, 6=red. x Within columns, means followed by different letters are significantly different according w University of Florida, Institute of Food and Agriculture Science (UF/IFAS). v NS ,*,** ***= Non significant or significance at 0.05 0.01, or 0. 0 01 respectively.

PAGE 131

131 Figure 4 1. Water table le vels for tomato grown with seepage irrigation in Immokalee, FL during F all 2011 and 2012

PAGE 132

132 Figure 4 2 Leaf tissue nitrogen (N) concentration for tomatoes grown with five cont rolled release fertilizer (CRF)/ soluble nitrogen fertilizer (SNF) programs in Immokalee, FL during F all 2011 ( A ) and Fall 2012 ( B ). NS ,*,** ***= Non significant or significance at 0.05 0.01, or 0. 0 01 respectively.

PAGE 133

133 CHAPTER 5 EFFECT OF CONTROLLED RELEASE FER TILIZER NITROGEN RATE, PLACE MENT, SOURCE, AND RELEASE DURATION ON TOMATO GROWN WITH SEEPAGE IRRIGAT ION IN FLORIDA SANDY SOILS Introduction Fresh market tomato comprised 16% of the harvested vegetable area and 23% of Florida vegetable production with 11,700 ha harvested and a market value of $268 million in 2012 [U.S. Department of Agriculture (USDA), 2013]. The Federal Clean Water Act of 1972 and the Florida Restoration Act of 1999 codified the m aintenance and improvement of water quality for human consump tion, wildlife habitat, crop irrigation, etc. (Bartnick et al., 2005) To improve polluted water bodies, the Florida Department of Agriculture and Consumer Services adopted a series of best management practices (B MPs), which includes the use of controlled release fertilizer (CRF) (Bartnick et al., 2005). Controlled release fertilizers are soluble fertilizers (SFs) occluded in a polymer, resin, sulfur, or a polymer covering a sulfur coated urea (SCU) that protect n utrients against leaching from the root zone to become an environmental pollutant (Slater, 2010; Trenkel, 2010). Approximately 40% of the Florida fresh market tomato industry uses seepage irrigation due to low operating costs and straightforward use comp ared to drip irrigation (E.J. McAvoy, personal communication; Zotarelli et al., 2013). In seepage irrigation, ground or surface water pumped into a series of canals creates a water table perched on a slowly permeable layer (agrillic or textural). Growers maintain the top of the water table at 0.4 to 0.6 m below the bed surface to irrigate the crop by capillarity (Smajstrla and Muoz Carpena, 2011). Oscillation in the water table causes nutrient leaching,

PAGE 134

134 primarily nitrate nitrogen (NO 3 N) and potassium (K); thus, a stable water table must be sustained (Sato et al., 2009). Producers of seepage irrigated tomato use raised beds covered with polyethylene mulch and the gradient fertilizer system, in which fertilizers are applied in a in bed shoulders after bed formation (Geraldson, 1980 ; Liu et al., 2012) The University of Florida/Institute of Food and Agricultural Science (UF/IFAS) r ecommends placement of 100% of the P and micronutrients, and 10% to 20% of the N and K in the bottom mix. The remaining 80% to 90% of the N and K should be placed in the top mix The UF/IFAS recommended fertilizer ra 1 N, and P and K fertilization based on calibrated soil test results (Olson et al., 2012 a ). Additional N fertilizer applications are recommended in the event of leaching rainfall, defined as 76 mm of rainfall in 3 d or 102 mm of rainfall in 7 d, extended harvest season, or low leaf tissue N concentration (LTN C ) or petiole sap NO 3 N concentration (Olson et al., 2012 a ) When methylene urea and CRFs [resin coated urea and KNO 3 polymer coated urea (PCU), and polymer coated SCU (PSCU)] were placed as the only N source in a top mix or bottom mix in plasticulture tomato production, similar or lower total marketable tomato yields were found compared to SFs at a similar N rate (Csizinszky, 1994; Ozores Hampton et al., 2009) The reduced yields were due to low soil NO 3 N concentrations and environmental conditions. To increase soi l NO 3 N content, Ozores Hampton et al. (2009) placed PCU and SF N (80% CRF:20% SF N ratio) as a bottom 1 N, which resulted in similar tomato yields compared to the UF/IFAS

PAGE 135

135 SF recommendation during a winter production season. However, high plant mortality and reduced plant biomass was associated with high NH 4 + N soil concentration from the PCU (Ozores Hampton et al., 2009). To overcome the NH 4 + F placed in the bottom mix with the remaining N as SF placed in the top mix. Use of this system resulted in similar marketable tomato yields when CRF (KNO 3 or urea and NH 4 NO 3 ) was applied at equal or 25% reduced N rates compared to SF (Ozores Hampton et al ., 2009). Soil fumigation and staggered plantings extend the time CRFs are in the ground releasing nutrients before planting. For instance, a soil fumigant application requires a 2 to 3 week period between bed formation (and fumigation) and planting, an d staggered plantings allowing for continual harvest that may increase the production season by 3 weeks (Noling et al., 2012). Therefore, the extended production season must be considered in selection of CRF release duration (Carson and Ozores Hampton, 20 nutrient release determining temperature will shorten or increase the release duration (Carson and Ozores Hampton, 2013). For instance, Carson et al. (2013) found that the releas e duration of 90 120 and 180 d release CRFs was shortened by 46% to 69% due to high soil temperatures that averaged 25.1 C in white polyethylene mulch covered raised beds during a fall season. Thus, the objective of this research was to evaluate the effects of CRF N rate, source, release duration, and bed placement on marketable tomato yield, LTN C post season soil N content, and postharvest fruit firmness and color.

PAGE 136

136 Material and Methods A CRF study was conducted during Fall 2011 and Fall 2012 on a co mmercial tomato farm near Immokalee, FL (lat. 26 14' 5" N long. 81 28' 55" W) on Basinger fine sand (hyperthermic Spodic Psammaquents) using seepage irrigation (Natural Resources Conservation Service, 2012). Each trial was arranged in a randomized comp lete block design with four replications and placed between a set of irrigation ditches spaced 15 m apart, which contained three beds, a drive road, and another three beds. On 6 Sept. 2011 and 3 Sept. 2012, tomato cultivar BHN726 was planted 51 cm apart o n raised beds that measured 76 cm wide and 20 cm high, with 1.8 m between row centers. Pest and disease control followed UF/IFAS recommendations (Olson et al., 2012 a ). On 15 Aug. 2011 and 17 Aug. 2012, beds were fertilized, formed, fumigated with methyl 1 (ICL IP, South Charleston, WV.), and covered with white virtually impermeable film (0.038 mm; Berry Plastic, Evansville, IN.). Two SF treatments and six and seven CRF treatments were used, in Fall 2011 and Fal l 2012, respectively (Table 5 1). Three treatments were replicated over years 1 K in 2011 compared to 2012 (Table 5 1). Ozores Hampton, Snodgrass, et al. (2012) obtained maximum yield between 33 1 K as calculated using a quadratic plateau model; thus, 1 K in 2011 and 2012, respectively, the additional K supplied as K 2 SO 4 should not affect yields. The fertil izer gradient system was used in T1 and T2 at 224 an 1 SF N, respectively. The CRFs were placed in the bottom mix as the only N source for T3 to T8 and T3 to T5 in 2011 and 2012, respectively. In 2012, fertilizer placement for T6 to T8 used the hybrid fertilizer system, and all N was applied

PAGE 137

137 in the bottom mix for T9 [75% CRF: 25% SF as Ca(NO 3 ) 2 and KNO 3 ]. In both years, soluble P was applied as triple super phosphate in the bottom mix. Soluble K was supplied as potassium magnesium sulfate except in T9 of 2012, where K and Mg were supplied from KNO 3 and MgSO 4 in the bottom mix. Potassium or N fertilizer in the top mix was applied as soluble K 2 SO 4 or NH 4 NO 3 Soil temperature data were collected every 30 min at 10 cm below the bed surface using a Watchdog data logger (model B100; Spectrum Techn ologies Inc., Plainfield IL.). The water table depth was recorded 7 (2011) and 15 (2012) times from monitoring wells in each replicate as described by Smajstrla and Muoz Carpena (2011). Plant mortality data were collected as number of dead plants from each row of the three bed plot on 7 Oct. 2011. Beginning at first flower appearance (26 Sept. 2011 and 24 Sept. 2012), six most recently matured whole leaves were collected in each plot at 15 d intervals for seven collection dates. The leaves were placed in an oven at 50 C until dry and milled to pas s through a 60 mesh sieve. LTNC was measured by combustion using a NA2500 C/N Analyzer (Thermo Quest CE Instruments, Waltham, MA). Treatments were applied to plots that were 9.1 m long and three beds wide. Fruit yield data were collected from 5.1 m or 10 plants in the center bed of the plot. Fruits ranging from marketable mature green to ripe were harvested three times (23 Nov., 7 Dec., and 21 Dec. 2011, and 11 Nov., 7 Dec., and 21 Dec. 2012) and graded in to size categories extra large (> 7.00 cm), large (6.35 to 7.06 cm), medium (5.72 to 6.43 cm) and unmarketable fruit according to USDA grade standards (USDA, 199 7 ),

PAGE 138

138 and weighed. In 2011, yield data were corrected for plant mortality by dividing plot yield by the number of producing plants in the plot then multiplying by the number of plants per acre. In 2011, a subsample of 10 mature green fruit was collected from each plot at FH, washed with chlorinated water (150 ppm), dried at room temperature, transp orted to a commercial packing facility in Immokalee, FL, and ripened with 150 ppm ethylene at 20 C and 85% to 90% relative humidity to simulate commercial handling (Sargent et al., 2005). After 13 d, the tomatoes were at red ripe stage and were transporte d to the UF/IFAS Southwest Florida Research and Education Center (SWFREC) Vegetable Horticulture Laboratory (VegLab) in Immokalee, FL, where fruit firmness was measured as fruit deformation after 5 s using a deformation meter equipped with a 1 kg weight an d 16 mm probe (Model C125EB; Mitutoyo Corp., Aurora, IL); fruit were rated for external color using the official USDA grade standards, a 1 to 6 scale (1=green; 6=red) (USDA, 199 7 ). In 2012, to reduce variability due to maturity differences, the subsample s ize was increased to 20 mature green fruit, which were collected and ripened as described for 2011. However, the tomato fruit were removed from the ripening room at the first sign of breaker stage (3 d) and transported to the UF/IFAS SWFREC VegLab. Ten f ruit from each plot, at breaker stage of development, were selected and ripened at room temperature until red ripe, which occurred at 10 d after harvest. Fruit firmness and color were measured and rated as described for 2011. On 22 Dec. 2011 and 2 Jan. 20 13, post season soil samples were collected using a soil slicer as described by Mu oz Arboleda et al. (2006). A 9 cm slice of soil was taken perpendicular to the bed at the center of each plot. The slice of soil was

PAGE 139

139 divided into three vertical sections, which were homogenized and subsampled. The subsamples were stored below 4 C until analysis. Before analysis, the soil samples were sieved, and the CRF prills were collected, weighed, crushed, and extracted separately. Urea N, NH 4 + N, and NO 3 N were ex tracted from a 4.5 g wet soil sample and from CRF prills collected from each soil sample using 40 mL of 2 M KCl containing 1 phenyl mercuric acetate (Mulvaney and Bremner, 1979; Sato and Morgan, 2008). A flow analyzer (QuikChem 8500, Lachat Co ., Loveland, CO) using the salicylate hypochlorite, cadmium reduction method measured NH 4 + N and NO 3 N concentrations in soil and fertilizer extracts at 660 nm and 520 nm, respectively. Urea N concentrations in the extracts were measured by the modified d iacetyl monoxime method using a DR/4000U Spectrophotometer (Hach Co., Loveland, CO) at 527 nm (Sato and Morgan, 2008; Sato et al., 2009). Since the treatment make up was different in each year, data for yield, LTNCs plant mortality, post season soil N c ontents, and postharvest measurements were analyzed separately by year using analysis of variance (SAS version 9.3, SAS Institute Inc, Cary, NC, 2011). Plant mortality data were normalized using the arcsin transformation before analysis of variance. Sing le degree of freedom orthogonal contrasts were used to compare treatments means for yield, post season soil N compare LTN Cs Results and Discussion Weather C onditions Overall, weather during the 2011 and 2012 seasons was similar, 0.2 C higher and 0.3 C lower, respectively, compared to the previous 10 year average fall

PAGE 140

140 temperature (September through December) [Florida Automated Weather Network (FAWN), 2013]. Air tempe ratures from transplant to third harvest were similar between seasons, with a minimum, mean, and maximum of 9.3 and 9.4 C, 22.4 and 22.1C, and 33.4 and 33.3 C for 2011 and 2012, respectively (Table 5 2) (FAWN, 2013). The cumulative season rainfall was 3.8 (2011) and 9.3 cm (2012) higher than the previous 10 year average (FAWN, 2013). Total cumulative rainfall was 31.4 (2011) and 37.4 cm (2012) with a leaching rainfall (7.6 cm of rainfall in 3 d) on 28 Oct. 2011. Thus, following UF/IFAS recommendations 1 N as NH 4 NO 3 was added to the UF/IFAS (T2) treatment by hand punching holes in the mulch and applying dry granular fertilizer (Olson et al. 2012 a ). No additional N was added in 2012 since there were no leaching rain events. The manufacturer o f the CRF used in the study determines nutrient release at a constant 20 C. Since mean air temperatures were above 20 C for 13 (2011) and 12 (2012) weeks, the CRF nutrient release rate would be expected to increase with a compressed nutrient release per iod (Carson and Ozores Hampton, 2013). Soil T emperature Season average minimum, mean, and maximum soil temperatures 10 cm below the bed surface during the fall seasons were 20.4 and 20.2 C, 25.1 and 24.7 C, and 31.1 and 30.7 C in 2011 and 2012, respec tively (Table 5 3) Daily air and soil temperatures were strongly correlated ( r = 0.95) indicating that air temperature may be an effective tool to estimate soil temperature. Similarly, Zheng et al. (1993) reported that air and soil temperatures were high ly correlated ( r = 0.85 to 0.96) in bare soil and sod and that air temperature may be used as a soil temperature prediction tool. Since the manufacturer of the CRFs used in the study determined nutrient release at a constant 20 C and weekly mean field soi l temperatures were greater than 20 C until 22 Dec.

PAGE 141

141 2011 (the entire season) and 13 Nov. 2012 (greater than half the season) an increase of the CRF nutrient release rate and shorter nutrient release durations would be expected. Carson et al. (2013) repor ted that the periods of nutrient release of four polymer coated fertilizers were reduced by 46% to 69% under white polyethylene mulch during the Fall 2011 tomato season. Thus, the appropriate CRF N release duration must be determined for use in the fall, winter, and spring seasons. Water T able D epth Water table depths below the bed surface fluctuated between 0.39 and 0.67 m in 2011 and 0.36 to 0.55 m in 2012, which were comparable to water table levels found in studies near Immokalee, FL ( Figure 5 1) (Ca rson Ozores Hampton, and Morgan, 2012; Ozores Hampton Simonne, et al., 2012). Intervals between readings were 15 (2011) and 7 d (2012) or longer. However, back to back measurements between 6 Dec. and 7 Dec. 2012, indicated a 7 cm increase in the water table as a result of the grower pumping water for irrigation. Thus, some daily water table fluctuations may not have been detected during the season with these reading intervals. Mortality Plant mortality was observed in 2011 but not in 2012. No interact ion between bed location (beside the ditch, middle, or beside the drive road) and fertilizer treatment was found in 2011 ( P = 0.83). Therefore, plant mortality was likely related to fertilizer treatment ( Figure 5 2 ). CRF urea (T4 to T8) treatments resulte d in greater mortality when contrasted ( P = 0.0001) with SF and CRF NPK (T1, T2, and T3) treatments. Plant mortality increased when CRF urea was rototilled into the bed ( P = 0.0062) compared with CRF urea placed in the bottom mix. In 2011 and 2012, CRF ur ea provided 100% and 75% of the total N, respectively. The remaining N was supplied by

PAGE 142

142 SF (NO 3 N) in 2012, which minimized plant mortality in the CRF urea treatments. Barker and Mills (1980) indicated that accumulation of NH 4 + and volatilization of NH 3 the end products of enzymatic urea degradation, may cause damage to tomato plants under the correct environmental field conditions. In a tomato study by Ozores Hampton et al. (2009), 29% to 54% plant mortality occurred due to NH 4 + toxicity when using PCU during the winter season with seepage irrigation. In another study, total marketable yields decreased linearly when PCU was included as an increasing percentage of the total N (0% to 100%) in a spring trial in central Florida (Csizinszky et al., 1993). S oil microbial activity and CRF urea nutrient release increases with higher temperature. Thus, fall seasons should have an accelerated microbial nitrification and detoxification of the urea and NH4 + compared to the winter and early spring season. High plant mortality from the CRF urea occurred, which was probably due to the use of soil fumigation that limited nitrifying bacteria in the soil (Ivors, 2010). CRF urea may be included in a tomato fertili ty program due to higher N content and low cost per unit, though more research will be needed to determine the percentage of the total N that may be applied as urea without crop injury or reduced yields. Plant N utritional S tatus LTNC decreased from first buds to third harvest for all treatments in 2011 and 2012 ( Figure 5 3 A and B). In 2011, no differences among treatments were found in LTN C for any sample date and all samples were within or greater than the sufficiency range. In 2012, there were differenc es among treatments at 67, 85, and 95 d after transplant (DAT); however, all LTN Cs were above the sufficiency range. At 67 DAT, plants in T1, T6, T7, and T8 had the greatest LTNC At 85 DAT plants in a ll treatments had a greater LTNC than T5. At 95 DAT T1, T7, T8 and T9 resulted in the greatest

PAGE 143

143 LTN C Tr eatment 5 led to the lowest LTNC from 67 DAT through 95 DAT and showed visible symptoms of N deficiency. Monitoring LTNC allows growers to maximize yield potential and fertilizer management efficiency with the goal of determining if supplemental N may be necessary during the crop cycle (Hoc hmuth et al., 2010). Since LTNCs were greater than or within the sufficiency range, N was not a limiting factor for yield during 2011 or 2012 (Hochmuth et al., 2010) However, visible symptoms of N deficiency at LTNCs above the upper sufficiency range indicates that the sufficiency ranges may not discriminate between crop N adequacy or deficiency. Yield R esponses to CRF N R ates In 2011 and 2012, contrasts between SF [grower (T1) and UF/IFAS (T2)] were nonsignificant, except FH large tomato yield in 2012 (Tables 5 4 and 5 4 ). Thus, T1 and T2 were used in contrasts when comparing SF and CRF treatments, except for FH large tomato yield in 2012 where only T2 was used for comparisons. In 2011, rototilling CRF urea (T8) into the bed increased FH medium, first and second harvests combined (FSHC) medium and total, and season total medium and total marketable tomato yields compared to CRF urea (T5) as the only N source in the bottom mix. There were no marketable yield differences between CRF NPK (T3) and CRF urea (T5, T7, and T8) at 1 N. When SF was compared to CRF urea (T4, T5, or T6), SF led to a greater total season large tomato yield compared to CRF urea at 190 1 N. The 120 d release CRF urea (T5) resulted in greater FH medium tomato yield compared to the CRF urea release duration mix (T7). In 2012, no differences in yield were found between CRF NPK 120 and 180 d 1 (T3 and T4); ther efore T3 and T4 were combined for comparison

PAGE 144

144 to the low CRF 1 N, CRF NPK (T5) led to lower FSHC large, total season large, and total marketable yields compared to CRF 1 (T3 and T4). When, compared to SF, CRF NPK at 1 (T3 and T4) increased extra large and total marketable FH yields. In contrast, CRF 1 N (T5) resulted in lower FSHC large, total season large, and total marketable fruit yields compared to SF. Treatment 9, CRF urea with SF co ntaining NO3 -N in the bottom mix, resulted in greater total season large marketable tomato yield compared with CRF urea in the hybrid system (T8). In the hybrid fertilizer system, CRF NPK (T6 and T7) resulted in greater season total large and total marke table yields compared with the CRF urea treatments (T8 and T9). No yield differences were found when CRF (NPK or urea) comprised 50% (T7 and T8) compared to 75% (T6 and T9) of the total N in the hybrid fertilizer system. A nitrogen rate reduction betwee n 15% to 25% as CRF urea or CRF NPK compared to UF/IFAS N rate resulted in similar or lower season total marketable yields, respectively. However, CRF 1 N resulted in similar or higher FH yield compared to SF. Therefore, a 0% to 15% N rat e reduction may be acceptable with use conditions (Ozores Hampton Simonne, et al., 2012); however, a 25% reduction in N rate should not be recommended. Urea N and NH4+ N sources were 100% in 2011 and 75% in 2012 of the TN in treatments containing CRF urea, which probably caused the high plant mortality in 2011. However, when tomato yield was corrected for plant mortality in 2011, there were no differences between CRF urea or CRF NPK. Although in 2012, (without mortality) CRF NPK resulted in greater season total marketable

PAGE 145

145 tomato yields than CRF urea. Csizinszky et al. (1993) found that FH extra large and total season marketable tomato yields decreased linearly as CRF urea incre ased from 0% to 100% of the TN. In a similar study, Csizinszky et al. (1992) reported a quadratic response to methylene urea with a maximum FH extra large and total, and season total extra large marketable tomato yields when methylene urea provided 50% of the TN. Thus, due to mortality and lower total season marketable yields, CRF urea and NH 4 + N should not contribute greater than 50% of the TN. Even though Carson et al. (2013) reported that high soil temperatures decreased fertilizer release duration un der white polyethylene mulch during Fall 2011, only FH medium tomato yields were negatively affected by CRF urea release duration when corrected for mortality. Some yields may be adjusted lower by 7.5% to 17.9% to take into consideration plant mortality ( Figure 5 2 ). Rototilling CRF urea into the bed increased marketable tomato yields compared to placement in the bottom mix. Similarly, Hochmuth (1998) rototilled CRF NPK into the bed resulting in increased drip irrigated marketable tomato yields compared to CRF NPK banded on the bed surface. During 2012, when CRF NPK and CRF urea were placed in the hybrid fertilizer system with 25% and 50% soluble N (T6 and T7) no yield differences were found compared to 100% CRF NPK in the bottom mix (T3 and T4). No re search studies have directly compared the hybrid fertilizer system, rototilling, and bottom mix CRF placements for seepage irrigated tomato production. However, Ozores Hampton et al. (2009) found that CRF urea and SF in the bottom mix and CRF NPK in the h ybrid fertilizer system produced increased and similar marketable tomato yields compared to SF, respectively.

PAGE 146

146 Post S eason S oil T est In 2011, TN remaining post season (1 after the last harvest) ranged from 37.9 to 1 (Table 5 6 ). The SF grower 1 resulted in higher residual NH4+ N concentrations compared to UF/IFAS treatment (T2). However, the TN content remaining post season was similar. Lower residual soil urea N and higher CRF prill NH 4 + N and NO 3 N contents rem ained for soils with CRF NPK (T3) compared to CRF urea (T5, T7, and T8), but no differences were found in residual TN. Greater NO3 -N content but lower urea N content remained in the soil with SF treatments compared to CRF urea (T4, T5, and T6) at any rat e. No differences were found in the amount of N remaining in the soil due to CRF urea release duration or use of CRF urea as a bottom mix compared to rototilling incorporated. In 2012, TN remaining post season (12 d after last harvest) ranged from 7.6 t o 1 (Table 5 7 ). No differences were found in residual N between grower and UF/IFAS treatments. CRF NPK of 180 d release (T4) resulted in greater residual TN content as a result of greater NH 4 + N and NO 3 N contents in the CRF prills than CRF NPK of 120 d release (T2). Greater NO 3 N remained in CRF NPK fertilizer prills at 224 1 (T5), but similar TN contents remained post season. CRF 1 (T3, T4, and T5) resulted in a greater residual soil NH4+ N and TN contents remaining post season than SF treatments. Soils of T8 (CRF urea in the hybrid fertilizer system) had higher NO 3 N, CRF prill urea N, and residual TN contents post season compared to T9 (CRF urea with SF in the bottom mix). How ever, T9 resulted in similar NO3 -N contents, more CRF, and similar TN rates applied at the beginning of the season. When comparing CRF NPK (T6 and T7) to CRF urea (T8 and T9) in the hybrid fertilizer system, no differences were found in

PAGE 147

147 residual TN. How ever, CRF urea resulted in higher residual soil urea N, but lower NO 3 N and NH 4 + N CRF prill contents. When 50% of the TN applied was CRF (NPK or urea), higher residual NO 3 N and TN was found in the soil compared to treatments containing 75% of the N as CRF (NPK or urea). This difference was probably due to the lower residual N content in the prills of CRF urea compared to CRF NPK and the lower soil N content of T9 that was likely due to leaching of SF N placed in the bottom mix. Similar to this study, 1 N remaining at the UF/IFAS SF N rate in the fall tomato season. Overall in 2011, CRF rate, placement, duration and source had no effect on TN remaining post season. But, CRF urea resulted in the highes t urea N content in the soil and CRF urea prills. In 2012, CRF NPK and SF rates did not affect TN remaining or N species distribution. However, a CRF 180 d release had greater N remaining in the CRF NPK prills compared to a CRF NPK 120 d release resultin g in higher TN. Differences in N release would not be expected since soil temperatures were similar between years and Carson et al. (2013) reported similar nutrient release durations for CRF urea with 120 and 180 d release duration when used in plasticul ture tomato production during a Fall 2011. However, higher residual TN was found with CRF (NPK and urea) in 2012 compared to SF at similar N rates as a result of higher soil NO 3 N contents and higher residual CRF prill N contents. Treatment 9 resulted i n low residual soil TN overall, but similar soil and CRF prill N contents were found when compared to residual N for T6 and T8, which had a similar pre season SF to CRF distribution and lower CRF urea contents, respectively. Overall, when T6 and T7 were u sed to compare 50% to 75% CRF in the hybrid fertilizer system, there were no differences in residual TN post season; however, the distribution

PAGE 148

148 of the N is different (contrast not shown). When T8 and T9 are included in the analysis of 50% and 75% CRF N in the hybrid fertilizer system, results become less clear due to high and low residual N in T8 and T9, respectively. Postharvest Q uality No differences were found in tomato firmness at red ripe stage ( P = 0.15 and 0.06) with 3.4 and 2.2 mm deformation, and external tomato color ( P = 0.15 and 0.25), with USDA color scores of 5.6 and 5.9, at the red ripe stage in 2011 and 2012, respectively (data not shown). Therefore, N source, CRF duration, rate, and placement had no practical commercial significance for po stharvest quality. Similarly, external color of field 1 was not affected by N rate (Warner et al., 2004). In conclusion, the high soil temperatures potentially decreased the duration o f CRF (urea and NPK) N release compared to manufacturer predicted release period. Although there were no detrimental effects on plant health when CRF NPK nutrient release was accelerated, the accelerated N release from CRF urea may have caused plant morta lity and toxicity due to reduced nitrification of NH 4 + A CRF NPK N rate 1 may be recommended since similar FH marketable yields and total season marketable yields were produced during fall weather conditions, which is a 0% t o 15% reduced N rate compared to UF/IFAS recommended rates. The CRF (urea or NPK) release durations of 120 and 180 d had similar effects on tomato marketable yields. Further research must be conducted to explore the percentage urea composition usable in a tomato fertility program, though we suggest NH 4 + N sources be limited to 50% of the TN due to potential plant toxicity and reduced marketable tomato yields. Placement of CRF (NPK and urea) in the bottom mix with or without SF and

PAGE 149

149 tilling CRFs into the bed performed similar to SF in the seepage irrigated gradient fertilizer system. CRF N rate, source, release duration, and bed placement did not affect postharvest tomato quality.

PAGE 150

150 Table 5 1. Nutrient rat es ( 1 ) and bed placement used in testing soluble fertilizer (SF)/controlled release fertilizer (CRF) fertility programs on tomato in southwest Florida during Fall 2011 and Fall 2012. Bottom mix Top mix Total N y P K N K N P K T reatment z SF CRF SF CRF SF CRF SF SF SF CRF T SF CRF T SF CRF T -------------------------------------------------------------------------2011 --------------------------------------------------------------------T1: Grower standard 24 11 x 49 0 37 0 245 363 269 11 280 49 0 49 400 0 400 T2: UF/IFAS w 24 11 49 0 37 0 189 363 213 11 224 49 0 49 400 0 400 T3: PCF120 0 224 18 31 0 127 0 363 0 224 224 18 31 49 363 127 490 T4: PCU120 0 190 49 0 37 0 0 363 0 190 190 49 0 49 400 0 400 T5: PCU120 0 224 49 0 37 0 0 363 0 224 224 49 0 49 400 0 400 T6: PCU120 0 280 49 0 37 0 0 363 0 280 280 49 0 49 400 0 400 T7: PCU120/180 0 224 49 0 37 0 0 363 0 224 224 49 0 49 400 0 400 T8: PCU120T 0 224 49 0 37 0 0 363 0 224 224 49 0 49 400 0 400 -------------------------------------------------------------------------2012 -------------------------------------------------------------------------T1: Grower standard 24 11 49 0 37 0 245 363 269 11 280 49 0 49 400 0 400 T2: UF/IFAS 24 11 49 0 37 0 189 363 213 11 224 49 0 49 400 0 400 T3: PCF120 0 224 18 31 37 127 0 235 0 224 224 18 31 49 272 127 400 T4: PCF180 0 224 18 31 37 117 0 245 0 224 224 18 31 49 283 117 400 T5: PCF180 0 168 26 23 37 88 0 274 0 168 168 26 23 49 311 88 400 T6: PCF180 0 168 26 23 37 88 56 274 56 168 224 26 23 49 311 88 400 T7: PCF180 0 112 33 16 37 59 112 304 112 112 224 33 16 49 341 59 400 T8: PCU180 0 112 49 0 37 0 112 363 112 112 224 49 0 49 400 0 400 T9: PCU180 56 168 49 0 37 0 0 363 56 168 224 49 0 49 400 0 400 z PCU120 = polymer coated urea 120 d release (43 0 0), PCU120/180 = PCU120 and a polymer coated urea 180 d release (43 0 0) in a 2:1 mix, PCF120 = polymer coated compound nitrogen (N), phosphorus (P), and potassium (K) fertilizer with 120 d release, PCU12 0T = PCU120 applied on top of the false bed, rototilled in prior to bedding. y N=nitrogen, P=phosphorus, K=potassium, and T=total. x 1 from methylene urea. w After a leaching rain event on 28 Oct. 2011, 34 kg 1 N SF was added

PAGE 151

151 Table 5 2 Summary of minimum (Min.), mean and maximum (Max.) air temperature and total rainfall in Immokalee, FL during Fall 2011 and 2012. Period Min. Mean Max. Total rainfall 2011 2012 2011 2012 2011 2012 2011 z 2012 -------------------(C) -----------------------(cm) ----September y 18.4 19.6 26.8 25.9 37.4 35.8 8.3 21.9 October 10.2 7.6 23.0 23.8 33.5 36.4 21.3 9.3 November 8.6 3.2 20.7 18.1 33.7 30.3 0.3 0.3 December 0.0 7.0 19.3 20.5 29.2 30.8 1.4 5.9 Average/total 9.3 9.4 22.4 22.1 33.4 33.3 31.4 37.4 z A leaching rain event occurred on 28 Oct. 2011. y The temperature averages and rainfall totals are for 6 Sept. 2011 and 3 Sept. 2012 through 21 Dec. 2011 and 2012.

PAGE 152

152 Table 5 3 Summary of minimum (Min.), mean and maximum (Max.) soil temperatures at 10 cm below the bed surface in Immokalee, FL during F all 2011 and 2012. Min. Mean Max. Week ending z 2011 2012 2011 2012 2011 2012 --------------------(C) ------------------21 Aug. 24.2 26.1 28.8 30.9 38.6 36.1 28 Aug. 24.7 24.6 30.3 28.3 40.6 36.6 4 Sept. 24.2 25.1 27.2 30.0 35.2 36.1 11 Sept. 24.2 24.1 29.6 28.9 38.6 36.6 18 Sept. 24.2 24.6 30.3 28.6 39.1 35.1 25 Sept. 24.7 24.1 28.7 27.8 36.7 35.6 2 Oct. 22.2 24.1 28.2 28.1 35.2 36.1 9 Oct. 22.2 24.6 26.4 28.6 31.7 35.1 16 Oct. 23.7 22.1 26.6 27.0 31.7 33.6 23 Oct. 18.2 21.6 23.1 26.3 26.7 33.6 30 Oct. 19.7 17.1 23.6 23.3 27.2 29.6 6 Nov. 16.7 16.6 22.7 21.3 27.2 27.1 13 Nov. 16.2 14.6 21.3 19.9 25.7 25.6 20 Nov. 18.7 17.6 23.8 20.8 28.2 26.6 27 Nov. 18.7 13.6 23.0 17.4 27.7 21.6 4 Dec. 14.2 16.6 20.1 19.8 26.2 23.1 11 Dec. 17.2 17.6 20.9 21.3 25.2 25.6 18 Dec. 17.7 18.1 21.4 21.7 25.2 25.1 22 Dec. 15.7 11.1 19.7 18.1 24.2 24.6 Avg. 20.4 20.2 25.1 24.7 31.1 30.7 z Data collection began on 15 Aug. 2011 and 17 Aug. 2012 and ended on 22 Dec. 2011 and 2012.

PAGE 153

153 Table 5 4 Fruit yield by size categories for first harvest, first and second harvest combined, and season total harvest (three harvests combined) fo r two soluble fertilizer (SF) and six controlled release fertilizer (CRF) tomato fertility programs used to grow tomato in Immokalee, FL during Fall 2011. N Rate First harvest First and second harvest Season total harvest Treatment (SF/CRF) Xlg z Lrg Med Total Xlg Lrg Med Total Xlg Lrg Med Total Cull -----------------------------------------------------------------1 ) ---------------------------------------------------------------T1 269/11 9.1 4.6 2.9 16.5 14.9 11.5 10.0 36.4 15.5 14.2 16.0 45.6 12.4 T2 y 247/11 8.9 4.9 2.8 16.6 14.9 15.1 16.2 46.2 15.6 17.9 24.6 58.1 10.7 T3 0/224 9.2 5.9 3.8 18.9 14.9 14.2 11.7 40.7 15.7 17.7 20.2 53.6 11.2 T4 0/190 9.5 4.8 4.3 18.7 14.6 11.3 12.7 38.7 14.9 13.5 18.9 47.3 10.7 T5 0/224 7.6 4.4 4.1 16.1 12.9 10.5 10.9 34.4 13.7 12.9 16.4 43.0 10.0 T6 0/280 8.3 3.8 3.2 15.3 11.4 10.4 10.6 32.3 11.8 12.3 16.3 40.4 9.9 T7 0/224 7.4 4.5 3.5 15.4 12.2 10.7 12.0 34.9 13.0 12.9 18.2 44.1 10.6 T8 0/224 10.0 5.8 5.3 21.1 13.6 12.1 12.2 37.9 13.7 14.5 18.3 46.5 9.6 P value 0.51 0.35 0.28 0.31 0.17 0.11 0.02 0.02 0.22 0.06 0.01 0.01 0.68 Significance x NS NS NS NS NS NS * NS NS * NS -------------------------------------Single degree of freedom contrast ( P value ) ---------------------------------------T1 vs T2 SF rate 0.12 0.79 0.43 0.22 0.13 0.72 0.64 0.30 0.22 0.75 0.77 0.48 0.92 T3 vs T5,7,8 NPK vs urea w 0.13 0.35 0.58 0.35 0.23 0.12 0.16 0.06 0.32 0.12 0.08 0.07 0.49 T1,2 vs T4 Rate 0.53 0.14 0.86 0.42 0.28 0.052 0.62 0.21 0.21 0.014 0.38 0.053 0.66 T1,2 vs T5 Rate 0.21 0.16 0.15 0.08 0.90 0.49 0.91 0.72 0.95 0.43 0.88 0.80 0.45 T1,2 vs T6 Rate 0.89 0.29 0.41 0.43 0.14 0.69 0.20 0.17 0.13 0.61 0.23 0.19 0.57 T5 vs T7 Duration 0.50 0.19 0.028 0.09 0.38 0.74 0.18 0.69 0.32 0.85 0.30 0.81 0.08 T5 vs T8 Placement v 0.45 0.33 0.024 0.10 0.37 0.11 0.021 0.03 0.28 0.10 0.007 0.018 0.50 z Xlg=extra large (> 7.00 cm), Lrg=large (6.35 to 7.06 cm), Med=medium (5.72 to 6.43 cm). y Total 1 1 fertilizer applied following a leaching rain event on 28 Oct. 2011. x NS ,*,** = Nonsignificant or significant at 0.05 or 0.01, respectively. w N, P, K = nitrogen, phosphorus, and potassium, respectively. v Hybrid fertilizer system vs. rototilled.

PAGE 154

154 Table 5 5 Fruit yield by size categories for first harvest, first and second harvest combined, and season total harvest (three harvests combined) for two soluble fertilizer (SF) and seven controlled release fertilizer (CRF) tomato fertility programs used to grow tomato in Immokalee, FL during Fall 2012. N Rate Fi rst harvest First and second harvest Season total harvest Treatment (SF/CRF) Xlg z Lrg Med Total Xlg Lrg Med Total Xlg Lrg Med Total Cull ----------------------------------------------------------------1 ) ---------------------------------------------------------------T1 269/11 19.3 1.4 y 20.7 27.3 14.8 3.5 45.5 30.8 27.9 9.7 68.4 9.1 T2 213/11 17.7 2.5 0.1 20.3 28.5 14.9 4.5 47.8 32.5 27.2 12.5 72.2 7.3 T3 0/224 24.9 2.5 27.3 31.8 13.5 3.9 49.2 36.2 27.1 10.8 74.2 10.5 T4 0/224 22.2 3.0 25.2 30.6 15.0 3.2 48.9 33.1 27.8 10.1 71.0 9.2 T5 0/168 22.8 3.4 0.1 26.3 28.5 12.1 3.3 43.9 29.9 20.5 9.8 60.1 7.6 T6 56/168 25.0 3.0 27.9 33.3 14.3 4.7 52.3 35.5 26.7 13.7 75.8 8.0 T7 112/112 20.5 2.4 0.1 23.0 28.5 14.9 3.8 47.2 31.1 28.6 12.0 71.7 8.7 T8 112/112 20.8 2.6 0.0 23.5 30.4 13.4 4.1 47.9 33.0 22.1 11.0 66.2 8.0 T9 56/168 19.0 2.3 21.3 26.0 14.9 3.7 44.6 28.9 27.8 11.0 67.8 8.6 P value 0.25 0.025 0.066 0.19 0.30 0.27 0.72 0.19 0.33 0.0004 0.50 0.0005 0.33 Significance x NS NS NS NS NS NS NS NS *** NS *** NS ---------------------------------------Single degree of freedom contrast ( P value ) --------------------------------------T1 vs T2 SF rate 0.60 0.029 0.08 0.89 0.68 0.94 0.25 0.43 0.59 0.71 0.17 0.19 0.28 T3 vs T4 Duration 0.40 0.31 0.52 0.69 0.21 0.46 0.93 0.33 0.72 0.70 0.26 0.45 T3,4 vs T5 CRF Rate 0.78 0.10 0.005 0.99 0.28 0.049 0.73 0.052 0.09 0.0001 0.68 0.0001 0.12 T1,2 vs T3,4 SF vs CRF 0.029 0.66 w 0.22 0.020 0.11 0.53 0.49 0.26 0.18 0.93 0.63 0.28 0.17 T1,2 vs T5 SF vs low CRF rate 0.12 0.07 w 0.048 0.052 0.80 0.016 0.37 0.28 0.51 0.0001 0.43 0.0003 0.66 T8 vs T9 Urea vs urea + ntirate 0.56 0.41 0.38 0.50 0.14 0.22 0.71 0.28 0.20 0.0026 0.97 0.58 0.70 T6,7 vs T8,9 Hybrid NPK v vs Urea 0.20 0.47 0.53 0.19 0.19 0.64 0.57 0.11 0.30 0.036 0.19 0.0024 0.98 T6,9 vs T7,8 50% CRF vs 75% CRF 0.55 0.79 0.07 0.56 0.92 0.59 0.67 0.65 0.95 0.13 0.55 0.17 0.99 z Xlg= extra large (> 7.00 cm), Lrg=large (6.35 to 7.06 cm), Med=medium (5.72 to 6.43 cm). y Medium fruit were not harvested in all treatments during first harvest. x NS ,*,**,*** = Nonsignificant or significant at 0.05, 0.01, or 0.001, respectively. w Only T2 was used in comparisons due to a significant contrast between T1 and T2. v N, P, K = nitrogen, phosphorus, and potassium, respectively.

PAGE 155

155 Table 5 6 Residual soil ammonium nitrogen (NH 4 + N), nitrate N (NO 3 N), urea N, and total N from two soluble fertilizer (SF) and six controlled release fertilizer (CRF) programs used to grow tomato in Immokalee, FL during Fall 2011. N Rate Soil CRF prills Total Treatments (SF/CRF) NH 4 + N NO 3 N Urea N NH 4 + N NO 3 N Urea N N release z --------------------------------------------1 ---------------------------------------(%) T1 269/11 23.4 57.0 0.0 y 80.4 T2 247/11 11.9 47.4 0.3 59.6 T3 0/224 21.4 22.0 1.9 0.3 0.2 1.5 47.3 99.1 T4 0/190 13.1 15.7 12.8 0.2 0.0 3.1 44.8 98.3 T5 0/224 14.3 24.9 9.0 0.2 0.0 1.9 50.3 99.1 T6 0/280 24.3 33.8 9.8 0.2 0.0 2.5 70.6 99.0 T7 0/224 12.9 14.6 8.3 0.1 0.0 1.9 37.9 99.1 T8 0/224 16.3 16.4 10.8 0.1 0.0 2.1 46.0 99.0 P value 0.08 0.002 0.002 0.61 0.0004 0.73 0.15 Significance x NS ** ** NS *** NS NS ------------------Single degree of freedom contrast ( P value ) ---------------T1 vs T2 SF rate 0.02 0.34 0.93 0.19 T3 vs T5,7,8 NPK vs urea w 0.10 0.68 0.009 0.008 0.0001 0.52 0.84 T1,2 vs T4 Rate 0.28 0.0004 0.0001 0.07 T1,2 vs T5 Rate 0.43 0.005 0.004 0.16 T1,2 vs T6 Rate 0.13 0.04 0.002 0.97 T5 vs T7 Duration 0.78 0.31 0.83 0.22 0.38 0.96 0.43 T5 vs T8 Placement v 0.67 0.40 0.58 0.082 0.70 0.79 0.78 z N release = (total CRF N applied N remaining in CRF prills)/total CRF N applied. y No CRF were used in the Grower (T1) and UF/IFAS (T2) treatments, thus there were no CRF prills collected and analysis of variance was carried among CRF treatments for these co lumns. x NS ,*,**,*** = Nonsignificant or significant at 0.05, 0.01, or 0.001, respectively. w P = phosphorus and K = potassium. v Hybrid fertilizer system vs. rototilled.

PAGE 156

156 Table 5 7 Residual soil ammonium nitrogen (NH 4 + N), nitrate N (NO 3 N), urea N, and total N from two soluble fertilizer (SF) and six controlled release fertilizer (CRF) programs used to grow tomato in Immokalee, FL during Fall 2012. Soil CRF prills Total Treatments N rate (Soluble/CRF) NH 4 + N NO 3 N Urea N NH 4 + N NO 3 N Urea N N release z -------------------------------------1 ------------------------------------(%) T1 269/11 7.9 7.9 0.0 y 15.8 T2 213/11 5.9 1.5 0.2 7.6 T3 0/224 12.5 5.1 0.1 10.0 6.6 0.0 34.3 92.5 T4 0/224 12.9 6.4 0.2 31.3 23.5 0.0 74.2 75.5 T5 0/168 9.7 5.9 0.0 23.3 16.0 0.0 55.0 76.6 T6 56/168 7.6 5.3 0.0 15.2 10.5 0.0 38.5 84.7 T7 112/112 5.8 19.0 0.0 8.4 6.0 0.1 39.1 87.1 T8 112/112 5.8 39.9 4.0 0.2 0.2 0.2 50.3 99.5 T9 56/168 4.7 3.0 3.1 0.1 0.0 1.7 12.7 98.9 P value 0.0007 0.0002 0.0001 0.0001 0.0001 0.34 0.0003 Significance x *** *** *** *** *** NS *** ------------Single degree of freedom contrast ( P value ) ----------T1 vs T2 SF rate 0.28 0.36 0.81 0.52 T3 vs T4 Duration 0.83 0.86 0.89 0.0002 0.0001 0.99 0.004 T4 vs T5 Rate 0.10 0.95 0.83 0.12 0.048 0.99 0.14 T1,2 vs T3,4 SF vs CRF 0.0002 0.83 0.93 0.0001 T1,2 vs T5 SF vs low CRF rate 0.09 0.84 0.92 0.0005 T8 vs T9 Urea vs urea + nitrate 0.56 0.0001 0.27 0.99 0.97 0.04 0.006 T6,7 vs T8,9 Hybrid NPK vs Urea 0.29 0.07 0.0001 0.002 0.004 0.08 0.41 T6,9 vs T7,8 50% CRF vs 75% CRF 0.79 0.0001 0.43 0.37 0.40 0.16 0.04 z N release = (total CRF N applied N remaining in CRF prills)/total CRF N applied. y No CRF were used in the Grower (T1) and UF/IFAS (T2) treatments, thus there were no CRF prills collected and analysis of variance was carried out on only CRF treatments for these columns. x NS ,*, **, *** = Nonsignificant or significant at P 0.05, 01, or 0.001, respectively

PAGE 157

157 Figure 5 1. Water table levels for tomato grown with seepage irrigation in Immokalee, FL during Fall 2011 and 2012.

PAGE 158

158 Figure 5 2 Plant mortality (death) by treatment for tomato grown with soluble fertilizer (T1 and T2) and different CRF rates and sources (T3 T8) in Immokalee, FL. during Fall 2011. Table 5 1 provides treatment descriptions. 0 2 4 6 8 10 12 14 16 18 20 T1 T2 T3 T4 T5 T6 T7 T8 Mortality (%) Treatment

PAGE 159

159 Figure 5 3 Changes in leaf tissue nitrogen (N) concentration for tomato grown with soluble fertilizer and controlled release fertilizer programs in Immokalee, FL during Fall 2011 and 2012 with University of Florida/Institute of Food and Agricu lture Sciences (UF/IFAS) sufficiency ranges. Table 5 1 provides treatment descriptions.

PAGE 160

160 CHAPTER 6 CONCLUSION S Results from laboratory and field studies on mulch covered, seepage irrigation, of tomatoes grown in south Florida during the fall season are summarized below. The conclusions must be limited to seepage irrigated tomato c rop s under the environmental constraints of temperature and rainfall found during the fall season in south Florida. The same conclusions may not be applicabl e to crops grown elsewhere in Florida, to drip irrigated fall tomato crops, o r to drip or seepage irrigated tomato crops grown during the spring season in south Florida. High s oil temperatures in polyethylene mulched tomato beds compared to the 20 to 25 C incubation temperatures used by manufacturers to determine release durations of controlled release fertilizer ( CRF ), were recorded during a nitrogen (N) release study that incubated CRFs in the pouch field method during 2011 and 2013 The high soil tem perature resulted in CRF N release duration reduc tions of 23% to 88 % in 2011 and 23% to 79% in 2013 Because the pouch field method lasts for a tomato season of 120 to 140 d and requires numerous samples with high laboratory N analysis costs, an N release model that correlat e s the accelerated temperature controlled incubation method (ATCIM) and pouch field method was used to predict CRF N release in a tomato production system. The model predicted the percentage N release of individual CRF with R 2 of 0.95 to 0.99 and 0.61 to 0.99 and CRFs grouped by release duration with R 2 of 0.64 to 0.99 and 0.38 to 0.95 in 2011 and 2013, respectively. Modeling CRF N release using CRFs grouped by release duration would not be recommended for 180 d release (DR) CRFs, be cause coating technologies behaviors apparently differ in response to high fall soil

PAGE 161

161 temperature in polyethylene mulched tomato beds. However, with further model validation grouping CRFs of 90 to 140 DR to simulate the CRF N release profile may allow the ATCIM to predict CRF N release without performing the pouch field method, which currently negated the usefulness of the ATCIM in a tomato production system. The CRF fall mixes, composed of 100, 140, and 180 DR CRFs, were used in the hybrid fertilizer syste marketable tomato yields and low residual soil N post season with CRF112/SNF56 (168 1 ) or CRF168/SNF5 1 ) compared to the grower standard SNF (280 1 1 N), or the University of Florida/Institute of Food and Agricultural Sciences (UF/IFAS) SNF 1 N) rates. Thus, the hybrid fertilizer system may allow fo r reduce d N rates by 25% to 46%. There were no commercially important differences in red ripe tomato firmness and color for any fertilizer rate or material after mature green tomatoes were subjected ethylene treatment Similarly, when individual CRF con taining urea (CRF urea) or N, phosphorus, and potassium (CRF NPK) were placed in the bottom mix without SNF in the top mix, N rates of 1 produced similar total season yields compared to UF/IFAS recommended SNF rates. Thus, CRFs allow for an N rate reduction of 15% or lower compared to UF/IFAS recommended SNF rates during the fall season. However, incorporation of CRF urea in the tomato fertility program as a bottom mix without SNF in the top mix caused 7.5% to 17.9% plant mortality in 201 1 and the use of CRF urea in the hybrid system resulted in approximately 9% lower marketable yields in 2012, which

PAGE 162

162 was due to reduced nitrification of ammonium (NH 4 + ) in fumigated polyethylene mulched tomato beds. Thus, based on these results and literature, NH 4 + N sources should be limited to 50% of the total N due to potential plant toxicity and reduced marketable tomato yields. Marketable tomato yields were similar when tomato was grown with CRF NPK of 120 or 18 0 DR Placement of CRF (NPK and urea) in the bottom mix with or without SNF in the top mix and rototilling CRFs into the bed performed similar to UF/IFAS and growers standard S N F rates There were no effects of CRF N rate, source, release duration, and b ed placement on postharvest tomato quality. Nitrogen release from CRFs is shorter during the fall season than stated on the manufacture label. In the future, N release form CRFs may be predicted using the ATCIM. Based on this dissertation, the hybrid f ertilizer system containing CRF fall 1 1 SNF, and CRF NPK of 120 to 180 DR incorporated as a bottom mix with or without SNF in the top mix may be recommended for polyethylene mulched tomato pro duction during the fall season at 168 to 224 and 190 to 224 1 total N respectively. However, CRFs must release greater than 75% N during the season, which was not found with all CRFs tested in these studies. Therefore, on a horticultural basis, CR Fs may be a viable best management practice (BMP) to supply a portion of the N in the current tomato fertility program in Florida. Proposed IFAS Recommendations A BMP must be and based on sou (Bartnick et al., 2005) Using CRF may be considered a socially acceptable crop fertilization practice, since home gardeners use CRF and environmentalist advocate CRF as a solution to decrease environmental nutrient

PAGE 163

163 pollution and improved wate r quality in Florida. From a scientific standpoint, tomato growers may use CRF at a 15% to 25% reduced N rate to produce similar yields to UF/IFAS recommended SNF rates; thus as a BMP, CRF use can be a considered a technically feasible horticultural ferti lization practice. However, facts from the dissertation do not support the conclusion that CRF reduces N loss to the environment. Two conflicting but viable arguments may be made regarding the ability of CRFs to reduce the N load introduced into the envi ronment. First, since SFs had similar and lower residual soil N contents and similar marketable tomato yields compared to CRFs, an argument may be that higher amounts of N were lost to the environment using SFs than CRFs. Second, since CRFs had similar a nd higher residual soil N contents and similar tomato yields compared to SFs at higher N rates, an argument may be that CRF prills retained N that impeded plant uptake, which would result in higher N uptake of SF treatments and higher environmental loss fo r CRF treatments. However, collecting leachate in seepage irrigated commercial tomato fields was not feasible in small experimental units and tomato plant biomass was not measured during the field trials. Therefore, these arguments may not be validated a nd the value of CRF as a N management BMP to reduce environmental impact needs further investigation. In regards to the residual N in the soil and CRF prills, a cover crop should follow a tomato crop grown with CRF N. Furthermore, the economic viability o f using CRF in a fertility program can be questionable due to high CRFs cost compared to SFs. Although an economic analysis was not part of this study, a fertility program with a large portion of the N as CRF would increase the cost of a tomato fertility 1 to

PAGE 164

164 1 (unpublished data). Additionally, the recommended cover crop following the use of a CRF tomato fertility program would increase the cost further. To be considered a BMP, a production practice must m eet all the criteria in the BMP manual ( www.floridaagwaterpolicy.com ) Despite the fact that CRF utilization may be socially acceptable and science indicates that it can be technically feasible, use of CRF does not meet the economic and environmental criteria to be a BMP for seepage produced tomato in south Florida. Therefore, further investigations into CRF as a BMP must include an environmental and economical analysis. Future Research Grouping CRFs in the two step process for CRF N release prediction using the ATCIM and CRF N release from the pouch field method has the ability to predict CRF N release with and acceptable R 2 However, several additional CRF N release studies using different coating technol ogies should be evaluated to validate the predictive ability of the ATCIM. After validation, growers will be able to send new CRF samples to a laboratory and obtain a predicted N release profile to determine CRF release in field conditions under white pol yethylene mulch during the fall season in Florida. Currently, seepage irrigated tomato growers use the traditional gradient fertilizer system with fertilizer placed in a bottom mix or broadcast in row and a top mix or bands on the bed shoulder. Typica lly, 10% to 20% of the N is placed in the bottom mix with the remainder of the N in the top mix. This placement allowed vegetable growers to use high rates of SFs without increasing the electrical conductivity of the bed, which can damage plants and reduc ed marketable yields. In the 2012 field tomato study, evidence 1 SF NO 3 N was placed in 1 N from CRF NPK. In the 2011 field tomato study, tilling

PAGE 165

165 the CRF urea in the b ottom mix into the false bed increased marketable yields. Therefore, to increase tomato marketable yields and to reduce N leaching from the bottom mix, tilling CRF NPK into the false bed should be investigated further. The higher N content of CRF urea an d lower cost of the constituent SFs compared to CRF NPK, make CRF urea more inexpensive a unit N price basis. The use of 100% CRF urea caused tomato plant mortality and 75% CRF urea reduced marketable tomato yields compared with CRF NPK. Therefore, the am ount of CRF urea that may be used without reducing marketable yields should be investigated to reduce the cost of a tomato fertility program based on CRF during the fall season in Florida. A lysimeter study using seepage irrigation should be conducted to compare the potential N losses among the UF/IFAS SF and two or three CRF tomato fertility programs to allow for an evaluation of CRF as a BMP in fall tomato production in Florida. Additionally, crop biomass, residual soil and CRF prill N contents, and loss of gaseous N from the soil should be measured to determine N movement in the tomato production system.

PAGE 166

166 LIST OF REFERENCES Agrium Advanced Technologies. 2010. DurationCR: Controlled release fertilizer. 29 Aug. 2013. < http://agriumat.com/includes/duration_sell_sheet.pdf >. Abeles, F.B., P.W. Morgan, and M.E. Saltveit. 1992. Fruit ripening, ab s c i ssion and postharvest disorders p. 182 221. In: Anonymous Ethylene in plant biology 2 nd ed. Acad. Press, San Diego, CA. Ahmed, I.U., O.J. Attoe, L.E. Engelbert, and R.B. Corey. 1963. Factors affecting the rate of release of fertilizer from capsules. Agron. J. 55:495 499. Almeselmani, M., R.C. Pant, and B. Singh. 2012. Potassium level and physiological response and fruit quality in hydroponically grown tomato. Intl. J. Veg. Sci. 16:85 99. AOAC International. 2000. Official methods of analysis of AOAC International. AOAC International, Arlington VA. Attoe, O.J., F.L. Rasson, W.C. Dahnke, and J.R. Boyle. 1970. Fertilizer release from packets and its effect on tree growth. Soil Sci. Soc. Amer. Proc. 34:136 142. Barker, A.V. and H.A. Mills. 1980. Ammonium and nitrate nutrition of horticultural crops. p. 395 423. In: J. Janick (ed ). Horticultural reviews. Wiley, Hoboken, N.J. Bartnick, B., G. Hochmuth, J. Hornsby, and E. Simonne. 2005. Water quality/quantity best management practices for Florida vegetable and agronomic crops. Florida Dept. Agr. Consumer Serv., Tallahassee, FL. Ba su, S.K., N. Kumar, and J.P. Srivastava. 2010. Modeling NPK release from spherically coated fertilizer granules. Simulation Modeling Practice and Theory 18:820 835. Benard, C., H. Gautier, F. Bourgaud, D. Grasselly, B. Navez, C. Caris Veyrat, M. Weiss, a nd M. Genard. 2009. Effects of low nitrogen supply on tomato ( Solanum lycopersicum ) fruit yield and quality with special emphasis on sugars, acids, ascorbate, carotenoids, and phenolic compounds. J. Agric. Food Chem. 57:4112 4123. < http://dx.doi.org/10.1021/jf8036374 >. Bonczek, J.L. and B.L. McNeal. 1996. Specific gravity effects on fertilizer leaching from surface sources to shallow water tables. Soil Sci. Soc. Amer. Proc. 60:978 985. Bottoms, T.G., R.F. Smith, M.D. Cahn, and T.K. Hartz. 2012. Nitrogen requirements and N status determination of lettuce. HortScience 47:1768 1774. Britto, D.T. and H.J. Kronzucker. 2002. NH4+ toxicity in higher plants: a critical review. J. P lant Physiol. 159:567 584.

PAGE 167

167 Broschat, T.K. 2005. Rates of ammonium nitrogen, nitrate nitrogen, phosphorus, and potassium from two controlled release fertilizers under different substrate environments. HortTechnology 15:332 335. Broschat, T.K. and K.K. Moo re. 2007. Release rates of ammonium nitrogen, nitrate nitrogen, phosphorus, potassium, magnesium, iron, and manganese from seven controlled release fertilizers. Commun. Soil Sci. Plant Anal. 38:843 850. Brown, M.J., R.E. Luebs, and P.F. Pratt. 1966. Effec t of temperature and coating thickness on the release of urea from resin coated granules. Agron. J. 58:175 178. Brust,G. 2008. Using nitrate N petiole sap testing for better nitrogen management in vegetable crops. Univ. Maryland Ext. Serv. 10 July 2013. < http://extension.umd.edu/sites/default/files/_docs/articles/PlantPetioleNitrateSap Testing.update.pdf > Cantliffe, D., P. Gilreath, D. Haman, C Hutchinson, Y. Li, G. McAvoy, K. Migliaccio, T. Olczyk, S. Olson, D. Parmenter, B. Santos, S. Shukla, E. Simonne, C. Stanley, and A. Whidden. 2006. Review or nutrient management systems for Florida vegetable producers: A white paper from the UF/IFAS vege table fertilizer task force. Proc. Fla. State Hort. Soc. 119:240 248. Cantwell, M.I. and R.F. Kasmire. 2002. Postharvest handling systems: Fruit vegetables. p. 407 421. In: A.A. Kader (ed). Postharvest technology of horticulture crops. Regents Univ. Calif ornia, Oakland, CA. Carson, L.C. and M. Ozores Hampton. 2012. Methods for d etermining n itrogen r elease from c ontrolled r elease f ertilizers u sed for v egetable p roduction HortTechnology 22:20 24. Carson, L.C. and M. Ozores Hampton. 2013. Factors Affecting Nutrient Availability, Placement, Rate, and Application Timing of Controlled Release Fertilizers for Florida Vegetable Production using Seepage Irrigation. HortTechnology 23:553 562. Carson, L.C., M. Ozores Hampton, and J.B. Sartain. 2012. Controlled rele ase fertilizer drying methods effect on nitrogen recovery analysis. HortScience 47(9):S320. Carson, L.C., M. Ozores Hampton, and K.T. Morgan. 2012. Effect of controlled release fertilizer on tomatoes grown with seepage irrigation in Florida sandy soils. Pr oc. Fla. State Hort. Soc. 125: 164 168 Carson, L.C., M. Ozores Hampton, and K.T. Morgan. 2013. Nitrogen release from controlled release fertilizers in seepage irrigated tomato production in south Florida. Proc. Fla. State Hort. Soc. 126: In Press

PAGE 168

168 Carson, L.C., M. Ozores Hampton, K.T. Morgan, and S.A. Sargent. 201 4 Effect of controlled release and soluble fertilizer on tomato production and postharvest quality in seepage irrigation. HortScience 49:1 7 C haib, J., M. Devaux, M. Grotte, K. Robin, M. Causse, M. Lahaye, and I. Marty. 2007. Physiological relationships among physical, sensory, and morphological attributes of texture in tomato fruits. J. Exp. Bot. 58:1915 1925. Chen, Z. and C.M. Hutchinson. 2008. Evaluation of alternative fertilizer programs in s eepage irrigated potato production. Proc. Fla. State Hort. Soc. 121:187 190. Christianson, C.B. 1988. Factors affecting N release of urea from reactice layer coated urea. Fert. Res. 16:273 284. Cristo, C.H. and J.P. Mitchell. 2002. Preharvest factors aff ecting fruit and vegetable quality. p. 49 54. In: A.A. Kader (ed). Postharvest technology of horticulture crops, 3 rd Regents of Univ. California, Oakland, CA. Csizinszky, A.A. 1989. Effect of controlled (slow) release nitrogen sources on tomato, Lycopers icon esculentum Mill. cv. Solar Set. Proc. Fla. State Hort. Soc. 102:348 351. Csizinszky, A.A. G.A. Clark, and C.D. Stanley 1992. Evaluation of methylene urea for fresh market tomato with seepage irrigation. Proc. Fla. State Hort. Soc. 105:370 372. Csi zinszky, A.A. 1994. Yield response of bell pepper and tomato to controlled release fertilizers on sand. J. Plant Nutr. 7:1535 1549. Csizinszky, A.A., C.D. Stanley, and G.A. Clark. 1993. Evaluation of controlled release urea for fresh market tomato. Proc. Fla. State Hort. Soc. 106:183 187. Dai, J., X. Fan, J. Yu, F. Liu, and Q. Zhang. 2008. Study on the rapid method to predict longevity of controlled release fertilizer coated by water soluble resin. Agr. Sci. China 7:1127 1132. Davies, J.N. and G.W. Winsor. 1967. Effect of nitrogen, phosphorus, potassium, magnesium, and liming on the composition of tomato fruit. J. Sci. Food Agr. 18:459 466. Davis J.M. and R.G. Gardner. 1994. Harvest maturity affects fruit yield, size, and grade of fresh market tomat o cultivars. HortScience 29:613 615. Decoteau, D.R., M.J. Kasperbauer, and P.G. Hunt. 1990. Bell pepper plant development over mulches of diverse colors. HortScience 25:460 462.

PAGE 169

169 Di Gioia, F., E.H. Simonne, M. Gonnella, P. Santamaria, A. Gazula, and Z. She ppard. 2010. Assessment of ion interferences to nitrate and potassium analyses with ion selective electrodes. Commun. Soil Sci. Plant Analysis 41:1750 1768. Diaz Perez, J.C. and K.D. Batal. 2002. Colored plastic film mulches affect tomato growth and tield via changes in root zone temperature. J. Amer. Soc. Hort. Sci. 127:127 135. Diaz Perez, J.C., S.C. Phatak, D. Giddings, and D. Bertrand. 2005. Root zone temperature, plant growth, and fruit yield of tomatillo as affected by plastic fim mulch. HortScience 40:1312 1319. Du, C., J. Zhou, and A. Shaviv. 2006. Release characteristics of nutrients from polymer coated compound controlled release fertilizers. J. Polym. Environ. 14:223 230. Elkashif, M.E., S.J. Locascio, and D.R. Hensel. 1983. Isobutylidene diure a and sulfur coated urea as N source for potatoes. J. Amer. Soc. Hort. Sci. 108:523 526. Engelsjord, M., O. Fostad, and B. Singh. 1996. Effects of temperature on nutrient release from slow release fertilizers. Nutrient Cycling in Agroecosystems 46:179 187 Environmental Protection Agency. 2009. Clean Water Act Section 303. U.S. Environ. Protection Agency, Washington, DC. Errebhi, M.M. 1990. Tomato growth and nutrient uptake pattern as influenced by nitrogen form ratio. J. Plant Nutr. 13:1031 1043. Europ ean Committee for Standardization. 2002. Slow release fertilizers: Determination of the of the nutrients method for coated fertilizers. European Committee for Standardization, Brussels BS EN 13266:2001. Everris. 2013. O smocote classic. 29 Aug. 2013. < http://www.everris.us.com/sites/default/files/e90551_.pdf > Fan, X. 2009. Research and development of controlled release fertilizers as high efficient nutrient management materials in Chin a. Proc. Intl. Plant Nutr. Colloq 16:1 6. Feigin, A., M. Zwibel, I. Rylski, N. Zamir, and N. Levav. 1980. The effect of ammonium/nitrate ratio in the nutrient solution on tomato yield and quality. Acta Hort. 98:149 160. Florikan ESA. 2012a. Technologies & brands Florikan. 29 Aug. 2013. < http://florikan.com/flktech.html >. Florikan ESA. 2012b. Technologies & brands Nutricote. 29 Aug. 2013. < http://florikan.com/nutt ech.htm l >.

PAGE 170

170 Florida Automated Weather Network (FAWN). 201 3 Archived weather data. UF/IFAS, Gainesville, FL. 7 June 201 3 < http://fawn.ifas.ufl.edu/data/ >. Fluck, R.C. and D.D. Gull. 1972. Mechanical properties of tomatoes affecting harvesting and handling damage. Florida St. Hort. Soc. 85:160 165. Fraisse, C.W., Z. Hu, and E.H. Simonne. 2010. Effect of el nino southern oscillation on the number of leaching rain events in Florida and implications on nutrient management for tomato. HortTechnology 20:120 132. Gandeza, A.T., S. Shoji, and I. Yamada. 1991. Simulation of crop response to polyolefin coated urea: I. Field dissolution. Soil Sci. Soc. Am. J. 55:1462 1467. Geraldson, C.M. 198 0. Importance of water control for tomato production using the gradient mulch system. Proc. Fla. State Hort. Soc. 93:278 279. Greenberg, A.E., R.R. Trussell, and L.S. Clersceri. 1985. Standard methods for the examination of water and waste water. 16th ed. American Public Health Association, Washington, D.C. Guertal, E.A. and J.M. Kemble. 1998. Responses of field grown tomatoes to nitrogen sources. HortTechnology 8:386 391. Guilbault, G.G., R.K. Smith, and J.G. Montalvo. 1969. Use of ion selective electro des in enzymic analysis. Cation electrodes for deaminase enzyme systems. Anal. Chem. 41:600 605. < http://dx.doi.org/10.1021/ac60273a016 >. Gweyi Onyango, J.P., G. Neumann, and V. Roemheld. 2009. Effects o f different forms of nitrogen on relative growth rate and growth components of tomato (Lycopersicon esculentum mill.). African J. Hort. Sci. 2:43 55. Haase, D.L., P. Alzugaray, R. Rose, and D.F. Jacobs. 2007. Nutrient release rates of controlled release f ertilizers in forest soil. Commun. Soil Sci. Plant Analysis 38:739 750. Harris, L.J., D. Zagory, and J.R. Gorny. 2002. Saftey factors. p. 301 314. In: A.A. Kader (ed). Postharvest technology of horticultural crops. Regents Univ. California, Oakland, CA. Hartz, T.K. 2006. Vegetable production best management practices to minimize nutrient loss. HortTechnology 16:398 403. Hartz, T.K., R.F. Smith, M. LeStrange, and K.F. Schulbach. 1993. On farm monitoring of soil and crop nitrogen status by nitrate selective electrode. Commun. Soil Sci. Plant Anal ysis. 24:2607 2615. Hartz, T.K. and T.G. Bottoms. 2009. Nitrogen requirements for drip irrigated processing tomatoes. HortScience 44:1988 1993.

PAGE 171

171 Havlin, J.L., J.D. Beaton, S.L. Tisdale, and W.L. Nelson. 2005. Soil fer tility and fertilizers: An introduction to nutrient management. 7th ed. Pearson Prentice Hall, Upper Saddle River, N.J. Hendricks, G.S. and S.Shukla. 2011. Water and nitrogen management effects on water and nitrogen fluxes in Florida flatwoods. J. Environ Quality 40:1844 1856. Hochmuth, G.J. 1994. Efficiency ranges for nitrate nitrogen and potassium for vegetable petiole sap quick tests. HortTechnology 4:218 222. Hochmuth, G.J. 1998. Response of mulched tomato to meister controlled release fertilizers 98 08.29 June 2013. < http://nfrec.ifas.ufl.edu/files/pdf/publications/SVReports/mulch/97 08.pdf >. Hochmuth, G. 2009. Plant petiole sap testing for vegetable crops. Univ. Florida, IFA S, EDIS CIR 1144. 26 Nov. 2011.< http://edis.ifas.ufl.edu/pdffiles/CV/CV00400.pdf >. Hochmuth, G. and K. Cordasco. 2008. A summary of N, P, K research with tomato in Florida. Univ. Florida IFAS. EDIS HS759. 31 July 2012. < http://edis.ifas.ufl.edu/cv236 >. Hochmuth, G. and E. Hanlon. 2011. A summary of N,P, and K research with potato in Florida. University of Florida Institute of Food and Agriculture Sciences, Gainesville, FL. Hochmuth, G., D. Maynard, C. Vavrina, E. Hanlon, and E. Simonne. 2010. Plant tissue analysis and interpretation for vegetable crops in Florida. Univ. Florida, Inst. Food Agr. Sci., Electronic Data Info. Source, H S964. 26 Oct. 2013. < http://edis.ifas.ufl.edu/ep081 >. Hochmuth, G., D. Maynard, C. Vavrina, E. Hanlon, and E. Simonne. 2012. Plant tissue analysis and interpretation for vegetable crops in Florida. Univ. Florida IFAS. EDIS HS964. 25 July 2013. < http://edis.ifas.ufl.edu/ep081 > Hochmuth, G., K. Shuler, E. Hanlon, and N. Roe. 1994. Pepper response to fertilization with soluble and controlled release potassium fertilizer s. Proc. Fla. State Hort. Soc. 107:132 139. Holcomb, E.J. 1981. A technique for determining potassium release from a slow release fertilizer. Commun. Soil Sci. Plant Anal. 12(3):271 277. Huett, D.O. and B.J. Gogel. 2000. Longevities and nitrogen, phosphor us, and potassium release patterns of polymer coated controlled release fertilizers at 30C and 40C. Commun. Soil Sci. Plant Analysis 31:959 973. Hurst, W.C. 2010. Harvest, handling and sanitation. p. 28 42. In: Anonymous Commercial toamto production han dbook. Univ. Georgia Coop. Ext. Serv.

PAGE 172

172 Husby, C.E., A.X. Niemiera, J.R. Harris, and R.D. Wright. 2003. Influence of diurnal temperature on nutrient release patterns of three polymer coated fertilizers. HortScience 38(3):387 389. Hutchinson, C.M. 2004. Con trolled release fertilizer potato production system for Florida. Proc. Fla. State Hort. Soc. 117:76 78. Hutchinson, C.M. 2005. Influence of a controlled release nitrogen fertilizer program on potato ( Solanum tuberosum L. ) tuber yield and quality. Acta Hor t. 684:99 102. Hutchinson, C.M. and E.H. Simonne. 2003. Controlled release fertilizer opportunities and costs for potato production in Florida. Institute of Food and Agricultural Science, University of Florida, Gainesville, FL. Hutchinson, C., E. Simonne P. Solano, J. Meldrum and P. Livingston Way. 2002. Testing of controlled release fertilizer programs for seep irrigated Irish potato production. J. Plant Nutr. 26:1709 1723. Ivors, K. 2010. Commercial production of staked tomatoes in the Southeast. North Carolina State Univ. Coop. Ext., Raleigh, N.C. Jacobs, D.F., R. Rose, and D.L. Haase. 2003. Development of douglas fir seedling root architecture in response to localized nutrient supply. Can. J. For. Res. 33:118 125. Jarrell, W.M. and L. Boersma. 1979. Model for the release of urea by granules of sulfur coated urea applied to the soil. Soil Sci. Soc. Am. J. 43:1044 1050. Junejo, N., M.Y. Khanif, M.M. Hanifi W.M.Z. Wan Yunus, and K.A. Dharejo. 2011. Role of inhibitors and biodegradable material i n mitigation of nitrogen losses from fertilized lands. African J. Biotechnol. 10:3504 3514. Kader, A.A. 2002. Postharvest biology and technology: An overview. p. 39 48. In: A.A. Kader (ed). Postharvest technology of horticulture crops, 3rd. Regents of Uni v. California, Oakland, CA. Kader, A.A., L.L. Morris, and P. Chen. 1978. Evaluation of two objective methods and a subjective rating scale for measuring tomato fruit firmness. J. Amer. Soc. Hort. Sci. 103:70 73. Kader, A.A. and L.L. Morris. 1976. Correlating subjective and objective measurements of maturation and ripeness of tomatoes. p. 57 62. In: Anonymous Proc. 2nd tomato quality wkshp. veg. crops series 178. Univ. California, Davis, CA. Kavanagh, E.E., W.B. McGlasson, and R.L. McBride. 1986. Harvest maturity and acceptability J. Amer. Soc. Hort. Sci. 111:78 82.

PAGE 173

173 Kirkby, E.A., J. Le Bot, S. Adamowicz, and V. Romheld. 2009. Nitrogen in physiology: An agronomic perspective and implications for the use of different n itrogen forms. Intl. Fert. Soc., York, United Kingdom 653. Ko, B.S., Y.S. Cho, and H.K. Rhee. 1996. Controlled release of urea from rosin coated fertilizer particles. Ind. Eng. Chem. Res. 35:250 257. Kochba, M., S. Gambash, and Y. Avnimelech. 1990. Studi es on slow release fertilizers: I. Effects of temperature, soil moisture, and water vapor pressure. Soil Sci 149:339 343. Lammel, J. 2005. Cost of the different options available to farmers: Current situation and prospects, Frankfurt, Germany, 28 30 June 2005. Lamont, G.P., R.J. Worrall, and M.A. O'Connell. 1987. The effects of temperature and time on the solubility of resin coated controlled release fertilizers under laboratory and field conditions. Scientia Hort. 32:265 273. Locascio, S.J., G.J. Hochmu th, F.M. Rhoads, S.M. Olson, A.G. Smajstrla, and E.A. Hanlon. 1997. Nitrogen and potassium application scheduling effects on drip irrigated tomato yield and leaf tissue analysis. HortScience 32:230 235. Liu, G.D., E.H. Simonne, and G.J. Hochmuth. 2012. Soi l and fertilizer management for vegetable production in Florida, p. 3 27. In: S.M. Olson and B.S. Santos (eds.). Vegetable production handbook for Florida. IFAS/UF, Gainesville, FL Lui, K., T.Q. Zhang, C.S. Tan, and T. Astatkie. 2011. Response of fruit yie ld and quality of processing tomato to drip irrigation and fertilizers phosphorus and potassium. Agron. J. 103:1339 1345. Lunt, O.R. and J.J. Oertli. 1962. Controlled release of fertilizer minerals by incapsulating membranes: II. Efficiency of recovery, i nfluence of soil moisture, mode of application, and other considerations related to use. Soil Sci. Soc. Am. J. 26:584 587. Mansour, M.M.F. 2000. Nitrogen containing compounds and adaptation of plants to salinity stress. Biologia Plantarum 43 :491 500. Mau l, F. 1999. Flavor of fresh market tomato ( Lycopersicon esculentum Mill.) as influenced by harvest maturity and storage temperature. University of Florida, Gainesville, FL, PhD. McColloch, L.P. 1962. Bruising injury to tomato. USDA MRR No. 513. Medina, C 2006. Nutrient release patterns of coated fertilizers used for citrus production and their effect on fruit yield and foliar nutrition. University of Florida, Gainesville, Fla.

PAGE 174

174 Medina, C. 20 11 Method development to characterize nutrient release patterns of enhanced efficiency fertilizers. Univ. Florida, Gainesville, PhD Diss Medina, L.C., T.A. Obreza, J.B. Sartain, and R.E. Rouse. 2008. Nitrogen release patterns of a mixed controlled release fertilizer and its components. HortTechnology 18:475 480. Med ina, L.C., J.B. Sartain, and T.A. Obreza. 2009. Estimation of release properties of slow release fertilizer materials. HortTechnology 19:13 15. Mrigout, P., M. Lelandais, F. Bitton, J. Renou, X. Briand, C. Meyer, and F. Daniel Vedele. 2008. Physiological and transcriptomic aspects of urea uptake and assimilation in arabidopsis plants. Plant Physiol. 147:1225 1238. Mikkelsen, R.L. 2005. Tomato flavor and plant nutrition: A brief review. Better Crops 89(2):14 15. Mulvaney, R.L. and J.M. Bremner. 1979. A m odified diacetyl monoxime method for colorimetric determination of urea in soil extracts. Commun. Soil Sci. Plant Anal. 10:1163 1170. Mu oz Arbooleda F., R.S. Mylavarapu, C.M. Hutchinson, and K.M. Portier. 2006. Root distribution under seepage irrigated potatoes in northeast Florida. Amer. J. Potato Res. 83:463 472. Natural Resources Conservation Service (NRCS). 201 2 Web soil survey. 12. July 2013. < http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm >. Noling, J.W., D.A. Botts, and A.W. MacRae. 2012. Alternatives to methyl bromide soil fumigation for Florida vegetable production, p. 47 54. In: S.M. Olson and B. Santos (eds.). Veg. Production Hdbk. Fl orida. Vance Lenexa, KS. Oertli, J.J. and O.R. Lunt. 1962. Controlled release of fertilizer minerals by incapsulating membranes: I. Factors influencing the rate of release. Soil Sci. Soc. Am. J. 26:579 583. Olson, S.M., P.J. Dittmar G.E. Vallad, S.E. We bb, S.A. Smith, E.H. E.J. McAvoy, B.M. Santos and M. Ozores Hampton 201 2a Tomato production in Florida. p. 295 315. In: S.M. Olson and B. Santos (eds.). Vegetable production handbook for Florida. Vance, Lenexa, KS. Olson, S.M., P.J. Dittmar, G.E. Valla d, S.E. Webb, E.J. McAvoy, S.A. Smith, M. Ozores Hampton, and B.M. Santos. 2012 b Pepper production in Florida. p. 223 242. In: S.M. Olson and B. Santos (eds.). Vegetable production handbook for Florida. Vance, Lenexa, KS.

PAGE 175

175 Ott Borrelli, K.A., R.T. Koenig, and C.A. Miles. 2009. A comparison of rapid potentiometric and colorimetric methods for measuring tissue nitrate concentration in leafy green vegetables. HortTechnology 19:439 444. Ozores Hampton, M. C. Snodgrass, and K. Morgan. 2012 Effects of potassium rates in yield, fruit quality, plant biomass and uptake on mature green tomatoes in seepage irrigation. Proc. Fla. Tomato Inst. PRO528:17 20 Ozores Hampton, M.P., E. Simonne, E. McAvoy, P. Stansly, S. Shukla, P. Roberts, F. Roka, T. Obreza, K. Cushman, P. Gilreath, and D. Paramenter. 2006. Nitrogen best management practice with tomato production in Florida in the 2005 2006 season. Proc. Fla. State Hort. Soc. 119:284 288. Ozores Hampton, M., E. Simonne, P. Gilreath, S. Sargent, D.C. M cClure, T. Wilkes, E. McAvoy, P. Stansly, S. Shukla, P. Roberts, F. Roka, T. Obreza, K. Cushmas, and D. Parmenter. 2007. Effect of nitrogen rate on yield of tomato grown with seepage irrigation and reclaimed water. Proc. Florida State Hort. Soc. 120:184 18 8. Ozores Hampton, M.P., E.J. McAvoy, M. Lambert, and D. Sui. 2011. A survey of the effectiveness of current methods used for the freeze protection of vegetables in South Florida. Proc. Fla. State Hort. Soc. 123:128 133. Ozores Hampton, M.P., E.H. Simonn e, K. Morgan, K. Cushman, S. Sato, C. Albright, E. Waldo, and A. Polak. 2009. Can we use controlled release fertilizers (CRF) in tomato production?, Proc. Fla. Tomato Inst PRO526:10 13. Ozores Hampton, M., E. Simmone, F. Roka, K. Morgan, S. Sargent, C. Sn odgrass, and E. McAvoy. 2012. Nitrogen rates effects on the yield, nutritional status, fruit quality, and profitability of tomato grown in the spring with subsurface irrigation. HortScience 47:1129 1133. Pack, J.E., C.M. Hutchinson, and E.H. Simonne. 2006 Evaluation of controlled release fertilizers for northeast Florida chip potato production. J. Plant Nutr. 29:1301 1313. Parks, S.E., D.E. Irving, and P.J. Milham. 2012. A critical evaluation of on farm rapid tests for measuring nitrate in leafy vegetabl es. Scientia Hort. 134:1 5. Perez Garcia, S., M. Fernandez Perez, M. Villafranca Sanchez, E. Gonzalez Pradas, and F. Flores Cespedes. 2007. Controlled release of ammonium nitrate from ethylcellulose coated formulations. Ind. Eng. Chem. Res. 46:3304 3311. Pitts, D.J., A.G. Smajstrla, D.Z. Haman, and G.A. Clark. 2002. Irrigation costs for tomato production in Florida. Institute of Food and Agriculture Sciences, University of Florida, Gainesville, FL. AE74.

PAGE 176

176 Rawluk, C.D.L., C.A. Grant, and G.J. Racz. 2001. Amm onia volatilization from soils fertilized with urea and varying rates of urease inhibitor NBPT. Can. J. Soil Sci. 81:239 246. Reid, M.S. 2002. Ethylene in postharvest technology. p. 149 162. In: A.A. Kader (ed). Postharvest technology of horticulture crop s. Regents Univ. California, Oakland, CA. Ritenour, M.A., E.M. Lamb, P.J. Stoffela, S.A. Sargent. 2002. A portable, digital device for measuring tomato firmness. Proc. Florida State Hort. Soc. 115:49 52. Rosencrans, M. 2012. Early start to the 2012 rainy season. Miami South Florida National Weather Service Forecast Office, Miami, FL. Salman, O.A., G. Hovakeemian, and N. Khraishi. 1989. Polyethylene coated urea. 2. Urea release as affected by coating material, soil type and temperature. Ind. Eng. Chem. Res 28:633 638. Sams, C.E. and W.S. Conway. 2003. Preharvest nutritional factors affecting postharvest physiology. p. 174 190. In: J.A. Bartz and J.K. Brecht (eds.). Postharvest physiology and pathology of vegetables. Marcel Dekker, New York, NY. Sargent, S.A., J.K. Brecht, and J.J. Zoellner. 1992. Sensitivity of tomatoes at mature green and breaker ripeness stages to internal bruising. J. Amer. Soc. Hort. Sci. 117:119 123. Sargent, S.A., J.K. Brecht, and T. Olczyk. 2005. Handling Florida vegetables serie s: Round and roma tomato types. Institute of Food and Agriculture Sciences, University of Florida, Gainesville, FL SS VEC 928. Sartain, J.B., W.L. Hall, R.C. Littell, and E.W. Hopwood. 2004a. Development of methodologies for characterization of slow relea se fertilizers. Soil and Crop Sci Soc of Florida Proc 63:72 75. Sartain, J.B., W.L. Hall, R.C. Littell, and E.W. Hopwood. 2004b. New tools for the analysis and characterization of slow release fertilizers. p. 180 195. In: W.L. Hall and W.P. Robarge (eds.) Environmental Impact of Fertilizer on Soil and Water. American Chemical Society. Sato, S. and K.T. Morgan. 2008. Nitrogen recovery and transformation from a surface or sub surface application of controlled release fertilizer on a sandy soil. J. Plant Nu tr. 31:2214 2231. Sato, S., K.T. Morgan, M. Ozores Hampton, and E.H. Simonne. 2009. Spatial and temporal distribution in sandy soils with seepage irrigation: I. Ammonium and nitrate. Soil Sci. Soc. Am. J. 73:1044 1052.

PAGE 177

177 Sato, S K.T. Morgan, M. Ozores Ha mpton, K. Mahmoud, and E.H. Simonne. 2012. Nutrient b alance and f ertilizer u se e fficiency in s andy s oils c ropped with t omatoes under s eepage i rrigation. Soil Sci. Soc. Am er J. 76:1867 1876. Savant, N.K., J.R. Clemmons, and A.F. James. 1982. A technique for predicting urea release from coated urea in wetland soil. Commun. Soil Sci. Plant Anal. 13:793 802. Scholberg, J. 1996. Adaptive use of crop growth models to simulate the growth of field grown tomato. University of Florida, UMI, PhD Diss. 9800184. Shaviv, A. 1996. Plant response and environmental aspects as affected by rate and pattern of nitrogen release from controlled release N fertilizers. p. 285 291. In: O. Van Cleemput, G. Hofman and A. Vermoesen (eds.). Progress in Nitrogen C ycling Studies. Kluwer Academic Publishers, Netherlands. Shaviv, A., S. Raban, and E. Zaidel. 2003a. Modeling controlled nutrient release from a release. Environ. Sci. Tech nol. 37:2257 2261. Shaviv, A., S. Raban, and E. Zaidel. 2003b. Modeling controlled nutrient release from Technol. 37:2251 2256. Shaviv, A. 2001. Advances in controlled release fertilizers. p. 1 49. In: D. Spark (ed). Advances in Agronomy. Academic Press, Burlington, MA. Shoji, S., J. Delgado, A. Mosier, and Y. Miura. 2001. Use of controlled release fertilizers and nitrification inhibitors to increase nitrogen use efficiency and to conserve air and water quality. Commun. Soil Sci. Plant Anal. 38:1051 1070. Simo n ne, E.H. and G.J. Hochmuth. 2010. Soil and fertilizer management for vegetable production in Florida. In: S.M. Olson and B.S. Santos (eds.). Vegetable production handbook for Florida. IFAS/UF, Gainesville, FL. Simonne, E.H. and C.M. Hutchinson. 2005. Controlled release fertilizers for vegetable production in the era of best management practices: Teaching new tricks to an old dog. HortTechnology 15:36 46 Singh, S.N. and A. Verma. 2007. The potential of nitrification inhibitors to manage the pollution effect of nitrogen fertilizers in agricultural and other soils: A review. Environ. Practice 9:266 279. < http://dx.doi.org/10.1017/S1466046607070482 >. Slater, J.V. 2010. Official Publication AAPFCO. Association of American Plant Food Control Officials, West Lafayette, Indiana.

PAGE 178

178 Smajstrla, A.G. and R. Mu oz Carpena 2011. Simple water level indicator f or seepage irrigation. Institute of Food and Agriculture Sciences, University of Florida, Gainesville, FL. AE085. Taber, H.G. 2001. Petiole sap nitrate sufficiency values for fresh market tomato production. J. Plant Nutr. 26:945 959. Taber, H.G., D.F. Cox, B.C. Smith, and K.A. Klock. 1995. Comparison of specific electrode techniques for measuring bell pepper petiole sap nitrate concentration. HortScience 30:759 (abstr.). Taylor, M.D., S.J. Locascio, and M.R. Alligood. 2004. Blossom end rot incidence of toma to as affected by irrigation quantity, calcium source and reduced potassium. HortScience 39:1110 1115. Thompson, J.F. 2002. Transportation. p. 259 269. In: A.A. Kader (ed). Postharvest technology of horticultural crops. Regents Univ. California, Oakland, C A. Thompson, J.F., F.G. Mitchell, and R.F. Kasmire. 2002. Cooling horticultural commodities. p. 97 112. In: A.A. Kader (ed). Postharvest technology of horticultural crops. Regents Univ. California, Oakland, CA. Thomson, G.E. and J.P. Lopresti. 2008. Impa ct collisions during handling and their effect on internal buising and surface splitting of 'Tempest' tomatoes ( Lycopersicon esculentum). N. Z. J. Crop Hort. Sci. 36:41 51. Tomaszewska, M. and A. Jarosiewicz. 2002. Use of polysulfone in controlled release NPK fertilizer formulations. J. Agr. Food Chem. 50:4634 4639. Trenkel, M.E. 1997. Controlled release and stabilized fertilizers in agriculture. IFA, Paris, France. Trenkel, M.E. 2010. Slow and controlled r elease and stabilized fertilizers: an option for enhancing nutrient use efficiency in agriculture. 2nd ed. IFA, Paris, France. Tzika, M., S. Alexandridou, and C. Kiparissides. 2003. Evaluation of the morphological and release characteristics of coated fer tilizer granules produced in a Wurster fluidized bed. Powder Technol 132(1):16 24. U.S. Dep artment of Agr iculture. 2013. Vegetable 2012 summary. U.S. Dept. Agr., Washington, D.C. U.S. Department of Agriculture Agr. Mrkt. Srv. 1997. United States standard s for grades of fresh tomatoes. 10 Apr. 2013. < http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5050331 >. van der Eerden, L.J.M. 1982. Toxicity of ammonia to plants. Ag r. Environ. 7:223 235. < http://dx.doi.org/10.1016/0304 1131(82)90015 7 >.

PAGE 179

179 Vitosh, M.L. and G.H. Silva. 1994. A rapid petiole sap nitrate nitrogen test for potatoes. Communications Soil Sci. Plant Anal. 25:183 190. Wang, S., A.K. Alva, Y. Li, M. Zhang. 2011. A rapid technique for prediction of nutrient release from polymer coated controlled release fertilizers. Open J. Soil Sci. 1:40 44. Warner, J., T.Q. Zhang, and X. Hao. 2004. Effects of nitrogen fertilization on fruit yield and quality of processing tomatoes. Can. J. Plant Sci. 84:865 871 Wilcox, G.E., J.R. Magalhaes, and F.L.I.M. Silva. 1985. Ammonium and nitrate concentrations as factors in tomato growth and nutrient uptake. J. Plant Nutr. 8:98 9 998. < http://www.informaworld.com/10.1080/01904168509363401 >. Wilson, M.L., C.J. Rosen, and J.F. Moncrief. 2009. A comparison of techniques for determining nitrogen release from polymer coated urea in the field. HortScience 44:492 494. Wright, D.H. and N.D. Harris. 1965. Effect of nitrogen and potassium fertilization on tomato flavor. J. Agric. Food Chem. 33:355 358. Zheng, D., E.R. Hunt Jr, and S.W. Running. 1993. A daily soil temperat ure model based on air temperature and precipitation for continental applications. Clim. Res. 2:183 191. Zotarelli, L., L. Rens, C. Barret, D.J. Cantliffe, M.D. Dukes, M. Clark, and S. Lands. 2013. Subsurface drip irrigation (SDI) for enhanced water distr ibution: SDI Seepage Hybrid System. Univ. Florida, Inst. Food Agr. Sci., Electronic Data Info. Source, HS 1217. 15 Nov. 2013. < http://edis.ifas.ufl.edu/hs1217 > Zotarelli, L., P.D. Roberts, P.J. Dittmar, S.E. W ebb, S.A. Smith, B.M. Santos, and S.M. Olson. 2012. Potato production in Florida. p. 243 259. In: S.M. Olson and B.M. Santos (eds.). Vegetable production handbook for Florida. Vance, Lenexa, KS. Zvomuya, F., C.J. Rosen, M.P. Russelle, and S.C. Gupta. 2003. Nitrate leaching and nitrogen recovery following application of polyolefin coated urea to potato. J. Environ. Qual. 32:480 489.

PAGE 180

180 BIOGRAPHICAL SKETCH Luther Carson grew up in Grand Rapids, Ohio. He attended Wilmington College of Ohio and griculture and e ducation in 2006. He began studies in horticulture science at Virginia Polytechnic Institute and State Universi completion of his doctoral studies, Luther would like to work in the agriculture indust ry as a research scientist.