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Impact of Crop-Management History on Organically Fertilized Sweet Corn (Zea mays L.)

Permanent Link: http://ufdc.ufl.edu/UFE0010525/00001

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Title: Impact of Crop-Management History on Organically Fertilized Sweet Corn (Zea mays L.)
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Copyright Date: 2008

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Source Institution: University of Florida
Holding Location: University of Florida
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System ID: UFE0010525:00001

Permanent Link: http://ufdc.ufl.edu/UFE0010525/00001

Material Information

Title: Impact of Crop-Management History on Organically Fertilized Sweet Corn (Zea mays L.)
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0010525:00001


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IMPACT OF CROP-MANAGEMENT HISTORY ON ORGANICALLY FERTILIZED SWEET CORN ( Zea mays L.) By KIMBERLY A. SEAMAN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2005

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Copyright 2005 by Kimberly A. Seaman

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To my parents, Jeffrey and Karen Seaman

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iv ACKNOWLEDGMENTS I would like to extend my greatest thanks, acknowledge ments, and praise to Dr. R. N. Gallaher, my major professor, fo r his extensive instruc tion, guidance, support, and friendship during my studies at the University of Florida. I would also like to thank Dr. R. McSorley for all of his support a nd editorial assistance. I would like to acknowledge Dr. E. Whitty and Dr. R. Gilbert for their editing and advice. Special thanks are given to Dr. K-H. Wang, Mr. J. Chic hester, and Mr. H. Palmer for all of their assistance in the labo ratory and in the field. I w ould also like to acknowledge the providers of the USDA-CREES grant entitl ed, ‘Effects of Management Practices on Pests, Pathogens, and Beneficials in Soil Ecosystems’ which has supported my research and education. My deepest thanks and love are given to my parents, Jeffrey and Karen Seaman, and my sister, Kelly. Their support and advice have been constant and I never could have completed such a task without them. I woul d also like to specially thank Ms. Belkys Bracho for her friendship and advice throughout my studies in Gainesville. Finally, I want to thank all of my friends for th eir unending support and confidence.

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v TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES.............................................................................................................ix LIST OF FIGURES........................................................................................................xvii ABSTRACT...................................................................................................................xvii i CHAPTER 1 INTRODUCTION........................................................................................................1 Multiple Cropping........................................................................................................1 No-Tillage Cropping.....................................................................................................2 Cropping History..........................................................................................................2 Organic Mulches...........................................................................................................3 2 YIELD AND PLANT NUTRITION FO R NINE SWEET CORN HYBRIDS RECEIVING THREE NITROGEN MANAGEMENT TREATMENTS....................6 Introduction................................................................................................................... 6 Materials and Methods.................................................................................................7 Nitrogen Application.............................................................................................8 Sweet Corn Varieties.............................................................................................9 Nitrogen Analysis..................................................................................................9 Mineral Analysis.................................................................................................10 Yield....................................................................................................................11 Soil Analysis........................................................................................................11 Statistical Analysis..............................................................................................13 Results........................................................................................................................ .13 Data for 2002.......................................................................................................13 Data for 2003.......................................................................................................16 Discussion and Conclusion.........................................................................................18 Data for 2002.......................................................................................................18 Data for 2003.......................................................................................................19

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vi 3 YIELD AND NUTRIENT ELEMENT RELA TIONSHIPS OF FIVE VARIETIES OF COWPEA AND LIMA BEAN.............................................................................52 Introduction.................................................................................................................52 Materials and Methods...............................................................................................54 Experimental Design...........................................................................................55 Nitrogen Analysis................................................................................................56 Mineral Analysis.................................................................................................57 Soil Analysis........................................................................................................57 Nematode Analysis..............................................................................................59 Statistical Analysis..............................................................................................59 Results........................................................................................................................ .59 Discussion and Conclusion.........................................................................................61 4 MINERAL CONTENT AND YIELD OF SUNN HEMP DUE TO CLIPPING HEIGHTS AND PLANT POPULATIONS...............................................................74 Introduction.................................................................................................................74 Materials and Methods...............................................................................................76 Plant Population...................................................................................................76 Yield....................................................................................................................77 Nitrogen Analysis................................................................................................77 Mineral Analysis.................................................................................................78 Soil Analysis........................................................................................................79 Statistical Analysis..............................................................................................81 Results........................................................................................................................ .81 Yield....................................................................................................................81 Mineral Analysis: Clipped Material....................................................................82 Mineral Analysis: Final Non-clipped Material....................................................82 Mineral Analysis: To tal Plant Material...............................................................83 Discussion and Conclusion.........................................................................................83 Yield: Clipped Fresh Matter................................................................................83 Yield: Non-clipped Fresh Matter.........................................................................84 Yield: Total Fresh Matter....................................................................................84 Yield: Clipped Dry Matter...................................................................................85 Yield: Non-clipped Dry Matter...........................................................................86 Yield: Total Dry Matter.......................................................................................87 Mineral Content: Total Clipped Material............................................................87 Mineral Content: Total Final Non-clipped Material...........................................93 Mineral Content: Total Clipped Pl us Final Non-clipped Material......................97 Summary............................................................................................................100

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vii 5 NO-TILL AUSTRIAN WINTER PEA AS A COVER CROP AFFECTED BY CROPPING HISTORY............................................................................................140 Introduction...............................................................................................................140 Materials and Methods.............................................................................................142 Yield..................................................................................................................143 Nitrogen Analysis..............................................................................................143 Mineral Analysis...............................................................................................144 Soil Analysis......................................................................................................145 Statistical Analysis............................................................................................146 Results.......................................................................................................................1 47 Yield and Plant Mineral Concentration.............................................................147 Plant Mineral Content........................................................................................147 Soil Properties...................................................................................................148 Discussion and Conclusion.......................................................................................149 Yield and Plant Mineral Concentration.............................................................149 Plant Mineral Content........................................................................................151 Soil Properties...................................................................................................151 6 SWEET CORN (Zea mays L.) YIELD AFFECTED BY CROPPING HISTORY AND NITROGEN FERTILIZATION.....................................................................167 Introduction...............................................................................................................167 Materials and Methods.............................................................................................168 Cropping Histories.............................................................................................169 Nitrogen Sources...............................................................................................171 Nitrogen Rates...................................................................................................171 Nitrogen Analysis..............................................................................................172 Mineral Analysis...............................................................................................173 Yield..................................................................................................................173 Soil Analysis......................................................................................................173 Statistical Analysis............................................................................................175 Results.......................................................................................................................1 76 Yield: Ear for 2003............................................................................................176 Yield: Diagnostic Leaf for 2003........................................................................177 Mineral Analysis: Diagnostic Leaf for 2003.....................................................177 Mineral Analysis: Soil for 2003........................................................................177 Yield: Ear for 2004............................................................................................178 Yield: Diagnostic Leaf for 2004........................................................................179 Mineral Analysis: Diagnostic Leaf for 2004.....................................................179 Mineral Analysis: Soil for 2004........................................................................179 Discussion and Conclusion.......................................................................................180 Yield: Ear for 2003............................................................................................180 Yield: Diagnostic Leaf for 2003........................................................................182 Mineral Analysis: Diagnostic Leaf for 2003.....................................................183 Mineral Analysis: Soil for 2003........................................................................184 Yield: Ear for 2004............................................................................................185

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viii Yield: Diagnostic Leaf for 2004........................................................................187 Mineral Analysis: Soil for 2004........................................................................189 Summary............................................................................................................191 7 PLANT-PARASITIC NEMATODE POPULATION CHANGES ASSOCIATED WITH CROPPING HISTORIES..............................................................................229 Introduction...............................................................................................................229 Materials and Methods.............................................................................................233 Nematode Populations Following Final Sweet Corn, 2003 and 2004...............233 Pi and Pf Nematode Populations for Final Sweet Corn, 2003 and 2004...........233 Pi and Pf Nematode Populations for Austrian Winter Pea, 2003 and 2004.............234 Nematode Analysis............................................................................................234 Statistical Analysis............................................................................................234 Results.......................................................................................................................2 35 Nematode Populations Following Final Sweet Corn, 2003 and 2004...............235 Pi and Pf Nematode Populations for Final Sweet Corn, 2003 and 2004...........235 Pi and Pf Nematode Populations for Austrian Winter Pea, 2003 and 2004......236 Discussion and Conclusion.......................................................................................236 8 SUMMARY..............................................................................................................245 LIST OF REFERENCES.................................................................................................248 BIOGRAPHICAL SKETCH...........................................................................................255

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ix LIST OF TABLES Table page 1-1 Cropping histories from fall 2002 to spring 2004....................................................5 2-1 Sweet corn ear yield for N manageme nt treatments and sweet corn hybrids for 2002 analysis of variance.......................................................................................21 2-2 Sweet corn diagnostic leaf yield, seed emergence, and plant and ear height for N management treatments and sweet corn hybrids for 2002 analysis of variance..................................................................................................................22 2-3 Sweet corn diagnostic leaf minera l concentrations for N management treatments and sweet corn hybrids for 2002 analysis of variance.........................23 2-4 Soil mineral concentrations and char acteristics for N management treatments and sweet corn hybrids for 2002 analysis of variance...........................................24 2-5 Sweet corn ear yield for N manageme nt treatments and sweet corn hybrids for 2003 analysis of variance.......................................................................................25 2-6 Sweet corn diagnostic leaf yield, leaf area index, seed emergence for N management treatments and sweet corn hybrids for 2003 analysis of variance....26 2-7 Soil mineral concentrations and ch aracteristics for N management of sweet corn for 2003 analysis of variance...............................................................27 2-8 Number of ears for different grad es of sweet corn for three nitrogen management treatments and five hybrids, fall 2002..............................................28 2-9 Fresh weight of ears for different gr ades of sweet corn for three nitrogen management treatments and five hybrids, fall 2002..............................................30 2-10 Yield of 5th leaf for sweet corn for three ni trogen management treatments and five hybrids, fall 2002............................................................................................32 2-11 Percent seed emergence of sweet corn for three nitrogen management treatments and five hybrids, fall 2002....................................................................33 2-12 Plant and ear height of sweet corn fo r three nitrogen management treatments and five hybrids, fall 2002.....................................................................................33

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x 2-13 Mineral analysis for 5th leaf of sweet corn for three nitrogen management treatments and five hybrids, fall 2002....................................................................34 2-14 Mineral analysis for soil samp les following sweet corn, fall 2002........................37 2-15 Number of ears for different grad es of sweet corn for three nitrogen management treatments and five hybrids, fall 2003..............................................41 2-16 Fresh weight of ears for different gr ades of sweet corn for three nitrogen management treatments and five hybrids, fall 2003..............................................43 2-17 Yield of 5th leaf of sweet corn for three ni trogen management treatments and five hybrids, fall 2003............................................................................................45 2-18 Plants emerged for sweet corn for th ree nitrogen management treatments and five hybrids, fall 2003............................................................................................46 2-19 Mineral analysis for 5th leaf of sw eet corn for three nitrogen management treatments and five hybrids, fall 2003....................................................................47 2-20. Mineral analysis for soil samples fo llowing sweet corn harvest, fall 2003..............50 2-21 Soil characteristic analysis for soil samples following sweet corn harvest, fall 2003........................................................................................................................50 2-22 Sufficiency range of macroand micr onutrients for di agnostic leaf of sweet corn during tasseling and early silking........................................................51 3-1 Cowpea plant yield, pod yield, and per centage of plant that was pods for cowpea variety analysis of variance......................................................................63 3-2 Cowpea plant mineral content and cowpea pod mineral content for cowpea variety analysis of variance....................................................................................64 3-3 Lima bean pod yield, percent pods that were beans, and nematode ratings for lima bean variety analysis of variance...................................................................65 3-4 Fresh weights of cowpea for three experi mental designs and five varieties, fall 2002........................................................................................................................66 3-5 Dry weights of cowpea for three experi mental designs and five varieties, fall 2002........................................................................................................................66 3-6 Percent of cowpea plant that was pods for three experimental designs and five varieties, fall 2002..................................................................................................67 3-7 Mineral content in cowpea plant for three experimental designs and five varieties, fall 2002..................................................................................................68

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xi 3-8 Mineral content in cowpea pod for th ree experimental designs and five varieties, fall 2002..................................................................................................70 3-9 Pod yield for six lima bean variet ies over three experimental designs, fall 2003.................................................................................................................72 3-10 Percent of lima bean pods that were beans for six lima bean varieties over three experimental designs, fall 2003....................................................................72 3-11 Nematode infestation ratings for six lima bean varieties over three experimental designs, fall 2003.............................................................................73 3-12 Soil mineral analysis for samples following lima bean harvest for three experimental designs, fall 2003.............................................................................73 4-1 Analysis of variance fo r a split-split plot experi mental design with main treatments in a randomized complete block design.............................................102 4-2 Statistics key for two years, three pl ant populations and four clipping heights of sunn hemp........................................................................................................103 4-3 Fresh matter for total clipped sunn hemp for two years, four clipping heights and three plant populations..................................................................................104 4-4 Fresh matter for final non-clipped sunn hemp for two years, four clipping heights and three plant populations......................................................................105 4-5 Fresh matter for total sunn hemp plan t for two years, four clipping heights and three plant populations..................................................................................106 4-6 Dry matter for total clipped sunn hemp for two years, four clipping heights and three plant populations..................................................................................107 4-7 Dry matter for final non-clipped sunn hemp for two years, four clipping heights and three plant populations......................................................................108 4-8 Dry matter for total sunn hemp plant fo r two years, four clipping heights and three plant populations.........................................................................................109 4-9 Nitrogen content in total clipped sunn hemp for two years, four clipping heights and three plant populations......................................................................110 4-10 Phosphorus content in total clipped s unn hemp for two years, four clipping heights and three plant populations......................................................................111 4-11 Potassium content in total clipped su nn hemp for two years, four clipping heights and three plant populations......................................................................112

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xii 4-12 Calcium content in total clipped sunn hemp for two years, four clipping heights and three plant populations......................................................................113 4-13 Magnesium content in total clipped s unn hemp for two years, four clipping heights and three plant populations......................................................................114 4-14 Sodium content in total clipped s unn hemp for two years, four clipping heights and three plant populations......................................................................115 4-15 Copper content in total clipped sunn hemp for two years, four clipping heights and three plant populations......................................................................116 4-16 Iron content in total clipped sunn hemp for two years, four clipping heights and three plant populations..................................................................................117 4-17 Manganese content in total clipped s unn hemp for two years, four clipping heights and three plant populations......................................................................118 4-18 Zinc content in total clipped sunn hemp for two years, four clipping heights and three plant populations..................................................................................119 4-19 Nitrogen content in total final non-cl ipped sunn hemp for two years, four clipping heights and thr ee plant populations.......................................................120 4-20 Phosphorus content in to tal final non-clipped sunn he mp for two years, four clipping heights and thr ee plant populations.......................................................121 4-21 Potassium content in total final non-c lipped sunn hemp for two years, four clipping heights and thr ee plant populations.......................................................122 4-22 Calcium content in total final non-cl ipped sunn hemp for two years, four clipping heights and thr ee plant populations.......................................................123 4-23 Magnesium content in total final non -clipped sunn hemp for two years, four clipping heights an d three plant populations................................................124 4-24 Sodium content in total final non-cli pped sunn hemp for two years, four clipping heights and thr ee plant populations.......................................................125 4-25 Copper content in total final non-cli pped sunn hemp for two years, four clipping heights and thr ee plant populations.......................................................126 4-26 Iron content in total final non-clipped sunn hemp for two years, four clipping heights and three plant populations......................................................................127 4-27 Manganese content in to tal final non-clipped sunn he mp for two years, four clipping heights and thr ee plant populations.......................................................128

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xiii 4-28 Zinc content in total final non-clippe d sunn hemp for two years, four clipping heights and three plant populations......................................................................129 4-29 Nitrogen content in total clipped pl us final non-clipped sunn hemp for two years, four clipping heights and three plant populations.....................................130 4-30 Phosphorus content in total clipped pl us final non-clipped sunn hemp for two years, four clipping heights and three plant populations.....................................131 4-31 Potassium content in total clipped pl us final non-clipped sunn hemp for two years, four clipping heights and three plant populations.....................................132 4-32 Calcium content in total clipped pl us final non-clipped sunn hemp for two years, four clipping heights and three plant populations.....................................133 4-33 Magnesium content in total clipped pl us final non-clipped sunn hemp for two years, four clipping heights and three plant populations.....................................134 4-34 Sodium content in total clipped plus final non-clipped sunn hemp for two years, four clipping heights and three plant populations.....................................135 4-35 Copper content in total clipped plus final non-clipped sunn hemp for two years, four clipping heights and three plant populations.....................................136 4-36 Iron content in total clipped plus fi nal non-clipped sunn hemp for two years, four clipping heights an d three plant populations................................................137 4-37 Manganese content in total clipped pl us final non-clipped sunn hemp for two years, four clipping heights and three plant populations.....................................138 4-38 Zinc content in total clipped plus fi nal non-clipped sunn hemp for two years, four clipping heights an d three plant populations................................................139 5-1 Above ground plant dry matter of Austri an winter pea analysis of variance......153 5-2 Yield of Austrian winter pea at early bloom stage..............................................153 5-3 Mineral concentration in Austrian winter pea above ground plant dry matter at early bloom stage of grow th analysis of variance............................................154 5-4 Mineral concentration for Austrian winter pea at early bloom stage...................155 5-5 Mineral content in Austrian winter pea above ground plant dry matter at early bloom stage of growth analysis of variance.........................................................157 5-6 Mineral content for Austrian wi nter pea at early bloom stage.............................158 5-7 Soil mineral concentrations in Austri an winter pea above ground plant dry matter at early bloom stage of growth analysis of variance.................................160

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xiv 5-8 Soil mineral concentration and proper ties following harvest of Austrian winter pea.............................................................................................................161 5-9 Correlation coefficients (r) between 2003 Austrian winter pea dry matter yield (DM), plant mineral con centration and soil properties...............................163 5-10 Correlation coefficients (r) between 2004 Austrian winter pea dry matter yield (DM), plant mineral c ontent and soil properties.........................................164 6-1 Analysis of variance fo r a split-split plot experi mental design with main treatments in a CRD experimental design...........................................................193 6-2 Statistics key to treatment means and interactions in sweet corn for three cropping histories, three sources of nitr ogen, and five nitrogen rates in 2003 and 2004...............................................................................................................194 6-3 Sweet corn ears (>15.2 cm in length) produced for three cropping histories, three sources of nitrogen, a nd five nitrogen rates in 2003...................................195 6-4 Sweet corn ears (12.7–15.2 cm in length) produced for three cropping histories, three sources of nitroge n, and five nitrogen rates in 2003...................196 6-5 Sweet corn ears (10.2–12.7 cm in length) produced for three cropping histories, three sources of nitroge n, and five nitrogen rates in 2003...................197 6-6 Sweet corn ears (<10.2 cm in length) produced for three cropping histories, three sources of nitrogen, a nd five nitrogen rates in 2003...................................198 6-7 Total sweet corn ears produced for th ree cropping histories, three sources of nitrogen, and five nitrogen rates in 2003.............................................................199 6-8 Sweet corn ear (>15.2 cm in length) yi eld for three croppi ng histories, three sources of nitrogen, and five nitrogen rates in 2003, Gaines ville, Florida..........200 6-9 Sweet corn ear (12.7–15.2 cm in length) yield for three cropping histories, three sources of nitrogen, a nd five nitrogen rates in 2003...................................201 6-10 Sweet corn ear (10.2–12.7 cm in length) yield for three cropping histories, three sources of nitrogen, a nd five nitrogen rates in 2003...................................202 6-11 Sweet corn ear (<10.2 cm in length) yi eld for three croppi ng histories, three sources of nitrogen, and five nitrogen rates in 2003............................................203 6-12 Total sweet corn ear yi eld for three cropping histor ies, three sources of nitrogen, and five nitrogen rates in 2003.............................................................204 6-13 Diagnostic leaf (5th leaf from top) area for th ree cropping histories, three sources of nitrogen, and five nitrogen rates in 2003............................................205

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xv 6-14 Diagnostic leaf (5th leaf from top) weight for three cropping hi stories, three sources of nitrogen, and five nitrogen rates in 2003............................................206 6-15 Nitrogen concentrati on of diagnostic leaf (5th leaf from top) for three cropping histories, three sources of nitr ogen, and five nitrogen rates in 2003....207 6-16 Phosphorus concentratio n of diagnostic leaf (5th leaf from top) for three cropping histories, three sources of nitr ogen, and five nitrogen rates in 2003....208 6-17 Potassium concentration of diagnostic leaf (5th leaf from top) for three cropping histories, three sources of nitr ogen, and five nitrogen rates in 2003....209 6-18 Soil analysis for three cropping histor ies and three nitrogen sources in 2003.....210 6-19 Sweet corn ears (>15.2 cm in length) produced for three cropping histories, three sources of nitrogen, a nd five nitrogen rates in 2004...................................212 6-20 Sweet corn ears (12.7–15.2 cm in length) produced for three cropping histories, three sources of nitroge n, and five nitrogen rates in 2004...................213 6-21 Sweet corn ears (10.2–12.7 cm in length) produced for three cropping histories, three sources of nitroge n, and five nitrogen rates in 2004...................214 6-23 Total sweet corn ears produced for th ree cropping histories, three sources of nitrogen, and five nitrogen rates in 2004.............................................................216 6-24 Sweet corn ear (>15.2 cm in length) yi eld for three croppi ng histories, three sources of nitrogen, and five nitrogen rates in 2004............................................217 6-25 Sweet corn ear (12.7–15.2 cm in length) yield for three cropping histories, three sources of nitrogen, a nd five nitrogen rates in 2004...................................218 6-26 Sweet corn ear (10.2–12.7 cm in length) yield for three cropping histories, three sources of nitrogen, a nd five nitrogen rates in 2004...................................219 6-27 Sweet corn ear (<10.2 cm in length) yi eld for three croppi ng histories, three sources of nitrogen, and five nitrogen rates in 2004............................................220 6-28 Total sweet corn ear yi eld for three cropping histor ies, three sources of nitrogen, and five nitrogen rates in 2004.............................................................221 6-29 Diagnostic leaf (5th leaf from top) area for th ree cropping histories, three sources of nitrogen, and five nitrogen rates in 2004............................................222 6-30 Diagnostic leaf (5th leaf from top) weight for three cropping hi stories, three sources of nitrogen, and five nitrogen rates in 2004............................................223 6-31 Nitrogen concentrati on of diagnostic leaf (5th leaf from top) for three cropping histories, three sources of nitroge n, and five nitrogen rates in 2004...................224

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xvi 6-32 Phosphorus concentratio n of diagnostic leaf (5th leaf from top) for three cropping histories, three sources of nitr ogen, and five nitrogen rates in 2004....225 6-33 Potassium concentration of diagnostic leaf (5th leaf from top) for three cropping histories, three sources of nitr ogen, and five nitrogen rates in 2004....226 6-34 Soil analysis for three cropping histor ies and three nitrogen sources in 2004.....227 7-1 Nematodes following spring planted sweet corn for three cropping histories and three nitrogen sources analysis of variance...................................................239 7-2 Analysis of variance for nematodes prior to and following spring planted sweet corn for three cropping histories................................................................240 7-3 Analysis of variance for nematodes prior to and following winter planted cover crop of Austrian winter pea for three cropping histories...........................241 7-4 Nematodes following spring planted sweet corn crop for three cropping histories and three nitrogen sources.....................................................................242 7-5 Nematodes prior to and following sp ring planted sweet corn crop for three cropping histories.................................................................................................243 7-6 Nematodes prior to and following wint er planted cover cr op of Austrian winter pea for three cropping histories................................................................244

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xvii LIST OF FIGURES Figure page 5-1 Temperature, monthly averag e, for Alachua County, Florida (Florida Automated Weather Service, 2005).........................................................165 5-2 Rainfall, monthly average, for Alachua County, Florida (Florida Automated Weather Service, 2005).........................................................165 5-3 Solar radiation, monthly averag e, for Alachua County, Florida, (Florida Automated Weather Service, 2005).........................................................166

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xviii Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science IMPACT OF CROP-MANAGEMENT HISTORY ON ORGANICALLY FERTILIZED SWEET CORN ( Zea mays L.) By Kimberly A. Seaman May 2005 Chair: R.N. Gallaher Major Department: Agronomy Farmers make decisions daily that impact the environment. Multiple cropping, no-tillage management, and organic fertilizer s are all agronomic techniques that promote sustainable agriculture a nd benefit the environment and farmer alike. Research was conducted to investigate th e effects of no-tilla ge multiple cropping systems on organically fertilized sweet corn ( Zea mays L.). A split-split plot experiment was conducted to examine cropping history, N s ource, and N rate. Production, in terms of yield and quality, and plant nutrient concentrations were determined. Sweet corn yield was not affected by cropping hi story; but was affected by N source, with the inorganic source producing significantly higher yields than organic sources (5.2, 5.2, and 6.0 ears m-2 for lupine ( Lupinus angustifolius L.), vetch ( Vicia villosa L. Roth), and ammonium nitrate, respectively) ( p < 0.05). Diagnostic leaf N c oncentration was affected by cropping history and N source ( p < 0.05). Equal response of sw eet corn to organic and inorganic N sources may be achieved by c hoosing appropriate ra tes of organic N.

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xix Crops within the systems were also exam ined. An experiment was conducted to investigate applied N management, yield, and pl ant mineral concentrations of sweet corn hybrids. Nitrogen treatments had a minor eff ect on measured variables compared to hybrids, with ‘Silver Queen’ and ‘8102R’ proving to be the best hybrids for fall production in Florida. Cowpea ( Vigna unguiculata (L.) Walp.) and lima bean ( Phaseolus lunatus L.) were also examined for yield and plant mineral content. For produc tion in Florida in a cropping system or for use as an organic mulch, ‘Iron Clay’ cowpea was the best candidate, while ‘California Bl ackeye #5’ was the best for consumption. The lima bean hybrid ‘Fordhook’ was the top choice for food crop production. Sunn hemp ( Crotalaria juncea L.) was also investigated, to determine the effects of plant height and population on yi eld and mineral concentration. Plants grown at densities of 18 and 30 plants m-2 and maintained at heights of 0.4 and 0.8 m produced highest yields and highest mineral concentrations. The effect of previous crops on Austrian winter pea ( Pisum arvense L.) was also investigated, with N concentration in dry matter highest (4.4% N) following sweet corn. Plant-parasitic nema tode populations were also examined following each crop, and were f ound to be lowest following sunn hemp and Austrian winter pea.

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1 CHAPTER 1 INTRODUCTION Multiple Cropping Multiple cropping is an agronomic practice us ed by farmers for thousands of years. The practice of harvesting more than one cr op from the same land over the course of a year is especially successful in areas with tropical or s ubtropical climates. Florida’s climate is suitable for the production of multiple crops in 1 yr, and as many as 3 or more sequential crops can be harvested. Multiple cropping used in conjunction with no-tillage cropping can increase the success of crop production (Gallaher, 1980). No-tillage practices are defined as any til lage and planting system that maintains at least 30% of the soil surface covered by residue af ter planting in order to decrease soil erosion by water (Gallaher and Ferrer, 1987). Th e characteristics of Florida’ s climate are conducive to the implementation of both of these practices, the high temperatures and humidity helping to rapidly break down crop residues and avoid over-accumulation. Multiple cropping also offers many benefits when crops such as legumes are included in the system. Legumes have the cap acity to fix N, which reduces the need for added N fertilizers. The use of legumes in a cropping system can increase the amount of N in the soil and the N that is available to subsequent crops, decreasing the need for added inorganic fertilizers. Specific legume species have also been found to aid in nematode control, possessing suppressive qualities that reduce nematode populations, which can be very destructive especially in the Southeast (Dav is et al., 1991).

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2 No-Tillage Cropping The utilization of both multiple cropping and no-tillage cropping can be very beneficial. No-tillage cropping greatly reduces soilbed preparation, which can contribute to timely planting over more land area. Less labor is requ ired, and also less equipment and fuel use, which can help re duce maintenance and upke ep costs (Gallaher, 1980). Less tillage also greatly helps to improve soil health by reducing erosion and maintaining soil moisture. The organic matter of soil can also be greatly increased by notillage practices. In a 6-yr study conducted in Florida, soil 0 to 5 cm in depth was found to be 36% higher in organic matter than th at in conventional cropping systems (Gallaher and Ferrer, 1987). Cropping History Diversified cropping histories also influence the supply of nutrients to growing crops. Crops differ considerably in the amount of N, one of the most important nutrients for crop growth, returned in residue for use by subsequent crops because N supplied depends on volume of residue as well as N c oncentration of the residue (Grant et al., 2002). Varying crop species and nutrient mana gement of those species will affect the nutrient content of crop residues and the amount of nutrients that will become available for subsequent crops. The inclusion of crops such as legumes into cropping histories can increase available N for (and also reduce i norganic N requirements of) subsequent nonlegume crops. Phosphorus and N availability are necessary to optimize crop yield and quality and efficiency of crop production (Grant et al., 1996). Cropping history can also influence P levels in soil. A history of crops high in P produced in a no-tillage system can greatly

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3 benefit subsequent crops. Increased availa bility of P can occur through biocycling of crop residue and litter. Another important nutrient for crop health and productivity is K. Approximately 80% of plant K is located in stubble (Whitb read et al., 1998) and th e potential for return to the soil for use by succeeding crops is gr eatly influenced by residue management. Crops containing higher levels of K would be more suited for inclusion in a cropping history managed with no-tillage practices, potentially supplying more K for later crops through residue. Careful consideration must be paid to what crops should be chosen for inclusion in cropping systems. Variations in croppi ng history influence many aspects of crop production, especially soil prop erties. Diversification of cropping systems affects physical, chemical, and microbiological char acteristics of soil Increasing crop production can increase the amount of plant biom ass produced and returned to the soil as residue and root material (Gra nt et al., 2002). As a result soil organic matter content may increase (Wood et al., 1990) and this can imp rove the stability an d structure of the soil (Campbell and Zentner, 1993) as well as nutrient cycling. Cropping history can impact soil respiration, microbial bioma ss, and soil microbiological diversity (Lupwayi et al., 1999). Organic Mulches The use of organic mulches and fertilizers is another agricultur al technique often used in conjunction with multiple cropping and no-tillage practices. Organic mulches bring many benefits to cropping systems, especi ally to the soil. Legumes can add N to soil, especially in the form of a mulch. Other nutrients are also made available to subsequent crops by using organic mulches, th e most important of which include P, K,

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4 Ca, and Mg. Applying mulches can reduce soil erosion, conserve soil moisture, and prevent weed infestation. Also, the stru cture of the soil can be improved with the addition of organic matter from the br eakdown of the organic mulch. Crop yield and quality, including nutrient production, can be improved with the proper utilization of multip le cropping and no-tillage cr opping systems. Nitrogen management is also important for achieving hi gh yields of healthy crops. An efficient cropping system will balance crop demands for N with timing and rate of N supply so that crop yield is maximized while N is neit her depleted from the soil nor accumulated (potentially contaminating ground or surface wa ters) (Grant et al., 2002). The source, rate, and timing of applied fertilizer can be determined to meet these goals. A 2-yr investigation that in tegrated these agronomic pr inciples was conducted from the fall of 2002 to the spring of 2004. Three different multiple cropping systems were established each year and maintained using notillage techniques (Table 1-1). The first history included sweet corn ( Zea mays L.), followed by Austrian winter pea ( Pisum arvense L.), followed by sweet corn. This same sequence of crops was repeated during both years of the study for the first hist ory. The second crop ping history included cowpea ( Vigna unguiculata (L.) Walp.), followed by Austrian winter pea, followed by sweet corn for the first year of the study. In the second year, lima bean ( Phaseolus lunatus L.) replaced cowpea, and the remainder of the history was repeated. The third history included sunn hemp ( Crotalaria juncea L.), followed by Austrian winter pea, followed by sweet corn. The same sequence of crops was grown for both years of the study for the third cropping hist ory. The investigation focu sed on the final sweet corn crop of each year of the study and the impact that each multiple cropping history had on

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5 the sweet corn. Different ra tes and sources of N were also examined during the final sweet corn crop. The individual crops within each history were also examined. The specific objectives of this research were as follows: Evaluate yield and plant nut rition of sweet corn due to varying N management treatments and varieties. Evaluate yield and plant nutrition of cowpea and lima bean varieties. Analyze sunn hemp for mineral concentr ation to determine mineral content and find the best clipping height and populat ion for maximum yield and N content. Compare three cropping histories for their e ffect on yield of an Austrian winter pea cover crop and analyze the legume for mine ral concentration to compare mineral content across three cropping histories. Evaluate yield and plant nut rition of sweet corn due to varying cropping histories, N sources (organic and inor ganic), and N rates. Determine which cropping histories resulted in low nematode population densities. Table 1-1. Cropping histories from fall 2002 to spring 2004. Cropping histories Season 1 2 3 Fall 2002 Sweet corn Cowpea Sunn hemp Winter 2003 Austrian winter pea Austri an winter pea Austrian winter pea Spring 2003 Sweet corn Sweet corn Sweet corn Fall 2003 Sweet corn Lima bean Sunn hemp Winter 2004 Austrian winter pea Austri an winter pea Austrian winter pea Spring 2004 Sweet corn Sweet corn Sweet corn

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6 CHAPTER 2 YIELD AND PLANT NUTRITION FO R NINE SWEET CORN HYBRIDS RECEIVING THREE NITROGEN MANAGEMENT TREATMENTS Introduction Sweet corn ( Zea mays L.) is an economically impo rtant crop for Florida. The Florida climate provides a suit able environment for sweet corn production at a time when most of the US is too cold for corn growth (Gallaher and McSorley, 1998). Florida is the major source of sweet corn during the winter and early spring, w ith harvesting most active from November to June (Florida Commodities, 2002). In 1998, Florida was the top ranking state in gross r eceipts from sweet corn producti on (Orzolek et. al., 2003). Over 15,900 ha of sweet corn were planted in Florida in the 2002-03 season, yielding over 16,100 kg ha-1 of fresh produce and bringing in well over $89 million to the state’s economy (Florida Agricultural Statistics Service, 2004). The recommended amount of N fertilizer for sweet corn in Florida is 224 kg ha-1 (Hochmuth et al., 1996). In a study conduc ted from 1992-95 in Iowa, sweet corn grown in cropping systems following rye ( Secale cereale L.) exhibited a linear response in yield to increasing rates of N fertilizer, with affects peaking at an N rate of 156 kg N ha-1 (Griffin et al., 2000). In a study in Minnesota sweet corn (var. Rugosa Bonaf.) silage waste was applied to a crop of field corn ( Zea mays L.) and was found to significantly increase in-season and post-harvest soil N con centrations and to op timize grain yield and N uptake of the field corn (Fritz et al., 2001) These studies illustra te the variation and importance of N management in corn production.

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7 Sweet corn can provide farmers with a very viable option for multiple cropping systems. The cultivation of sw eet corn following strawberry ( Fragaria x Ananassa ) in a cropping system cultivated in Taiwan was found to be effective in utilizing the high residual N after the strawberry harvest (L ian, 1991). Conversely, production of sweet corn, which was chosen for its high N require ment and early maturity, in Quebec was found to benefit from the use of cover crops that absorbed excess fertilizers following harvest (Isse et al., 1999). Sw eet corn can be a beneficial component of cropping systems because succeeding crops can absorb residual so il N, reducing the need for applied N, as well as minimize losses of fertilizer to leaching (Isse et al., 1999). The use of sweet corn in cropping systems, especia lly after several ye ars of a cover crop such as alfalfa ( Medicago sativa L.), was also found to reduce weed pressure during th e year the sweet corn was produced (Delahaut and Thiede, 2002). Due to increasing interest in the reduction of nutrient leaching and the more precise application of fertilizers, a 2-yr experime nt was conducted to investigate applied N management on 9 different varieties of sweet co rn. This test was also part of a larger study (see Chapter 6) conducted to investigat e the effects of croppi ng histories on no-till sweet corn. This particular portion of th e overall study comprised the first of 3 cropping histories tested. The objectives of this study were to evaluate the yield and plant nutrition of sweet corn due to varying N manage ment treatments and varieties. Materials and Methods For this study, a split-plot experiment was conducted from August to November of 2002 and 2003. Main effects were 3 N applic ation treatments (4, 3, and 2 equal split applications) of ammonium nitrate (AN) each totaling the recommended 224 kg N ha-1 (IFAS Extension Soil Testing Laboratory, 2002). The main effects allowed us to

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8 determine the optimum N management for sw eet corn. Sub-effects were 5 different hybrids of sweet corn (‘Merrit t’, ‘Silver Queen’, ‘Golden Qu een’, ‘Florida Stay Sweet’, and ‘Peaches and Cream’ in 2002), (‘Silver Qu een’, ‘8100R’, ‘Prime Plus’, ‘8102R’, and ‘Big Time’ in 2003). Throughout both years of the study, corn was irri gated to ensure at least 3 cm of water per week, and weeded both mechanically and manually. Data from each year was analyzed separately, because with the exception of ‘Silver Queen’, hybrids differed each year. The split-plot design is specifically suited for a 2-factor experiment that has more treatments than a randomized complete block design can accommodate (Gomez and Gomez, 1984). In this design, the precision for the measurement of the effects of the main-plot factor is sacrificed to improve th at of the subplot factor. The randomization process in this design is perfor med separately for each effect. Nitrogen Application In order to more precisely examine applie d N fertilizer and any subsequent nutrient leaching, we evaluated the effects of vary ing N management treatments on a crop of sweet corn. Three different management pl ans were implemented and the null hypothesis stated that the various plans would not a ffect final sweet corn yield or nutrient concentration in diagnos tic leaf samples. Sweet corn was planted on 29 August of 2002 and on 25 August of 2003. Each plot contained four 0.76 m wide rows and meas ured 2 m by 3 m. Varieties were planted by hand at a rate of 10 seeds m-2 into Millhopper fine sand (loamy siliceous semiactive hyperthermic Grossarenic Paleodults [USDANRCS, 2003]). Plants were thinned by hand to approximately 6 plants m-2 during both years of the study.

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9 The N treatments were all applied by hand during both years of the study. Treatment 1 was split into 4 equal applications of AN at 56 kg N ha-1. Application began 1 week after planting and continued every 12 days following until the total recommended N had been applied. Treatment 2 was split into 3 equal AN applications at 75 kg N ha-1. Application began 1 week following planti ng and continued every 16 days following until the total recommended N had been appl ied. Treatment 3 was split into 2 equal applications of AN at 112 kg N ha-1. The initial application took place 1 week following planting and a second 24 days later to complete the total recommended N. Sweet Corn Varieties Five different varieties of sweet corn were tested during the first year of the study. Four additional varieties were tested during the second year of the study in conjunction with the highest yielding variety from the firs t year. New varieties were tested during the second year in order to increas e the number of hybrids tested Also, during the first year of the study, some hybrids did not grow tall enough to avoid damage from rodents and taller-growing hybrids were needed. Each crop of sweet corn was analyzed separately for yield and nutrient concentrations. Soil sa mples were taken from a depth of 20 cm directly following harvest. Nitrogen Analysis Five diagnostic leaves, or th e fifth leaf from the top of each plant, were obtained during early tassel stage from each plot during both years of the experiment for analysis (Mills and Jones, 1996). Sample leaves were combined from each plot and analyzed for leaf area with a LI 3100 Area Meter (LI-COR Inc., Lincoln, NE), weighed for fresh matter yield, dried in a forced air oven at 70C, and weighed again for dry matter yield.

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10 Leaf samples were then ground in a Wiley mill to pass a 2-mm stainless steel screen. The samples were then stored in plastic sample bags before analysis. Nitrogen analysis of the di agnostic leaf samples was performed using a modified micro-Kjedahl procedure. A mixture of 0.100 g of each leaf sample, 3.2 g salt-catalyst (9:1 K2SO4:CuSO4), 2 to 3 glass boiling beads and 10 mL of H2SO4 were vortexed in a 100 mL test tube. In order to reduce frothing, 2 mL 30% H2O2 were added in 1 mL increments and tubes were then digested in an aluminum block digester at 370 C for 3.5 hours (Gallaher et al., 1975). Cool digested solutions were brought to 75 mL volume and were filtered to remove the boiling beads. Solutions were then transferred to square Nalgene storage bottles, sealed, mixed, and stored. Nitrogen trapped as (NH4)2SO4 was analyzed on an automatic solution sampler a nd a proportioning pump. A plant standard with a known N concentration value was subject ed to the same procedure as the leaf samples and used as a check (Multiple Croppi ng Agronomy Lab, University of Florida). Fresh matter, dry matter, and nutrient concen trations were recorded for each crop of sweet corn. Mineral Analysis For mineral analysis, 1.0 g from each leaf sample was weighed into 50 mL beakers and ashed in a muffle furnace at 480C for 6 h. The samples were then cooled to room temperature and moistened with de-ionized wate r. Twenty mL of de-ionized water and 2 mL of concentrated HCl were added to each beaker, which were then placed on a hot plate and slowly boiled to dryness before be ing removed. An additional 20 mL of deionized water and 2 mL concentrated HCl were then added and small watch glasses were used to cover the beakers for reflux. They were brought to a vigorous boil and then removed from the hot plate and again allowed to cool to room temperature. The samples

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11 were then brought to volume in 100 mL flasks and mixed. The flasks were set aside overnight to allow the Si to settle. The so lutions were decanted into 20 mL scintillation vials for analysis. Phosphorus was an alyzed by colorimetry, K and Na by flame emission, and Ca, Mg, Cu, Fe, Mn, and Zn by atomic adsorption spectrometry (AA). Data from each year were analyzed by ANO VA for a split-plot expe rimental design using MSTAT 4.0 (1985). Means were separated by least significant diffe rence (LSD) at the 0.05 level of probability (Gomez and Gomez, 1984). Yield For both years of the experiment, the ear s from each plot were hand collected before being graded and separated into >15.2 cm, 12.7 to 15.2 cm, 10.2 to 12.7 cm, and <10.2 cm length categories (USDA, 1954). The ears were then counted and weighed in order to obtain fresh weights. Soil Analysis During both years of the study, soil samples were obtained from the top 20 cm of soil directly following harvest. Samples were air-dried in open paper bags, then screened through a 2.0-mm stainless steel sieve to rem ove any rocks or debris and stored for further analysis. The samples were then analyzed for N, mineral concentrations, pH, buffer pH (BpH), organic matter (OM), a nd cation exchange capacity (CEC ). For soil N, a mixture of 2.0 g of each soil sample, 3.2 g of salt catalyst (9:1 K2SO4:CuSO4), and 10 mL of H2SO4 were subjected to the same procedures for N analysis as leaf tissue was, except that boiling beads were not used because the pa rticles of soil served the same purpose. A soil sample of known N concentration was also analyzed and used as a check. For soil mineral analysis, a Mehlich I (Mehlich, 1953), extraction method was used. Five g of

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12 each soil sample were weighed and extracted with 20 mL of a combination of 0.025 N H2SO4 and 0.05 N HCl. Using an Eberach shak er at 240 oscillations minute-1, mixtures were shaken for 5 min. The mixtures were then filtered using Schleischer and Schuell 620 (11 cm) filter paper and poured into scintilla tion vials. The remaining solutions were then subjected to analysis of P, K, Ca, Mg, Na, Cu, Fe, Mn, and Zn in the same manner as described for leaf tissue analysis. Soil pH was found using a 1:2 soil to water volume ratio using a glass electrode pH meter (Peech, 1965). Buffer pH was found using Adams/Evans buffered solution (Adams and Evans, 1962). Cation exchange capacity was estimated by the summation of relevant cations (Hesse, 1972; Jackson, 1958) Estimated soil CEC was calculated by summing the milliequivalents of the determined bases of Ca, Mg, K, and Na (where applicable) and adding them to exchangeable H+ expressed in milliequivalents per 100 grams (meq 100 g-1 or cmol kg-1) (Hesse, 1972). For the determination of OM, a modified version of the Walkley Black me thod was used, in which 1.0 g of soil was weighed into a 500-mL Earlenme yer flask, and 10 mL of 1 N K2Cr2O7 solution was then pipetted into the flask. Twenty mL of concentrated H2SO4 was added and mixed by gentle rotation for 1 min using care to avoid throwing soil up onto th e sides of the flask. The flask was then left to stand for 30 mi n, and then diluted to 200 mL with de-ionized water. Five drops of indi cator were added, and the solution was titrated with 0.5 N ferrous sulfate solution until the color sharply changed from a dull green to a reddish brown color. A flask without soil was prep ared in the same manner and titrated to determine the blank titrant, along with a flask containing a check soil with a known amount of OM. Percent OM was determined using the equation: percent OM = (1-T/S) x

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13 6.8, where S is blank-titration in mL of fe rrous ammonium sulfate solution, and T is sample titration in mL ferrous ammonium sulfate solution (Walkley, 1935; Allison, 1965). Statistical Analysis Data was recorded in Quattro Pro (Anony mous, 1987) spreadsheets and transferred to MSTAT 4.0 (Anonymous, 1985) for analysis of variance using the appropriate model for the experimental design (Tables 2-1 to 2-7). Mean separation was performed using fixed LSD at the 0.05 level of pr obability (Gomez and Gomez, 1984). Results Data for 2002 The number of sweet corn ears measuring >15.2 cm in length for 2002 displayed no significant ( p >0.05) differences among N manage ment treatments (Table 2-8). Significant ( p < 0.05) differences occurred among sweet co rn hybrids, with ‘Silver Queen’ producing the highest number of top grade ears (Table 2-8). Ears measuring 12.7 to 15.2 cm in length did not differ ( p >0.05) among N management treatments, but again, differences ( p < 0.05) were found among hybrids (Table 28). Number of ears measuring 10.2 to 12.7 cm did not differ ( p >0.05) among N management treatments, but differences ( p < 0.05) were found among hybrids (Table 2-8). The lowest grade ears differed ( p >0.05) among N management treatments as well as among sweet corn hybrids (Table 2-8). Total ears produced in 2002 also differed ( p < 0.05) among N management treatments and hybrids, with 4 N splits yielding highest and ‘Silver Queen’ as the top-producing hybrid (Table 2-8). In summary, ‘Silver Queen’ produced the highest num ber of total ears as well as the highest number of top grade ears.

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14 The fresh weight of ears >15.2 cm in length produced in 2002 exhibited no significant ( p >0.05) differences among N manage ment treatments (Table 2-9). Significant ( p < 0.05) differences occurred among sweet co rn hybrids for the weight of top grade ears, with ‘Silver Queen’ as the top-producing hybrid (Tab le 2-9). Fresh weight of ears measuring 12.7 to 15.2 cm were not statistically different ( p >0.05) among N management treatments, but differed among hybrid s (Table 2-9). Weights of sweet corn ears 10.2 to 12.7 cm in length were not statistically different ( p >0.05) among N management treatments, but disp layed significant differences ( p < 0.05) among hybrids (Table 2-9). Fresh weight of ears measur ing <10.2 cm in length exhibited significant ( p < 0.05) differences among both N management tr eatments and hybrids (Table 2-9). No statistical differences ( p >0.05) were demonstrated among N management treatments for total ear weight produce d, while significant ( p < 0.05) differences occurred among sweet corn hybrids, again with ‘Silver Queen’ as top-producing hybrid (Table 2-9). ‘Silver Queen’ produced not only the most total ear weight, but also the most top grade ear weight in 2002. The fresh weights of the fifth leaf, or diagnostic leaf, harvested in 2002 were found to exhibit no significant ( p >0.05) differences among N mana gement treatments (Table 210). Statistical differences ( p < 0.05) were found among sweet corn hybrids, with ‘Silver Queen’ producing the heaviest leaves (Table 210). The dry weights of the fifth leaves were not statistically different ( p >0.05) among N management treatments, but were among hybrids with ‘Silver Queen’ producing the h eaviest leaves (Table 2-10). The leaf area index did not display any significant ( p >0.05) differences among N management

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15 treatments, but did among hybrids, with ‘P eaches and Cream’ producing the largest leaves (Table 2-10). Percent seed emergence of sweet corn in 2002 displayed an interaction between N management treatments and the sweet corn hybrids (Table 2-11). Both plant and ear height of sweet corn for 2002 did not exhibit significant ( p >0.05) differences among N management treatments, while both did exhibit differences ( p < 0.05) among corn hybrids (Table 2-12). ‘Silver Queen’ and ‘Golden Qu een’ hybrids produced the tallest plants and highest ears on the stalk. Among the macronutrients in the diagnostic leaf in 2002, only Ca, P, and N were not significantly ( p > 0.05) different among N management treatments (Table 2-13). The N management treatments were statistically different ( p < 0.05) for Mg, K, and Na (Table 2-13). While interactions were pr esent in Mg and Na between N management treatments and hybrids, K and P di splayed statistical differences ( p < 0.05) among sweet corn hybrids (Table 2-13). Among the micronutrients, inter actions between N management treatments and hybrids were pr esent in Cu, Mn, and Zn (Table 2-13). Significant ( p < 0.05) differences were displayed am ong N management treatments as well as among sweet corn hybrids for Fe (Table 2-13). For soil macroand micronutrients, no significant ( p >0.05) differences were exhibited, either among N management treatme nts or among sweet corn hybrids (Table 2-14). Soil pH was not statistically different ( p >0.05) among N management treatments, but was among hybrids (Table 214). Soil BpH displayed an interaction between N management treatments and hybrids (Table 2-14). Soil CEC was not statistically different ( p >0.05) among N treatments or hybr ids (Table 2-14). Soil OM

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16 displayed significant ( p < 0.05) differences among N manage ment treatments, but not among hybrids (Table 2-14). Data for 2003 The number of sweet corn ears produced in 2003 measuring >15.2 cm in length were not statistically different ( p >0.05) among N management treatments, but were among sweet corn hybrids (Table 2-15). Hybr id ‘8102R’ was the top producer for the highest-grade ears (Table 2-15). The numbe rs of ears 12.7 to 15.2 cm in length were statistically different ( p < 0.05) among N management tr eatments as well as among hybrids (Table 2-15). Ears measuring 10.2 to 12.7 cm were not significantly ( p > 0.05) different among N management treatments, but were among corn hybrids (Table 2-15). Ears <10.2 cm were also not significantly ( p > 0.05) different among N management treatments, but were among hybrids (Table 215). The total ears produced in 2003 did not differ ( p > 0.05) among N management treatments, but did among sweet corn hybrids (Table 2-15). ‘Silver Queen’, ‘8100R’, a nd ‘8102R’ were all top-producing hybrids in 2003 (Table 2-15). The fresh weights of ears >15.2 cm produ ced in 2003 did not display significant ( p >0.05) differences among N management treatments, but did among corn hybrids (Table 2-16). Hybrid ‘8102R’ produced the highest number of top-grade ears (Table 216). An interaction was displayed between N management treatments and hybrids in ears measuring 12.7 to 15.3 cm (Table 2-16). No statistical differences ( p >0.05) were exhibited among N management treatments in ears 10.2 to 12.7 cm, while sweet corn hybrids were statistically different ( p < 0.05) (Table 2-16). Ears <10.2 cm were significantly ( p < 0.05) different among N management treatments as well as among hybrids (Table 2-9). Fresh weights of total ea rs produced were not st atistically different

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17 ( p >0.05) among N management treatments, but differed ( p < 0.05) among hybrids (Table 2-16). Hybrid ‘8102R’ was the highest producing hybrid in 2003 (Table 2-16). Fresh weights of fifth leaves from 2 003 displayed statistical differences ( p < 0.05) among both N management treatments and corn hybrids (Table 2-17). Dry weights also were not significantly ( p >0.05) different among N manage ment treatments but were among sweet corn hybrids (Table 2-17). No statistical differences ( p >0.05) were displayed among N management treatments for leaf area index, but differences ( p < 0.05) occurred among hybrids (Table 2-17). Plant emergence of sweet corn in 2003 was not statistically different ( p >0.05) among N management tr eatments, but was among sweet corn hybrids, with ‘8102R’ having hi ghest emergence (Table 2-18). Among the macronutrients in the diagnostic leaves sampled in 2003, only Mg and N displayed significant ( p < 0.05) differences among N manage ment treatments (Table 219). Significant ( p < 0.05) differences among sweet corn hybrids were only exhibited in Ca, K, and N (Table 2-19). Among mi cronutrients, statistical differences ( p < 0.05) among N management treatments were only demonstrated in Mn (Table 2-19). Significant ( p < 0.05) differences among sweet corn hybrids were displayed for Fe, Mn and Zn, but not Cu (Table 2-19). Soil mineral analysis for 2003 did not exhibit any significant ( p > 0.05) differences among N management treatments for any mine rals (Table 2-20). In addition, no statistical differences ( p >0.05) were found among N manage ment treatments for soil pH, BpH, or CEC (Table 2-21). Soil OM was greatest ( p < 0.05) when N was applied in 4 splits.

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18 Discussion and Conclusion Data for 2002 The objectives of this study were to inve stigate yield and plant nutrition due to N management treatments and sweet corn hybrids. The varying N treatments were found to have a minor effect on the measured variable s in comparison to th e hybrids, which had a much more significant effect. In 2002, ‘Silv er Queen’ was the highest producing hybrid of top grade and total ears. ‘Silver Qu een’ produced the heavie st, but not largest diagnostic leaves. This hybrid also produced some of the tallest plants and highest ears from the ground. From our 2002 data, for fall sw eet corn production in central Florida, ‘Silver Queen’ was the best hybrid choice fo r high yields in combination with split applications of N. The cause for the interaction in seed em ergence between N management and sweet corn hybrids is not known. It is most likely due to germination differences among hybrids and possible differences in N requi rements. The seedlings were receiving varying amounts of N during seedling emergen ce, which may have affected some hybrids differently. Mineral analysis of the diagnostic leaf i ndicated that all macronutrients were well within sufficiency ranges appropriate for sweet corn during the tasseling stage (Hochmuth et al., 1991; Mills a nd Jones, 1996). The N levels in ‘Silver Queen’ were not found to be the highest among the hybrids. This could be due to a dilution effect since this hybrid did produce the largest plants. All of the micronutrients were found to be sufficient for sweet corn (Hochmuth et al., 1991; Mills a nd Jones, 1996). The interactions between N splits and hybr ids found for several minerals may be due to a timing of N splits in relation to hybr id maturity. A lessening of N split effect

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19 with the 4-split management treatment may ha ve occurred, with the fourth split being applied too late to give any real benefit to the plants. Also, the 2-split treatment may have not been as effective. The first of th e 2 applications may have occurred too early, leaving only half of the recommended N to be applied to the plants throughout the experiment. If any adverse weather, such as a heavy rain, occurred, the N may have been leached away before the plants could benefit from it. Soil mineral analysis displayed no hybr id effects and only one N management treatment effect. The mineral that was affect ed by N treatments was Ca. Plant uptake of this mineral can be depressed by ammonium (Mills and Jones, 1996), which is the form of the N used here, but there is no significant evidence of this occurr ence. The pH of the soil was in an acceptable range for nutrient av ailability and the high nutrient levels were demonstrated by OM and CEC (Brady and Buckman, 1969). Data for 2003 In 2003, sweet corn hybrids we re again found to have more significant effects than the N management treatments. Hybrid ‘ 8102R’ was the highest pr oducer of top grade ears as well as total ears. The hybrid also produced some of the heaviest and largest diagnostic leaves and also had the best pl ant emergence. Hybrid ‘8102R’ would be another possible choice for fall production of sw eet corn in central Fl orida with applied N split into at least 2 applications. The cause of the interactions between N splits and hybrids in ear productio n are unknown. Mineral analysis of the diagnostic le aves demonstrated that all of the macronutrients were within suggested suffici ency ranges for sweet corn during tasseling (Hochmuth et al., 1991; Mills a nd Jones, 1996). The interac tion in N levels between N managements and hybrids could be due to prob lems with N availability with early and

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20 late application. Micronutrien ts were all found to be within suggested sufficiency ranges as well (Hochmuth et al., 1991, Mills and Jones, 1996). Mineral analysis of the soil samples ag ain demonstrated no effects due to N management treatments or to hybrids. Soil wa s not a variable in hybrid response. Levels of N, P, and K were found to be slightly elev ated. These elevated levels could be due to the application of organic amendments in th is same test area during the prior growing season. Soil pH was in good range for nutrien t availability (Brady and Buckman, 1969). Soil OM was the only characteristic to be affected by N treatments. Both ‘Silver Queen’ and ‘8102R’ were found to be superior hybrid choices for fall production of sweet corn in central Florida. However, greater yield potential would likely occur from earlier planting dates than occurred in this study. A particular number of N splits cannot be suggested, although the management of N fertilizer for sweet corn should be split into at least 2 applications, in order to diminish the effects of sandy soils and possible leaching. The number of split applications should be economically based.

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21 Table 2-1. Sweet corn ear yield for N management treatments and sweet corn hybrids for 2002 analysis of variance. >15.2 cm‡ 15.2–12.7 cm 12.7–10.2 cm <10.2 cm Total ears >15.2 cm 15.2–12.7 cm 12.7–10.2 cm <10.2 cm Total ears Source of variation df ————————————No of ears————————— ————————Fresh weight of ears———————— Replications 4 — — — — — — — — — N splits (N) 2 ns† ns ns ** ns ns ns ** ns Error 8 — — — — — — — — — Hybrids (H) 4 *** *** *** *** *** *** *** *** *** *** N x H 8 ns ns ns ns ns ns ns ns ns ns Error 48 — — — — — — — — — Total 74 — — — — — — — — — Significant at the 0.05 level. ** Significant at the 0.01 level. *** Significant at the 0.001 level. †ns = not significant. ‡Sweet corn ear lengths, according to USDA standards (USDA, 1954).

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22Table 2-2. Sweet corn diagnostic leaf yield, seed emergence, and plant and ear height for N management treatments and sweet co rn hybrids for 2002 analysis of variance. _______________________________________________________________________________________________________________________________ __ Source of variation df Leaf fresh weight Leaf dry weight Leaf area index % Seed emergence Plant height Ear height Replications 4 — — — — — — N splits (N) 2 ns† ns ns ns ns ns Error 8 — — — — — — Hybrids (H) 4 *** *** *** ** *** *** N x H 8 ns ns ns *** ns ns Error 48 — — — — — — Total 74 — — — — — — ** Significant at the 0.01 level. *** Significant at the 0.001 level. †ns = not significant.

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23Table 2-3. Sweet corn diagnostic leaf mineral concentrations for N management treatments and sw eet corn hybrids for 2002 analy sis of variance. _______________________________________________________________________________________________________________________________ __ Source of variation df Ca Mg K N P Na Cu Fe Mn Zn Replications 4 — — — — — — — — — — N splits (N) 2 ns† ** ns ns *** ns ns ns Error 8 — — — — — — — — — — Hybrids (H) 4 *** ** *** *** *** ** ns *** ns *** N x H 8 ns ns ns ns *** *** ns *** Error 48 — — — — — — — — — — Total 74 — — — — — — — — — — Significant at the 0.05 level. ** Significant at the 0.0 level. *** Significant at the 0.001 level. †ns = not significant.

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24Table 2-4. Soil mineral concentrations a nd characteristics for N management treatment s and sweet corn hybrids for 2002 analysi s of variance. _______________________________________________________________________________________________________________________________ __ Source of variation df Ca Mg K N P Na Cu Fe Mn Zn pH BpH OM CEC Replications 4 — — — — — — — — — — — — — — N splits (N) 2 ns† ns ns ns ns ns ns ns ns ns ns ns ** ns Error 8 — — — — — — — — — — — — — — Hybrids (H) 4 ns ns ns ns ns ns ns ns ns ns *** ** ns ns N x H 8 ns ns ns ns ns ns ns ns ns ns ns ns ns Error 48 — — — — — — — — — — — — — — Total 74 — — — — — — — — — — — — — — Significant at the 0.05 level. ** Significant at the 0.01 level. *** Significant at the 0.001 level. †ns = not significant.

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25Table 2-5. Sweet corn ear yield for N management treatments and sweet corn hybrids for 2003 analysis of variance. _______________________________________________________________________________________________________________________________ __ >15.2 cm‡ 15.2–12.7 cm 12.7–10.2 cm <10.2 cm Total ears >15.2 cm 15.2–12.7 cm 12.7–10.2 cm <10.2 cm Total ears Source of variaion df ————————————N o. of ears————————— ————————Fresh weight of ears———————— Replications 4 — — — — — — — — — N splits (N) 2 ns† ns ns ns ns ns ns ns Error 8 — — — — — — — — — Hybrids (H) 4 *** *** *** *** *** *** *** *** *** *** N x H 8 ns ns ns ns ns ns ns ns Error 48 — — — — — — — — — Total 74 — — — — — — — — — Significant at the 0.05 level. *** Significant at the 0.001 level. †ns = not significant. ‡Sweet corn ear lengths, according to USDA standards (USDA, 1954).

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26Table 2-6. Sweet corn diagnosti c leaf yield, leaf area index, seed emergence for N manageme nt treatments and sweet corn hybrid s for 2003 analysis of variance. _______________________________________________________________________________________________________________________________ __ Source of variation df Leaf fresh weight Leaf dry weight Leaf area index Seed emergence Replications 4 — — — — N splits (N) 2 ns† ns ns Error 8 — — — — Hybrids (H) 4 *** *** *** *** N x H 8 ns ns ns ns Error 48 — — — — Total 74 — — — — Significant at the 0.05 level. *** Significant at the 0.001 level. †ns = not significant.

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27Table 2-7. Soil mineral concentrations a nd characteristics for N management of swee t corn for 2003 anal ysis of variance. _______________________________________________________________________________________________________________________________ __ Source of variation df Ca Mg K N P Na Cu Fe Mn Zn pH BpH OM CEC Replications 4 — — — — — — — — — — — — — — N splits 2 ns† ns ns ns ns ns ns ns ns ns ns ns ns ns Error 8 — — — — — — — — — — — — — — Total 14 — — — — — — — — — — — — — — †ns = not significant at p< 0.05.

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28 Table 2-8. Number of ears for different grades of sweet corn for three nitrogen management treatments and five hybrids, fall 2002. Nitrogen management Hybrid Two splits Three splits Four splits X ——————————No ears ha-1——————————— Ears > 15.2 cm Silver Queen 13000 20667 15667 16444 a† Golden Queen 6667 6667 5000 6111 bc Meritt 6667 8667 11667 9000 b Florida Stay Sweet 3667 3667 4333 3889 c Peaches & Cream 0 0 0 0 d X 6000 x‡ 7933 x 7333 x LSD at p < 0.05 for nitrogen management = ns LSD at p < 0.05 for sweet corn hybrids = 3880 Ears 12.7–15.2 cm Silver Queen 24000 20667 17000 20556 b Golden Queen 8000 10334 7333 85556 a Meritt 2000 4333 4333 3556 cd Florida Stay Sweet 8000 7667 4667 6778 c Peaches & Cream 333 1333 667 778 d X 8467 x 8867 x 6800 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 3568 Ears 10.2–12.7 cm Silver Queen 16334 15333 16000 15889 a Golden Queen 7000 10000 9333 8778 b Meritt 2667 3000 4333 3333 cd Florida Stay Sweet 5334 3667 6333 5111 c Peaches & Cream 4000 1667 667 2111 d X 7067 x 6733 x 7333 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 2793 Ears < 10.2 cm Silver Queen 43667 32667 53333 43222 b Golden Queen 53667 67333 79000 66667 a Meritt 37667 42333 44333 41444 b Florida Stay Sweet 36000 41333 41000 39445 b Peaches & Cream 36667 33667 36333 35556 b X 41533 x 43467 y 50800 y LSD at p< 0.05 for nitrogen management = 4696 LSD at p< 0.05 for sweet corn hybrids = 11736 Total ears Silver Queen 97000 89334 102000 96111 a Golden Queen 75333 94334 100667 90111 ab Meritt 49000 58333 64667 57333 bc Florida Stay Sweet 53000 56333 56333 55222 c

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29 Table 2-8. Continued. Nitrogen management Hybrid Two splits Three splits Four splits Average Total ears Peaches & Cream 41000 36667 37667 38444 c X 63067 y 67000 xy 72267 x LSD at p< 0.05 for nitrogen management = 5526 LSD at p< 0.05 for sweet corn hybrids = 3401 †Values in columns (a,b,c) not followed by the same letter are significantly different (p< 0.05) according to LSD. ‡Values in rows (x, y, z) not followed by th e same letter are significantly different (p< 0.05) according to LSD. `

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30 Table 2-9. Fresh weight of ears for different grades of sweet corn for three nitrogen management treatments and five hybrids, fall 2002. Nitrogen management Hybrid Two splits Three splits Four splits X ———————Fresh weight, kg ha-1—————————— Ears > 15.2 cm Silver Queen 2354 3599 2702 2885 a† Golden Queen 1203 1239 896 1113 bc Meritt 1122 1420 2101 1548 b Florida Stay Sweet 603 535 700 612 cd Peaches & Cream 0 0 0 0 d X 1056 x‡ 1359 x 1280 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 733 Ears 12.7–15.2 cm Silver Queen 2983 2560 2186 2576 a Golden Queen 1023 1458 1041 1174 b Meritt 244 554 571 456 cd Florida Stay Sweet 859 842 516 739 bc Peaches & Cream 43 136 69 83 d X 1031 x 1110 x 877 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 450 Ears 10.2–12.7 cm Silver Queen 1751 1426 1672 1616 a Golden Queen 657 1069 1122 949 b Meritt 260 308 454 341 cd Florida Stay Sweet 432 323 516 424 c Peaches & Cream 358 153 56 189 d X 692 x 656 x 764 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 213 Ears < 10.2 cm Silver Queen 2318 1578 2636 2177 b Golden Queen 2814 3738 4114 3555 a Meritt 993 1110 1608 1237 c Florida Stay Sweet 1278 1306 1501 1362 c Peaches & Cream 891 816 921 876 c X 1659 y 1710 y 2156 x LSD at p< 0.05 for nitrogen management = 305 LSD at p< 0.05 for sweet corn hybrids = 504 Total ears Silver Queen 9407 9163 9195 9255 a Golden Queen 5697 7503 7173 6791 b Meritt 2619 3392 4733 3581 c Florida Stay Sweet 3172 3006 3233 3137 c

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31 Table 2-9. Continued. Nitrogen management Two splits Two splits Two splits Average Total ears Peaches & Cream 1292 1105 1046 1148 d X 4437 x 4834 x 5076 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 1072 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD.

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32 Table 2-10. Yield of 5th leaf for sweet corn for three nitrogen management treatments and five hybrids, fall 2002. Nitrogen management Hybrid Two splits Three splits Four splits X ———————————kg ha-1———————————— Fresh weight Silver Queen 1268 1190 1221 1226 a† Golden Queen 1049 1058 1066 1058 b Meritt 878 854 860 864 d Florida Stay Sweet 1047 989 906 981 c Peaches & Cream 755 646 698 700 e X 999 x‡ 947 x 950 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 66 Dry weight Silver Queen 246 235 240 241 a Golden Queen 202 210 217 210 b Meritt 197 193 198 196 c Florida Stay Sweet 209 196 184 196 c Peaches & Cream 131 117 131 126 d X 197 x 190 x 194 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 11 ————Leaf area index, cm 2 leaf -1 cm -2 ground area ——— Silver Queen 0.378 0.376 0.364 0.373 b Golden Queen 0.328 0.334 0.342 0.335 c Meritt 0.368 0.372 0.372 0.371 b Florida Stay Sweet 0.426 0.424 0.390 0.413 a Peaches & Cream 0.226 0.198 0.208 0.211 d X 0.345 x 0.341 x 0.335 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.02 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD.

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33 Table 2-11. Percent seed emergence of sw eet corn for three nitrogen management treatments and five hybrids, fall 2002. Nitrogen management Hybrid Two splits Three splits Four splits X —————————Emergence, %——————————— Silver Queen 79 b† y‡ 86 ab x 87 a x 84 Golden Queen 84 a x 84 b x 78 b y 82 Meritt 85 a x 86 ab x 79 b y 83 Florida Stay Sweet 85 a x 88 a x 88 a x 87 Peaches & Cream 83 a x 72 c y 85 a x 80 X 83 83 83 LSD at p< 0.05 for nitrogen management = 3.5 LSD at p< 0.05 for sweet corn hybrids = 3.5 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD. Table 2-12. Plant and ear height of sweet co rn for three nitrogen management treatments and five hybrids, fall 2002. Nitrogen management Hybrid Two splits Three splits Four splits X ———————————Height, m——————————— Plant height Silver Queen 1.99 1.90 2.14 2.01 a† Golden Queen 1.91 2.02 2.10 2.01 a Meritt 1.87 1.84 1.92 1.87 b Florida Stay Sweet 1.63 1.60 1.55 1.60 c Peaches & Cream 1.77 1.63 1.63 1.67 c X 1.83 x‡ 1.79 x 1.87 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.10 Ear height Silver Queen 0.51 0.60 0.69 0.60 a Golden Queen 0.57 0.56 0.67 0.60 a Meritt 0.57 0.56 0.57 0.56 ab Florida Stay Sweet 0.50 0.49 0.51 0.50 b Peaches & Cream 0.40 0.35 0.39 0.38 c X 0.51 x 0.51 x 0.57 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.06 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x, y, z) not followed by th e same letter are si gnificantly different (p< 0.05) according to LSD.

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34 Table 2-13. Mineral analysis for 5th leaf of sweet corn for three nitrogen management treatments and five hybrids, fall 2002. Nitrogen management Hybrid Two splits Three splits Four splits X ———————Mineral concentration, g kg-1——————— Ca Silver Queen 5.9 5.9 5.9 5.9 a† Golden Queen 4.6 5.1 4.9 4.9 cd Meritt 4.9 5.5 5.1 5.2 bc Florida Stay Sweet 4.1 4.4 4.8 4.5 d Peaches & Cream 5.4 6.4 5.4 5.7 ab X 5.0 x‡ 5.5 x 5.2 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.58 Mg Silver Queen 2.8 c x 2.7 c x 2.4 b y 2.6 Golden Queen 3.2 ab y 3.9 a x 2.6 b z 3.2 Meritt 3.3 a x 3.54a x 2.5 b y 3.1 Florida Stay Sweet 3.0 abc x 2.7 c x 2.7 b x 2.8 Peaches & Cream 2.9 bc x 3.1 b x 3.1 a x 3.0 X 3.00 3.2 2.7 LSD at p< 0.05 for nitrogen management = 0.28 LSD at p< 0.05 for sweet corn hybrids = 0.35 K Silver Queen 15.6 15.1 17.6 16. c Golden Queen 16.8 17.2 20.4 18.13 b Meritt 18.3 17.1 22.4 19.3 b Florida Stay Sweet 18.1 18.4 17.8 18.1 b Peaches & Cream 24.7 22.0 22.8 23.2 a X 18.7 xy 18.0 y 20.2 x LSD at p< 0.05 for nitrogen management = 1.7 LSD at p< 0.05 for sweet corn hybrids = 1.9 P Silver Queen 3.9 3.7 3.7 3.8 d Golden Queen 4.7 4.3 4.3 4.4 b Meritt 4.9 4.4 4.7 4.7 a Florida Stay Sweet 4.2 4.2 4.1 4.2 c Peaches & Cream 4.1 4.1 4.2 4.1 c X 4.4 x 4.1 x 4.20 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.21 N Silver Queen 26.8 28.5 28.5 28.0 c Golden Queen 29.1 30.9 29.7 29.9 a Meritt 29.3 29.9 30.3 29.8 ab Florida Stay Sweet 28.7 28.2 28.5 28.5 bc

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35 Table 2-13. Continued. Nitrogen management Hybrid Two splits Three splits Four splits X ———————Mineral concentration, g kg-1——————— N Peaches & Cream 30.4 31.4 31.8 31.2 a X 28.8 x 29.8 x 29.8 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 1.4 Na Silver Queen 0.6 c y 0.9 a x 0.5 a y 0.7 Golden Queen 0.8 b x 0.6 b y 0.5 a z 0.6 Meritt 0.8 b x 0.3 d z 0.4 ab y 0.5 Florida Stay Sweet 0.8 ab x 0.3 d y 0.3 b y 0.5 Peaches & Cream 0.9 a x 0.5 c y 0.5 a y 0.6 X 0.8 0.5 0.5 LSD at p< 0.05 for nitrogen management = 0.08 LSD at p< 0.05 for sweet corn hybrids = 0.11 ———————Mineral concentration, mg kg-1—————— Cu Silver Queen 6.00 ab y 3.20 d z 7.00 a x 5.40 Golden Queen 6.20 a x 4.20 c z 5.20 c y 5.20 Meritt 5.60 ab y 6.40 ab x 5.40 c y 5.80 Florida Stay Sweet 5.40 b x 5.80 b x 5.40 c y 5.53 Peaches & Cream 5.80 ab x 6.80 a x 6.20 b xy 6.27 X 5.80 5.28 5.84 LSD at p< 0.05 for nitrogen management = 0.63 LSD at p< 0.05 for sweet corn hybrids = 0.80 Fe Silver Queen 96.00 94.00 98.00 96.00 c Golden Queen 84.00 92.00 98.00 91.33 c Meritt 94.00 90.00 94.00 92.67 c Florida Stay Sweet 98.00 106.00 106.00 103.33 b Peaches & Cream 108.00 122.00 114.00 114.67 a X 96.00 y 100.80 xy 102.00 x LSD at p< 0.05 for nitrogen management = 5.9 LSD at p< 0.05 for sweet corn hybrids = 6.8 Mn Silver Queen 23.00 a x 19.60 b y 20.60 b y 21.07 Golden Queen 18.80 b y 25.00 a x 17.20 c y 20.33 Meritt 16.20 bc z 24.20 a x 19.20 bc y 19.87 Florida Stay Sweet 18.00 b y 20.60 b x 18.20 bc y 18.93 Peaches & Cream 13.60 c z 24.40 a y 30.20 a x 22.73 X 17.92 22.76 21.08

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36 Table 2-13. Continued. Nitrogen management Hybrid Two splits Three splits Four splits X ———————Mineral concentration, mg kg-1—————— Mn LSD at p< 0.05 for nitrogen management = 2.3 LSD at p< 0.05 for sweet corn hybrids = 3.4 Zn Silver Queen 23.20 a y 23.80 b y 27.40 a x 24.80 Golden Queen 24.60 a x 21.20 b y 24.20 b x 23.33 Meritt 22.60 a y 27.00 a x 22.80 b y 24.13 Florida Stay Sweet 19.40 b y 21.80 b x 18.60 c y 19.93 Peaches & Cream 16.40 c z 21.40 b x 18.60 c y 18.80 X 21.24 23.04 22.32 LSD @ 0.05 for nitrogen management = 1.9 LSD @ 0.05 for sweet corn hybrids = 2.6 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD.

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37 Table 2-14. Mineral analysis for soil samples following sweet corn, fall 2002. Nitrogen management Hybrid Two splits Three splits Four splits X ———————Mineral concentration, mg kg-1—————— Ca Silver Queen 673.8 641.6 688.0 667.5 a† Golden Queen 700.0 656.0 755.2 704.7 a Meritt 603.2 746.4 838.4 729.3 a Florida Stay Sweet 678.4 751.2 668.8 699.5 a Peaches & Cream 745.6 821.6 704.0 757.1 a X 680.0 x‡ 723.4 x 730.9 x LSD at p< 0.05 for nitrogen management = 109 LSD at p< 0.05 for sweet corn hybrids = ns Mg Silver Queen 54.2 51.4 53.0 52.8 a Golden Queen 52.8 52.0 54.4 53.1 a Meritt 47.8 57.2 59.6 54.9 a Florida Stay Sweet 60.0 55.4 50.6 55.3 a Peaches & Cream 56.6 51.0 52.6 53.4 a X 54.3 x 53.4 x 54.0 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns K Silver Queen 25.0 26.6 25.8 25.8 a Golden Queen 23.6 22.6 25.8 24.0 a Meritt 22.4 26.4 27.2 25.3 a Florida Stay Sweet 29.0 25.8 24.0 26.3 a Peaches & Cream 33.6 24.8 27.4 28.6 a X 26.7 x 25.2 x 26.0 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns P Silver Queen 50.0 54.4 58.2 54.2 a Golden Queen 65.0 43.6 55.0 54.5 a Meritt 43.8 35.0 46.2 41.7 a Florida Stay Sweet 27.8 52.8 46.4 45.7 a Peaches & Cream 58.6 48.8 53.2 53.5 a X 51.0 x 46.9 x 51.8 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns N Silver Queen 379.0 401.0 412.2 397.4 a Golden Queen 406.2 407.0 426.0 413.1 a Meritt 365.6 454.0 430.4 416.7 a Florida Stay Sweet 395.8 444.6 411.0 417.1 a Peaches & Cream 438.2 472.8 447.4 452.8 a

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38 Table 2-14. Continued. Nitrogen management Hybrid Two splits Three splits Four splits Average ———————Mineral concentration, mg kg-1—————— N X 397.0 x 435.9 x 425.4 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns Na Silver Queen 15.0 15.6 14.4 15.0 a Golden Queen 16.8 15.4 15.4 15.9 a Meritt 15.2 14.4 15.0 14.9 a Florida Stay Sweet 15.8 15.2 14.8 15.3 a Peaches & Cream 15.8 15.6 14.6 15.3 a X 15.7 x 15.2 x 14.8 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns Cu Silver Queen 0.18 0.15 0.32 0.22 a Golden Queen 0.18 0.18 0.17 0.18 a Meritt 0.17 0.14 0.15 0.15 a Florida Stay Sweet 0.16 0.14 0.22 0.17 a Peaches & Cream 0.17 0.16 0.18 0.17 a X 0.17 x 0.15 x 0.21 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns Fe Silver Queen 9.12 9.52 9.68 9.44 a Golden Queen 8.88 6.88 9.44 8.40 a Meritt 6.4 8.16 8.8 7.79 a Florida Stay Sweet 10.0 8.48 7.6 8.69 a Peaches & Cream 9.68 8.4 9.12 9.07 a X 8.82 x 8.29 x 8.93 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns Mn Silver Queen 3.92 3.66 3.42 3.67 a Golden Queen 3.82 3.06 3.52 3.47 a Meritt 3.2 3.80 4.24 3.75 a Florida Stay Sweet 3.32 3.78 2.88 3.33 a Peaches & Cream 4.12 3.82 3.36 3.77 a X 3.68 x 3.62 x 3.48 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns

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39 Table 2-14. Continued. Nitrogen management Hybrid Two splits Three splits Four splits Average ——————Mineral concentration, mg kg-1——————— Zn Silver Queen 3.8 3.9 2.86 3.52 a Golden Queen 2.82 2.46 4.86 3.38 a Meritt 3.48 5.04 5.54 4.69 a Florida Stay Sweet 3.04 5.02 4.94 4.33 a Peaches & Cream 4.80 5.42 2.86 4.36 a X 3.59 x 4.37 x 4.21 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns —————————————pH——————————— Silver Queen 6.5 6.8 6.5 6.6 d Golden Queen 6.6 6.7 6.6 6.7 cd Meritt 6.6 6.7 6.7 6.7 bc Florida Stay Sweet 6.7 6.9 6.7 6.8 ab Peaches & Cream 6.8 6.8 6.8 6.8 a X 6.6 x 6.8 x 6.7 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.08 ———————————BpH————————————— Silver Queen 7.84 d z 7.86 ab x 7.85 b y 7.85 Golden Queen 7.87 bc x 7.85 bc z 7.86 b y 7.86 Meritt 7.89 a x 7.84 c z 7.85 b y 7.86 Florida Stay Sweet 7.88 ab y 7.86 ab z 7.89 a x 7.88 Peaches & Cream 7.86 c z 7.87 a y 7.88 a x 7.87 X 7.87 7.86 7.87 LSD at p< 0.05 for nitrogen management = 0.0005 LSD at p< 0.05 for sweet corn hybrids = 0.01 ———————CEC, meq 100 g-1 (cmol kg-1) —————— Silver Queen 9.26 8.77 9.16 9.06 Golden Queen 9.11 8.91 9.54 9.19 Meritt 8.04 9.95 10.5 9.49 Florida Stay Sweet 9.47 9.57 8.57 9.21 Peaches & Cream 9.74 9.52 9.01 9.42 X 9.12 9.35 9.35 LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns ————————————OM, %——————————— Silver Queen 0.98 1.01 1.09 1.03 Golden Queen 0.91 0.95 1.18 1.02 Meritt 0.91 1.05 1.28 1.08 Florida Stay Sweet 1.13 0.86 1.14 1.04 Peaches & Cream 0.98 1.11 1.39 1.16

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40 Table 2-14. Continued. Nitrogen management Hybrid Two splits Three splits Four splits Average ———————————OM, %———————————— X 0.98 y 1.0 y 1.22 x LSD at p< 0.05 for nitrogen management = 0.1 LSD at p< 0.05 for sweet corn hybrids = ns †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD.

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41 Table 2-15. Number of ears for different grades of sweet corn for three nitrogen management treatments and five hybrids, fall 2003. Nitrogen management Hybrid Two splits Three splits Four splits X ——————————No ears ha-1 ——————————— Ears > 15.2 cm Silver Queen 21333 14333 16667 1744 c† 8100R 17333 14333 18667 16778 b Prime Plus 0 667 667 444 c 8102R 21333 29667 19667 23556 a Big Time 333 0 333 223 c X 12067 x‡ 11800 x 11200 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 4832 Ears 12.7–15.2 cm Silver Queen 18333 a x 18667 a x 9667 b y 15556 8100R 20667 a x 17000 a y 12667 a z 16778 Prime Plus 333 b x 1333 b x 1667 c x 1111 8102R 19667 a x 17333 a y 12000 ab z 16333 Big Time 1000 b x 333 b x 0 c x 445 X 12000 10933 7200 LSD at p< 0.05 for nitrogen management = 1994 LSD at p< 0.05 for sweet corn hybrids = 2855 Ears 10.2–12.7 cm Silver Queen 13333 15000 15667 14667 a 8100R 12667 12666 13667 13000 a Prime Plus 6333 5667 5333 5778 b 8102R 10667 11667 16667 13000 a Big Time 3333 4667 4667 4222 b X 9267 x 9933 x 11200 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 3525 Ears < 10.2 cm Silver Queen 13333 18667 26000 19333 b 8100R 12667 16333 17000 15333 bc Prime Plus 32000 28333 33000 31111 a 8102R 12667 5667 14333 10889 c Big Time 33667 36000 36333 35333 a X 20867 x 21000 x 25333 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 6074 Total ears Silver Queen 66333 66667 68000 67000 a 8100R 63333 60333 62000 61889 a Prime Plus 38667 36000 40667 38445 b 8102R 64333 64333 62666 63778 a

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42 Table 2-15. Continued. Nitrogen management Hybrid Two splits Three splits Four splits Average ——————————No ears ha-1 ——————————— Total ears Big Time 38333 41000 41333 40222 b X 54200 x 53667 x 54933 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 5684 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD.

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43 Table 2-16. Fresh weight of ears for different grades of sweet corn for three nitrogen management treatments and five hybrids, fall 2003. Nitrogen management Hybrid Two splits Three splits Four splits X —————————Ear weight, kg ha-1————————— Ears > 15.2 cm Silver Queen 4169 2927 3218 3438 ab† 8100R 2804 2461 3230 2832 b Prime Plus 0 109 131 80 c 8102R 3767 5260 3893 4307 a Big Time 72 0 52 41 c X 2162 x‡ 2151 x 2105 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 916 Ears 12.7–15.2 cm Silver Queen 2573 a x 2736 a x 1485 a y 2264 8100R 2317a x 2099 b x 1539 a y 1985 Prime Plus 35 b x 148 c x 183 b x 122 8102R 2427 a x 2098 b x 1553 a z 2026 Big Time 113 b x 46 c x 0B x 53 X 1493 1425 952 LSD at p< 0.05 for nitrogen management = 264 LSD at p< 0.05 for sweet corn hybrids = 362 Ears 10.2–12.7cm Silver Queen 1483 1741 1817 1680 a 8100R 1038 1159 1473 1224 b Prime Plus 655 578 481 571 c 8102R 931 1229 1584 1248 b Big Time 322 432 400 385 c X 886 x 1028 x 1151 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 369 Ears < 10.2 cm Silver Queen 901 1273 1693 1289 a 8100R 529 858 912 766 b Prime Plus 1463 1211 1307 1327 a 8102R 705 313 753 590 b Big Time 995 1418 1525 1313 a X 918 y 1015 y 1238 x LSD at p< 0.05 for nitrogen management = 223 LSD at p< 0.05 for sweet corn hybrids = 325 Total ears Silver Queen 9125 8676 8212 8671 a 8100R 6689 6577 7154 6807 b Prime Plus 2153 2046 2102 2100 c

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44 Table 2-16. Continued. Nitrogen management Hybrid Two splits Three splits Four splits X —————————Ear weight, kg ha-1————————— Total ears 8102R 7829 8900 7784 8171 a Big Time 1503 1896 1978 1792 c X 5460 x 5619 x 5446 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 674 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD.

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45 Table 2-17. Yield of 5th leaf of sweet corn for three nitrogen management treatments and five hybrids, fall 2003. Nitrogen management Hybrid Two splits Three splits Four splits X —————————Leaf weight, kg ha-1————————— Fresh weight Silver Queen 1289 1470 1477 1412 a† 8100R 1174 1067 1128 1123 bc Prime Plus 976 1063 1002 1014 c 8102R 1317 1502 1497 1439 a Big Time 1110 1241 1114 1155 b X 1173 y‡ 1269 x 1244 xy LSD at p< 0.05 for nitrogen management = 89 LSD at p< 0.05 for sweet corn hybrids = 129 Dry weight Silver Queen 251 275 238 260 a 8100R 215 200 210 209 b Prime Plus 168 177 171 172 c 8102R 145 280 275 267 a Big Time 187 208 189 195 b X 214 x 228 x 220 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 22 ————Leaf area index, cm 2 leaf -1 cm –2ground area———— Silver Queen 0.442 0.485 0.461 0.463 b 8100R 0.447 0.411 0.443 0.434 bc Prime Plus 0.340 0.358 0.353 0.350 d 8102R 0.513 0.567 0.576 0.552 a Big Time 0.390 0.457 0.387 0.411 c X 0.426 x 0.456 x 0.444 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.04 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD.

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46 Table 2-18. Plants emerged for sweet corn fo r three nitrogen management treatments and five hybrids, fall 2003. Nitrogen management Hybrid Two splits Three splits Four splits X ——————————Plants m-2 ———————————— Silver Queen 9.6 10.2 9.8 9.9 b† 8100R 10.1 8.9 9.7 9.6 b Prime Plus 7.9 8.2 8.3 8.1 c 8102R 10.6 11.0 11.3 11.0 a Big Time 9.3 11.0 8.9 9.7 b X 9.5 x‡ 9.9 x 9.6 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.83 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the sa me letter are significantly different (p< 0.05) according to LSD.

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47 Table 2-19. Mineral analysis for 5th leaf of sweet corn for three nitrogen management treatments and five hybrids, fall 2003. Nitrogen management Hybrid Two splits Three splits Four splits X ———————Mineral concentration, g kg-1——————— Ca Silver Queen 4.7 4.5 4.8 4.7 a† 8100R 3.5 4.1 4.1 3.9 b Prime Plus 4.7 5.2 5.2 5.0 a 8102R 3.6 4.0 3.9 3.9 b Big Time 4.6 4.2 4.9 4.6 a X 4.2 x‡ 4.4 x 4.6 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.41 Mg Silver Queen 2.8 2.9 3.4 3.1 a 8100R 2.3 2.6 2.9 2.6 a Prime Plus 2.7 2.9 3.2 2.9 a 8102R 2.3 3.1 3.3 2.9 a Big Time 2.7 2.7 3.0 2.8 a X 2.6 y 2.9 xy 3.2 x LSD at p< 0.05 for nitrogen management = 0.38 LSD at p< 0.05 for sweet corn hybrids = ns K Silver Queen 23.0 23.4 23.6 23.3 b 8100R 23.9 24.3 22.6 23.6 b Prime Plus 26.9 28.4 26.2 27.2 a 8102R 23.6 24.2 21.7 23.2 b Big Time 27.0 27.0 29.4 27.8 a X 24.9 x 25.5 x 24.7 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 1.7 P Silver Queen 3.9 3.9 4.0 3.9 ab 8100R 4.0 4.1 3.8 4.0 a Prime Plus 3.8 3.8 3.8 3.8 bc 8102R 3.8 4.2 4.0 4.0 a Big Time 3.8 3.7 3.8 3.7 c X 3.9 x 3.9 x 3.9 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 0.17 N Silver Queen 30.1 a x 29.8 b x 28.1 ab y 29.3 8100R 28.8 a y 32.3 a x 27.1 b z 29.4 Prime Plus 30.8 a x 29.2 b y 27.1 b z 29.0

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48 Table 2-19. Continued. Nitrogen management Hybrid Two splits Three splits Four splits X ———————Mineral concentration, g kg-1——————— N 8102R 28.9 a x 29.3 b x 29.0 ab x 29.1 Big Time 28.7 a x 26.1 c y 30.0 a x 28.3 X 29.5 29.4 28.3 LSD at p< 0.05 for nitrogen management = 1.5 LSD at p< 0.05 for sweet corn hybrids = 2.2 Na Silver Queen 0.3 0.3 0.4 0.3 a 8100R 0.2 0.8 0.4 0.5 a Prime Plus 0.3 0.3 0.5 0.4 a 8102R 0.3 0.3 0.4 0.3 a Big Time 0.4 0.4 0.3 0.4 a X 0.3 x 0.4 x 0.4 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns ———————Mineral concentration, mg kg-1——————— Cu Silver Queen 4.0 2.8 3.4 3.4 a 8100R 4.8 3.2 2.8 3.6 a Prime Plus 3.6 6.0 3.2 4.3 a 8102R 4.0 3.2 2.6 3.3 a Big Time 3.4 2.6 4.4 3.5 a X 4.0 x 3.6 x 3.3 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = ns Fe Silver Queen 100.0 114.0 104.0 106.0 b 8100R 106.0 124.0 118.0 116.0 a Prime Plus 104.0 116.0 106.0 108.7 b 8102R 108.0 110.0 108.0 108.7 b Big Time 106.0 100.0 102.0 102.7 b X 104.8 x 112.8 x 107.6 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 6.2 Mn Silver Queen 17.8 20.2 32.2 23.4 a 8100R 15.0 18.0 22.4 18.5 bc Prime Plus 18.8 17.4 25.6 20.6 ab 8102R 13.6 17.2 14.2 15.0 c Big Time 17.6 21.2 26.2 21.7 ab X 16.6 x 18.8 x 24.1 y

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49 Table 2-19. Continued. Nitrogen management Hybrid Two splits Three splits Four splits X ——————Mineral concentration, mg kg-1——————— Mn LSD at p< 0.05 for nitrogen management = 4.7 LSD at p< 0.05 for sweet corn hybrids = 3.6 Zn Silver Queen 23.6 30.8 27.0 27.1 a 8100R 22.8 25.6 23.2 23.9 ab Prime Plus 21.2 24.4 24.2 23.3 b 8102R 22.0 21.0 21.0 21.3 bc Big Time 17.4 17.4 20.6 18.5 c X 21.4 x 23.8 x 23.2 x LSD at p< 0.05 for nitrogen management = ns LSD at p< 0.05 for sweet corn hybrids = 3.7 †Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. ‡Values in rows (x,y,z) not followed by the same letter are signi ficantly different (p< 0.05) according to LSD.

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50 Table 2-20. Mineral analysis for soil samp les following sweet corn harvest, fall 2003. N management Mineral concentration ——————————mg kg-1—————————— Ca Mg K N Two splits 776 a 52.9 a 32.7 a 471.8 a Three splits 716 a 53.6 a 35.0 a 496.2 a Four splits 684 a 51.2 a 33.4 a 469.0 a LSD at p< 0.05 ns† ns ns ns P Na Cu Two splits 82.9 a 8.5 a 0.3 a Three splits 80.2 a 9.0 a 0.3 a Four splits 72.6 a 7.9 a 0.3 a LSD at p< 0.05 ns ns ns Fe Mn Zn Two splits 32.7 a 4.8 a 4.7 a Three splits 29.4 a 4.4 a 3.8 a Four splits 29.0 a 3.9 a 3.6 a LSD at p< 0.05 ns ns ns †ns = not significant. ‡Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD. Table 2-21. Soil characteristic analysis for soil samples following sweet corn harvest, fall 2003. N management pH BpH OM CEC % meq 100 g-1‡ Two splits 6.8 a§ 7.9 a 1.0 b 10.4 a Three splits 6.9 a 7.9 a 1.0 b 10.0 a Four splits 7.0 a 7.9 a 1.3 a 10.0 a LSD at p< 0.05 ns† ns ns ns †ns = not signigicant. ‡ ( cmol kg-1) §Values in columns (a,b,c) not followed by the same letter are signifi cantly different (p< 0.05) according to LSD

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51 Table 2-22. Sufficiency range of macroand mi cronutrients for dia gnostic leaf of sweet corn during tasseling and early silking. Hochmuth et al.† Mills and Jones† sufficiency range sufficiency range ————————Macronutrients———————— g kg-1 N 15–25 25–30 P 2–4 2.5–4 K 12–20 15–28 Ca 3–6 6–9 Mg 1.5–4 2–8 Na NA NA ————————Micronutrients———————— mg kg-1 Cu 4–10 5–25 Fe 30–100 50–350 Mn 20–100 20–300 Zn 20–40 20–150 †(Hochmuth et al., 1991; Mills and Jones, 1996).

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52 CHAPTER 3 YIELD AND NUTRIENT ELEMENT RELATI ONSHIPS OF FIVE VARIETIES OF COWPEA AND LIMA BEAN Introduction Cowpea (Vigna unguiculata (L.) Walp.) is one of many legume species that are very important world food crops. This particular legume, which dates back as far as ancient West African cereal farming 6,000 yr ag o, remains a widely grown crop (Davis et al., 1991). It is cultivated on about 7 million ha worldwide, ranging from warm temperate regions to tropical areas of Africa, Asia, and Amer ica (Ehlers and Hall, 1997). Cowpea is used in cropping systems to improve soil quality and fertility in addition to being a major source of high quality fodder and forage. It is also an important crop for human consumption in the southern U.S. and Africa, providing affordable and good quality protein and B vitamins. Cowpea has many beneficial attr ibutes. It has been used successfully as a means of nematode control as well as helping to redu ce soil erosion (Davis et al., 1991). Being a legume, cowpeas have a unique symbiotic relationship with certain N2 fixing bacteria, Bradyrhizobim sp., allowing them to actually increase the amount of N in soil (Luyindula and Weaver, 1989). In a study conducted in Nigeria, the apparent N contribution of cowpea to late season corn (Zea mays L.) was approximately 30 kg N ha-1 (Carsky and Schultz, 1999). Cowpea is also well adapte d to sandy soil, which makes it a viable candidate for use in cropping systems in Florida. It has also been found to tolerate heat and drought better than almost any ot her legume (Auguiar et al., 1999).

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53 Lima bean (Phaseolus lunatus), another legume species, is native to Central America, its culture dating back as far as 7,000 years ago (Redden and Wright, 1998). The United States was the top-ranking count ry in lima bean production in 1996 with Florida being one of the main production areas by acreage of harves ted beans (Luo, 2000; Nwosolo, 1996; Peet, 2002). Lima beans have be en found to thrive in sandy or clay loam soils and have also been found to be drought-resistant, making them well suited for inclusion in cropping systems in Florida. A considerable amount of variation can be a ssumed to be present in any test field. Use of a proper blocking technique can signifi cantly reduce experiment al error that might occur due to that va riation (Gomez and Gomez, 1984). Th e 3 single-factor experimental designs chosen for this study were a co mpletely randomized (CRD), a randomized complete block (RCB), and a Latin square (LS). Differences in blocking are what define these 3 designs. The main purpose of bloc king is to decrease experimental error by eliminating the contribution of known sources of variation among experimental plots (Gomez and Gomez, 1984). Blocking maxi mizes the difference among blocks while minimizing the differences among treatment plots. Correct blocking can increase precision, though an increase in blocking does caus e a decrease in the degrees of freedom in the error term used for statistical analysis of the experimental results. A CRD has no blocking at al l and is only applicable for homogenous experimental plots. When a known source of variation is present among plots, a RCB design should be utilized. This deign is characterized by bloc ks of equal size, each containing all of the treatments in the study. When 2 known sour ces of variation are present among plots, they can be controlled using a LS design. The LS is characterized by 2-directional

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54 blocking, or rowand column blocking. Every treatment of the study appears once in each row-block and once in each column-block. These 3 different experimental designs were utilized for teaching purposes as well as to account for a physical slope in the experimental field. There was no slope vari ation in the area where the CRD experiment was conducted. There was a single-direc tion slope in the field where the RCB experiment was conducted. There was a 2-direct ional slope present in the field where the LS experiment was conducted. A 2-yr experiment was conducted to examin e how well various varieties of cowpea and lima bean would perform in Florida. This test was also part of a larger study (see Chapter 6) that was performed to investigat e the effects of vari ous cropping histories on no-till sweet corn. This speci fic portion of the overall st udy comprised the second of 3 cropping histories examined. The objectives of this study were to evaluate the yield and plant nutrition of the cowpea and lima bean varieties. Minor objectives were to demonstrate the use of 3 single factor experimental designs and to fulfill statistical teaching purposes. Materials and Methods Three cowpea variety experiments were established on 31 July of 2002 and 3 lima bean experiments on 29 July of 2003 on a Millhopper fine sand (loamy siliceous hyperthermic Grossarenic Paleodults) (USDANRCS, 2003) at Gainesville, Florida. Five varieties of cowpea (‘Cal ifornia Blackeye #5’, ‘White Acre’, ‘Texas Cream 12’, ‘Mississippi Cream’, and ‘Iron Clay’) and 5 va rieties of lima bean (‘Fordhook’, ‘Florida Butter Lima’, ‘Henderson Bush’, ‘Cangreen’, and ‘White Dixie Butter Lima’) were planted by hand at a rate of 25 seeds m-1 of row. Experime ntal plots were 6 m2, each containing four 0.75 m wide rows, 2.0 m long.

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55 Experimental Design Three experiments were established for both cowpea and lima bean, using 3 single-factor experimental designs incl uding a CRD, a RCB, and a LS. The CRD experiment was established on a level area of the field with no appa rent variation. We established the RCB in an area of the field w ith an evident slope running east to west. The LS was placed in an area of the experime ntal field where a slope was observed to run in 2 directions, east to west as well as north to south. Varieties were the single factor in all of the cowpea and lima bean experiments. In the lima bean RCB study, ‘Jackson Wonder’ replaced ‘Fordhook’ due to germination problems. All designs tested the same hypothesis and were used to fulfill statistic al teaching purposes. The hypothesis stated that cowpea and lima bean would not significan tly differ in yield or nutrient content by variety. After the implementation of the treatments, the plots were rotortilled as well as hand-weeded several times to minimize compe tition. Lannate LV was applied at 2 L ha-1 to control pests. The cowpea and lima b ean received water from rainfall and from overhead sprinkler irrigation. The 3 cowpea and the 3 lima bean experiments were harvested on 26 September 2002 and on 29 Se ptember 2003, respectively, all by hand. Pods from all rows in the cowpea and lima beans studies and whole plants from the center 2 rows of each plot of the cowpea stud ies were bagged and removed from the field to obtain fresh and dry weight s and for mineral analysis. Soil samples were obtained from the top 20 cm of soil from each plot of the lima bean studies and were combined across treatments. Data from each experime nt of each year was analyzed separately.

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56 Nitrogen Analysis Cowpea pods and plants were separated and fresh and dry weight yields obtained for each. Fresh and dry weights were also obtained for lima bean pods. Plant fresh weight was determined using the stems, leaves and roots before placing them in a forced air oven at 70C before obtai ning dry weights. Whole plan t samples were then chopped in a hammer mill, mixed well, and grab samples were ground to pass through a 2 mm stainless steel screen using a Wiley mill. The pod samples were ground using a Wiley mill after they were dried in the forced air oven and weighed for dry weight yields. All samples were stored in plastic sample bags. For N analysis, a micro-Kjeldahl procedur e was used (Gallahe r et al., 1975). A mixture of 0.100 g of each cowpea pod or plant sample, 3.2 g salt-catalyst (9:1 K2SO4:CuSO4), 2 to 3 glass boiling beads and 10 mL of H2SO4 were vortexed in a 100-mL test tube under a hood. To reduce frothing, 2 mL 30% H2O2 were added in 1 mL increments and tubes were then digested in an aluminum block digester at 370C for 3.5 h (Gallaher et al., 1975). Tubes were capped with small Pyrex funnels that allowed for evolving gases to escape while preserving reflux action. Cool digested solutions were vortexed with approximately 30 mL of de-i onized water, allowed to cool to room temperature, brought to 75 mL volume, and filtered to remove the boiling beads. Solutions were then transfe rred to square Nalgene storag e bottles, sealed, mixed, and stored. Nitrogen trapped as (NH4)2SO4 was analyzed on an automatic solution sampler and a proportioning pump. A plant standard with a known N concen tration value was subjected to the same procedure as the cowp ea pod and plant samples and used as a check (Multiple Cropping Agronomy Lab, University of Florida). Fresh weight, dry weight, and N concentration, as appropria te, were recorded for each study.

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57 Mineral Analysis For mineral analysis, 1.0 g from each cowpea pod and plant sample was weighed into 50 mL beakers and ashed in a muffle furnace at 480C for 6 h. The samples were then cooled to room temperature and mois tened with de-ionized water. Under a hood, 20 mL of de-ionized water and 2 mL of concen trated HCl were added to each beaker. The beakers were placed on a hot plate, slowly boiled until dry, and then removed. An additional 20 mL of de-ionized water and 2 mL concentrated HCl were then added to the beakers before small Pyrex watch glasses were used to cover the beakers for reflux. The samples were placed on the hot plate and brought to a forceful boil. They were then removed and again allowed to cool to room te mperature. Each sample was then brought to volume in 100 mL flasks and mixed. The fl asks were set aside ove rnight to allow the Si to settle. The solutions were then decante d into 20 mL scintillation vials for analysis. Phosphorus concentration was analyzed by colorimetry, K and Na concentrations by flame emission, and Ca, Mg, Cu, Fe, Mn, and Zn concentrations by atomic adsorption spectrometry (AA). Mineral concentrations were multiplied by dry matter yield to obtain mineral content (yield of or crop removal of minerals). Soil Analysis During the lima bean studies, soil samples were obtained from the top 20 cm of soil directly following harvest of each experime nt. Samples were air-dried in open paper bags, then screened through a 2.0 mm stainless st eel sieve to remove any rocks or debris and stored for further analysis. The samp les were then analyzed for N, mineral concentrations, pH, buffer pH (BpH), organi c matter (OM), and cati on exchange capacity (CEC). For soil N, a mixture of 2.0 g of each soil sample, 3.2 g of salt catalyst (9:1 K2SO4:CuSO4), and 10 mL of H2SO4 were subjected to the same procedures for N

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58 analysis as leaf tissue was, except that boili ng beads were not used because the particles of soil served the same purpose. A soil sample of known N concentration was also analyzed and used as a check. For soil mineral analysis, a Mehlich I (Mehlich, 1953), extraction method was used. Five g of each soil sample were weighed and extracted with 20 mL of a combination of 0.025 N H2SO4 and 0.05 N HCl. Using an Eberach shaker at 240 oscillations minute-1, mixtures were shaken for 5 min. The mixtures were then filtered using Schleischer and Schuell 620 (1 1 cm) filter paper and poured into scintillation vials. The remaining solutions were then subjected to analysis of P, K, Ca, Mg, Na, Cu, Fe, Mn, and Zn in the same manner as desc ribed for leaf tissue analysis. Soil pH was found using a 1:2 soil to water volume ratio using a glass electrode pH meter (Peech, 1965). Buffer pH (BpH) was found using Adams/Evans buffered solution (Adams and Evans, 1962). Cation exchange capacity (C EC) was estimated by the summation of relevant cations (Hesse, 1972; Jackson, 1958). Estimated soil CEC was calculated by summing the milliequivalents of the determined bases of Ca, Mg, K, and Na (where applicable) and a dding them to exchangeable H+ expressed in milliequivalents per 100 g (cmol kg-1) (Hesse, 1972). For the determination of soil organic ma tter (OM), a modified version of the Walkley Black method was used, in which 1.0 g of soil was weighed into a 500 mL Earlenmeyer flask, and 10 mL of 1 N K2Cr2O7 solution was then pipetted into the flask. Twenty mL of concentrated H2SO4 was added and mixed by ge ntle rotation for 1 min using care to avoid throwing soil up onto the si des of the flask. The flask was then left to stand for 30 min, and then diluted to 200 mL with de-ionized water. Five drops of

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59 indicator were added, and the solution was titrated with 0.5 N Ferrous Sulfate Solution until the color sharply changed from a dull green to a reddish brown color. A flask without soil was prepared in the same manner and titrated to determine the blank titrant, along with a flask containing a check soil with a known amount of OM Percent OM was determined using the equation: percent OM = (1-T/S) x 6.8, where S is blank-titration in mL of ferrous ammonium sulfate solution, and T is sample titration in mL ferrous ammonium sulfate solution (W alkley, 1935; Allison, 1965). Nematode Analysis Five lima bean plants from each variety in each experimental design were sampled for nematode infestation ratings. Visual gall rating of plant roots was performed for each of the samples. The rating scheme for eval uation of nematode galls was based on a scale from 1-10, 0 signifying no infestation and 10 signifying root death (Netscher and Sikora, 1990). Statistical Analysis Data were recorded in Quattro Pr o (Anonymous, 1987) spreadsheets and transferred to MSTAT 4.0 (Anonymous, 1985) for analysis of variance using the appropriate model for the experimental design (Table 3-1 to 3-3). Mean separation was performed using fixed LSD at the 0.05 level of probability (Gomez and Gomez, 1984). Results When comparing the 5 cowpea varieties in terms of fresh whole plant (no pods) yield, differences (p> 0.05) were exhibited and ‘Iron Clay ’ produced the highest yields in all 3 experiments (Table 3-4). ‘Calif ornia Blackeye #5’and ‘Mississippi Cream’ produced the highest (p< 0.05) fresh pod yields (Table 34). ‘Iron Clay’ produced the highest (p< 0.05) dry whole plant matte r for all 3 experimental designs while ‘California

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60 Blackeye #5’ did for pods (Table 3-5). The highest (p< 0.05) pod yielding varieties, in terms of percentage of pods produced, we re ‘Mississippi Cream’ and ‘California Blackeye #5’ (Table 3-6). Mineral analysis of macronutrient conten t in cowpea plant determined that ‘Iron Clay’ had the highest (p< 0.05) P content in all 3 experime nts and some of the highest N and K contents, along with the hybrids ‘Califor nia Blackeye #5’ and ‘Mississippi Cream’ (Table 3-7). ‘Iron Clay’ also had some of the highest (p< 0.05) contents of Ca and Na and had the highest (p< 0.05) levels of Mg and P (Table 3-7). Analysis of micronutrient content in cowpea plant determined that the highest (p< 0.05) contents of Cu and Mn and some of the highest (p< 0.05) contents of Fe and Zn occurre d in ‘Iron Clay’ (Table 3-7). Highest (p< 0.05) content of N, Mg, and P in cowpea pods for all 3 experiments were found in ‘California Blackeye #5’ (Table 3-8). ‘California Blackeye #5’ was among the varieties found to have the highest (p< 0.05) Ca, K, and Na contents (Table 3-8). Micronutrient analysis of the pod determined that ‘Iron Clay’ contained the highest (p< 0.05) content of Cu, Mn, and Zn while al so containing some of the highest (p< 0.05) content of Fe (Table 3-8). When comparing varieties of lima bean for differences in pods produced, no particular variety stood out as producing the highest (p< 0.05) fresh weight of pods. In the CRD, ‘Fordhook’ and ‘Henderson Bush’ were top producers, while in the RCB, ‘Florida Butter’ and Jackson Wonder’ were top producers (Table 3-9). In the LS, ‘Fordhook’ and ‘Florida Butte r’ were the highest (p< 0.05) producers of fresh pods (Table 3-9). ‘Henderson Bush ’ had some of the highest (p< 0.05) percent of pods that

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61 were beans for all experiments (Table 3-10). This variety also had some of the highest (p< 0.05) nematode infestation ratings (Table 3-11). Mehlich I (Mehlich, 1953) extractable minera ls for soil samples taken directly after harvest of lima bean was averaged over 5 replications taken from each experimental design (Table 3-12). Macronutrient levels were all found to be within acceptable ranges (Table 3-12). Micronutrients we re also found to be at adequate levels, except for Cu (Table 3-12), which was low possibly due to higher pH in the so il (Kidder and Rhue, 1983). Discussion and Conclusion Of the cowpea varieties tested, there was no specific variety that stood out as being the most suitable for production in Florida. Both ‘Iron Clay’ a nd ‘California Blackeye #5’ proved to be strong varieties, but each ha d very different strengths. ‘Iron Clay’ produced the highest whole plant matter yield of all of the varieties. The plant biomass produced by this variety also had some of the highest contents of the important minerals N, P, and K. ‘Iron Clay’ also had the lowe st percentage of pods produced, therefore producing more plant biomass than any other variety tested. ‘Ca lifornia Blackeye #5’ had some of the highest pod yields as well as some of the highe st percentage of pod production. The pods from this variety were very healthy, containi ng the highest levels of N, Mg, P, Cu, Mn, and Zn. Each of the 2 varieties would be appropria te for use in different situations. For production in Florida as part of a cropping system or for use as organic mulch, ‘Iron Clay’ would make the strongest choice. Th is variety of cowpea has the capacity to provide extra N for succeeding crops, when used in a system, following the harvest of its pods. The remaining plant residue would be hi gh in K and P, as well as N, which would

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62 become available for utilization by other cr ops. ‘Iron Clay’ also produces more plant biomass than pods, which makes it preferable fo r use as a mulch. This particular variety of cowpea has also been found to suppress populations of the ex tremely detrimental plant-parasitic nematode, M. incognita, which can pose a huge problem in crop production in Florida (Wang et al., 2002). For use as a cove r crop in cropping systems in Florida, ‘Iron Clay’ would be the most appropriate variety choice. ‘California Blackeye #5’ is a variety of cowpea that would make a good candidate for a very different situation, of consumption. This variety has several advantages over other varieties of cowpea for use in this ar ea and is basically grown for consumption purposes. ‘California Blackeye #5’ pods ar e high in many nutrients and have the potential to be very beneficial when consumed. This variety of cowpea also has a higher percentage of pod production than other varietie s, which is preferable for varieties grown as food crops. ‘California Blackeye #5’ would be the most appropriate variety of cowpea for production for consumption purposes in Florida. The lima bean pods were harvested from the field before whole plant samples could be obtained, so the information for comparis on of lima bean varieties was minimal. No particular variety stood out when pod yi eld was examined. ‘Henderson Bush’, ‘Cangreen’, and ‘Fordhook’ ha d the highest bean percenta ge of harvested pods. The varieties that had the lowest nematode infest ation ratings were ‘Flo rida Butter’, ‘White Dixie Butter’, and again ‘Fordhook’ The variety that seems to be the most suited for production, possibly as a food crop, in Florida is ‘Fordhook’. Lima bean is a crop that is produced primarily for consumption, and this variety would be the most appropriate of those tested for this purpose.

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63Table 3-1. Cowpea plant yield, pod yield, a nd percentage of plant that was pods for cowpea variety analysis of variance. ____________________________________________________________________________________________________________ Plant Pod Plant Pod Pod % of Pod % of Source of variation df fr. wght. fr. wght. dry wght. dry wght. plant, fr. plant, dry CRD Variety 4 * * * Error 20 — — — — — — Total 24 — — — — — — RCB Replications 4 — — — — — — Variety 4 * * * Error 16 — — — — — — Total 24 — — — — — — LS Row 4 — — — — — — Column 4 — — — — — — Variety 4 * * * Error 12 — — — — — — Total 24 — — — — — — Significant at the 0.05 level.

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64Table 3-2. Cowpea plant mineral content and cowpea pod mine ral content for cowpea variety analysis of variance. ____________________________________________________________________________________________________________ Source of variation df N Ca Mg K Na P Cu Fe Mn Zn N Ca Mg K Na P Cu Fe Mn Zn ——————————————Plant—————————— ————————————Pod———————————— CRD Variety 4 ns† * ns * * * * * * * Error 20 — — — — — — — — — — — — — — — — — — — — Total 24 — — — — — — — — — — — — — — — — — — — — RCB Replications 4 — — — — — — — — — — — — — — — — — — — — Variety 4 * * * * * * ns * * * Error 16 — — — — — — — — — — — — — — — — — — — — Total 24 — — — — — — — — — — — — — — — — — — — — LS Row 4 — — — — — — — — — — — — — — — — — — — — Column 4 — — — — — — — — — — — — — — — — — — — — Variety 4 * * * * * * * * * * Error 12 — — — — — — — — — — — — — — — — — — — — Total 24 — — — — — — — — — — — — — — — — — — — — *Significant at the 0.05 level. †ns = not significant.

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65Table 3-3. Lima bean pod yield, percent pods that were beans, and nematode ratings fo r lima bean variety analysis of variance. ____________________________________________________________________________________________________________ Source of variation df Pod yield, fr. Pod yield, dry Bean % of pod, dry Nematode rating CRD Variety 4 * * Error 20 — — — — Total 24 — — — — RCB Replications 4 — — — — Variety 4 * * Error 16 — — — — Total 24 — — — — LS Row 4 — — — — Column 4 — — — — Variety 4 * * Error 12 — — — — Total 24 — — — — Significant at the 0.05 level.

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66 Table 3-4. Fresh weights of cowpea for three ex perimental designs and five varieties, fall 2002. Variety CRD RCB LS —————————Fresh weight, g m-2————————— Plant Iron Clay 4910 a† 4310 a 2402 a TX Cream 12 3056 b 2156 b 964 b MS Cream 2982 b 2340 b 880 b White Acre 2800 bc 2112 b 906 b CA Blackeye #5 2262 c 1912 b 1264 b LSD at p< 0.05 636 518 633 Pod Iron Clay 256 c 227 c 112 c TX Cream 12 483 b 340 bc 88 c MS Cream 755 a 560 a 237 b White Acre 492 b 380 b 148 c CA Blackeye #5 687 a 580 a 373 a LSD at p< 0.05 128 137 88 †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD. Table 3-5. Dry weights of cowpea for three ex perimental designs and five varieties, fall 2002. Variety CRD RCB LS —————————Dry weight, g m-2————————— Plant Iron Clay 836 a† 764 a 428 a TX Cream 12 514 b 354 b 176 c MS Cream 488 b 442 b 176 c White Acre 460 b 384 b 162 c CA Blackeye #5 452 b 442 b 306 b LSD at p< 0.05 113 115 108 Pod Iron Clay 41 c 37 c 18 c TX Cream 12 101 b 71 b 18 c MS Cream 119 b 88 b 40 b White Acre 105 b 82 b 32 bc CA Blackeye #5 197 a 166 a 106 a LSD at p< 0.05 25 28 20 †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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67 Table 3-6. Percent of cowpea plant that was pods for three experiment al designs and five varieties, fall 2002. Variety CRD RCB LS ————————% plant that was pods————————— Fresh Iron Clay 5.25 d† 5.43 c 4.95 c TX Cream 12 16.24 c 16.84 b 8.42 bc MS Cream 25.98 ab 24.09 b 26.80 a White Acre 17.95 bc 19.67 b 16.70 b CA Blackeye #5 32.20 a 31.62 a 29.12 a LSD at p< 0.05 8.0 7.0 8.0 Dry Iron Clay 4.84 c 4.95 c 4.41 c TX Cream 12 20.26 b 21.83 b 9.46 c MS Cream 24.76 b 20.48 b 22.35 b White Acre 23.09 b 22.01 b 19.39 b CA Blackeye #5 45.07 a 38.35 a 34.37 a LSD at p< 0.05 8.0 9.0 9.0 †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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68 Table 3-7. Mineral content in cowpea plant for three experimental designs and five varieties, fall 2002. Variety CRD RCB LS —————————Mineral content, g m-2———————— N Iron Clay 19.4 a† 14.9 a 10.1 a TX Cream 12 14.4 b 10.5 b 5.1 bc MS Cream 13.0 b 10.4 b 5. bc White Acre 13.8 b 10.5 b 4.33 c CA Blackeye #5 12.4 b 10.5 b 7.6 ab LSD at p< 0.05 3.7 2.7 2.9 Ca Iron Clay 7.3 a 8.6 a 5.4 a TX Cream 12 5.0 a 3.8 b 2.3 b MS Cream 4.7 a 4.9 b 2.2 b White Acre 4.1 a 4.0 b 2.1 b CA Blackeye #5 4.0 a 4.1 b 3.4 b LSD at p< 0.05 ns 1.2 1.4 Mg Iron Clay 2.8 a 3.2 a 1.9 a TX Cream 12 1.5 b 1.3 c 0.8 c MS Cream 1.4 b 1.4 bc 0.7 c White Acre 1.5 b 1.5 bc 0.7 c CA Blackeye #5 1.4 b 1.7 b 1.3 b LSD at p< 0.05 0.5 0.4 0.5 K Iron Clay 14.9 a 10.1 a 4.3 a TX Cream 12 9.8 b 6.4 b 2.1 b MS Cream 9.8 b 7.6 ab 2.0 b White Acre 10.2 b 6.0 b 2.0 b CA Blackeye #5 6.3 c 5.2 b 3.1 ab LSD at p< 0.05 3.4 2.8 1.8 Na Iron Clay 0.7 a 0.8 a 0.5 a TX Cream 12 0.4 a 0.3 b 0.2 c MS Cream 0.4 a 0.3 b 0.2 bc White Acre 0.3 a 0.2 b 0.2 c CA Blackeye #5 0.3 a 0.3 b 0.4 ab LSD at p< 0.05 ns 0.2 0.2 P Iron Clay 2.8 a 2.7 a 1.7 a TX Cream 12 1.9 b 1.4 b 0.8 bc MS Cream 1.6 b 1.5 b 0.7 c White Acre 1.7 b 1.4 b 0.6 c CA Blackeye #5 1.6 b 1.4 b 1.2 b LSD at p< 0.05 0.5 0.4 0.4

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69 Table 3-7. Continued. Variety CRD RCB LS ————————Mineral content, mg m-2———————— Cu Iron Clay 4.86 a 3.84 a 2.06 a TX Cream 12 2.80 b 2.03 b 0.88 c MS Cream 2.52 b 2.30 b 0.74 cd White Acre 2.19 b 2.17 b 0.70 d CA Blackeye #5 2.58 b 2.26 b 1.48 b LSD at p< 0.05 0.85 0.81 0.17 Fe Iron Clay 142.26 a 193.60 a 75.84 a TX Cream 12 65.02 b 62.76 b 33.94 b MS Cream 89.52 b 76.46 b 34.28 b White Acre 74.74 b 63.10 b 28.28 b CA Blackeye #5 74.46 b 70.77 b 65.58 a LSD at p< 0.05 37.3 89.0 22.7 Mn Iron Clay 16.31 a 15.63 a 13.24 a TX Cream 12 7.95 b 6.64 bc 5.34 bc MS Cream 8.42 b 6.33 c 5.41 bc White Acre 6.30 b 8.61 bc 4.13 c CA Blackeye #5 7.67 b 9.93 b 7.77 b LSD at p< 0.05 4.4 3.4 3.3 Zn Iron Clay 30.16 a 32.13 a 16.53 a TX Cream 12 18.10 b 13.74 c 10.16 bc MS Cream 15.92 b 14.04 c 8.10 c White Acre 13.99 b 14.34 c 6.55 c CA Blackeye #5 16.11 b 20.71 b 14.74 ab LSD at p< 0.05 5.3 5.0 5.4 †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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70 Table 3-8. Mineral content in cowpea pod fo r three experimental designs and five varieties, fall 2002. Variety CRD RCB LS ————————Mineral content, g m-2———————— N Iron Clay 1.7 c† 1.3 c 0.7 c TX Cream 12 3.7 b 2.6 b 0.7 c MS Cream 4.8 b 3.4 b 1.7 b White Acre 3.8 b 3.0 b 1.2 bc CA Blackeye #5 7.0 a 5.6 a 3.7 a LSD at p< 0.05 2.0 1.0 0.7 Ca Iron Clay 0.2 c 0.1 c 0.1 cd TX Cream 12 0.2 c 0.1 c 0.1 d MS Cream 0.4 b 0.3 ab 0.2 b White Acre 0.2 c 0.2 b 0.1 c CA Blackeye #5 0.4 a 0.3 a 0.2 a LSD at p< 0.05 0.01 0.1 0.04 Mg Iron Clay 0.1 d 0.1 d 0.1 b TX Cream 12 0.3 c 0.2 c 0.1 b MS Cream 0.4 b 0.3 b 0.1 b White Acre 0.3 c 0.2 bc 0.1 b CA Blackeye #5 0.5 a 0.4 a 0.3 a LSD at p< 0.05 0.09 0.07 0.06 K Iron Clay 0.6 d 0.5 a 0.2 b TX Cream 12 1.2 c 0.7 a 0.2 b MS Cream 1.6 b 1.2 a 0.5 b White Acre 1.3 c 1.0 a 0.4 b CA Blackeye #5 2.2 a 1.3 a 1.0 a LSD at p< 0.05 0.29 ns 0.32 Na Iron Clay 0.03 b 0.02 b 0.01 b TX Cream 12 0.1 ab 0.03 ab 0.01 b MS Cream 0.1 a 0.1 ab 0.03 ab White Acre 0.1 ab 0.04 ab 0.02 b CA Blackeye #5 0.1 a 0.1 a 0.1 a LSD at p< 0.05 0.04 0.04 0.04 P Iron Clay 0.2 c 0.2 c 0.1 c TX Cream 12 0.4 b 0.3 b 0.1 c MS Cream 0.6 b 0.4 b 0.2 b White Acre 0.5 b 0.4 b 0.2 bc CA Blackeye #5 0.9 a 0.7 a 0.5 a LSD at p< 0.05 0.13 0.12 0.10

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71 Table 3-8. Continued. Variety CRD RCB LS ————————Mineral content, mg m-2———————— Cu Iron Clay 0.25 d 0.22 c 0.08 c TX Cream 12 0.46 c 0.31 bc 0.06 c MS Cream 0.68 b 0.50 b 0.19 b White Acre 0.57 bc 0.44 b 0.09 c CA Blackeye #5 1.32 a 0.97 a 0.50 a LSD at p< 0.05 0.13 0.19 0.07 Fe Iron Clay 33.10 d 30.34 c 13.80 d TX Cream 12 67.86 c 46.70 bc 47.48 bc MS Cream 100.38 b 67.30 b 60.58 ab White Acre 90.58 b 59.98 b 28.08 cd Ca Blackeye #5 141.28 a 145.74 a 76.64 a LSD at p< 0.05 21.3 22.4 26.1 Mn Iron Clay 1.00 c 0.62 c 0.46 c TX Cream 12 1.22 c 1.01 bc 0.33 c MS Cream 2.21 b 1.21 b 0.93 b White Acre 1.27 c 1.33 b 0.62 bc CA Blackeye #5 2.70 a 2.46 a 1.54 a LSD at p< 0.05 0.40 0.48 0.35 Zn Iron Clay 1.61 d 1.18 c 0.81 bc TX Cream 12 2.61 c 1.96 bc 0.66 c MS Cream 4.45 b 2.49 b 1.71 b White Acre 3.18 c 2.87 b 1.22 bc CA Blackeye #5 5.99 a 5.77 a 4.45 a LSD at p< 0.05 0.87 1.0 0.93 †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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72 Table 3-9. Pod yield for six lima bean vari eties over three experi mental designs, fall 2003. Variety CRD RCB LS ———————————Yield, g m-2—————————— Fresh Fordhook 891 a† — 629 a FL Butter 685 b 687 a 530 ab Henderson Bush 753 ab 658 b 466 b Cangreen 722 b 577 b 431 b White Dixie Butter 678 b 588 b 467 b Jackson Wonder — 763 a — LSD at p< 0.05 48 78 122 Dry Fordhook 159 c — 188 a FL Butter 131 c 131 b 116 c Henderson Bush 245 a 156 a 155 b Cangreen 209 b 145 ab 154 b White Dixie Butter 136 ab 125 b 119 c Jackson Wonder — 160 a — LSD at p< 0.05 32 24 33 †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD. Table 3-10. Percent of lima bean pods that we re beans for six lima bean varieties over three experimental designs, fall 2003. Variety CRD RCB LS ————————% of plant that was pods———————— Fordhook 17.8 c† — 30.4 ab FL Butter 19.2 c 19.1 b 21.8 c Henderson Bush 32.9 a 23.8 a 33.2 a Cangreen 29.0 b 25.3 a 37.4 a White Dixie Butter 20.1 c 21.2 b 25.5 bc Jackson Wonder — 20.9 b — LSD at p< 0.05 3.5 2.1 7.4 †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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73 Table 3-11. Nematode infest ation ratings for six lima b ean varieties over three experimental designs, fall 2003. Variety CRD RCB LS ——————————Rating†———————————— Fordhook 2.3 b‡ — 4.2 bc FL Butter 2.8 b 3.2 b 3.4 c Henderson Bush 7.7 a 6.0 ab 5.7 abc Cangreen 7.3 a 8.8 a 7.3 a White Dixie Butter 6.4 a 2.8 b 6.5 ab Jackson Wonder — 3.0 b — LSD at p< 0.05 2.3 3.9 2.6 †Nematode infestation rating scale: 0-10, 0 = no infestat ion, 10 = severe infestation. ‡Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD. Table 3-12. Soil mineral analysis for samples following lima bean harvest for three experimental designs, fall 2003. Average† CRD RCB LS ———————Mineral concentration, mg kg-1—————— Ca 624 463 253 Mg 207.2 77.0 55.3 K 81.0 41.0 30.6 N 700 666 519 P 227 190 127 Na 11.1 10.2 7.0 Cu 0.40 0.30 0.27 Fe 50.2 37.7 33.2 Mn 11.30 8.66 5.79 Zn, 10.47 8.51 4.44 —————————Soil characteristics————————— pH 7.3 7.4 7.3 BpH 7.86 7.88 7.88 OM, % 1.53 1.55 1.43 CEC, meq 100 g-1‡ 5.13 4.03 2.76 †Values are averages of 5 replications taken from each experimental design. ‡cmol kg-1

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74 CHAPTER 4 MINERAL CONTENT AND YIELD OF SUNN HEMP DUE TO CLIPPING HEIGHTS AND PLANT POPULATIONS Introduction Sunn hemp (Crotalaria juncea L.) is a tropical branching annual legume that has recently become a crop of interest for sustaina ble farmers. The reason for their interest stems from the crop’s wide array of benef its, including erosion pr evention, improvement of soil properties, weed suppr ession and reduction of nemat ode populations. This crop could possibly be a simple and inexpensive solution to many of the problems that the average farmer faces. Sunn hemp is native to India and Pakistan where it has been used to produce cloth, twine, and rope for centuries (Li et al., 2000) Today, it is cultivated in many regions of the world, ranging from Hawaii and California to the tropics of Ug anda, Zimbabwe, and Brazil to the southwestern United States (D uke, 1981). Traditionally, it has been utilized as a green manure, livestock feed, a nd a non-wood fiber crop (USDA, 1999). The possibility of using sunn hemp in cropping systems and as a cover crop has been the focus of many tests recently. Sunn hemp has proven to be a valuable crop to grow for high-protein forage in late summer when pastur es perform poorly (Li et al., 2000). When grown as a summer annual, it was found to produce over 5,600 kg ha-1 of dry biomass (USDA, 1999). It can be used to prevent erosion of soil and to suppress weed growth (Li et al., 2000). Sunn hemp has also shown good resistance to root-knot nematodes (Meloidogyne incognita) and has actually reduced nematode populations

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75 (Li et al., 2000; Marshall, 2002; Wang et al., 200 2a). Since it is a legume, sunn hemp can also fix much of the N needed for succeeding crops. Sunn hemp can contribute a significant amount of N to the soil, over 112 kg N ha-1 (USDA, 1999). When it is used as a cover crop, it can conserve soil water a nd recycle plant nutrients (USDA, 1999). Sunn hemp has also been found to be very benefi cial when used as an amendment in crop production (Marshall et al., 2002). Sunn hemp has proven to be very benefici al in multiple cropping systems in the southeast U.S. The cultivar Tropic Sunn was grown in Alabama as a cover crop/green manure after corn (Zea mays L.) harvest. The dry matter biomass achieved was on average 5,829 kg ha–1 in a 9-12 week period over the 2-yr study (Mansoer et al., 1997). In an additional study conducted with ‘Tropi c Sunn’, the crop was found to have added 150 to 164 kg N ha-1 to the soil after a 60-d growth period (Rotar and Joy, 1983). The legume yielded a total of 3,495 kg of dry bi omass (roots and shoots) and fixed 204 kg N ha-1 in three months after seeding in a study conducted in Homestead, FL (Li et al., 2002). In attempts to investigate this beneficial crop even further, a 2-yr experiment was conducted at the University of Florida to dete rmine the effects of different plant heights and plant populations on plant yield and mineral concentration. This test was also part of a larger study (see Chapter 6) conducted to examine the effects of cropping histories on no-till sweet corn. The objectives of the te st were to analyze sunn hemp for mineral concentrations to determine mineral contents as well as to find the best clip height and population for maximum yield and N content. Our null hypothesis stated that the varying clip heights and populations tested would not affect yield or mineral content.

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76 Materials and Methods This study involved a split-split plot experiment, conducted from August to December of 2002 and again in 2003 on a Millhopper fine sand, classified as loamy siliceous semiactive hyperthermic Grossa renic Paleodults (USDA-NRCS, 2003) in Gainesville, FL. Main effects were the year during which the test was performed (2002, 2003). Sub-effects were 3 different plant populations (6, 18, and 30 plants m-2) of sunn hemp. Sub-sub effects for the test were 5 different plant heights (0.4, 0.8, 1.2, 1.6, and 2.0 m) at which the sunn hemp was maintain ed. The 2003 portion of the experiment was re-randomized and year was treated as the main effect in a split-split plot experimental design. Data from each year we re analyzed together. The split-split plot design is uniquely suited for a 3-factor experiment when 3 different levels of precision are desired for various effects (Gomez and Gomez, 1984). Each level of precision is assigned to the eff ects associated with each of the 3 factors. The main-plot factor receives the lowest degr ee of precision and the sub-sub plot factor receives the highest. Plant Population Sunn hemp seed was planted with a Fl ex 71 planter and a tractor on 29 August 2002 and 30 August 2003 at a rate of 200 seeds 6 m-1 of row (44 seeds m-2). Each plot contained 4 rows, each 0.76 m wide. Plot size was 6 m2. Plant populations were established by hand thinning on 17 September 2002 and 15 September 2003. After the implementation of the plant populations, Lannate LV was applied to control pests at a rate of 1.2 L ha-1 during both years of the study. The hemp received water from rainfall and from overhead sprinkler irrigation, ensuring at least 3 cm of water per week. Weeds were c ontrolled with plowing by cultivator sweeps.

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77 Yield Plant height treatments were maintain ed by hand trimming. The plants were checked on a weekly basis to ensure specifi c heights were maintained. When plants exceeded the specific height by 0.6 m, the tops we re clipped back to that height. Sub-plot treatments 1 and 2, the 0.4 m (4 clippings required) and 0.8 m (3 clippings required) heights, were initially implemented on 10 October and 13 October of 2002 and 2003, respectively. Treatment 3, the 1.2 m (2 cl ippings required) he ight, was initially implemented on 30 October and 8 November of 2002 and 2003, respectively. Treatment 4, the 1.6 m (1 clipping required) height, was initially implemented 8 November of 2002 and 12 November of 2003, respectively. Trea tment 5, the 2.0 m height, never had to be implemented because the plants never exceeded this specific height. Whole plants were harvested on 5 December 2002 and 7 December 2003. The plant material that was harvested with the implementation of each treatment as well as the whole plants were kept for anal ysis. Fresh weights were obtained and then the hemp was placed into a 60C forced air ov en to dry. Dry matter yields were obtained from the dried plant material before it wa s chopped in a hammer mill, mixed well, and ground to pass a 2-mm stainless steel screen us ing a Wiley mill. All plant material was stored in plastic sample ba gs before analysis. Nitrogen Analysis For N analysis of the plant material, a micro-Kjeldahl procedure was used (Gallaher et al., 1975). A mixture of 0.100 g of each sunn hemp plant material sample, 3.2 g salt-catalyst (9:1 K2SO4:CuSO4), 2 Pryrex beads and 10-mL of H2SO4 were vortexed in a 100-mL Pyrex test-tube under a hood. To reduce frothing, 2 mL of 30% H202 was added in 1 mL increments and tube s were digested in an aluminum block

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78 digester at 370C for 3.5 hr. Tubes were capped with small Pyrex funnels that allowed for evolving gases to escape while preserving reflux action. Cool digested solutions were vortexed with approximately 30 mL of de-i onized water, allowed to cool to room temperature, brought to 75 mL volume, transf erred to square Nalgene bottles (glass beads were filtered out), sealed, mixed, and stored. Nitrogen trapped as (NH4)2SO4 was analyzed on an automatic Technicon Sampler IV (solution sampler) and an Alpkem Cor poration Proportioning Pump III. A plant standard with known N concentration was subj ected to the same procedure as above and used as a check. Fresh weight, dry matter yi eld, and N concentration were recorded for each of the tests. Nitrogen concentration (g kg-1) was multiplied by dry matter yield to obtain N content (g m-2). Mineral Analysis For the determination of nutrient concentrations of other elements in the plant material, 1.0 g from each of the samples was weighed into 50 mL Pyrex beakers and ashed in a muffle furnace at 480C for 6 hr. The samples were then cooled to room temperature and mixed with de-ionized water. Under a hood, 20 mL of de-ionized water and 2 mL of concentrated HCl were added to each beaker. The beakers were placed on a hot plate, slowly boiled until dry, and then removed. An additional 20 mL of de-ionized water and 2 mL of concentrated HCl were added to the beakers before small Pyrex watc h glasses were used to cover the tops for reflux. The samples were placed on the hot pl ate and brought to a forceful boil. They were then removed and allowed to cool to room temperature. Each sample was then brought to volume in 100 mL flasks and mixed. They were then left for several hours to

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79 allow all of the Si to settle out. Twen ty mL of solution was decanted into 20 mL scintillation vials for analysis. Phosphorus was analyzed by colorimetr y, K and Na by flame emission, and Ca, Mg, Cu, Fe, Mn, and Zn by atomic ad sorption spectrometry (AA). Mineral concentrations were multiplied by dry matter yield to obtain mineral content. Data was analyzed by ANOVA for a splitsplit plot experimental de sign using MSTAT 4.0 (1985). Means were separated by l east significant difference (LSD) at the 0.05 level of probability (Gomez and Gomez, 1984). Soil Analysis Soil samples were obtained from the top 20 cm of soil directly following harvest of each experiment. Samples were air-dried in open paper bags, then screened through a 2.0-mm stainless steel sieve to remove any rocks or debris and stored for further analysis. The samples were then analyzed for N, mineral concentrations, pH, buffer pH (BpH), organic matter (OM), a nd cation exchange capacity (CEC ). For soil N, a mixture of 2.0 g of each soil sample, 3.2 g of salt catalyst (9:1 K2SO4:CuSO4), and 10-mL of H2SO4 were subjected to the same procedures for N analysis as leaf tissue was, except that boiling beads were not used because the pa rticles of soil served the same purpose. A soil sample of known N concentration was also analyzed and used as a check. For soil extractable minera l analysis a Mehlich I (M ehlich, 1953) extraction method was used. Five g of each soil sample were weighed and extracted with 20 mL of a combination of 0.025 N H2SO4 and 0.05 N HCl. Using an Eberach shaker at 240 oscillations minute-1, mixtures were shaken for 5 min. The mixtures were then filtered using Schleischer and Schuell 620 (1 1 cm) filter paper and poured into scintillation vials.

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80 The remaining solutions were then subjected to analysis of P, K, Ca, Mg, Na, Cu, Fe, Mn, and Zn in the same manner as desc ribed for leaf tissue analysis. Soil pH was found using a 1:2 soil to water volume ratio using a glass electrode pH meter (Peech, 1965). Buffer pH (BpH) was found using Adams/Evans buffered solution (Adams and Evans, 1962). Cation excha nge capacity (CEC) was estimated by the summation of relevant cati ons (Hesse, 1972; Jackson, 1958). Estimated soil CEC was calculated by summing the milliequivalents of the determined bases of Ca, Mg, K, and Na (where applicable) and a dding them to exchangeable H+ expressed in milliequivalents per 100 grams (cmol kg-1) (Hesse, 1972). For the determination of OM, a modified version of the Walkley Black method was used, in which 1.0 g of soil was weighed into a 500-mL Earlenmeyer flask, and 10 mL of 1 N K2Cr2O7 solution was then pipetted into the flask. Twenty mL of concentrated H2SO4 was added and mixed by gentle rotation for 1 min using care to avoid throwing soil up onto the sides of the flask. The flask was then left to stand for 30 min, and then diluted to 200 mL with de-ionized water. Five drops of indicator were added, and the solution was titrated with 0.5 N Ferrous Sulfate Solution unt il the color changed from a dull green to a reddish brown color. The tit rating solution was added one drop at a time until the end point when the color sharply shif ted to a brilliant reddish brown. A flask without soil was prepared in the same manner and titrated to determine the blank titrant, along with a flask containing a check soil with a known amount of OM Percent OM was determined using the equation: percent OM = (1-T/S) x 6.8, where S is blank-titration in mL of ferrous ammonium sulfate solution, and T is sample titration in mL ferrous ammonium sulfate solution (W alkley, 1935; Allison, 1965).

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81 Statistical Analysis Data was analyzed as a split-split plot with the main treatments (year) in a randomized complete block design. An exam ple of the breakdown of the degrees of freedom (df) is shown in Table 4-1. Analys is of variance (ANOVA) for this split-split plot experimental design was conducted by use of MSTAT 4.0 (Anonymous, 1985). Data from each ANOVA was placed in a 4-wa y table as illustra ted in Table 4-2. Explanation of the location of each of the treatment effects and all of the possible interactions in the table are keyed at the bottom of Table 42. Means were separated by least significant diffe rence (LSD) at the 0.05 level of probability (Gomez and Gomez, 1976). All treatments and interact ions that were significant at p< 0.05 were highlighted in bold in the data tables (Tables 43 to 4-38). Plant mineral data were analyzed as split-split plot designs and means were sepa rated using least signi ficant difference (LSD) at the 0.05 level of probability. Results Yield For total clipped sunn hemp fresh matte r produced, a year and clip height interaction as well as a plant population and clip height interaction we re displayed (Table 4-3). For final non-clipped sunn hemp fresh matter, year was significant (p< 0.05) and there was a population and height interaction (Table 4-4). Fo r total plant fresh matter, a year and population, a year a nd height, and a population and height interaction were all displayed (Table 4-5). Two interactions we re exhibited for total clipped dry matter, between year and height and between populat ion and height (Tab le 4-6). Final nonclipped dry matter exhibited several interac tions, between year and population, year and

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82 height, and between population and height (Table 4-7). Fo r total sunn hemp dry matter, year, population, and height al l displayed significant (p< 0.05) differences (Table 4-8). Mineral Analysis: Clipped Material For total clipped sunn hemp matter, conten t of N (Table 4-9), P (Table 4-10), Ca (Table 4-12), and Mg (Table 4-13) exhibited year and clip height as well as population and height interactions. Three interac tions, between year and population, year and height, and population and height were exhibited in K content (Table 4-11). For Na content, population was significant (p< 0.05) and a year and he ight interaction was displayed (Table 4-14). For Cu (Table 415) and Zn (Table 4-18) content, year and height interactions as well as population and height inte ractions were displayed. Population was found to be significant (p< 0.05) in addition to an in teraction between year and height for Fe content (Table 4-16). Fo r Mn content, a year and population interaction as well as a year and height inte raction were present (Table 4-17). Mineral Analysis: Final Non-clipped Material In total final non-clipped sunn hemp matte r, N (Table 4-19) and P (Table 4-20) content displayed significant (p< 0.05) differences due to ye ar, population, and height. For K content, both year and height and population and height interactions were present (Table 4-21). Population was found to be significant (p< 0.05), in addition to a year and height interaction, for both Ca (Table 4-22) and Na (Table 4-24) content. For Mg content, year and population as well as year and height intera ctions were displayed (Table 4-23). A year and clip height interacti on as well as a population and clip height interaction were exhibited in Cu content (T able 4-25). Plant populat ion and clip height were both significant (p< 0.05) for Fe content (Table 4-26 ). Year, population, and clip height were all significant (p< 0.05) for Mn (Table 4-27) and Zn (Table 4-28) content.

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83 Mineral Analysis: Total Plant Material For N content in total clipped plus final non-clipped material, both a year and clip height interaction as well as a population a nd clip height intera ction were displayed (Table 4-29). Year, population, and clip height were found to be significant (p< 0.05) for P (Table 4-30), Ca (Table 4-32), and Na (Tab le 4-34) content. Fo r K content, population was significant (p< 0.05) and a year and clip height interaction was e xhibited (Table 31). Year and plant population were both significant (p< 0.05) in Mg content (Table 4-33). Plant population was significant (p< 0.05) for Cu content, which also displayed a year and clip height interaction (Table 4-35). Plant population as well as clip height were significant (p< 0.05) for Fe content (Table 4-36). Year, population, and height were all significant (p< 0.05) for Mn (Table 4-37) and Zn (Table 4-38) content. Discussion and Conclusion Yield: Clipped Fresh Matter The tested plant populations and clip height s were found to affect sunn hemp yield; therefore the null hypothesis could not be suppor ted. For total clipped sunn hemp fresh matter, several interactions we re displayed. The interaction between year and clip height was due to a greater fresh matter yield at the 0.8 m clip height compared to the 0.4 m clip height in 2003. For both years, there was a trend for fresh yield to decrease as clip height increased with the exception of the 0.8 m clip height as mentioned above. Also, greater fresh matter tended to be produced in 2003 th an 2002 for each clip height, with the exception of the 0.4 m and 1.6 m clip heights. Fresh matter produced was the same for both years at the 0.4 m height and actually lower in 2003 than 2002 at the 1.6 m height. The interaction between populat ion and clip height was cau sed by the yield increase between 6 and 30 plants m-2 for the 0.4 m clip height compared to the increase between

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84 the 6 and 18 plants m-2 populations for the other clip he ights. Highest yields were obtained at the 0.4 m an d 0.8 m clip heights. Yield: Non-clipped Fresh Matter Significant (p< 0.05) differences due to year were displayed in final non-clipped sunn hemp fresh matter. Yield was significantly (p< 0.05) higher in 2002 than in 2003. For final non-clipped sunn hemp fresh ma tter, only one interaction was exhibited, between plant population and clip height. Th is was due to a trend for fresh matter to increase as population increas ed from 6 to 18 plants m-2, and then decrease from 18 to 30 plants m-2. This trend was followed with the exception of the 1.2 and 2.0 m clip heights, which increased in fresh matter as population increased. Fresh yield was also found to increase for 6 and 18 plants m-2 as clip height increased, until the 1.6 m clip height. For 30 plants m-2, fresh matter stopped increasi ng at the 1.2 m clip height. Yield: Total Fresh Matter Three interactions were present for total sunn hemp fresh matter and they were all due to differing trends in yield production. Th e first was an interaction between year and plant population. Year did not di ffer in yields at 30 plants m-2, but higher yields occurred in 2002 than 2003 at 6 and 18 plants m-2. In 2002, 18 and 30 plants m-2 produced higher yield compared to 6 plants m-2. In 2003, 30 plants m-2 gave higher yield compared to the other populations. In 2002, yiel d increased as population incr eased from 6 to 18 plants m-2. But in 2003, yield increased as populat ion increased from 6 to 30 plants m-2. The second interaction was between year and clip height and was due to differing trends displayed by each year. In 2002, fresh yield in creased as clip height increased while in 2003, the 0.8 and 1.2 m heights and the 1.6 a nd 2.0 m heights did not differ in yield, respectively. A trend was displayed within clip heights to pr oduce equal amounts of

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85 fresh matter for both 2002 and 2003 with the exception of the 1.6 and 2.0 m clip heights, which produced greater fresh matter in 2002 than in 2003. The third interaction occurred between plant population and clip height. A trend was displayed in fresh matter production, with yield increasi ng from 6 to 18 plants m-2 and remaining equal from 18 to 30 plants m-2. The 1.6 and 2.0 m heights did not follow the trend, with fresh matter decreasing from 18 to 30 plants m-2 for the 1.6 m height and increasing from 18 to 30 plants m-2 for the 2.0 m height. Popul ations 6 and 18 plants m-2 increased in yield produced from 0.4 to 0.8 m clip heights and de creased from 1.2 to 1.6 m. The remaining population, 30 plants m-2, increased in yield produced from 1.6 to 2.0 m. Yield: Clipped Dry Matter For total clipped sunn hemp dry matter, 2 in teractions occurred. The first was due to differing trends in yield production and was between year and clip height. In 2002, clip height tended to produce less dry matte r than in 2003, with th e exception of the 1.6 m clip height, which produced more dry matter in 2002. Also in 2002, dry matter produced decreased as clip he ights increased. In 2003, dry matter increased between the 0.4 and 0.8 m clip heights, but then decrea sed as following heights increased. The second interaction was between population and cl ip height and was also due to differing trends. Within clip heights, dry matter tended to increase from 6 to 18 plants m-2 and then remain equal from 18 to 30 plants m-2. This trend was not followed in the 0.4 m height where dry matter increased as popul ation increased. The 18 and 30 plants m-2 populations increased in yield from 0.4 to 0.8 m and then decreased as following heights increased. The 6 plants m-2 population did not follow th is trend, with dry matter remaining equal from 0.4 to 0.8 m clip heig hts and then decreasing as clip height increased.

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86 Yield: Non-clipped Dry Matter Three significant in teractions were present in final non-clipped sunn hemp dry matter. The first was between year and plan t population and was due to differing trends in yield production. A trend was exhibited by populations to produce higher yield in 2002 than 2003. The trend was followed w ith the exception of the 6 plants m-2 population, which produced equal dry matter in 2002 and 2003. In 2002, yield increased from 6 to 18 plants m-2 and remained equal from 18 to 30 plants m-2, while in 2003, yield produced was equal for all populations. Th e second interaction was between year and clip height. This interaction was due to cl ip heights in 2002 producing higher yields than in 2003, except for the 0.4 and 0.8 m height s. The 0.4 m height produced less in 2002 than 2003 while the 0.8 m height produced e qual yields in 2002 and 2003. In 2002, yield increased as clip height increased for th e heights 0.4 to 1.2 m. Heights 1.6 and 2.0 m produced equal dry matter yields. In 2003, he ights 0.4 to 1.2 m all produced equal yields while the last 2 heights, 1.6 and 2.0 m, also pr oduced equal yields that were higher than that of the first 3 heights. The final in teraction was between pl ant population and clip height. Several trends were exhibited by the clip height s and possibly led to this interaction. The 0.4 and 2.0 m heights produced constant yields for all populations. The 0.8 m height produced increasing yield as population increased. The 1.2 and 1.6 m heights produced constant yield for the 6 and 18 plants m-2 populations, but the 1.2 m height yield decreased for the 30 plants m-2 population and the 1.6 m height increased. For the 6 plants m-2 population, yield remained cons tant between the 0.4 and 0.8 m heights, but for both 18 and 30 plants m-2, yield increased between the 2 heights.

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87 Yield: Total Dry Matter No significant interactions occurred for total sunn hemp dry matter. Year, plant population, and clipping height were all significant. Dr y matter produced in 2002 was significantly higher than that produced in 2003. Plants grown at 30 plants m-2 produced the highest dry matter. Plants maintained at 0.8 and 1.2 m clipping heights produced the highest dry matter. Mineral Content: Total Clipped Material The tested plant populations and clip hei ghts were also found to effect sunn hemp mineral content. Two interactions were pres ent for N content in total clipped sunn hemp. The first was between year and clip hei ght and was due to differing trends in N production. In 2002, clip heights produced lower N content than in 2003, with the exception of the 1.6 m clip height, which pr oduced higher N content in 2002 than in 2003. In 2002, the 0.4 and 0.8 m clip heights pr oduced equal N content, after which it decreased as clip height in creased. In 2003, N content produced increased between the 0.4 and 0.8 m clip heights before decreasing as clip heights increased. The second interaction occurred between plant population and clip he ight and again was due to differing trends. A trend was exhibited among populations wher e N content produced increased between 6 and 18 plants m-2 and then remained cons tant between populations 18 and 30 plants m-2. This trend was followed with the exception of the 0.8 m clip height, which increased N content produced as population increased. Another trend was exhibited by plant populations to produce increased N content between 0.4 and 0.8 m clip heights before decreasing cont ent as clip height increase d. The lowest population, 6 plants m-2, did not follow the trend and produced equal N content at both the 0.4 and 0.8 m clip heights.

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88 Two significant interactions occurred for P content in total clipped sunn hemp and were due to differing trends in P production. The first was be tween year and clip height. In 2002, P content produced remained constant from the 0.4 to the 1.2 m clip height before finally decreasing at the 1.6 m he ight. In 2003, P cont ent produced behaved differently, increasing between the 0.4 and 0.8 m clip heights and then decreasing as clip heights increased. Both the 0.4 and 1.6 m clip heights decreased in produced P content between 2002 and 2003 while the two remaini ng heights, 0.8 and 1.2 m, increased in produced content from 2002 to 2003. The s econd interaction, be tween population and clip height, was due to the trend among populati ons for P content produced to increase as population increased. This trend was not followed by only one height, 1.6 m, which produced constant P content between 18 and 30 plants m-2. Both plant populations 18 and 30 plants m-2 increased production of P content between 0.4 and 0.8 m clipping heights before decreasing production as he ights increased. The lowest population, 6 plants m-2, did not follow this trend, producing decreasing P content as clip height increased. For K content in total clipped sunn hemp, 3 interactions were present and were all due to differing trends in K production that we re expressed. The fi rst was between year and plant population. In 2002, K content produc ed increased between the 6 and 18 plants m-2 populations but then remained constant between 18 to 30 plants m-2. In 2003, production of K content increased as plan t population incr eased. In 2002, K content produced was consistently less than that pr oduced in 2003 for all plant populations. An interaction between year and clip height was also displayed. A trend was exhibited within clipping heights to produce less K c ontent in 2002 than in 2003. The interaction

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89 was due to 1 clip height not following this trend, the 1.6 m height, and producing equal K content in both 2002 and 2003. In 2002, K content produced remained constant between the 0.4 and 0.8 m clipping heights before decreas ing as remaining heights increased. In 2003, K content produced behaved differentl y, increasing between the 0.4 and 0.8 m heights before decreasing as clip height in creased. The third interaction displayed was between plant population and clip height and was due to differing tr ends in K production. Two clip heights, 0.4 and 1.2 m, behaved si milarly, increasing produced K content as population increased. The remaining heights, 0.8 and 1.6 m, both increased in K content production between populations 6 and 18 plants m-2 and produced equal content for both 18 and 30 plants m-2. Both 6 and 30 plants m-2 exhibited similar trends, with K content produced remaining equal between 0.4 and 0.8 m clip heights before decreasing as heights increased. The rema ining population, 18 plants m-2, did not follow the trend, producing increased K content between 0.4 and 0.8 m clip heights before decreasing content as heights increased. Calcium content in total clipped s unn hemp displayed only 2 significant interactions. The first, between year a nd clip height, was due to differing trends exhibited among populations and among clip hei ghts. Two clip heights, 0.4 and 1.6 m, exhibited similar trends, producing equal Ca content in 2002 and 2003. Clip heights 0.8 and 1.2 m also displayed similar trends, increasing in Ca content produced between 2002 and 2003. In 2002, Ca content decreased in pr oduction as clip hei ghts increased. In 2003, Ca content increased in production betw een 0.4 and 0.8 m clip heights, and then decreased as clip heights increased. The second interaction, between population and clip height, was also caused by diffe ring trends of Ca production. Two of the clip heights,

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90 0.4 and 1.2 m, expressed similar trends, incr easing production of Ca as plant population increased. The remaining 2 heights, 0.8 a nd 1.6 m, increased Ca production between the 6 and 18 plants m-2 populations and then produced equal Ca for both populations 18 and 30 plants m-2 and produced equal Ca content in all populations, re spectively. The first population, 6 plants m-2, decreased in Ca production as clip heights increased. The remaining 2 populations, 18 and 30 plants m-2, both produced equal Ca content for the 0.4 and 0.8 m heights before decreasing in pr oduction as clip heights increased. Two interactions were present in Mg conten t, both due to conflicting trends in Mg production. The first was between year and clip height. Clip heights 0.8 and 0.2 m followed a similar trend, producing higher Mg content in 2003 than in 2002. The lowest clip height, 0.4 m, produced equal Mg content in both years, while the highest clip height, 1.6 m, produced lower Mg in 2003 than in 2002. In 2002, Mg produced decreased between 0.4 and 0.8 m clip heights, remained constant between 0.8 and 1.2 m, and decreased again from 1.2 to 1.6 m. In 2003, Mg produced increased between 0.4 and 0.8 m clipping heights and then decreased as clip height increased. The second interaction was between plant population and clip height. Two clip heights, 0.4 and 1.2 m, exhibited similar trends, increasing Mg produced as plant population increas ed. The 0.8 m height increased Mg produced between populations 6 and 18 plants m-2 and then produced constant Mg between 18 and 30 plants m-2. The final clip height, 1.6 m, produced equal Mg for all clip heights. Th e lowest population, 6 plants m-2, produced equal Mg for the 0.4 and 0.8 m clip heights before decreasing pr oduction as clip heights increased. The 2 remaining populations, 18 and 30 plants m-2, produced equal Mg content from 0.4 to 1.2 m heights and then lower Mg for the 1.6 m height.

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91 Significant (p< 0.05) differences occurred in Na c ontent due to pl ant population. Plants grown at a population of 30 plants m-2 produced higher Na than those grown at 18 and 6 plants m-2. For Na content in total clipped sunn hemp, 1 interaction was exhibited, between year and clip height, due to conflicting trends in Na production. Two clip heights, 0.4 and 1.2 m, differed in Na production between 2002 and 2003. The remaining heights, 0.8 and 1.6 m, produced equal Na in both 2002 and 2003. The Na produced by the 0.4 m clip height in 2002 decr eased as clip height increased to 0.8 m, where Na then remained constant between it and the 1.2 m height before decreasing at the 1.6 m height. In 2003, Na content increased between 0.4 and 0.8 m clip heights before decreasing as clip heights increased. Two significant interactions were displa yed for Cu content in total clipped sunn hemp. The first, between year and clip height, was due to di ffering trends of Cu production. All clip heights produce higher Cu in 2003 than in 2002 except the 1.6 m height, which produced lower Cu in 2003 than in 2002. In 2002, Cu content decreased as clip height increased. In 2003, Cu conten t increased between 0.4 and 0.8 m heights but then decreased as clip heights increased. The second interaction was also due to conflicting trends and exceptions and was betw een plant population and clip height. The 0.8 and 1.2 m clipping heights followed a similar trend, increasing Cu production between 6 and 18 plants m-2 and then remaining constant between 18 and 30 plants m-2. The 0.4 m clip height increased Cu produc tion as population incr eased, while the 1.6 m clip height produced equal Cu fo r all populations. The 6 plants m-2 population produced constant Cu from heights 0.4 to 1.2 m, but d ecreased Cu for the 1.6 m height. The last 2

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92 populations, 18 and 30 plants m-2, both increased in Cu production between 0.4 and 0.8 m heights before decreasing production as remaining heights increased. Significant (p< 0.05) differences due to plant popul ation occurred in Fe content in total clipped sunn hemp. Plants grown at the 30 plants m-2 population produced higher Fe than plants grown at the 18 and 6 plants m-2 populations. Only 1 significant interaction was displayed in Fe content in to tal clipped sunn hemp. The interaction was between year and clip height and was due to different trends in Fe production. Clip heights from 0.4 to 1.2 m increased in Fe production between 2002 and 2003. Only the 1.6 m height differed from this trend, with Fe producti on decreasing from 2002 to 2003. In 2002, Fe produced remained constant from the 0.4 to 0.8 m heights before decreasing from the 0.8 to 1.2 m height. It also remain ed constant from 1.2 to 1.6 m. In 2003, Fe produced increased from 0.4 to 0.8 m before decreasing as remaining clip heights increased. Two interactions for Mn content in tota l clipped sunn hemp were exhibited. The first was between year and plant population and was due to conflicting trends displayed by each population in Mn production. The lowest population, 6 plants m-2, produced less Mn in 2002 than in 2003. The 18 plants m-2 population decreased Mn production from 2002 to 2003. The final population, 30 plants m-2, maintained Mn production for both 2002 and 2003. In 2002, production of Mn in creased from 6 to 18 plants m-2, but remained constant from 18 to 30 plants m-2, while in 2003, Mn increased as plant population increased. The second interaction was also due to diffe ring patterns of Mn production and was between year and clip he ight. Clip heights 0.4 and 1.6 m behaved similarly, both producing high Mn content in 200 2 than 2003. Remaining heights

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93 0.8 and 1.2 m also behaved similarly to each other, producing less Mn in 2002 than 2003. In 2002, production of Mn decreased as clip height increased, while in 2003 content increased between 0.4 and 0.8 m before decreas ing as remaining heights increased. For Zn content in total cli pped sunn hemp, 2 interactions were displayed. The first, between year and clip height, was due to c onflicting trends in Zn production. The first clip height, 0.4 m, produced equal Zn in both 2002 and 2003. Both the 0.8 and 1.2 m heights behaved similarly, producing less Zn in 2002 than 2003. The final height, 1.6 m, produced higher Zn in 2002 than in 2003. In 2002, Zn production decreased as clip height increased while in 2003, production increased between 0.4 and 0.8 m clip heights before decreasing as clip height increase d. The second interac tion, between population and clip height, was also due to differing trends of Zn producti on. Clip height 0.4 m produced increasing Zn as popula tion increased. The remaini ng clip heights all produced increasing Zn between 6 and 18 plants m-2 and constant Zn from 18 to 30 plants m-2. Populations 6 and 30 plants m-2 exhibited similar trends, both producing constant Zn from 0.4 to 0.8 m clip heights before d ecreasing production as remaining heights increased. The 18 plants m-2 population increased Zn pr oduction between 0.4 and 0.8 m clip heights and then decreased prod uction as clip heights increased. Mineral Content: Total Final Non-clipped Material For N and P content in total final non-cli pped sunn hemp, significant differences were displayed due to year, plant population, and clipping height. Both N and P content produced in 2002 were higher than that produc ed in 2003. Plants grown at 30 plants m-2 produced the highest N and P. Plants main tained at the highest clip height, 2.0 m, produced the highest N and P.

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94 Two significant interactions were displaye d for K content in total final non-clipped sunn hemp. The first was between year and c lip height and was due to different trends expressed in K production. Cli pping heights followed the same trend, producing constant K from 2002 to 2003. The exception was the final clip height, 2.0 m, which produced lower K in 2002 than 2003. In 2002, K produc tion increased between 0.4 and 0.8 m clip heights, remained constant between 0.8 a nd 0.2 m, then increased as clip height increased. In 2003, production of K increased as clip height increased. The second interaction was between plan t population and clip height and was due to the several different trends of K production. The 0.4 m c lip height produced constant K content for all plant populations. The 0.8 m height pr oduced constant K from 6 to 18 plants m-2 and higher, but constant, K be tween 18 and 30 plants m-2. Both the 1.2 and 1.6 m heights produced increasing K betw een 6 and 18 plants m-2 populations and constant K for both the 18 and 30 plants m-2 populations. Finally, the 2.0 m he ight produced increasing K as population increased. The 6 and 30 plants m-2 populations followed the same pattern of K production, each increasing as clip height increased. The 18 plants m-2 population increased K production as clip ping heights increased, but K was equal for the 1.6 and 2.0 m heights. Significant (p< 0.05) differences due to plant pop ulation were displayed in Ca content in total final non-cli pped sunn hemp. The highest Ca content was produced by plants grown at the 30 plants m-2 population. Only one inter action was displayed by Ca content in total final non-clippe d sunn hemp. It occurred between year and clip height and was caused by conflicting patterns in Ca production. Most cli pping heights produced more Ca in 2002 than in 2003. The 0.4 m hei ght was the exception, producing equal Ca

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95 for both years. Clip heights in 2002 incr eased Ca production from the 0.4 to the 1.2 m height and produced constant Ca from the 1.2 to the 2.0 m height. In 2003, clip heights produced constant Ca between the 0.4 and 0.8 m height, higher but constant Ca from the 0.8 to the 1.6 m height, and higher still and c onstant Ca from the 1.6 to the 2.0 m height. For Mg content in total final non-clipped sunn hemp, 2 significant interactions were displayed. The first was between year a nd plant population and wa s due to conflicting trends in the production of M g. Plant populations in 2002 co nsistently produced higher Mg than in 2003. In 2002, Mg produced between 6 and 18 plants m-2 increased, but remained constant between 18 and 30 plants m-2. In 2003, all 3 plant populations produced equal Mg. The second interacti on, also due to diffe ring trends of Mg production, occurred between year and clip height. A ll clip heights cons istently produced less Mg in 2002 than in 2003. In 2002, produced Mg increased as clip height increased from 0.4 to 1.2 m, and remained constant from the 1.2 to 2.0 m heights. In 2003, production of Mg increased between clip heights 0.4 and 0.8 m, remained constant between 0.8 and 1.2 m, and then increased be tween 1.2 and 1.6 m before increasing at the highest height, 2.0 m. Significant differences in Na content of total final non-clipped sunn hemp occurred due to plant population. Plants grown at the 30 plants m-2 population produced more Na than plants grown at the 18 and the 6 plants m-2 populations. Sodium content in total final non-clipped sunn hemp displayed only one interaction. The in teraction occurred between year and clip height and was due to conflicting trends in Na production. Three clipping heights, 0.8, 1.2, and 2.0 m, behave d similarly in Na production, decreasing from 2002 to 2003. In 2002, Na produced increased from heights 0.4 to 1.2 m, then

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96 decreased at the 1.6 m height before increasing again with the final clip height, 2.0 m. In 2003, production of Na remained equal betw een the 0.4 and 0.8 m heights, increased between the 0.8 and 1.2 m heights, and finally remained constant across the final three clip heights. Two significant interactions occurred in Cu content in total final non-clipped sunn hemp. The first, between year and clip hei ght, occurred due to conf licting trends in Cu production. The first 2 clipping heights, 0.4 and 0.8 m, behaved similarly, both producing equal Cu in 2002 and 2003. The 1.2 and 2.0 m heights also behaved similarly to each other, producing higher Cu in 2002 than 2003. In 2002, Cu production increased between the 0.4 and 0.8 m clip heights and th en remained constant as clip height increased. In 2003, Cu production increased between the 0.4 and 0.8 m heights, remained constant between the 0.8 and 1.2 m heights and between the 1.2 and 1.6 m heights, and finally increase d at the 2.0 m height. The second, between plant population and clip height, was also due to several diffe rent trends displayed of Cu production. Both the 0.4 and 0.8 m clip heights produced equa l Cu for all plant populations. The 1.2 m height produced equal Cu for both the 6 and 18 plants m-2 populations and equal, but increased, Cu for the 18 and 30 plants m-2 populations. The 1.6 m height increased Cu content production between 6 and 18 plants m-2, but produced constant Cu between 18 and 30 plants m-2. Finally, the 2.0 m clip height produ ced equal levels of Cu for both the 6 and 18 plants m-2 populations, but higher Cu for 30 plants m-2. Each plant population behaved differently. The 6 plants m-2 population increased Cu production between the 0.4 and 0.8 m clip heights, produced constant Cu from the 0.8 to 1.6 m heights, and increased production between the 1.6 a nd 2.0 m heights. The 18 plants m-2 population

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97 increased Cu production between the 0.4 and 0.8 m heights, produced equal Cu from the 0.8 to the 0.2 m height, increased producti on again between the 1.2 and the 1.6 m height, and then produced equal Cu for both the 1.6 and 2.0 m heights. Finally, the 30 plants m-2 population increased Cu production between the 0.4 and the 1.2 m clip heights, produced constant Cu from the 1.2 to the 1.6 m height, a nd increased Cu at the 2.0 m clip height. Significant (p< 0.05) differences occurred in Fe c ontent in total final non-clipped sunn hemp due to plant population and clippi ng height. The highest Fe was produced by plants grown at 30 plants m-2. Plants maintained at the 2.0 m height produced the highest Fe. Year, plant population, and c lip height caused significant differences in both Mn and Zn content in total final non-clipp ed sunn hemp. Sunn hemp grown in 2002 produced more Mn and Zn than plants grow n in 2003. Plants grown at the 30 plants m-2 population produced the highest Mn and Zn. S unn hemp maintained at the 2.0 clip height produced the highest Mn and Zn. Mineral Content: Total Clipped Pl us Final Non-clipped Material For N content in total clipped and fi nal non-clipped sunn hemp, two significant interactions were displayed. The first, due to conflicting trends in N production, was between year and clip height. Clip hei ghts 0.4 and 1.2 m displaye d one trend, producing constant N for both 2002 and 2003. The 0.8 m height displayed another trend, producing lower N in 2002 than in 2003. The 1.6 and 2.0 m heights displayed still another trend, producing greater N in 2002 than in 2003. In 2002, N production peaked at the 0.8 and 1.2 m clip heights, with the 0.4, 1.6, and 2.0 m he ights all producing equa l, but lower, N. In 2003, N production increased between the 0.4 and the 0.8 m heights, remained constant between the 0.8 and 1.2 m heights, increased from the 1.2 to the 1.6 m height,

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98 and remained equal between the 1.6 and 2.0 m heights. The second interaction, between plant population and clip height was due to different N produ ction trends. The first 4 clipping heights displayed the same trend, in creasing N production from 6 to 18 plants m2 and producing equal N from 18 to 30 plants m-2. The remaining height, 2.0 m, did not follow the trend and produced constant N from 6 to 18 plants m-2 and from 18 to 30 plants m-2. All 3 populations exhibited a similar tr end, N production peaki ng at the 0.8 and 1.2 m heights. The 6 and 30 plants m-2 populations both pr oduced constant N between the 1.6 and 2.0 m heights while the 18 plants m-2 population produced decreasing N for the last clip height, 2.0 m. Significant (p< 0.05) differences were displayed in P content in total clipped plus final non-clipped sunn hemp. Sunn hemp grow n in 2002 produced significantly more P than that grown in 2003. Plants grown at 30 plants m-2 produced the highest level of P. Plants maintained at the 0.8 and the 1.2 m clip heights produced the high est levels of P. Significant (p< 0.05) differences due to plant popul ation occurred in K content for in total clipped plus final non-clipped sunn hemp. Plants grown at the 30 plants m-2 population produced the highest K. One significant intera ction also occurred in K content, between year and clip height, due to conflicting trends in K production. One trend was exhibited for all c lip heights, to produce less K in 2002 than in 2003, with the exception of the 1.6 m height, which produced equal K content for both 2002 and 2003. In 2002, all clip heights produced equal K. In 2003, clip heights 0.4 to 1.2 m produced equal K and clip heights 1.6 and 2.0 m pr oduced decreased, but constant, K. Significant differences due to year, plant population, and cl ip height occurred in Ca content in total clipped plus final non-cli pped sunn hemp. Significantly higher Ca was

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99 produced by plants grown in 2002 than in 2003. Plants grown at 30 plants m-2 produced the highest Ca. Sunn hemp maintained at the 0.8 and 1.2 m height s produced the highest Ca. Magnesium content in total clipped plus final non-clipped sunn hemp displayed significant (p< 0.05) differences, due to year and pl ant population. Sunn hemp grown in 2002 produced significantly more Mg than that grown in 2003. Plants grown at 30 plants m-2 produced the highest level of Mg. Significant (p< 0.05) differences due to year, plant population, and clip height were displayed in Na content in total clipped plus final non-clipped sunn hemp. Higher Na was produced by plants grown in 2002. Plants grown at the 30 plants m-2 population produced the highest Na. Plants maintain ed at the 0.8 and 1.2 m clipping heights produced the highest Na. For Cu content in total clipped plus final non-clipped sunn hemp, significant (p< 0.05) differences were displayed due to plant population. Plants gr own at the 30 plants m-2 population produced the highest Cu. A significant interaction also occurred in Cu content, between year and clip height. The inte raction was due to conflicting trends in Cu production. Two tr ends were exhibited by clip heights between years. The first was equal Cu production between 2002 a nd 2003, which was displayed by the 0.4 and the 1.6 m clip heights. The second was lower Cu production in 2002 than in 2003, displayed by the 0.8, 1.2, and 2.0 m heights. In 2002, the 0.4 to 1.6 m clip heights produced equal K. In 2003, the 0.4, 1.6, and 2.0 m heights produced equal K while the 0.8 and 1.2 m heights produced incr eased, but constant, K.

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100 Significant (p< 0.05) differences were displayed in Fe content in total clipped plus final non-clipped sunn hemp, due to plant populati on and clip height. Plants grown at the 30 plants m-2 population produced the highest Fe. Th e highest Fe was produced by plants maintained at the 1.2 and 1.6 m clip heights. Year, plant population, and clip height caused significant differences in both Mn and Zn content in total clipped plus final non-clipped sunn hemp. Plants grown in 2002 produced more Mn and Zn than plants grow n in 2003. Plants grown at the 30 plants m-2 population produced the highest Mn and Zn. Sunn hemp maintained at the 0.8 and the 1.2 m clip heights produced the highest Mn and Zn. Summary Clipping sunn hemp repeatedly in 30 d in tervals at 0.6 m above designated heights caused prolific and branched re-growth of the plants. Repetitive clipping of the young plant material did not cause any detrimental e ffects to the plants and produced material that was extremely high in minerals. Sunn hemp grown at 18 and 30 plants m-2 and maintained at 0.4 and 0.8 m produced plant ma terial that contained an N:P:K ratio of 10:1:5 kg ha-1. This ratio is equivalent to one of N:P2O5:K2O at 4.3:1:2.6 kg ha-1, as reported for general consumer fertilizers. Maximum yi eld and mineral content was produced by sunn hemp that was grown at 18 or 30 plants m-2 and maintained at heights of 0.4 or 0.8 m. These low clipping height s would be suitable for maintaining by mechanical means, which would be more economical than manual maintenance. A potential practical applicati on for an organic farmer would be to grow part of a sunn hemp crop for use as a green manure in order to increase OM, added minerals, especially N, and nematode suppression for use with another crop. The portion of the sunn hemp not harvested could be maintained for clipping and production of mulch. The

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101 mulch could be utilized for weed control, so il moisture conservation, and the slow release of additional N and other minerals.

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102 Table 4-1. Analysis of vari ance for a split-split plot e xperimental design with main treatments in a randomized complete block design. Source of variation Description df Total (1) Total for overall experiment (5*2*3*4) = 120-1= 119 Total (2) Total for year (5*2) = 10-1= 9 Reps (R) 5-1= 4 Main (A) 2-1= 1 Error a Error main treatment (a) 4 Total (3) Total plant popul ations (5*2*3) = 30-1-9= 20 Sub (B) 3-1= 2 A*B A*B (2-1)*(3-1) = 2 Error b Error sub treatment (b) 16 Total (4) Total clip height: Total (1) – Total (2) – Total (3) = 90 Sub-sub (c) Clip height (4-1) = 3 A*C A*C (2-1)*(4-1) = 3 B*C B*C (3-1)*(4-1) = 6 A*B*C A*B*C (2-1)*(3-1)*(4-1) = 6 Error c Error sub-sub treatment (c) 72

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103Table 4-2. Statistics key for two years, three plant populations and f our clipping heights of sunn hemp. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 y*p*h y*p*h y*p*h Y*H y*p*h Y*p*h y*p*h Y*H P*H P*H P*H H 0.80 y*p*h y*p*h y*p*h Y*H y*p*h Y*p*h y*p*h Y*H P*H P*H P*H H 1.20 y*p*h y*p*h y*p*h Y*H y*p*h Y*p*h y*p*h Y*H P*H P*H P*H H 1.60 y*p*h y*p*h y*p*h Y*H y*p*h Y*p*h y*p*h Y*H P*H P*H P*H H X Y*P Y*P Y*P Y*P Y*P Y*P P P P X X Y Y Y (y) = Main treatment (year, 1 to 2). P (p) = Sub treatment (plant populati on, 6 plants m-2 to 30 plants m-2). H (h) = Sub-sub treatment (maintai ned clipping height, 0.40 to 1.60 m). Y*P = Main treatment sub treatment interaction (year plant population). Y*H = Main treatment sub-sub treatment interaction (year clipping height). P*H = Sub treatment sub-sub treatment intera ction (plant populati on clipping height). y*p*h = Main treatment sub treatment sub-sub treatment interac tion (year plant populat ion clipping height).

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104Table 4-3. Fresh matter for total clipped sunn hemp for two years, four clipping heights and three plant populations. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 13337 11660 7554 10850 13324 10527 8963 10938 13330 11093 8259 10894 0.80 10934 10690 6920 9515 15113 14697 9713 13175 13023 12694 8317 11344 1.20 8543 8983 5230 7586 11313 10480 6897 9563 9928 9732 6063 8574 1.60 4167 3850 2217 3411 2756 2207 1260 2075 3462 3028 1738 2743 X 9245 8796 5480 10627 9478 6708 9936 9137 6094 X X 7840 8938 Relevant means are highlighted in bold. Significant year clip height intera ction. For comparison among clipping hei ght means within a year, LSD = 724 at p< 0.05. For comparison between year means w ithin a clipping height LSD = 2449 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 884 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 892 at p< 0.05.

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105Table 4-4. Fresh matter for final non-clippe d sunn hemp for two years, four clippi ng heights and three plant populations. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 5027 6560 3313 4967 3713 2687 2313 2905 4370 4623 2813 3936 0.80 8933 9863 6374 8390 6540 5940 4627 5702 7737 7902 5500 7046 1.20 14323 13757 9620 12567 9900 9453 6233 8529 12112 11605 7927 10547 1.60 14860 16040 12160 14353 12100 12246 8770 11039 13480 14143 10465 12696 2.00 20050 18380 12100 16843 16187 12153 10927 13089 18118 15267 11513 14966 X 12639 12920 8713 9688 8496 6574 11163 10708 7644 X X 11424 8253 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means LSD = 1566 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 1809 at p< 0.05. For comparison among clipping height mean s within a plant popul ation, LSD = 1770 at p< 0.05.

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106Table 4-5. Fresh matter for total sunn hemp plant for two years, four clip ping heights and three plant populations. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 18363 18220 10867 15817 17037 13213 11276 13842 17700 15717 11072 14829 0.80 19867 20553 13293 17904 21653 20637 14340 18877 20760 20595 13817 18391 1.20 22867 22740 14850 20152 21213 19933 13130 18092 22040 21337 13990 19122 1.60 19027 19890 14377 17764 14857 14453 10030 13113 16942 17171 12203 15439 2.00 20050 18380 12100 16843 16187 12153 10927 13089 18118 15267 11513 14966 X 20025 19957 13097 18189 16078 11941 19112 18017 12518 X X 17696 15403 Relevant means are highlighted in bold. Significant year plant population interacti on. For comparison between year means w ithin a plant population, LSD = 1819 at p< 0.05. For comparison among population m eans within a year LSD = 1455 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 2127 at p< 0.05. For comparison among clipping height means within a year, LSD = 1647 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 2065 at p< 0.05. For comparison among clipping height mean s within a plant popul ation, LSD = 2016 at p< 0.05.

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107Table 4-6. Dry matter for total clipped sunn hemp for two years, four clipping height s and three plant populations. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 2123 1800 1227 1717 2287 1923 1710 1973 2205 1862 1468 1845 0.80 1827 1833 1200 1620 3017 2787 2070 2625 2422 2310 1635 2122 1.20 1577 1670 983 1410 2650 2413 1753 2272 2113 2042 1368 1841 1.60 917 833 483 744 753 613 367 578 835 723 425 661 X 1611 1534 937 2177 1934 1475 1894 1734 1224 X X 1372 1862 Relevant means are highlighted in bold. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 147 at p< 0.05. For comparison among clipping height means within a year, LSD = 159 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 186 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 194 at p< 0.05.

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108Table 4-7. Dry matter for final non-clippe d sunn hemp for two years, four cli pping heights and thre e plant populations. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 1347 1470 914 1243 1003 2130 3070 2068 1175 1800 1992 1656 0.80 3383 3090 2357 2943 3557 3217 733 2502 3470 3154 1545 2723 1.20 3877 4100 2897 3624 1783 3083 4253 3040 2830 3592 3575 3332 1.60 5103 4800 3640 4514 4433 660 1456 2183 4768 2730 2548 3349 2.00 5873 5123 4284 5093 2023 2730 3417 2723 3948 3927 3850 3908 X 3917 3717 2818 2560 2364 2586 3238 3040 2702 X X 3484 2503 Relevant means are highlighted in bold. Significant Year Plant population interacti on. For comparison between year means with in a plant population, LSD = 428 at p< 0.05. For comparison among population m eans within a year, LSD = 396 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 621 at p< 0.05. For comparison among clipping height means within a year, LSD = 602 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 707 at p< 0.05. For comparison among clipping height mean s within a plant population LSD = 737 at p< 0.05.

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109Table 4-8. Dry matter for total sunn hemp plant for two years, four clipping height s and three plant populations. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 3470 3270 2140 2960 3290 4053 4780 4041 3380 3662 3460 3501 0.80 5210 4923 3557 4563 6573 6003 2803 5127 5891 5463 3180 4845 1.20 5453 5770 3880 5035 4433 5496 6007 5312 4943 5633 4943 5173 1.60 6020 5633 4123 5259 5187 1273 1823 2761 5603 3453 2973 4010 2.00 5873 5123 4284 5093 2023 2730 3417 2723 3948 3927 3850 3908 X 5205 4944 3597 4301 3911 3766 4753 4428 3681 X X 4582 3993 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 413 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 321 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 452 at p< 0.05.

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110Table 4-9. Nitrogen content in total cli pped sunn hemp for two years, four cli pping heights and thre e plant populations. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 85 75 51 71 101 85 75 87 93 80 63 79 0.80 78 77 52 69 124 115 83 107 101 96 67 88 1.20 67 72 41 60 96 91 63 83 81 82 52 72 1.60 37 33 19 30 23 21 12 19 30 27 16 24 X 67 64 41 86 78 58 76 71 50 X X 57 74 Relevant means are highlighted in bold. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 6 at p< 0.05. For comparison among clipping height means within a year, LSD = 6 at p< 0.05. Significant plant population clip height interaction. For comparison among plant population means w ithin a clipping height LSD = 7 at p< 0.05. For comparison among clipping height mean s within a plant population LSD = 7 at p< 0.05.

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111Table 4-10. Phosphorus content in total c lipped sunn hemp for two year s, four clipping heights and three plant populations. 2002 2003 2 yr X Clip ————Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 9.9 9.2 6.3 8.5 9.5 7.9 6.9 8.1 9.7 8.6 6.6 8.3 0.80 8.8 8.8 6.0 7.9 11.8 10.9 8.3 10.3 10.3 9.8 7.1 9.1 1.20 7.3 7.5 5.1 6.6 9.8 9.3 6.6 8.6 8.5 8.4 5.8 7.6 1.60 3.3 3.9 2.0 3.1 2.6 2.2 1.3 2.0 3.0 3.0 1.7 2.6 X 7.3 7.3 4.9 8.4 7.6 5.8 7.9 7.5 5.3 X X 6.5 7.3 Relevant means are highlighted in bold. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 0.6 at p< 0.05. For comparison among clipping height means within a year, LSD = 0.6 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 0.08 at p< 0.05. For comparison among clipping height m eans within a plant population, LSD = 0.07 at p< 0.05.

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112Table 4-11. Potassium content in total cl ipped sunn hemp for two years, four cli pping heights and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ————Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2————————————————————————— 0.40 35.6 31.1 21.9 29.6 59.2 48.9 39.8 49.3 47.4 40.0 30.1 39.4 0.80 29.4 30.3 19.7 26.5 66.3 62.8 44.8 58.0 47.9 46.6 32.3 42.2 1.20 22.9 24.5 14.9 20.8 47.4 43.2 31.9 40.8 35.1 33.9 23.4 30.8 1.60 13.3 12.3 7.1 10.9 11.2 9.7 5.9 9.0 12.2 11.0 6.5 9.9 X 25.3 24.6 15.9 46.0 41.2 30.6 35.7 32.9 23.3 X X 21.9 39.3 Relevant means are highlighted in bold. Significant year plant population interac tion. For comparison between year means within a plant population LSD = 3.0 at p< 0.05. For comparison among population means within a year LSD = 3.1 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 3.5 at p< 0.05. For comparison among clipping height means within a year, LSD = 3.4 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 4.2 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 4.3 at p< 0.05.

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113Table 4-12. Calcium content in total cli pped sunn hemp for two year s, four clipping heights a nd three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 34.3 30.6 18.8 27.9 32.5 27.6 24.6 28.2 33.4 29.1 21.7 28.1 0.80 24.2 21.8 15.3 20.4 36.1 33.3 24.7 31.4 30.1 27.6 20.0 25.9 1.20 17.7 16.6 10.1 14.8 32.4 30.1 17.9 26.8 25.0 23.4 14.0 20.8 1.60 9.0 8.6 8.6 8.7 9.5 6.5 3.4 6.6 9.2 7.6 6.1 7.6 X 21.3 19.4 13.2 27.6 24.4 17.7 24.5 21.9 15.5 X X 18.0 23.2 Relevant means are highlighted in bold. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 2.5 at p< 0.05. For comparison among clipping height means within a year, LSD = 2.3 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 3.1 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 3.1 at p< 0.05.

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114Table 4-13. Magnesium content in total c lipped sunn hemp for two year s, four clipping heights and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 9.2 7.6 4.6 7.1 8.3 6.9 5.6 6.9 8.8 7.2 5.1 7.0 0.80 6.7 6.6 3.9 5.7 10.0 8.9 6.1 8.3 8.3 7.7 5.0 7.0 1.20 8.0 5.3 3.0 5.4 8.4 7.5 4.6 6.8 8.2 6.4 3.8 6.1 1.60 2.7 2.5 1.3 2.1 1.7 1.5 0.8 1.3 2.2 2.0 1.1 1.7 X 6.7 5.5 3.2 7.1 6.2 4.3 6.9 5.8 3.8 X X 5.1 5.9 Relevant means are highlighted in bold. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 1.1 at p< 0.05. For comparison among clipping height means within a year, LSD = 1.0 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 1.3 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 1.4 at p< 0.05.

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115Table 4-14. Sodium content in total cli pped sunn hemp for two years, four clip ping heights and thr ee plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 1.6 1.2 0.7 1.2 0.9 0.9 0.9 0.9 1.2 1.0 0.8 1.0 0.80 1.1 1.0 0.5 0.9 1.6 1.4 1.0 1.3 1.3 1.2 0.8 1.1 1.20 1.0 1.0 0.5 0.8 1.4 1.3 1.0 1.2 1.2 1.1 0.8 1.0 1.60 0.4 0.4 0.2 0.4 0.3 0.2 0.2 0.2 0.4 0.3 0.2 0.3 X 1.0 0.9 0.5 1.1 0.9 0.7 1.0 0.9 0.6 X X 0.8 0.9 Relevant means are highlighted in bold. Significant Plant population treatment effect. Fo r comparison between year means, LSD = 0.1 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 0.2 at p< 0.05. For comparison among clipping height means within a year, LSD = 0.2 at p< 0.05.

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116Table 4-15. Copper content in total clipped sunn hemp for tw o years, four clipping height s and three plan t populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 7.1 6.9 4.5 6.2 8.8 6.7 6.5 7.3 7.9 6.8 5.5 6.8 0.80 6.0 6.5 3.9 5.5 10.8 10.5 7.2 9.5 8.4 8.5 5.6 7.5 1.20 4.9 5.2 3.1 4.4 7.9 8.2 6.5 7.5 6.4 6.7 4.8 6.0 1.60 2.8 2.7 1.5 2.4 1.8 1.8 1.1 1.6 2.3 2.3 1.3 2.0 X 5.2 5.4 3.3 7.3 6.8 5.3 6.3 6.1 4.3 X X 4.6 6.5 Relevant means are highlighted in bold. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 0.7 at p< 0.05. For comparison among clipping height means within a year, LSD = 0.8 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 1.0 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 1.0 at p< 0.05.

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117Table 4-16. Iron content in total clipped sunn hemp for tw o years, four clipping height s and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 294 246 173 238 380 285 256 307 337 265 215 272 0.80 248 237 162 216 407 351 276 345 328 294 219 280 1.20 243 206 157 202 308 311 210 276 276 258 183 239 1.60 141 156 91 129 71 64 33 56 106 110 62 93 X 232 212 146 292 253 194 262 232 170 X X 196 246 Relevant means are highlighted in bold. Significant plant population treatmen t effect. For comparison between year means, LSD = 16 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 34 at p< 0.05. For comparison among clipping height means within a year, LSD = 34 at p< 0.05.

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118Table 4-17. Manganese content in total c lipped sunn hemp for two year s, four clipping heights and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 48.4 47.0 23.8 39.7 43.4 36.6 31.8 37.3 45.9 41.8 27.8 38.5 0.80 37.2 36.4 21.8 31.8 53.6 42.4 32.2 42.7 45.4 39.4 27.0 37.3 1.20 37.2 36.4 17.8 30.5 38.6 37.8 27.4 34.6 37.9 37.1 22.6 32.5 1.60 19.2 19.4 8.6 15.7 6.0 8.4 4.4 6.3 12.6 13.9 6.5 11.0 X 35.5 34.8 18.0 35.4 31.3 24.0 35.5 33.1 21.0 X X 29.4 30.2 Relevant means are highlighted in bold. Significant year plant population interac tion. For comparison between year means within a plant population, LSD = 4.0 at p< 0.05. For comparison among population means within a year, LSD = 3.7 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 5.0 at p< 0.05. For comparison between clipping height mean s within a clipping year, LSD = 4.9 at p< 0.05.

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119Table 4-18. Zinc content in total clip ped sunn hemp for two years, four cli pping heights and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 7.1 6.6 4.6 6.1 7.4 6.1 5.2 6.2 7.2 6.3 4.9 6.2 0.80 6.7 6.6 4.3 5.9 8.9 8.6 6.2 7.9 7.8 7.6 5.3 6.9 1.20 6.0 6.4 4.0 5.4 7.0 7.2 4.9 6.4 6.5 6.8 4.4 5.9 1.60 3.6 3.7 1.8 3.1 1.9 1.6 0.9 1.5 2.7 2.7 1.4 2.3 X 5.9 5.8 3.7 6.3 5.9 4.3 6.1 5.9 4.0 X X 5.1 5.5 Relevant means are highlighted in bold. Significant Year Clip height interac tion. For comparison between year means within a clipping height LSD = 0.06 at p< 0.05. For comparison among clipping height means within a year LSD = 0.05 at p< 0.05. Significant plant population clip height interaction. For comparison among plant population means w ithin a clipping height LSD = 0.6 at p< 0.05. For comparison among clipping height mean s within a plant population LSD = 0.6 at p< 0.05.

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120Table 4-19. Nitrogen content in total fina l non-clipped sunn hemp for two years, four clipping heights a nd three plant populat ions. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 20 21 13 18 14 11 9 12 17 16 11 15 0.80 48 42 35 42 22 18 18 19 35 30 26 31 1.20 56 61 43 53 35 31 25 30 45 46 34 42 1.60 62 66 56 61 46 50 34 43 54 58 45 52 2.00 91 71 70 78 71 28 57 62 81 65 64 70 X 56 52 43 38 34 29 47 43 36 X X 50 33 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 17 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 5 at p< 0.05. Significant clipping height treatme nt effect. For comparison between year means, LSD = 8 at p< 0.05.

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121Table 4-20. Phosphorus content in total final non-clipped sunn he mp for two years, four clippi ng heights and three plant popul ations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 4.3 4.7 3.0 4.0 3.1 2.3 2.0 2.5 3.7 3.5 2.5 3.3 0.80 11.1 10.1 8.6 9.9 5.9 4.8 4.6 5.1 8.5 7.4 6.6 7.5 1.20 12.9 12.9 10.1 12.0 8.2 8.5 5.7 7.5 10.6 10.7 7.9 9.7 1.60 11.1 13.5 11.3 12.0 10.1 9.8 7.8 9.2 10.6 11.7 9.6 10.6 2.00 16.5 14.7 13.6 14.9 13.4 11.2 10.0 11.5 15.0 12.9 11.8 13.2 X 11.2 11.2 9.3 8.2 7.3 6.0 9.7 9.2 7.7 X X 10.6 7.2 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 1.4 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 1.2 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 1.4 at p< 0.05.

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122Table 4-21. Potassium content in total fina l non-clipped sunn hemp for two years, f our clipping heights a nd three plant popula tions. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 14.6 15.5 10.0 13.4 18.1 13.1 11.2 14.1 16.4 14.3 10.6 13.8 0.80 28.9 25.5 20.4 24.9 27.3 26.5 21.4 25.1 28.1 26.0 20.9 25.0 1.20 32.3 34.4 21.9 29.5 35.5 40.0 28.3 34.6 33.9 37.2 25.1 32.1 1.60 37.8 43.5 30.4 37.3 44.4 50.2 37.0 43.9 41.1 46.9 33.7 40.6 2.00 56.3 47.9 36.0 46.7 71.1 58.0 46.7 58.6 63.7 52.9 41.3 52.7 X 34.0 33.4 23.7 39.2 37.6 28.9 36.6 35.5 26.3 X X 30.4 35.3 Relevant means are highlighted in bold. Significant Year Clip height interac tion. For comparison between year means within a clipping height, LSD = 7.5 at p< 0.05. For comparison among clipping height means within a year, LSD = 6.0 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 7.5 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 7.0 at p< 0.05.

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123Table 4-22. Calcium content in total fina l non-clipped sunn hemp for two years, four clipping heights and three plant populati ons. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 19.0 16.8 12.9 16.2 11.4 9.4 6.8 9.2 15.2 13.1 9.8 12.7 0.80 51.1 36.0 33.6 40.3 17.4 10.5 14.2 14.0 34.3 23.3 23.9 27.2 1.20 57.4 60.1 39.9 52.5 22.7 20.2 15.5 19.5 40.1 40.2 27.7 36.0 1.60 64.8 42.6 44.3 50.6 28.9 26.8 20.1 25.3 46.8 34.7 32.2 37.9 2.00 43.3 45.7 49.5 46.2 38.0 27.1 28.4 31.2 40.7 36.4 38.9 38.7 X 47.1 40.3 36.1 23.7 18.8 17.0 35.4 29.5 26.5 X X 41.1 19.8 Relevant means are highlighted in bold. Significant plant population treatmen t effect. For comparison between year means, LSD = 6.4 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 12.5 at p< 0.05. For comparison among clipping height means within a year, LSD = 10.1 at p< 0.05.

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124Table 4-23. Magnesium content in total fina l non-clipped sunn hemp for two years, f our clipping heights a nd three plant popula tions. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 5.4 5.5 3.5 4.8 2.7 2.1 1.9 2.3 4.0 3.8 2.7 3.5 0.80 13.0 12.2 9.4 11.5 4.7 3.9 4.0 4.2 8.9 8.0 6.7 7.9 1.20 15.5 14.6 9.7 13.3 7.0 6.9 4.7 6.2 11.3 10.8 7.2 9.8 1.60 16.1 14.7 11.2 14.0 8.8 8.3 6.5 7.9 12.4 11.5 8.8 10.9 2.00 16.5 14.9 12.9 14.8 11.0 8.8 7.9 9.2 13.8 11.8 10.4 12.0 X 13.3 12.4 9.4 6.8 6.0 5.0 10.1 9.2 7.2 X X 11.7 6.0 Relevant means are highlighted in bold. Significant year plant population interac tion. For comparison between year means within a plant population, LSD = 1.3 at p< 0.05. For comparison among population means within a year, LSD = 1.3 at p< 0.05. Significant year clip height intera ction. For comparison among clipping height means within a year, LSD = 2.1 at p< 0.05. For comparison between year means w ithin a clipping height, LSD = 2.1 at p< 0.05.

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125Table 4-24. Sodium content in total fina l non-clipped sunn hemp for two years, f our clipping heights and three plant populatio ns. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 0.6 0.6 0.4 0.6 0.5 0.3 0.3 0.4 0.6 0.5 0.4 0.5 0.80 2.1 1.7 1.3 1.7 0.7 0.5 0.8 0.7 1.4 1.1 1.0 1.2 1.20 3.0 2.1 1.7 2.3 1.1 1.2 0.9 1.1 2.1 1.7 1.3 1.7 1.60 2.1 1.6 1.3 1.7 1.5 1.1 1.3 1.3 1.8 1.4 1.3 1.5 2.00 3.0 2.4 2.2 2.5 1.6 1.7 1.2 1.5 2.3 2.0 1.7 2.0 X 2.2 1.7 1.4 1.1 1.0 0.9 1.6 1.3 1.1 X X 1.7 1.0 Relevant means are highlighted in bold. Significant plant population treatmen t effect. For comparison between year means, LSD = 0.5 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 0.6 at p< 0.05. For comparison among clipping height means within a year, LSD = 0.4 at p< 0.05.

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126Table 4-25. Copper content in total final non-clipped sunn hemp for two years, four clipping heights and three plant populatio ns. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 2.5 2.4 1.9 2.3 2.6 2.4 2.6 2.6 2.5 2.4 2.3 2.4 0.80 4.5 4.4 4.5 4.4 4.6 6.1 5.2 5.3 4.6 5.3 4.9 4.9 1.20 6.0 5.8 4.7 5.5 9.2 7.4 6.1 7.6 7.6 6.6 5.4 6.5 1.60 6.3 7.7 5.1 6.4 9.5 10.0 6.6 8.7 7.9 8.9 5.8 7.5 2.00 7.1 7.3 4.9 6.4 15.6 9.6 9.7 11.6 11.3 8.4 7.3 9.0 X 5.2 5.5 4.2 8.3 7.1 6.0 6.8 6.3 5.1 X X 5.0 7.2 Relevant means are highlighted in bold. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 1.9 at p< 0.05. For comparison among clipping height means within a year, LSD = 1.6 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 2.0 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 2.0 at p< 0.05.

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127Table 4-26. Iron content in total final nonclipped sunn hemp for two years, four clipping heights and three plant populations 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 481 793 376 550 550 289 239 359 516 541 307 455 0.80 1624 1551 1114 1430 834 658 460 651 1230 1105 787 1041 1.20 1151 1783 989 1308 1086 1143 877 1036 1119 1463 933 1172 1.60 2167 587 1555 1437 1183 1523 971 1225 1675 1055 1263 1331 2.00 568 1560 1345 1158 2079 1643 851 1524 1323 1601 1099 1341 X 1198 1255 1076 1147 1051 680 1172 1153 878 X X 1176 959 Relevant means are highlighted in bold. Significant plant population treatmen t effect. For comparison between year means, LSD = 261 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 458 at p< 0.05.

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128Table 4-27. Manganese content in total final non-clipped sunn he mp for two years, four clippi ng heights and three plant popula tions. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 18 32 14 21 17 11 12 13 18 22 13 17 0.80 51 47 36 45 26 26 21 24 39 37 29 35 1.20 67 65 37 56 40 42 33 38 53 54 35 47 1.60 62 50 52 55 46 47 29 41 54 49 41 48 2.00 52 68 59 60 70 46 44 53 61 57 52 57 X 50 53 40 40 35 28 45 44 34 X X 47 34 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 6 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 9 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 11 at p< 0.05.

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129Table 4-28. Zinc content in total final non-clipped sunn hemp for two years, four clipping heights and three plant populations 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 30 38 20 29 23 16 18 19 26 27 19 24 0.80 78 73 62 71 35 29 35 33 57 51 48 52 1.20 84 95 65 81 48 54 44 49 66 75 54 65 1.60 97 91 78 89 69 71 56 65 83 81 67 77 2.00 104 103 91 99 102 86 64 84 103 94 78 92 X 78 80 63 56 51 43 67 66 53 X X 74 50 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 10 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 9 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 12 at p< 0.05.

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130Table 4-29. Nitrogen content in total cli pped plus final non-clipped sunn hemp for tw o years, four clippi ng heights and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 106 96 64 89 115 97 84 99 110 96 74 94 0.80 126 120 86 111 146 133 101 127 136 126 94 119 1.20 123 133 84 113 130 122 88 114 127 128 86 113 1.60 99 99 75 91 69 70 46 62 84 84 61 76 2.00 91 71 70 78 71 58 57 62 81 65 64 70 X 109 104 76 107 96 75 108 100 76 X X 96 92 Relevant means are highlighted in bold. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 14 at p< 0.05. For comparison among clipping height means within a year, LSD = 13 at p< 0.05. Significant plant population clip height interaction. For comparis on among plant population means within a clipping height, LSD = 16 at p< 0.05. For comparison among clipping height mean s within a plant population, LSD = 17 at p< 0.05.

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131Table 4-30. Phosphorus content in total clipped plus final non-clipped sunn hemp for two years, four clipping heights and thre e plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 14.2 13.9 9.4 12.5 12.6 10.2 8.9 10.6 13.4 12.0 9.1 11.5 0.80 20.0 18.8 14.6 17.8 17.6 15.7 12.8 15.4 18.8 17.3 13.7 16.6 1.20 20.2 20.4 15.2 18.6 18.0 17.8 12.3 16.0 19.1 19.1 13.8 17.3 1.60 17.4 17.4 13.4 16.1 12.7 12.0 9.1 11.3 15.1 14.7 11.2 13.7 2.00 16.5 14.7 13.6 14.9 13.4 11.1 10.0 11.5 15.0 12.9 11.8 13.2 X 17.7 17.0 13.2 14.9 13.4 10.6 16.3 15.2 11.9 X X 20.0 13.0 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 1.7 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 1.0 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 1.5 at p< 0.05.

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132Table 4-31. Potassium content in total cli pped plus final non-clipped sunn hemp for tw o years, four clipping heights and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 50 47 32 43 77 82 51 70 64 64 41 57 0.80 58 56 40 51 94 89 66 83 76 73 53 67 1.20 55 59 37 50 83 83 60 75 69 71 49 63 1.60 51 56 38 48 56 60 43 53 53 58 40 50 2.00 56 48 36 47 71 58 47 59 64 53 41 53 X 54 53 37 76 75 53 65 64 45 X X 48 68 Relevant means are highlighted in bold. Significant plant population treatmen t effect. For comparison between year means, LSD = 7 at p< 0.05. Significant year clip height interac tion. For comparison between year means within a clipping height, LSD = 10 at p< 0.05. For comparison among clipping height means within a year, LSD = 13 at p< 0.05.

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133Table 4-32. Calcium content in total clippe d plus final non-clipped sunn hemp for two years, four clipping heights and three p lant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 30 18 6 30 18 6 —m— —————————————————————kg ha-2———————————————————————— 0.40 53 47 32 44 44 37 31 38 49 42 32 41 0.80 75 58 49 61 54 44 39 45 65 51 44 53 1.20 75 77 50 67 55 50 33 46 65 64 42 57 1.60 74 51 53 59 38 33 24 32 56 42 38 46 2.00 43 46 50 46 38 27 28 31 41 36 39 39 X 64 56 47 46 38 31 55 47 39 X X 56 38 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 11 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 7 at p< 0.05. Significant clipping height treatme nt effect. For comparison between year means, LSD = 7 at p< 0.05.

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134Table 4-33. Magnesium content in total cli pped plus final non-clipped sunn hemp for tw o years, four clipping heights and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 30 18 6 30 18 6 —m— —————————————————————kg ha-2———————————————————————— 0.40 14.6 13.1 8.1 11.9 11.0 9.0 7.5 9.2 12.8 11.0 7.8 10.6 0.80 19.7 18.7 13.3 17.2 14.7 12.7 10.1 12.5 17.2 15.7 11.7 14.9 1.20 23.6 19.9 12.7 18.7 15.4 14.4 9.3 13.0 19.5 17.1 11.0 15.9 1.60 18.7 17.1 12.5 16.1 10.5 9.7 7.4 9.2 14.6 13.4 9.9 12.7 2.00 44.7 14.9 33.5 31.0 11.0 8.8 7.9 9.2 27.9 11.8 20.7 20.1 X 24.3 16.7 16.0 12.5 10.9 8.4 18.4 13.8 12.2 X X 19.0 10.6 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 8.0 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 4.9 at p< 0.05.

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135Table 4-34. Sodium content in total clippe d plus final non-clipped sunn hemp for two years, four clipping heights and three pl ant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————kg ha-2———————————————————————— 0.40 2.2 1.8 1.1 1.7 1.4 1.2 1.2 1.2 1.8 1.5 1.2 1.5 0.80 3.3 2.8 1.8 2.6 2.3 1.9 1.8 2.0 2.8 2.3 1.8 2.3 1.20 4.0 3.1 2.2 3.1 2.6 2.5 1.9 2.3 3.3 2.8 2.0 2.7 1.60 2.6 2.0 1.6 2.1 1.8 1.4 1.4 1.5 2.2 1.7 1.5 1.8 2.00 3.0 2.4 2.2 2.5 1.6 1.7 1.2 1.5 2.3 2.0 1.7 2.0 X 3.0 2.4 1.8 1.9 1.7 1.5 2.5 2.1 1.6 X X 2.4 1.7 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 0.6 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 0.6 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 0.3 at p< 0.05.

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136Table 4-35. Copper content in to tal clipped plus final non-clipped sunn hemp fo r two years, four cli pping heights and three pl ant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ————Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 9.6 9.3 6.4 8.4 11.3 9.1 9.0 9.8 10.4 9.2 7.7 9.1 0.80 10.4 10.9 8.4 9.9 15.5 16.6 12.4 14.8 13.0 13.8 10.4 12.4 1.20 10.9 11.0 7.7 9.9 17.1 15.6 12.6 15.1 14.0 13.3 10.2 12.5 1.60 9.1 10.4 6.6 8.7 11.4 11.8 7.6 10.3 10.2 11.1 7.1 9.5 2.00 7.1 7.3 4.9 6.4 15.6 9.6 9.7 11.6 11.3 8.4 7.3 9.0 X 9.4 9.8 6.8 14.2 12.5 10.3 11.8 11.1 8.5 X X 8.6 12.3 Relevant means are highlighted in bold. Significant plant population treatmen t effect. For comparison among pl ant population means, LSD = 1.1 at p< 0.05. Significant Year Clip height interac tion. For comparison between year means within a clipping height, LSD = 2.2 at p< 0.05. For comparison among clipping height means within a year, LSD = 1.9 at p< 0.05.

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137Table 4-36. Iron content in total clipped plus final non-clipped sunn hemp for two y ears, four clipping heights and three plan t populations. 2002 2003 2 yr X Clip ———Plants m-2——— ———Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 775 1038 549 787 931 573 495 666 853 806 522 727 0.80 1873 1789 1276 1646 1242 1009 736 996 1557 1399 1006 1321 1.20 1395 1989 1146 1510 1395 1454 1087 1312 1395 1721 1116 1411 1.60 2308 743 1646 1566 1254 1587 1005 1282 1781 1165 1325 1424 2.00 567 1560 1345 1158 2079 1643 852 1524 1323 1602 1099 1341 X 1384 1424 1192 1380 1253 835 1382 1339 1015 X X 1333 1156 Relevant means are highlighted in bold. Significant plant population treatmen t effect. For comparison between year means, LSD = 267 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 459 at p< 0.05.

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138Table 4-37. Manganese content in total cli pped plus final non-clipped sunn hemp for tw o years, four clipping heights and three plant populations. 2002 2003 2 yr X Clip ———Plants m-2——— ———Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 67 79 37 61 60 48 43 50 63 64 40 56 0.80 88 84 58 77 80 69 53 67 84 76 55 72 1.20 104 102 55 87 79 81 60 73 91 91 57 80 1.60 81 70 60 70 52 55 34 47 66 63 47 59 2.00 52 68 59 60 70 46 44 53 61 57 52 57 X 78 81 54 68 60 47 73 70 50 X X 71 58 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 7 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 10 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 11 at p< 0.05.

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139Table 4-38. Zinc content in total clipped plus final non-clipped sunn hemp for two y ears, four clipping heights and three plan t populations. 2002 2003 2 yr X Clip ———Plants m-2——— ———Plants m-2——— ———Plants m-2——— height 30 18 6 X 30 18 6 X 30 18 6 X —m— —————————————————————g ha-2———————————————————————— 0.40 10.0 10.4 6.6 9.0 9.7 7.7 7.0 8.1 9.9 9.0 6.8 8.6 0.80 14.6 13.9 10.5 13.0 12.4 11.5 9.7 11.2 13.5 12.7 10.1 12.1 1.20 14.4 15.9 10.5 13.6 11.8 12.6 9.3 11.2 13.1 14.3 9.9 12.4 1.60 13.2 12.9 9.7 11.9 8.8 8.8 6.5 8.0 11.0 10.8 8.1 10.0 2.00 10.4 10.3 9.1 9.9 10.2 8.6 6.5 8.4 10.3 9.5 7.8 9.2 X 12.5 12.7 9.3 10.6 9.8 7.8 11.6 11.3 8.5 X X 11.5 9.4 Relevant means are highlighted in bold. Significant year treatment effect. For co mparison between year means, LSD = 1.1 at p< 0.05. Significant plant population treatmen t effect. For comparison between year means, LSD = 0.9 at p< 0.05. Significant clipping height treatme nt effect. For comparison betw een year means, LSD = 1.3 at p< 0.05

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140 CHAPTER 5 NO-TILL AUSTRIAN WINTER PEA AS A COVER CROP AFFECTED BY CROPPING HISTORY Introduction Austrian winter pea (Pisum arvense L.), often called “field pea”, is a popular crop native to Europe, northern Afri ca, and western Asia. This low-growing viny legume is often used for hay, green manure, cover cr opping, and grazing mana gement. Austrian winter pea also may reduce the severity of soil borne diseases (Mahler and Auld, 1989). The legume has been found to be a high N2-fixer that can contribute to short-term soil conditioning (USDA-CSREES, 1998). When used as a cover crop, Austrian wint er pea can enrich the soil with organic matter, cycle nutrients, and protect soil from water and wind erosion. It can also suppress weed growth and reduce seed production by co mpeting directly for light and nutrients (Peachy et al., 1999). The succulent stems br eak down easily and are a quick source of available N (USDA-CSREES, 1998). Legumes reduce the overall C:N ratio of spring residues, decreasing the time it takes non-legum e residues to decompos e (Sattell et al., 1999). Legumes have been found too generally decay at a much faster rate than nonlegumes (Hargrove et al., 1991). Austrian winter pea often yields bountif ul biomass, having been found to produce more than 5,600 kg of dry matter ha-1. In a comparison of water use with Indian head lentils (Ascochyta lentis L.) and black medic (Medicago lupulina L.), Austrian winter pea was the most moisture-efficient crop in producing biomass (USDA-CSREES, 1998).

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141 Austrian winter pea has been found to be one of the top N producers among legumes, yielding up to 336 kg N ha-1 (Florida Agricultural St atistics Service, 2005). Winter pea harvested as hay and then app lied as mulch mineralized N at more than double the rate of alfalfa (Medicago sativa L.) hay (USDA-CSREES, 1998). Winter pea used as green manure provided the highest spring wheat (Triticum aestivum L.) yield the following year in a Montana trial comparing 10 types of medics, 8 clovers, and 3 grains (USDA-CSREES, 1998). No-till farming has consistently proven to be effective in c onserving soil moisture, reducing soil erosion, and improving water qua lity, in addition to benefiting wildlife, increasing labor use efficiency, limiting machinery investments, and sequestering atmospheric carbon dioxide (Beck et al., 1998; Gallaher, 1977; Gallaher and Hawf, 1997). No-till is the most effective conserva tion practice for reducing soil erosion and improving water quality. The crop residue cove r and infiltration rates associated with continuous no-till reduce agricu ltural runoff of contaminants more than other tillage systems (Doup, 2001; Gallaher and Laurent, 1983) No-till also increases the organic matter in the soil as well as improving many other soil properties (Gallaher and Ferrer, 1987). Decay rates of cover crops have been found to be more rapid under conventional tillage systems than no-tillage systems (Hargrove et al., 1991; Marshall, 2002). Utilizing these ideas, a 2-yr study was c onducted evaluating the effect of cropping history on Austrian winter pea yield. This study was also a component of a larger study (see Chapter 6) conducted to examine the e ffects of cropping hist ories on no-till sweet corn (Zea mays L.). Our main objective for this particular portion of the study was to compare 3 cropping histories for their effect on yield of Austrian winter pea that was to

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142 be utilized as a cover crop for a successive sweet corn crop. An additional objective was to compare mineral nutrient content of the crop across the 3 cropping histories. Our null hypothesis stated that the vari ous cropping histories would no t affect yield or mineral composition of the Austrian winter pea. Materials and Methods For this study, 2 completely randomized experiments were conducted, each from December to March of 2002-03 and 2003-04 at the University of FL, Gainesville, Florida. Treatments consisted of 3 differe nt previous crops [1, sweet corn; 2, cowpea (Vigna unguiculata L.); 3, sunn hemp (Crotalaria juncea L.)], each containing 5 replications. Austrian winter pea was plante d into 25 cm wide rows throughout the entire field with a no-till Tye drill for both experime nts. The experiments were established on a loamy siliceous semiactive hyperthermic Gr ossarenic Paleodults (USDA-NRCS, 2003) and, after inoculation with appropriate rhizobi a, the peas were no-till drilled into the residue of the 3 fall-planted crops: sweet co rn, cowpea, and sunn hemp. These previous crops were planted in the same plots both year s and sampled for Austri an winter pea data from the same replicates the second year as the first. Therefore, this necessitated that previous crops (or histories) be statistically analyzed as main effects in a completely randomized design and year treated as sub treatments. In February of both 2003 and 2004, 360 kg ha-1 of muriate of potash (KCl) and 200 kg ha-1 of sul-po-mag (K2SO4:MgSO4) were broadcast over the field. No N fertilizers were applied. Overhead sprinkler irrigation was applied when rainfall did not supply enough water for the peas. Only the above ground portion of the crop was examined for yield, mineral concentration, and mineral content.

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143 Yield On 24 March 2003 and 29 March 2004, 0.5-m2 samples were harvested from each plot by cutting plants at the soil surface. The plants were placed in 53 cm x 89 cm Midco Mesh Harvest bags (Midco Enterpri ses, Inc., Kirkwood, MO) and dried in a forced air oven at 70 C until completely dry and then weighed for dry matter yield determination and used for mineral analysis. These samples were chopped in a hammer mill, mixed well, and then representative gr ab samples were ground in a Wiley mill to pass through a 2-mm stainless steel screen. Th ese samples were stored in plastic sample bags and re-dried at 70 C for 4 h to ensure equal dry matter among all samples for mineral analysis. Weather data was collected for the 2 yr of this study at Gainesville, FL from the Florida Automated Weather Network (2005). M onthly averages for rainfall, temperature, and solar radiation was reco rded and graphed using Mi crosoft Excel spreadsheet. Nitrogen Analysis A mixture of 0.100 g of each winter pea plant sa mple, 3.2 g of salt-catalyst (9:1 K2SO4:CuSO4), 3 Pyrex beads, and 10 mL of H2SO4 were vortexed in a 100-mL Pyrex test-tube under a hood. To reduce frothing, 2 mL 30% H2O2 was added in 1 mL increments and tubes were digested in an aluminum block digester at 370 C for 3.5 h (Gallaher et al., 1975). Tubes were capped with small Pyrex funnels that allowed for evolving gases to escape while preserving refluxing action. C ool digested solutions were vortexed with approximately 30 mL of de-i onized water, allowed to cool to room temperature, brought to 75 mL volume, transf erred to square Nalgene storage bottles, sealed, mixed, and stored.

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144 Nitrogen trapped in the form of (NH)2SO4 was analyzed on an automatic Technicon Sampler IV (solution sampler) and an Alpkem Corpor ation Proportioning Pump III (Technicon Instruments Corporation, Tarrytown, NY). A plant standard with known N concentration was subjected to th e same procedure and used as a check. Mineral Analysis For other mineral analyses, 1.0 g from each sample of Austrian winter pea was weighed into 50 mL Pyrex beakers and ashed in a muffle furnace at 480C for 6 h. The samples were then cooled to room temperat ure and moistened with de-ionized water. Under a hood, 20 mL concentrated HCl were added to the beakers which were then placed on a hot plate and slowly boiled to dryness, then removed. Another 20 mL de-ionized water and 2 mL concentrated HCl were added and small Pyrex watch glasses were used to cover the beakers for reflux. Th ey were brought to a vigorous boil and removed from the hot plate to cool to room temperature. The samples were then brought to volume in 100 mL flasks, mixed, and allowed to set for 24 h to let Si settle out. Twenty mL of solution wa s decanted into 20 mL scintillation vials for analysis. Phosphorus was analyzed by colorimetery; K and Na by flame emission, and Ca, Mg, Cu, Fe, Mn, and Zn by atomic adsorption spectrometry (AA). Mineral content (yield of minerals) was determined once mineral concentrations were found for Austrian winter pea. Th is was determined by multiplying mineral concentrations in the Austrian winter pea on a unit basis by dry matter yield of Austrian winter pea. For example, if Austrian winter pea was 40 g N kg-1 concentration for a dry matter yield of 250 g m-2, then the content would be 10 g N m-2 [((40 g N kg-1/1000) 250 g DM m-2) = 10 g N m-2]. In this example the 10 g N m-2 is equivalent to 100 kg N ha-1 that would be produced in the above gr ound dry matter of Austrian winter pea.

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145 Soil Analysis Soil samples were obtained from the top 15 cm soil depth from each cropping history during both years of the study on the same dates that yield samples were collected. Samples were air-dried and siev ed through a 2-mm stainl ess steel screen to remove any rocks or debris and then were stored for further analysis. The samples were then analyzed for N, mineral concentrations, pH, buffer pH (BpH), organic matter (OM), a nd cation exchange capacity (CEC). Soil N analysis was identical to plant sample analysis except th at 2.00 g of soil was weighed instead of 1.00 g of plant material without gl ass beads. The samples were subjected to the same procedures for N analysis as for plant tissu e. A soil sample of known N concentration was also analyzed and served as a check. A Mehlich I (Mehlich, 1953) extraction method was used for the remaining soil mineral analyses. Five g of each soil sample were weighed and extracted with 20 mL of a combination of 0.025 N H2SO4 and 0.05 N HCl. Using an Eberach shaker at a rate of 240 oscillations min –1, mixtures were shaken for 5 min. The mixtures were then filtered using Schleischer and Schuell 620 (1 1 cm) filter paper and poured into scintillation vials. The remaining solutions were then subjected to analysis of P, K, Ca, Mg, Na, Cu, Fe, Mn, and Zn in the same manner desc ribed for plant tissue analyses. Soil pH was measured with a 1:2 soil to wa ter volume ratio using a glass electrode pH meter (Peech, 1965). Buffer pH (BpH) was measured using Adams/Evans buffered solution (Adams and Evans, 1962). Cation exchange capacity (C EC) was estimated by the summation of relevant cations (Hesse, 1972; Jackson, 1958). Estimated soil CEC was calculated by summing the milliequivalents of the determined bases of Ca, Mg, K and Na

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146 (where applicable) and adding them to exchangeable H+ expressed in milliequivalents per 100 grams [centimole per kilogram (c mol kg-1)] (Hesse, 1972). For the determination of OM, a modified version of the Walkley Black (Walkley, 1935) method was used, in which 1.0 g of soil was weighed into a 500-mL Erlenmeyer flask, and 10 mL of 1 N K2Cr2O7 solution was then pipetted into the flask. Twenty mL of concentrated H2SO4 was added and mixed by gentle rotation for 1 min, using care to avoid throwing soil up onto the sides of the flask. The flask was then left to stand for 30 min, and then diluted to 200 mL with de-ioni zed water. Five drops of indicator were added, and the solution was titrated with 0.5 N ferrous sulfate solution until the color sharply changed from a dull gr een to a reddish brown. A fl ask without soil was prepared in the same manner and titrated to determ ine the blank titrant, along with a flask containing a check soil with a known amount of OM. Percent OM was determined using the equation: percent OM = (1-T/S) x 6.8, wher e S is blank-titration in mL of ferrous ammonium sulfate solution and T is sample titration in mL of ferrous ammonium sulfate solution (Walkley, 1935; Allison, 1965). Statistical Analysis Data was recorded in Quattro Pro (Anony mous, 1987) spreadsheets and transferred to MSTAT 4.0 (Anonymous, 1985) for analysis of variance with the appropriate model for the experimental design (Gomez and Go mez, 1984). Mean separation was by fixed LSD at the 0.05 level of probability (Gomez and Gomez, 1984). Several correlations were determined between dry matter yield and mineral concentrations of Austrian winter pea and dry matter and soil properties. Also correlations were determined between dry matter yield and plant mineral content a nd between plant mineral content and soil

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147 properties. Statistical analyses for these correlations were determined by use of SAS (2000). Results Yield and Plant Mineral Concentration Statistically significant (p< 0.05) differences were found between years for dry yield of Austrian winter pea, but not among the cropping histor ies (Tables 5-1 and 5-2). Among the macronutrients, N and Na were the only minerals with concentrations not affected by year (Tables 5-3 and 5-4). The remaining macronutrients, P, K, Ca, and Mg all recorded significant differences (p< 0.05) in concentrations be tween years (Tables 5-3 and 5-4). Nitrogen, P, and K were the only m acronutrients with concentrations affected (p< 0.05) by cropping history (Table s 5-3 and 5-4). The pea that was grown following sweet corn displayed a definite N advantage over pea following sunn hemp. The pea grown after cowpea showed highe r concentrations of P than when following sweet corn or sunn hemp. The remaining macronutrients Ca, Mg, and Na were not different in concentrations among cropping histories (Tables 5-3 and 5-4). Of the micronutrients, Cu and Fe, and Mn were significantly different (p< 0.05) between years but were not different (p>0.05) among cropping histories (Table s 5-3 and 5-4). A significant (p< 0.05) interaction occurred between cropping history and years for Zn concentration (Tables 5-3 and 5-4). Zinc concentration was not diffe rent between years following sweet corn but was higher (p< 0.05) following cowpea and sunn hemp in 2004 (Tables 5-3 and 5-4). Plant Mineral Content The content of all minerals, except Na, in Austrian winter pea were all higher (p< 0.05) in 2004 than 2003 (Table 5-5 and 5-6). Mineral content of all minerals was not affected (p>0.05) by previous crop treatme nt (Table 5-5 and 5-6).

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148 Soil Properties Of the macronutrients in soil, N, P, and K, were not affected by year (Tables 5-7 and 5-8). Concentrations of N a nd P in soil all sh owed significant (p< 0.05) differences due to cropping history (Tables 5-7 and 5-8) with soil from the cowpea rotation having higher levels. Interactions between previous crop and year occurred (p< 0.05) for Ca and Mg (Tables 5-7 and 5-8). Calcium wa s highest following cowpea in 2004 but no differences were found among previous crops in 2003. Magnesium was highest following cowpea both years but Mg from cowp ea history was not different from the sunn hemp history in 2004. Potassium, Na, and Cu were the only mine rals that were not affected by cropping history (Tables 5-7 and 5-8). C oncentrations of Na, Cu, and Mn in soil were all affected by year with 2004 having the highest levels (T able 5-7 and 5-8). Zinc was the only soil micronutrient not affected by year (T able 5-7 and 5-8). A significant (p< 0.05) interaction occurred between cropping history and year fo r Fe, with no differences due to cropping history in 2003 but highest levels were found following sunn hemp in 2004 (Tables 5-7 and 5-8). Concentrations of Mn, and Zn we re affected by cropping history (Table 5-7 and 5-8) with highest values following cowpea history. For pH, BpH, and OM all displayed no significant (p>0.05) differences due to year ex cept for pH, which was higher in 2003. All three of these soil properties were lowest following the corn history (Table 5-7 and 5-8). An interaction occurr ed between year and cropping history (p< 0.05) for CEC, being highest in 2004 following co wpea history (Table 5-7 and 5-8).

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149 Discussion and Conclusion Yield and Plant Mineral Concentration Florida winter-grown Austrian winter p ea would make a good candidate for use as a cover crop, based on this study. The hypothesi s, that previous fall crop would impact yield of Austrian winter pea can not be supported based on these results. However, large differences were found between years with 47% greater yield in 2004 compared to 2003. The most likely explanation for Austrian winter pea yield being greater in 2004 compared to 2003 (Table 5-2) is differences in climate variables between the 2 winter growing seasons (Figure 5-1, 5-2 and 5-3). For example the average January temperature in 2004 was about 3C higher than in 2003 (Fi gure 5-1). Even though rainfall was lower during the months of November 2003 and D ecember of 2004 compared to the same months of 2002 and 2003 (Figure 5-2) wa ter requirements were supplemented by irrigation. Therefore, rainfall distribution shou ld not have impacted growth for either of the 2 yr. The lower rainfall during most of th e Austrian winter pea growing period in the 2004 season is likely the reason for higher so lar radiation recorded during 2004 compared to 2003 (Figure 5-3). The combination of highe r temperatures and solar radiation likely contributed to greater rate s of photosynthesis in 2004 co mpared to 2003. Although other factors could have contributed to year differences in yield, these environmental factors are likely the most important. The hypothesis that cropping hi story would not affect mine ral concentration of the legume cannot be supported for N, P and Zn (Table 5-4). The peas grown following sweet corn resulted in N levels up to 44.0 g N kg-1, or 4.4 % N. When compared with other sources of organic N, these results s uggest that Austrian wi nter pea would be a good choice for N production. Lupine (Lupinus angustifolius L.) has been found to

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150 produce 22 g N kg-1, sunn hemp (whole plant) 23 g N kg-1, crimson clover (Trifolium incarnatum L.) 30 g N kg-1, vetch (Vicia villosa L. Roth.) 33 g N kg-1, and sunn hemp (clipped) 42 g N kg-1 (Gallaher, unpublished data). Regardless of cropping history, Austrian winter pea could be left on th e ground as a source of N and comprise a substantial portion of N and other minerals for any subsequent crop as well as provide numerous benefits as a mulch (Gallaher, 1977; 1983). An additional benefit to leaving Austrian winter pea on the ground as a cove r crop mulch would be the prevention of leaching of such important minerals as N, P, and Mg from the plant matter due to slow mineralization (Hargrove et al., 1991). Nitrogen concentration in Austrian winter pea was highest following sweet corn. This might be due to the fact that the N recommendation for the crops grown previous to the pea was highest for sweet co rn. It is likely that sign ificant N was tied up in sweet corn residue and released more slowly compared to the cowpea residue. Decay of legumes is a rapid process with a quick rel ease of N in the residue (Marshall, 2002) as opposed to sweet corn residue which would ha ve a higher C:N ratio and thus a slower crop residue decay rate and availability of N in the residue for the succeeding crop. For Austrian winter pea following sunn hemp, all the sunn hemp above ground crop was completely removed from the plots each year Therefore, limited N would be available from the sunn hemp for recycling to the Austri an winter pea crop. As for P concentration in the Austrian winter pea being greater following cowpea histor y, soil test P was over 180% greater in this history compared to corn and sunn hemp histories. However, no significant correlation was found between soil te st P and concentra tion in plant tissue when correlated over all histories (Table 5-9) Correlations were not made on individual

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151 histories, but the principles of plant nutriti on would suggest that the high soil test P in the cowpea history is the reason for highest conc entration of P in the plant tissue. Plant Mineral Content It is expected that mineral content (Table 5-6) should mirror yiel d (Table 5-2). In other words, the more dry matter produced, th e more mineral content produced. This was indeed the case in this study as shown by th e high correlation values between dry matter and all of the minerals (Table 5-10). The r values for all minerals ranged from a low of 0.61 for Na and a high of 0.96 for K. All correlations were highly significant (p< 0.001) between yield of dry matter a nd content of minerals. Most micronutrients in soil were significantly correlated (p< 0.10) with micronutrient contents in the plant. This was especially true for Cu, Fe, and Mn. The pl ant biomass was not washed to remove any possible contamination that could have occurr ed from soil contamination due to wind or water splashing. In other words, if this ha ppened then the more plant biomass the more the possibility of contamination a nd thus a positive correlation. Soil Properties The pH of the soil was in a good range fo r nutrient availability, and the OM and CEC (Table 5-8) reflected the high nutrient le vels for the sandy soils in this study (Brady and Buckman, 1969). The interaction found be tween year and croppi ng history in the CEC was a result of a similar interaction in Ca levels. The soil CEC is primarily governed by 3 different factors, Ca ion activ ity being the primary factor (Tisdale and Nelson, 1975). Since no Ca was applied to any of the test area dur ing the 2 yr study, the large differences may be attributed to natu ral variances between actual sites. It was concluded that the soil from history 2 (p revious cowpea crop) was the most fertile, followed by history 3 (previous sunn hemp crop) and then history 1 (previous sweet corn

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152 crop). Generally, the plant nutrient concentratio ns (Table 5-4) and contents (Table 5-6) followed this trend. This can be partially explained by the type re sidue and its relative C:N ratio of the previous crops. Residue fr om all previous crops was left on the soil surface during the growth period of the no-till Aust rian winter pea. Sweet corn residue in history 1 would have had a higher C:N ratio th an the cowpea residue in history 2. Even though sunn hemp, a legume, was grown prior to Austrian winter pea in history 3 all the top growth of this crop was removed from the plots prior to planting the Austrian winter pea. Therefore, minerals would recycle quickly following cowpea, much slower following sweet corn and very little minerals were available from residue to recycle in history 3. In fact, significant minerals would have been removed from the plots in history 3 (Marshall, 2002). Austrian winter pea proved to be a good candidate for use as a cover crop in all systems in this study. It worked well as a legume for no-till management of a succeeding sweet corn crop (data not shown). Data show an N concentration of 37 to 42.5 g kg-1 (Table 5-4) that would likely make Austrian winter pea a good source of protein for farm animals. Data also show that it had N cont ent, much of which would have been from N fixation, in the range of 7.27 to 10.46 kg m-2, depending upon year and crop history (Table 5-6), as well as signifi cant quantities of other minerals Used as a cover crop for a following no-till crop, such as sweet corn, it would be a good source of slow release minerals as well as good for soil conservation.

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153 Table 5-1. Above ground plant dr y matter of Austrian winter pea analysis of variance. Source of variation df Dry matter yield Previous crop (PC) 2 ns† Error A 12 — Year (Y) 1 ** PC x Y 2 ns Error B 12 — Total 29 — **Significant at the 0.01 level. †ns = not significant. Table 5-2. Yield of Austrian wi nter pea at early bloom stage. Previous crop 2003 2004 Average ——————————Dry matter, g m-2————————— Sweet corn 181 276 229 a† Cowpea/Lima bean 176 296 236 a Sunn hemp 192 236 214 a Average 183 269** **Significant at the 0.01 level. †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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154Table 5-3. Mineral concentration in Austrian winter pea above ground plant dry matt er at early bloom stag e of growth analysis of variance. _______________________________________________________________________________________________________________________________ __ Source of variation df Ca Mg K N P Na Cu Fe Mn Zn Previous crop (PC) 2 ns† ns ns ** ns ns ns + + Error A 12 — — — — — — — — — — Year (Y) 1 *** *** *** ns ** ns ** *** *** ** PC x Y 2 ns + ns ns ns ns ns ns ns ** Error B 12 — — — — — — — — — — Total 29 — — — — — — — — — — + Significant at the 0.01 level. Significant at the 0.05 level. ** Significant at the 0.0 level. *** Significant at the 0.001 level. †ns = not significant.

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155 Table 5-4. Mineral concentr ation for Austrian winter pea at early bloom stage. Previous crop 2003 2004 X ———————Mineral concentration, g kg-1——————— N Sweet corn 44.0 40.9 42.5 a‡ Cowpea/Lima bean 39.1 37.2 38.2 ab Sunn hemp 36.2 37.7 37.0 b X 39.8 38.6 ns† P Sweet corn 4.17 3.81 3.99 b Cowpea/Lima bean 4.71 4.20 4.46 a Sunn hemp 3.97 3.64 3.80 b X 4.28 3.88 ** K Sweet corn 24.3 30.3 27.3 a Cowpea/Lima bean 27.4 34.4 30.9 a Sunn hemp 25.7 31.9 28.8 a X 25.8 32.2 *** Ca Sweet corn 5.59 8.02 6.81 a Cowpea/Lima bean 6.35 7.92 7.14 a Sunn hemp 6.49 8.55 7.52 a X 6.14 8.16 *** Mg Sweet corn 1.83 2.47 2.15 a Cowpea/Lima bean 1.65 2.28 1.96 a Sunn hemp 1.71 2.41 2.06 a X 1.73 2.39 *** Na Sweet corn 0.77 0.83 0.80 a Cowpea/Lima bean 0.73 0.55 0.64 a Sunn hemp 0.81 0.71 0.76 a X 0.77 0.70 ns ———————Mineral concentration, mg kg-1——————— Cu Sweet corn 5.0 5.4 5.2 a Cowpea/Lima bean 4.2 5.4 4.8 a Sunn hemp 2.6 5.0 3.8 a X 3.9 5.3 ** Fe Sweet corn 130 332 231 a Cowpea/Lima bean 108 416 262 a Sunn hemp 158 318 238 a X 132 355 ***

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156 Table 5-4. Continued. Previous crop 2003 2004 X ———————Mineral concentration, mg kg-1——————— Mn Sweet corn 27.6 32.4 30.0 a Cowpea/Lima bean 19.8 29.0 24.4 a Sunn hemp 23.6 30.8 27.2 a X 23.7 30.7 *** Zn Sweet corn 48.4 a 44.0 a ns 46.2 Cowpea/Lima bean 38.8 ab 52.8 a 45.8 Sunn hemp 33.0 a 41.8 a 37.4 X 40.1 46.2 Significant at the 0.01 level. ** Significant at the 0.05 level. *** Significant at the 0.001 level. †ns = not significant. ‡Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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157Table 5-5. Mineral content in Au strian winter pea above ground pl ant dry matter at early bloom stage of growth analysis of var iance. _______________________________________________________________________________________________________________________________ __ Source of variation df Ca Mg K N P Na Cu Fe Mn Zn Previous crop (PC) 2 ns† ns ns + ns ns ns ns ns Error A 12 — — — — — — — — — — Year (Y) 1 *** ** *** ns + ** *** *** ** PC x Y 2 ns ns ns ns ns ns ns ns ns ns Error B 12 — — — — — — — — — — Total 29 — — — — — — — — — — + Significant at the 0.01 level. Significant at the 0.05 level. ** Significant at the 0.0 level. *** Significant at the 0.001 level. †ns = not significant.

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158 Table 5-6. Mineral content for Austrian winter pea at early bloom stage. Previous crop 2003 2004 X —————————Mineral content, g m-2———————— N Sweet corn 7.92 11.15 9.54 a† Cowpea/Lima bean 6.89 11.31 9.10 a Sunn hemp 6.99 8.90 7.95 a X 7.27 10.46 ** P Sweet corn 0.75 1.06 0.90 a Cowpea/Lima bean 0.83 1.26 1.05 a Sunn hemp 0.76 0.86 0.81 a X 0.78 1.06 K Sweet corn 4.45 8.54 6.50 a Cowpea/Lima bean 4.84 10.2 7.54 a Sunn hemp 4.91 7.58 6.25 a X 4.73 8.79 *** Ca Sweet corn 1.01 2.18 1.59 a Cowpea/Lima bean 1.12 2.31 1.71 a Sunn hemp 1.24 1.99 1.62 a X 1.12 2.16 *** Mg Sweet corn 0.33 0.68 0.51 a Cowpea/Lima bean 0.29 0.66 0.48 a Sunn hemp 0.33 0.56 0.45 a X 0.32 0.64 ** Na Sweet corn 0.14 0.22 0.18 a Cowpea/Lima bean 0.13 0.16 0.15 a Sunn hemp 0.16 0.17 0.17 a X 0.14 0.18 + —————————Mineral content, mg m-2———————— Cu Sweet corn 0.92 1.52 1.22 a Cowpea/Lima bean 0.78 1.82 1.30 a Sunn hemp 0.50 1.18 0.84 a X 0.73 1.51 ** Fe Sweet corn 23.62 93.84 58.73 a Cowpea/Lima bean 19.10 130.52 74.81 a Sunn hemp 31.04 74.84 52.94 a X 24.59 99.73 ***

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159 Table 5-6. Continued. Previous crop 2003 2004 X —————————Mineral content, mg m-2———————— Mn Sweet corn 4.98 9.04 7.01 a Cowpea/Lima bean 3.46 8.78 6.12 a Sunn hemp 4.58 7.14 5.86 a X 4.34 8.32 *** Zn Sweet corn 8.70 11.86 10.28 a Cowpea/Lima bean 6.86 16.58 11.72 a Sunn hemp 6.34 9.82 8.08 a X 7.30 12.75 ** Significant at the 0.01 level. ** Significant at the 0.05 level. *** Significant at the 0.001 level. †Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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160Table 5-7. Soil mineral concentrations in Austrian winter pea above ground plant dry matter at early bloom stage of growth ana lysis of variance. _______________________________________________________________________________________________________________________________ __ Source of variation df Ca Mg K N P Na Cu Fe Mn Zn pH BpH OM CEC Previous crop (PC) 2 ns† ns ns + ns ns ns ns ns *** *** *** Error A 12 — — — — — — — — — — — — — — Year (Y) 1 *** ** *** ns + ** *** *** ** *** + ns ** PC x Y 2 ** ns ns ns + ns *** ns ns ns ns ns ** Error B 12 — — — — — — — — — — — — — — Total 29 — — — — — — — — — — — — — — + Significant at the 0.01 level. Significant at the 0.05 level. ** Significant at the 0.0 level. *** Significant at the 0.001 level. †ns = not significant.

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161 Table 5-8. Soil mineral concentration and properties following harvest of Austrian winter pea. Previous crop 2003 2004 X ———————Mineral concentration, mg kg-1——————— N Sweet corn 506 513 509 b‡ Cowpea/Lima bean 645 656 651 a Sunn hemp 530 528 529 b X 560 566 ns† P Sweet corn 64 69 67 b Cowpea/Lima bean 240 157 199 a Sunn hemp 68 78 73 b X 124 102 ns K Sweet corn 61.8 61.8 61.8 a Cowpea/Lima bean 63.4 65.4 64.4 a Sunn hemp 47.0 60.0 53.5 a X 57.4 62.4 ns Ca Sweet corn 597 a 665 b ns 631 Cowpea/Lima bean 1158 a 3047 a 2103 Sunn hemp 842 a 1050 b ns 946 X 866 1588 Mg Sweet corn 47.4 b 58.0 b 52.7 Cowpea/Lima bean 71.0 a 75.8 a ns 73.4 Sunn hemp 46.2 b 63.6 ab 54.9 X 54.9 65.8 Na Sweet corn 7.4 14.4 10.9 a Cowpea/Lima bean 11.2 14.6 12.9 a Sunn hemp 9.00 13.2 11.1 a X 9.20 14.1 *** Cu Sweet corn 0.17 0.31 0.24 a Cowpea/Lima bean 0.14 0.38 0.26 a Sunn hemp 0.08 0.33 0.21 a X 0.13 0.34 *** Fe Sweet corn 7.28 a 11.7 b 9.5 Cowpea/Lima bean 9.12 a 13.4 ab 11.3 Sunn hemp 8.72 a 15.5 a 12.1 X 8.37 13.5

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162 Table 5-8. Continued. Previous crop 2003 2004 X ———————Mineral concentration, mg kg-1——————— Mn Sweet corn 2.42 3.75 3.09 b Cowpea/Lima bean 5.68 6.69 6.18 a Sunn hemp 2.95 4.09 3.52 b X 3.69 4.84 *** Zn Sweet corn 3.70 3.97 3.83 b Cowpea/Lima bean 7.79 7.03 7.41 a Sunn hemp 2.46 2.28 2.37 b X 4.65 4.43 ns ————————————pH————————————— Sweet corn 6.46 6.32 6.39 b Cowpea/Lima bean 7.24 7.10 7.17 a Sunn hemp 7.32 7.12 7.22 a X 7.01 6.85 *** ————————————BpH——————————— Sweet corn 7.85 7.84 7.84 b Cowpea/Lima bean 7.88 7.89 7.89 a Sunn hemp 7.90 7.88 7.89 a X 7.88 7.87 + ————————————OM, %——————————— Sweet corn 1.37 1.46 1.42 b Cowpea/Lima bean 1.76 1.70 1.73 a Sunn hemp 1.65 1.65 1.65 a X 1.59 1.61 ns ——————————CEC, cmol kg-1—————————— Sweet corn 4.77 a 5.32 b ns 5.05 Cowpea/Lima bean 7.52 a 17.00 a 12.26 Sunn hemp 5.55 a 6.94 b ns 6.25 X 5.95 9.75 + Significant at the 0.01 level. Significant at the 0.05 level. ** Significant at the 0.0 level. *** Significant at the 0.001 level. †ns = not significant. ‡Values in columns not followed by the same letter are significantly different (p< 0.05) according to LSD.

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163 Table 5-9. Correlation coeffici ents (r) between 2003 Austrian winter pea dry matter yield (DM), plant mineral concentr ation and soil properties. Plant DM and soil Plant DM yield and plant mineral concentration prop. DM Ca Mg K N P Na Cu Fe Mn Zn DM 0.23 ns† 0.39 0.60 *** -0.04 ns -0.11 ns -0.19 ns 0.59 *** 0.66 *** 0.41 0.39 Soil Ca 0.32 + 0.39 0.09 ns 0.21 ns 0.20 ns 0.54 ** 0.31 + -0.31 + 0.71 *** 0.51 ** 0.26 ns Soil Mg 0.25 ns 0.32 + 0.27 ns 0.35 + 0.17 ns -0.10 ns -0.21 ns -0.29 + 0.23 ns 0.56 *** 0.33 + Soil K -0.14 ns 0.25 ns 0.25 ns 0.23 ns 0.41 -0.05 ns 0.25 ns -0.16 ns 0.43 0.38 0.05 ns Soil N 0.05 ns -0.14 ns 0.11 ns 0.16 ns 0.26 ns -0.11 ns 0.06 ns -.00 ns 0.22 ns 0.11 ns 0.17 ns Soil P -0.02 ns 0.05 ns 0.02 ns -0.06 ns 0.23 ns 0.00 ns 0.44 ** -.016 ns 0.32 + 0.21 ns -0.16 ns Soil Na 0.46 ** -0.03 ns -0.11 ns -0.27 ns 0.22 ns 0.08 ns 0.66 *** -0.09 ns 0.30 + 0.02 ns -0.36 Soil Cu 0.37 0.46 ** 0.56 *** 0.54 ** 0.72 *** -0.18 ns 0.00 ns -0.12 ns 0.44 0.60 *** 0.33 + Soil Fe 0.51 ** 0.38 0.68 *** 0.78 *** 0.50 ** 0.02 ns -0.29 + -0.27 ns 0.34 + 0.58 *** 0.52 ** Soil Mn 0.27 + 0.51 ** 0.53 ** 0.61 *** 0.73 *** -0.08 ns -0.13 ns -0.17 ns 0.34 + 0.58 *** 0.22 ns Soil Zn 0.11 ns 0.28 + 0.27 ns 0.18 ns 0.37 -0.08 ns 0.25 ns -0.24 ns 0.39 0.41 -0.01 ns Soil pH -0.02 ns 0.11 ns -0.04 ns 0.12 ns 0.10 ns 0.16 ns 0.52 ** -0.22 ns 0.44 0.16 ns -0.15 ns Soil BpH 0.01 ns -0.02 ns -0.00 ns -0.21 ns -0.11 ns -0.17 ns 0.16 ns -0.09 ns -0.27 ns -0.00 ns -0.47 ** Soil OM -0.04 ns 0.10 ns -0.07 ns -0.16 ns -0.16 ns -0.00 ns 0.02 ns -0.12 ns -0.20 ns 0.04 ns -0.36 Soil CEC 0.33 + -0.04 ns 0.10 ns -0.06 ns 0.18 ns -0.11 ns 0.38 0.03 ns -0.06 ns 0.04 ns -0.36 + Significant at the 0.01 level. Significant at the 0.05 level. ** Significant at the 0.0 level. *** Significant at the 0.001 level. †ns = not significant.

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164 Table 5-10. Correlation coefficients (r) be tween 2004 Austrian winter pea dry matter yield (DM), plant mineral c ontent and soil properties. Plant DM and soil Plant DM yield and plant mineral content prop. DM Ca Mg K N P Na Cu Fe Mn Zn DM 0.90 *** 0.91 *** 0.96 *** 0.94 *** 0.94 *** 0.61 *** 0.88 *** 0.86 *** 0.90 *** 0.87 *** Soil Ca 0.32 + 0.38 ns† 0.40 0.29 + 0.27 + 0.24 ns -0.00 ns 0.26 ns 0.48 ** 0.38 0.27 ns Soil Mg 0.25 ns 0.32 + 0.31 + 0.31 + 0.22 ns 0.30 + 0.06 ns 0.31 + 0.34 + 0.23 ns 0.26 ns Soil K -0.14 ns -0.05 ns -0.01 ns -0.04 ns -0.18 ns -0.14 ns -0.15 ns -0.03 ns -0.01 ns -0.02 ns -0.14 ns Soil N 0.05 ns 0.06 ns 0.05 ns 0.10 ns 0.06 ns 0.18 ns -0.11 ns 0.17 ns 0.18 ns 0.01 ns 0.06 ns Soil P -0.02 ns -0.06 ns -0.11 ns 0.04 ns 0.01 ns 0.16 ns -0.11 ns 0.13 ns 0.03 ns -0.14 ns 0.04 ns Soil Na 0.46 ** 0.62 *** 0.59 *** 0.57 *** 0.38 0.43 0.26 ns 0.43 0.54 ** 0.48 ** 0.37 Soil Cu 0.37 0.61 *** 0.61 *** 0.44 ** 0.35 + 0.26 ns 0.06 ns 0.32 + 0.48 ** 0.48 ** 0.35 + Soil Fe 0.51 ** 0.64 *** 0.64 *** 0.62 *** 0.45 ** 0.44 ** 0.29 + 0.39 0.52 ** 0.44 0.43 Soil Mn 0.27 + 0.35 + 0.31 + 0.32 + 0.24 ns 0.33 + 0.00 ns 0.33 + 0.39 0.23 ns 0.28 + Soil Zn 0.11 ns 0.08 ns 0.05 ns 0.12 ns 0.16 ns 0.25 ns -0.12 ns 0.29 + 0.20 ns 0.05 ns 0.22 ns Soil pH -0.02 ns -0.02 ns -0.09 ns -0.04 ns -0.06 ns 0.04 ns -0.09 ns -0.11 ns 0.02 ns -0.21 ns -0.03 ns Soil BpH 0.01 ns 0.04 ns 0.00 ns 0.03 ns 0.11 ns 0.12 ns -0.05 ns 0.00 ns 0.10 ns -0.09 ns 0.10 ns Soil OM -0.04 ns 0.01 ns -0.03 ns 0.02 ns -0.06 ns 0.08 ns -0.01 ns -0.06 ns -0.00 ns -0.17 ns -0.09 ns Soil CEC 0.33 + 0.39 0.42 0.30 + 0.28 + 0.25 ns 0.00 ns 0.27 + 0.49 ** 0.40 0.28 + + Significant at the 0.01 level. Significant at the 0.05 level. ** Significant at the 0.0 level. *** Significant at the 0.001 level. †ns = not significant.

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165 5 10 15 20 25 30 SeptOctNovDecJanFebMarAprMayJuneJulyAug MonthTemperature, Degrees C 02/03 03/04 Figure 5-1. Temperature, monthly averag e, for Alachua County, Florida (Florida Automated Weather Service, 2005). 0 50 100 150 200 250 300 350 SeptOctNovDecJanFebMarAprMayJuneJulyAug MonthsRainfall, m m 02/03 03/04 Figure 5-2. Rainfall, monthly average, for Alachua County, Florida (Florida Automated Weather Service, 2005).

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166 50 100 150 200 250 300 SeptOctNovDecJanFebMarAprMayJuneJulyAug MonthsSolar radiation, W/m^ 2 02/03 03/04 Figure 5-3. Solar radiation, monthly average, for Alachua County, Florida, (Florida Automated Weather Service, 2005).

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167 CHAPTER 6 SWEET CORN (Zea mays L.) YIELD AFFECTED BY CROPPING HISTORY AND NITROGEN FERTILIZATION Introduction In many parts of the world, the practices of multiple cropping have been in use for thousands of years. Farmers have long since been aware of the many benefits that accompany this type of agriculture and have adapted their practices in order to take advantage of them. Some of the most important benefits that accompany multiple cropping are the protection and improvement of soil healt h. Soil conservation can result from this practice, ranging from protection of soil that w ould otherwise be left bare from erosion to the prevention of surface water runoff to the pr eservation of soil moisture (Anderson, 1990). Multiple cropping can also contribute to the in crease of available nutrient levels in soils especially when leguminous crops are planted and their N fixation capabilities are utilized. The extensive rooting systems of several successive crops can also loosen and naturally aerate the soil. Additional advantages of utilizing mu ltiple cropping are the natural diversity provided and its effects on pest populations. By growing various crops in succession, diversity is increased in the natural sy stems surrounding crop production, which can help to reduce crop-specific pests and possibly attr act beneficials (Sullivan, 2003). Certain crops that can be integrated into croppi ng systems can also provide alleleopathic advantages in controlling nematode and other pest populations (Sullivan, 2003).

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168 Finally, multiple cropping can contribute to the reduction of the cost of crop production. This agronomic practice can reduc e the need for fertilizers by bringing in nutrients to the soil, can reduce the ne ed for herbicides by cutting down weed populations, and reduce the need for pesticides by naturally decreasing pest infestations. The decreased need for inputs can greatly cut down on production costs (Reginelli, 1990). Although multiple cropping can reduce the need for fertilizers with residual nutrients left from one crop to the next, a dditional nutrients may still be needed for adequate crop growth. Many farmers are becoming more concerned with sustainable farming methods that enhance soil fertility and the natura l resource base, while reducing synthetic production inputs and minimizing a dverse impacts on the public’s health and safety, wildlife, water quality, and the envi ronment. The use of organic fertilizers satisfies these concerns and is rapidly b ecoming utilized by more farmers across the nation. Because of the increasing focus on sustaina ble practices and the rising popularity of organically grown produce, a 2-yr study was conducted inve stigating the effects of organic and inorganic N sources in 3 differe nt cropping systems on no-till sweet corn. The objectives of this study were to evaluate the yield and plant nutrition of sweet corn due to varying cropping historie s, N sources (organic and in organic), and N rates. Materials and Methods For this study, a split-split plot expe riment was conducted from August 2002 to June 2004. Main effects were 3 cropping histor ies that each began in the fall with sweet corn (Zea mays L.) (history 1), cowpea (Vigna unguiculata (L.) Walp.) (history 2), and sunn hemp (Crotalaria juncea L.) (history 3), respectively. In the second year of the

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169 experiment, lima bean (Phaseolus lunatus L.) replaced cowpea in history 2 because seed was unavailable. Austrian winter pea (Pisum sativum L. subsp. arvense) was a winter cover crop for all histories and was followed by sweet corn in the spring. Sub-effects were 3 N sources, 2 organic [lupine (Lupinus angustifolius L.) and vetch (Vicia villosa (L.) Roth)] and one inorganic [ammoni um nitrate (AN)]. The sub-effects allowed us to compare the organic N sour ces to AN for use on sweet corn. Sub-sub effects were 5 N rates (0, 50, 100, 150, and 200 kg ha-1 in 2002) (0, 60, 120, 180, and 240 kg ha-1 in 2003). The sub-sub effects used allowe d us to determine the optimum N rate for sweet corn. Cropping Histories In order to examine the different cropping histories, we evaluated the affects of varying multiple cropping systems on a final crop of sweet corn. We examined 3 different histories and assumed that the vary ing histories would not affect final sweet corn yield or nutrient concentrati on in diagnostic leaf samples. History 1 began with a fall crop of sweet corn planted in August of 2002. Each plot contained 4 0.76 m wide rows and measured 2 m by 3 m. Seeds were planted by hand at a rate of 12 seeds m-1 of row into Millhopper fine sand (loamy siliceous semiactive hyperthermic Grossarenic Pale odults) [USDA-NRCS, 2003]. Five varieties (‘Merritt’, ‘Silver Queen’, ‘G olden Queen’, ‘Florida Stay Sweet’, and ‘Peaches and Cream’) were used to fulfill teaching purposes. After the sweet corn was harvested in November of 2002, Austrian winter pea was dri lled into the sweet corn stalk residue in December 2002. The peas were planted into 0.25 m wide rows throughout the entire field. Following the harvest of Austrian winter pea in March 2003, sweet corn was planted, the final crop of hist ory 1. ‘Silver Queen’ vari ety was used and was no-till

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170 planted into Austrian winter pea residue at a rate of 10 seeds m-2 and thinned back to about 6 plants m-2. Plots measured 2 m by 3 m. Sweet corn was harvested in June 2003. History 2 began with a fall crop of cowpea planted in July of 2002. Each experimental plot contained 4 0.75 m wide rows and measured 2 m by 3 m. Seeds were planted by hand at a rate of 50 seeds 2 m-1 of row into Millhopper fine sand (loamy siliceous semiactive hyperthermic Grossare nic Paleodults) [USDA-NRCS, 2003]. Five varieties of cowpea (‘California Blackeye #5’, ‘Wh ite Acre’, ‘Texas Cream 12’, ‘Mississippi Cream’, and ‘Iron Clay’) were used to fulfill teaching purposes. Directly following the harvest of cowpea in December of 2002, Austrian winter pea was no-till planted across the field in 0.25 m wide rows. After the winter pea was harvested in March 2003, the final crop of history 2, sweet corn, was planted. ‘Silver Queen’ variety sweet corn was planted into Austrian wint er pea residue at a rate of 10 seeds m–2 and thinned to about 6 plants m-2. Experimental plots measured 2 m by 3 m. Sweet corn was harvested in June 2003. History 3 started with a fall crop of sunn hemp planted in August of 2002. Each experimental plot measured 2 m by 3 m and contained 4 0.76 m wide rows. Seed was planted with a Flex 71 planter and a tractor at 200 seeds 6 m-1 of row into Millhopper fine sand (loamy siliceous semiactive hyperthermic Grossa renic Paleodults) [USDA-NRCS, 2003]. Sunn hemp was harvested in December 2002 and was immediately followed by a winter crop of Aust rian winter pea. The legume was no-till planted into sunn hemp stubble across the fiel d into 0.25 m wide rows After harvest of the Austrian winter pea in March 2003, sweet corn, the final crop of history 3, was no-till planted into the winter pea resi due. ‘Silver Queen’ sweet corn was planted at a rate of

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171 10 seeds m-2 and thinned back to about 7 plants m-2. Plots measured 2 m by 3 m. Sweet corn was harvested in June of 2003. Nitrogen Sources While examining the different N sources, we assumed that the source of N would have no effect on sweet corn yield or plant nutrition. Three different N sources were tested in each of the 3 histor ies during both years of the study. Each year, plots were side dressed with ha lf rates of AN (34% N) and full rates of lupine and vetch at the planting date. The re maining half of AN was side dressed 30 days after planting. The lupine and vetch were harvested in early February each year and placed in doubled industrial black ga rbage bags. After the bags were filled to half-capacity with either lupine or vetch, all of the air was pushed out of them and they were sealed to be airtight. The bags were left for about 6 wk before the ensiled plant material was removed and applied to the sweet corn as mulch. The silage of each legume was analyzed for N concentration before applic ation so that N rates could be established. Lupine was found to contain 3.6% N while vetch had 3.5% N. After fertilizer application, each plot was covered with a la yer of rye-straw mulch. Mulch was applied by hand at a rate of 4500 kg ha-1. Nitrogen Rates We assumed that the current extension recommendations for N fertilization for sweet corn were excessive (Hochmuth et al., 1996). Five different rates of applied N were tested on the final sweet corn crop of each of the 3 histories during both years of the study. The initial rates were te sted during the first year of the study and then adjusted for the second year in order to increase the precis ion of N fertilization. Each crop of sweet corn was analyzed separately for yield and nutrient concentrations.

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172 Throughout both years of the study, sweet corn was irrigated to ensure at least 3 cm of water per week, and weeded manually a nd mechanically. Sweet corn from each plot was harvested by hand and removed from the fi eld. Soil samples from a depth of 20 cm directly following harvest were also obtained. Leaf samples were taken from each plot at the early tassel stage for N and mineral analysis. Nitrogen Analysis Five diagnostic leaves, or th e fifth leaf from the top of each plant, were sampled at early tassel stage from each plot during both y ears of the experiment for analysis (Mills and Jones, 1996). Samples were analy zed for leaf area w ith a LI-3100 Area Meter (LI-COR, Inc., Lincoln, Nebraska ), weighed for fresh matter yi eld, dried in a forced air oven, and weighed again for dry matter yield. Leaf samples were then chopped in a hammer mill, mixed well, and ground to pass a 2-mm stainless steel screen using a Wiley mill. The samples were then stored in plastic sample bags before analysis. Nitrogen analysis of the di agnostic leaf samples was performed using a modified micro-Kjedahl procedure. A mixture of 0.100 g of each leaf sample, 3.2 g salt-catalyst (9:1 K2SO4:CuSO4), 2 to 3 boiling beads and 10 mL of H2SO4 were vortexed in a 100 mL test tube. To reduce frothing, 2 mL 30% H2O2 were added in 1 mL increments and then tubes were digested in an aluminum block digester at a temperature of 370C for 3.5 h (Gallaher et al., 1975). Cool digested solutions were brought to 75 mL volume, transferred to square Nalgene storage bottles (boiling beads were filtered out), sealed, mixed, and stored. Nitrogen trapped as (NH4)2SO4 was analyzed on an automatic solution sampler and a proportioning pump. A plant standard with a history of recorded N concentration

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173 values was subjected to the same procedure and used as a check. Fresh matter or dry matter and nutrient concentrations were r ecorded for each crop of sweet corn. Mineral Analysis For mineral analysis, 1.0 g from each diagnostic leaf sample was weighed into 50 mL beakers and ashed in a muffle furnace at 480C for 6 h. The samples were then cooled to room temperature and moistened with de -ionized water. Twenty mL of de-ionized water and 2 mL of concentrated HCl were added to each beaker, which were then placed on a hot plate and slowly bo iled to dryness before being removed. An additional 20 mL of de-ionized water and 2 mL concentrated HCl were then added and small watch glasses were used to cover the beakers for reflux. They were brought to a vigorous boil and th en removed from the hot plat e and allowed to cool to room temperature. The samples were then brought to volume in 100 mL flasks and mixed. They were then set aside overnight to allow the Si to settle. The solutions were decanted into 20 mL scintillation vials for analysis. Phosphorus was analyzed by colorimetry, K and Na by flame emission, a nd Ca, Mg, Cu, Fe, Mn, and Zn by atomic adsorption spectrometry (AA). Yield For both years of the experiment, the ears from all plots were hand collected and bagged. The ears were weighed to obtain fresh weights and th en graded. The ears were separated into size classes of > 15.2 cm, 12.7–15.2 cm, 10.2–12.7 cm, and <10.2 cm categories (USDA, 1954). Soil Analysis During each year of the study, soil samples were obtained from the top 20 cm of soil directly following harvest. Samples were air-dried in open paper bags, then screened

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174 to pass through a stainless stee l sieve with 2 mm holes to remove any rocks or debris and stored for further analysis. The samples were then analyzed for N, mineral concentrations, pH, buffer pH (BpH), organic matter (OM), a nd cation exchange capacity (CEC ). For soil N, a mixture of 2.0 g of each soil sample, 3.2 g salt catalyst (9:1 K2SO4:CuSO4), and 10 mL of H2SO4 were subjected to the same procedures for N analysis as leaf tissue was, except that boiling beads were not used because the partic les of soil served the same purpose. A soil sample of known N concentration was al so analyzed and used as a check. For soil mineral analysis, a Mehlich I (Meh lich, 1953) extraction method was used. Five g soil samples were weighed and extrac ted with 20 mL of a combination of 0.025 N H2SO4 and 0.05 N HCl. Using an Eberach shak er at 240 oscillations minute-1, mixtures were then shaken for 5 min. The mixtures were then filtered using Schleischer and Schuell 620 (11 cm) filter paper and poured into scintillation vials. The remaining solutions were then subjected to analysis of P, K, Ca, Mg, Na, Cu, Fe, Mn, and Zn in the same manner as described fo r leaf tissue analysis. Soil pH was found using a 1:2 soil to water volume ratio using a glass electrode pH meter (Peech, 1965). Buffer pH was found using Adams/Evans buffered solution (Adams and Evans, 1962). Cation exchange capacity was estimated by the summation of relevant cations (Hesse, 1972; Jackson, 1958). Estimated soil CEC was calculated by summing the milliequivalents of the determined bases of Ca, Mg, K, and Na (where applicable) plus exchangeable H+ expressed in milliequivalents per 100 g (Hesse, 1972). For organic matter determination, a modifi ed version of the Walkley Black method was used, in which 1.0 g of soil was weighed into a 500-mL Earlenmeyer flask, and

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175 10 mL of 1 N K2Cr2O7 solution was pipetted into the fl ask. Twenty mL of concentrated H2SO4 was added and mixed by gentle rotation for 1 min using care to avoid throwing soil up onto the sides of the flask. The flask was then left to stand for 30 min, and then diluted to 200 mL with de-ionized water. Five drops of indicator were added, and the solution was then titrated with 0.5 N Ferrous Sulfate Solution until the color sharply changed from a dull green to a reddish brown co lor. A flask without soil was prepared in the same manner and titrated to determine th e blank titrant, along with a flask containing a check soil with a pre-determined amount of organic matter. Percent OM was determined using the equation: percent OM = (1-T/S) x 6.8, where S is blank-titration in mL of ferrous ammonium sulfate solution, and T is sample titration in mL ferrous ammonium sulfate solution (W alkley, 1935; Allison, 1965). Statistical Analysis Sweet corn data from each year was analyzed separately for two reasons. First, the number of crops produced the second year was greater than the first year. Therefore, the 3 histories in the second year were not exactly the same as the first. Second, the N rates were adjusted to be higher the second year co mpared to the rates in the first year. Data for each year was analyzed as a split-split plot with the main effects (cropping history) in a completely randomized design. An example of the breakdown of the degrees of freedom (df) is shown in Table 6-1. Analys is of variance (ANOVA) for this split-split plot experimental design was conducted by use of MSTAT 4.0 (Anonymous, 1985). Data from each ANOVA was placed in a 4-way table as illustrated in Table 6-2. Means were separated by least significant differen ce (LSD) at the 0.05 level of probability (Gomez and Gomez, 1976). All treatments a nd interactions that were significant at p< 0.05 were highlighted in bold in the data ta bles (Tables 6-3 to 6-34). Plant mineral

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176 data from each year were analyzed as split -split plot designs and means were separated using least significant difference (LSD) at th e 0.05 level of probability. Soil data was analyzed as a split-plot with cropping hist ory as the main effect in a completely randomized design and N sources as split plot s. This was done because soil samples were collected and combined over all N rates. For soil data treatment s and/or interactions that were significant at the 0.05 level of probability or highe r, data was highlighted in bold in the data tables (Tables 6-18 and 6-34). Results Yield: Ear for 2003 For number of fancy (>15.2 cm) sweet corn ears produced, croppi ng histories were not significantly (p>0.05) different and an interaction between N source and N rate was displayed (Table 6-3). For number of ears 12.7 to 15.2 cm in length, no significant (p>0.05) differences were exhibited due to cropping history or to N source, while differences (p< 0.05) were displayed due to N rate (T able 6-4). For number of ears 10.2 to 12.7 cm in length, no significant (p>0.05) differences due to cropping history, N source, or N rate were exhibited (Table 6-5). Cropping history, N source, and N rate were all found to be significant (p< 0.05) for number of non-marketable (<10.6 cm) ears produced (Table 6-6). For number of total ears produced, N source was found to be significant (p< 0.05) as was an interaction between cropping history and N rate (Table 67). For ear weight of fancy (>15.2 cm) ears produced, no significant (p>0.05) differences due to cropping history were displayed while N source and N rate were significant (p< 0.05) (Table 6-8). Neither croppi ng history nor N source displayed significant (p>0.05) differences for weight of ears 12.7 to 15.2 cm in length, while N rate

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177 did (Table 6-9). For ear weight of ears 10.2-12.7 cm in length, no significant (p>0.05) differences were displayed due to cropping history, N source, or N rate (Table 6-10). For ear weight of non-marketable (<10.6 cm) ears, N source was significant (p< 0.05) as was an interaction between cropping history and N rate (Table 6-11). Ear weight of total ears produced displayed no significant (p>0.05) differences due to cropping history, while N source and N rate were significant (p< 0.05) (Table 6-12). Yield: Diagnostic Leaf for 2003 For diagnostic leaf area, significant (p< 0.05) difference occurred due to cropping history and to N rate, but not N source (Tab le 6-13). For diagnos tic leaf dry weight, cropping history and N rate exhibited significant (p< 0.05) differences while N source did not (Table 6-14). Mineral Analysis: Diagnostic Leaf for 2003 For N concentration in diagnostic leaf cropping history did not display any significant (p< 0.05) differences while N source and N ra te did (Table 6-15). Phosphorus concentration in diagnostic l eaf displayed a significant (p< 0.05) interaction between cropping history and N rate and significant (p< 0.05) differences due to N source (Table 6-16). For K concentration in dia gnostic leaf, cropping hi story was significant (p< 0.05) as was an interaction between N source and N rate (Table 6-17). Mineral Analysis: Soil for 2003 For N and P concentration in soil, cr opping history disp layed significant (p< 0.05) difference, while N source did not (Table 6-18). Potassium concentration in soil exhibited significant (p< 0.05) differences due to both cr opping history and N source (Table 6-18). Concentrations of Ca and Mg also displayed significant (p< 0.05) differences due to cropping history but not N source (Table 6-18). An interaction

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178 between cropping history and N source occurred in soil pH (Table 6-18). Significant differences due to cropping hi story, but not N source, occu rred in soil OM and CEC (Table 6-18). Yield: Ear for 2004 For number of fancy (>15.2 cm) ears produced, no significant (p>0.05) differences were exhibited due to croppi ng history, while both N source and N rate displayed differences (p< 0.05) (Table 6-19). For number of ears 12.7 to 15.2 cm in length, cropping history was significant (p< 0.05) while N source and N rate were not (Table 6-20). Neither croppi ng history, nor N source, nor N rate exhibited significant (p>0.05) differences for ears 10.2 to 12.7 cm in length (Table 6-21). For number of non-marketable (<10.6 cm) ears, cropping history and N source did not display differences (p>0.05) while N rate did (Table 6-22). For number of total ears produced, significant (p< 0.05) differences were displayed due to N source and an interaction between cropping history and N rate (Table 6-23). For ear weight of fancy (>15.2 cm) ears produced, cropping history was not significant (p>0.05), while N source and N rate were (Table 6-24). Cr opping history, N source, and N rate did not display significant (p>0.05) differences for ear weight of ears 12.7 to 15.2 cm in length (Table 6-25). For ear weight of ears 10.6 to 12.7 cm length, neither cropping history, N source, no r N rate displayed any differences (p>0.05) (Table 6-26). For ear weight of non-mark etable ears (<10.6 cm), cropping history was not significant (p>0.05), while N source and N rate did display differences (p< 0.05) (Table 6-27). For ear weight of total ears produ ced, significant (p< 0.05) differences were displayed due to N source as well as an in teraction between cropping history and N rate (Table 6-28).

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179 Yield: Diagnostic Leaf for 2004 Cropping history and N rate displayed significant (p< 0.05) differenced for diagnostic leaf area, but N s ource did not (Table 6-29). Fo r diagnostic leaf dry weight, again only cropping history and N source exhibited differences (p< 0.05), while N source did not (Table 6-30). Mineral Analysis: Diagnostic Leaf for 2004 For N concentration of dia gnostic leaf, 3 significant (p< 0.05) interactions were displayed: cropping history a nd N source, cropping history and N rate, and N source and N rate (Table 6-31). Significant (p< 0.05) differences due to cropping history and an interaction between N source and N rate were exhibited for p concentration of diagnostic leaf (Table 6-32). For K concentration of diagnostic leaf, cropping history was significant (p< 0.05) as was an interaction between N source and N rate (Table 6-33). Mineral Analysis: Soil for 2004 For both N and P concentrations in the soil, an interaction occurred between cropping history and N source (Table 6-34) For K concentration, neither cropping history nor N source displayed significant (p>0.05) differences (Table 6-34). Both cropping history and N source exhibited significant (p< 0.05) differences for Ca concentration, while only cropping hi story displayed differences (p< 0.05) for Mg concentration (Table 6-34). For soil pH both cropping history and N source displayed significant (p< 0.05) differences (Table 6-34). An interaction between cropping history and N source occurred in both soil OM and CEC (Table 6-34).

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180 Discussion and Conclusion Yield: Ear for 2003 For number of fancy (>15.2 cm) ears produced, 1 significant (p< 0.05) interaction between N source and N rate occurred, due to conflicting trends in ear production. Sweet corn receiving lupine as an N source increased in ear produ ction as N rate increased. Corn receiving vetch produced equa l ears at both N rates 0 and 60 kg N ha-1, and equal but increased ears for rates 100, 150, and 200 kg N ha-1. Corn receiving AN increased ear production as N rate increa sed, except at the 100 and 150 kg N ha-1 rates, which produced equal ears. Corn fe rtilized at 0 and 150 kg N ha-1 produced equal ears with all three N sources. Corn fertilized at the 50, 100, and 200 kg N ha-1 rates produced a greater increase in number of ears with AN than with either lupine or vetch. For ears 12.7 to 15.2 cm in length produce d, no interactions were displayed and only N rates displayed significant (p< 0.05) differences. Corn fe rtilized at rates 200, 150, and 100 kg N ha-1 produced highest numbers of ears. Corn fertilized at 0 kg N ha-1 produced the lowest number of ears. Cr opping history, N source, and N rate did not display any differences (p>0.05) for number of ears 10.6 to 12.7 cm in length produced and no interactions occurred. Differences due to cropping history, N source, and N rate were displayed for number of non-market able (<10.6 cm) ears produced, while again no interactions were displayed. Corn in cr opping history 2 produced the highest number of ears. Corn that received N rates of 0 and 50 kg N ha-1 produced the highest number of ears. One interaction was displayed for number of total ears produced, in addition to N source displaying significant (p< 0.05) differences. The inte raction occurred between cropping history and N rate and wa s due to conflicting trends in ear yield. Corn grown in

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181 cropping history 1 produced equal numbers of ears when it received N rates from 0 to 100 kg N ha-1. Ears then increased at 150 kg N ha-1 and then remained equal at 200 kg N ha-1. Corn grown in cropping history 2 produced equal numbers of ears at N rates 50 to 200 kg N ha-1, and lowest ears receiving N at 0 kg N ha-1. Ears produced by corn in cropping history 3 were lowe st in number receiving N at 0 kg N ha-1 and highest receiving N at 200 kg N ha-1. Corn fertilized at 0, 100, and 200 kg N ha-1 exhibited similar trends, producing equal numbers of ears in all 3 cropping histories. Corn receiving 50 kg N ha-1 produced the highest number of ears in cropping history 2. Corn fertilized at 150 kg N ha-1 produced the highest number of ears in both histories 1 and 2. No interactions occurred for ear weight of fancy (>15.2 cm) ears produced, but N source and N rate were significant (p< 0.05). Corn fertilized with AN produced the highest ear weight. Lu pine and vetch were used on corn that produced equal, but lower, weights compared to AN. Co rn that received the 200 kg N ha-1 rate produced the highest ear weight. Ear weight then decreased as N rate decreased, with only corn that received 100 and 150 kg N ha-1 producing equal ear weights. No interactions were displayed for ear weight of ears 12.7 to 15.2 cm in le ngth, while N rate wa s significant (p< 0.05). Corn that received the three highe st N rates, 200, 150, and 100 kg N ha-1, produced the highest ear weights. Corn that was fe rtilized at rates 50 and 100 kg N ha-1 produced equal, but lower ear weights. Corn fertilized at 0 kg N ha-1 produced the lowest ear weights. No differences (p>0.05) or interactions were displayed for ear weight of ears 10.2 to 12.7 cm in length. For ear weight of non-marketable (< 10.6 cm) ears, N source was significant (p< 0.05), with corn fertilized by lupine and ve tch producing the highest ear weights. One

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182 interaction also occurred, between croppi ng history and N rate, which was due to differing trends in weight of ears produced. Corn that was grown in cropping history 1 and fertilized at 0, 50, and 150 kg N ha-1 produced highest ear weights. Corn that received 100 and 200 kg N ha-1 produced equal but lower ear weights. Corn grown in cropping history 2 produced hi ghest ear weights when fertilized at 50 kg N ha-1. Corn that received N at 0, 100, and 100 kg N ha-1 produced equal but lower ear weights, while corn that received 200 kg N ha-1 produced the lowest weights. Corn grown in cropping history 3 that received 0 and 50 kg N ha-1 produced highest ears weights, corn that received 50 and 200 kg N ha-1 produced equal, but reduced ear weights, and corn that received 120, 180, and 200 kg N ha-1 produced equal and lowest ear weights. Corn fertilized at 0 and 200 kg N ha-1 produced equal weight for all 3 cropping histories. Corn that received 100 and 150 kg N ha-1 exhibited similar trends, with corn in history 2 producing highest ear weights a nd corn in histories 1 and 3 producing equal, but lower weights. Corn fertilized at 50 kg N ha-1 produced highest ear we ights in cropping history 2, followed by history 3 and then 1, respectively. No interactions occurred for total ear weight, but N source and N rate were significant (p< 0.05). Corn receiving N source AN produ ced the highest total ear weight, while the 2 organic sources, lupine and vetc h, produced equal but lo wer weights. Total ear weight increased as N rate incr eased, but with only the highest 2 N rates, 150 and 200 kg N ha-1, producing equal weights. Yield: Diagnostic Leaf for 2003 Diagnostic leaf area did not display any interactions, but cr opping history and N rate displayed significant (p< 0.05) differences. Diagnostic le aves from cropping history 2 had the largest area, while leaves from hi stories 1 and 3 had equa l but smaller area.

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183 Leaf area increased as N rate increased from 0 to 100 kg N ha-1, and then remained constant for the 3 highest N rates, 100, 150, and 200 kg N ha-1. No interactions occurred for diagnostic leaf dry weight while cropping history and N rate were significant. Leaves from cropping history 2 we re highest in weight, while leaves from histories 1 and 3 were equal but lower in wei ght. Dry weight of leaves increased as N rates increased, from 0 to 100 kg N ha-1 and then remained equal from rates 100 to 150 kg N ha-1. Leaves that received N at 150 and 200 kg N ha-1 had highest leaf weights. Mineral Analysis: Diagnostic Leaf for 2003 No interaction occurred for N concentra tion in diagnostic leaf, and only N source and N rate displayed differences (p< 0.05). Corn that received AN produced highest N in diagnostic leaves, while corn that received lupine and vetch produced equal, but lower N in leaves. Concentration of N increased as a pplied N rate increased. Corn fertilized at the 2 highest N rates, 150 and 200 kg N ha-1, produced the highest N concentrations. For P concentration in diagnostic leaf, an interaction between cropping history and N rate occurred, due to conf licting trends in P production in diagnostic leaves. Corn grown in history 1 produced hi ghest P concentration when fertilized at 0 to 150 kg N ha-1. Corn grown in cropping history 2 produ ced highest P when fertilized at rates 0, 100, 150, and 200 kg N ha-1. Corn grown in history 3 produced highest P when fertilized at 100, 150, and 200 kg N ha-1. Corn that was fertilized from 0 to 100 kg N ha-1 exhibited the same trend and produced equal an d highest P in historie s 1 and2. Corn that received N at 150 kg N ha-1 produced highest P in histor ies 1 and 2, while corn that received 200 kg N ha-1 produced highest P in history 2. For K concentration in diagnostic leaf, differences (p< 0.05) were displayed due to cropping history as well as an interaction between N source and N rate, which was due to

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184 differing trends in K production. Corn that received lupine produced highest K when fertilized at 200 kg N ha-1. When vetch was the N source, corn produced highest K when N rates were 150 and 200 kg N ha-1. When corn received AN, highest K was produced at fertilization rates 0 to 150 kg N ha-1. Corn fertilized at rates 100 and 200 kg N ha-1 exhibited similar trends, with corn recei ving lupine and vetch producing equal and highest concentrations of K. Corn fertilized at 0 kg N ha-1 produced equal K in when it received lupine and vetch and equal but lowe r K when N came from vetch and AN. Corn fertilized at 50 kg N ha-1 produced equal K with all 3 N s ources. Finally, corn fertilized at 150 kg N ha-1 produced highest K when it received vetch, followed by histories lupine and AN, respectively. Mineral Analysis: Soil for 2003 The same trend was exhibited by N and P concentrations in soil. Soil from cropping history 2 had the highest N and P concentrations, while soil from histories 1 and 3 had equal, but lower concentrations. No differences (p>0.05) in N or P concentrations were due to N source. The highest K con centrations were seen in soil from cropping histories 2 and 3. Differences (p< 0.05) in K were due to N source, with lupine and vetch used as fertilizer in areas with the highes t K. For Ca concentration, soil from cropping history 2 displayed the highest, followed by so il from histories 3 and 1, respectively. No differences (p>0.05) in Ca concentration were due to N source. Soil from history 2 displayed the highest Mg con centration, but no differences (p>0.05) were displayed due to N source. An interaction occurred in soil pH, betw een cropping history and N source. Soil for each N source followed the same trend, with highest pH found in soil from histories 2 and 3. Soil from history 1 had highest pH wh en fertilized with vetch and AN, while soil

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185 from histories 2 and 3 had equal pH with each N source. Soil from cropping history 2 displayed the highest OM, followed by soil fr om histories 3 and 2, respectively. No differences (p>0.05) in soil OM were due to N source. Soil from history 2 also displayed the highest CEC. Again, no differences (p>0.05) in CEC were due to N source. Yield: Ear for 2004 For number of fancy (>10.6 cm) ears produce d, no interactions occurred, while N source and N rate were significant (p< 0.05). Corn that received AN as an N source produced the highest number of fancy ears. Co rn that received lupi ne or vetch produced equal, but lower numbers of ears. Co rn fertilized at rates 0 and 60 kg N ha-1 produced equal, but lowest, ears. Corn that received 120 and 180 kg N ha-1 of fertilizer produced higher, but equal, ears. Finall y, corn that received 240 kg N ha-1 of fertilizer produced the highest number of ears. No interacti ons occurred for ears 12.7 to 15.2 cm in length, but cropping history displayed significant (p< 0.05) differences. Corn from histories 1 and 2 produced the highest numbers of ears, followed by history 3. No significant (p< 0.05) differences or interactions were di splayed for ears 10.2 to 12.7 cm produced. For non-marketable (<10.6 cm) ears produced, no interactions were displayed, while N rate was significant (p< 0.05). The highest number of non-marketable ears was produced by corn that received 0 kg N ha-1. The number of ears produ ced decreased as N rate increased, with the 2 highest N rates, 180 and 240 kg N ha-1, used on corn that produced the lowest numbers of ears. One interaction was displayed for number of total ears produced, between cropping history and N rate. This inte raction was due to conflicting tr ends in ear production. Corn in cropping history 1 fertilized at rates 0, 120, 180, and 240 kg N ha-1 produced the highest number of ears. Corn in histor y 2 fertilized at rates 0 to 180 kg N ha-1 produced

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186 lowest numbers of ears, while corn receiving 240 kg N ha-1 produced the highest number of ears. Corn in history 3, corn that received 0, 120, 180, and 240 kg N ha-1 produced highest numbers of ears. Corn fertilized at 0, 60, and 120 kg N ha-1 produced equal ears for all 3 cropping histories. Corn fertilized at 180 kg N ha-1 produced highest ears in history 3, while corn fertilized at 240 kg N ha-1 produced highest ears in history 2. Source of nitrogen was also significant (p< 0.05), with AN used on corn that produced the highest number of ears. For ear weight of fancy (>15.2 cm) ears, no interactions occu rred, while N source and N rate displayed significant (p< 0.05). Corn that received AN produced greater ear weights than corn that received lupine or vetch. Corn that received 0 and 60 kg N ha-1 produced lowest ears weights, while corn fertilized at 120 and 180 kg N ha-1 produced increased, but equal ear weights. Corn that received 240 kg N ha-1 produced the highest ear weights. No interactions or differences (p>0.05) were displaye d for ear weight of ears 12.7 to 15.2 cm or ears 10.2 to 12.7 cm in length. For ear weight of non-marketable (<10.6 cm) ears, no interactions were disp layed, while N source and N rate were significant (p< 0.05). Corn that received lupine and vetch both produced highest ear weights. Corn fertilized at rates 0 and 60 kg N ha-1 produced highest ear weights. For ear weight of total ea rs produced, differences (p< 0.05) due to N source and an interaction between cropping hi story and N rate were displa yed. The interaction was due to differing trends in ear weight producti on. Corn fertilized with AN produced the highest ear weights. Corn grown in cropping histories 1 and 3 that received 120, 180, and 240 kg N ha-1 produced highest ear weights. Corn in cropping history 2 that received 240 kg N ha-1 produced highest ear weights. Corn that was fertilized at

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187 rates 0, 60, and 120 kg N ha-1 exhibited similar trends, pr oducing equal ear weights in each cropping history. Corn fertilized at 180 and 240 kg N ha-1 produced highest ear weights in histories 2 and 3. Yield: Diagnostic Leaf for 2004 No interactions occurred for diagnostic l eaf area, while croppi ng history and N rate displayed differences (p< 0.05). Leaves from histories 2 and 3 had the largest area. Corn fertilized at rates 0 and 60 kg N ha-1 produced leaves with the smallest area, followed by corn fertilized at 60 and 120 kg N ha-1, which produced leaves w ith equal, but increased area. Finally, corn that received 120, 180, and 240 kg N ha-1 produced leaves with the largest area. For diagnostic leaf dry weight, onl y cropping history and N rate displayed significant (p< 0.05) differences. Corn grown in hist ories 2 and 3 produced leaves with the highest dry weights. Corn fe rtilized at rates 180 and 240 kg N ha-1 produced leaves with the highest dry weights. Dry weights of leaves then decreased as N rate decreased. Three interactions occurred for N concentr ation in diagnostic leaf. The first was between cropping history and N source and was due to conflicting trends in N production in diagnostic leaf. Corn grow n in cropping histories 1 and 3 followed similar trends in N production, with highest N produced with AN as an N source. Corn from history 2 produced equal N with all 3 N sources. Corn that received vetch and AN produced equal N in all 3 cropping histories. Corn grown in histories 2 and 3 th at received lupine produced highest N. The second interac tion occurred between cropping history and N rate and was due to differing trends in N production in leav es. Diagnostic leaves from histories 1 and 3 followed a similar trend, w ith N concentration remaining equal when corn received 0 to 180 kg N ha-1 and then increasing as N increased to 240 kg N ha-1. Leaves from history 2 did not follow this tre nd, increasing in N as N rate increased from

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188 0 to 180 kg N ha-1 and then decreasing at 240 kg N ha-1. Corn fertilized at rates 0, 60, 120, and 240 kg N ha-1 all followed the same trend, producing equal N in diagnostic leaves in all 3 cropping histor ies. Corn that received 180 kg N ha-1 did not follow this trend, producing equa l N in histories 1 and 2 and again in histories 1 and 3. The final interaction was between N source a nd N rate and occurred due to conflicting trends in N concentration production in di agnostic leaves. Corn fertilized with AN produced equal N in leaves at N rates 0 and 60 kg N ha-1, equal but increased N at rates 60, 120, and 180 kg N ha-1, and equal but increased N at rate 120, 180, and 240 kg N ha-1. Corn that received vetch produced equal N in leaves from N rates 0 to 180 kg N ha-1 and increased N at rates 180 and 240 kg N ha-1. Corn that received lupine produced equal N in leaves from N rates 0 to 60 kg N ha-1, equal but increased N from rates 60 to 120 kg N ha-1, and highest N at rate 180 kg N ha-1. Corn fertilized at 0 kg N ha-1 produced equal N with all 3 N sources, while corn fertilized at 60 kg N ha-1 produced equal N with lupine and vetch and lupine and AN. Corn fertilized at rates 120 and 240 kg N ha-1 exhibited similar trends, highest N produced by corn that received AN. Finally, corn fertilized at 180 kg N ha-1 produced equal and highest N concen trations with lupine and AN as N sources. Only 1 interaction was displayed for P con centration in diagnos tic leaf, in addition to significant (p< 0.05) differences due to cropping history. Corn grown in cropping histories 1 and 2 producing highest P in dia gnostic leaves. The interaction occurred between N source and N rate and was due to conflicting trends in P production in diagnostic leaves. Corn that received lupine produced equal P when fe rtilized from rates 0 to 120 kg N ha-1 and decreased, but equal P at rates 180 and 240 kg N ha-1. Corn

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189 fertilized with vetch produced equal P concen trations with all 3 N sources. Corn that received AN produced highest P at N rates 0 and 60 kg N ha-1 and lowest at rates 120, 180, and 240 kg N ha-1. Corn fertilized at rates 0 and 60 kg N ha-1 produced highest P concentrations with lupine and AN as N sources. Corn that received 120 kg N ha-1 produced highest P with lupine. Corn fertilized at rates 180 and 240 kg N ha-1 peaked in P production with vetch as an N source. Significant (p< 0.05) differences were displayed fo r K concentration in diagnostic leaf due to cropping history. Corn grown in history 2 produced highest K. One interaction also occurred in K concentration in diagnostic leaf, between N source and N rate. This interaction was due to differing trends in K produc tion in diagnostic leaves. Corn that received lupine peaked in K production at N rate 240 kg N ha-1, while corn the received vetch produced highest K at both rates 180 and 240 kg N ha-1. Corn fertilized with AN peaked in K production at rate 60 kg N ha-1. Corn that received 0 kg N ha-1 peaked in K production when lupine and vetch we re N sources. Corn fertilized at rates 60 and 120 kg N ha-1 produced equal K with all 3 N sources. Corn that received 180 and 240 kg N ha-1 produced highest K concentrations with lupine and vetch as N sources. Mineral Analysis: Soil for 2004 For N concentration in soil, an interac tion occurred between cropping history and N source, due to differing trends in N concen tration. Soil from cropping histories 1 and 3 had equal N for all N sources. Soil from hi story 2 had higher N with lupine as an N source than with either vetch or AN. Soil that had received lupine and vetch followed similar trends in N concentrations, N being highest in soil from history 2. Soil that received AN had highest N fr om histories 2 and 3.

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190 An interaction occurred for P concentra tion in soil, between cropping history and N source, due to conflicting tre nds in P concentration. Agai n, soil from cropping histories 1 and 3 followed the same trend and had equal P concentrations for all 3 N sources. Soil from history 2 had highest P with vetch and AN as N sources. Soil that received all 3 N sources followed the same trend in P con centrations, with soil from history 2 having highest P. Neither cropping history nor N source displayed significant (p>0.05) differences for K concentration in soil. Cr opping history wa s significant (p< 0.05) for Ca concentration, with soil from history 2 highest in Ca. Nitrogen source was also significant (p< 0.05), with soil that had received AN a nd lupine highest in Ca. For Mg concentration in soil, soil from history 2 ha d the highest concentra tion. Nitrogen source did not display any differences (p>0.05). Cropping history and N source displayed significant (p< 0.05) differences for soil pH. Soil from histories 2 and 3 had highest pH’s while soil that received AN as an N source also had the highest pH. An intera ction occurred for soil OM, between cropping history and N source. The soil from historie s 1 and 3 behaved sim ilarly, with equal OM from all 3 N sources. Soil from history 2 has highest OM when AN was the N source. Soil the received lupine had highest OM in histories 2 and 3, while soil that received vetch and AN had highest OM in history 2. An interaction between cropping history and N source also occurred in soil CEC. Again, soil from histories 1 and 3 behaved similarly, having equal CEC for all 3 N sources. Soil CEC was also highest in history 2 when AN was the N source. Soil that received lupine had highest CEC in histories 2 and 3, while

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191 soil that received vetch had equal CEC in all histories. Soil that received AN had highest CEC in history 2. Summary Cropping history 2 yielded the highest number of fancy (>15.2 cm) ears as well as the highest ear weight of fancy (>15.2 cm) ears in 2003, while in 2004, no difference among histories was displayed for fancy (>15.2 cm) ear production or weight. In terms of economic value, fancy (>15.2 cm) ears are the only ear size with marketable potential. Diagnostic leaves sampled in 2003 from a ll histories were not different in N concentration. An interaction for N concentr ation in diagnostic leaves occurred involving cropping history in 2004. Nitrogen is one of the most important limiting nutrients for plant growth and development. Mineral analys is of the diagnostic leaves indicated that macronutrients tested were well within, or even higher than, sufficiency ranges appropriate for sweet corn during the tasseling st age (Hochmuth, 1991; Mills and Jones, 1996). In 2003, N concentration in leaves wa s within suggested sufficiency ranges while P and K concentrations were slightly highe r than the suggested ranges when organic fertilizers were used. In 2004, N and P con centrations were within suggested ranges while K concentration was again higher than suggested ranges when applied fertilizer was organic. Soil samples taken from history 2 directly following harvest of final sweet corn crop in 2003 were highest in N concentr ation of all 3 histories. In 2004, an interaction occurred involving cropping history for N concentration of soil. In 2003, an interaction occurred for nu mber of fancy (>15.2 cm) ears produced involving N source. In 2004, AN was used on co rn that produced the highest number of fancy (>15.2 cm) ears. For both years of the study, AN-fertilized corn produced the highest fancy (>15.2 cm) weight, as well. Diagnostic leaves sampled in 2003 were

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192 highest in N concentration when corn rece ived AN. An interaction occurred for N concentration in leaves i nvolving N source in 2004. An interaction occurred involving N ra te for number of fancy (>15.2 cm) ears produced in 2003. Corn that rece ived fertilizer at 240 kg N ha-1 produced the highest number of fancy (>15.2 cm) ears in 2004. In both 2003 and 2004, corn that produced the highest ear weight for fanc y (>15.2 cm) ears produced rece ived fertilizer at 240 kg ha-1. Corn that received N at both 180 and 240 kg ha-1 produced the highest N concentrations in diagnostic leaves in 2003. In 2004, an interaction occurred i nvolving N rates for N concentration in leaves. For production of sweet corn in a notill multiple cropping system, a previous history involving cowpea and Au strian winter pea appears to be well suited. Of the cropping histories tested, the system includi ng these 2 legumes prior to sweet corn produced the most, as well as largest, marketable ears. The soil from this history also had the highest N concentration, wh ich could be due to N contri butions from the residue of the 2 consecutive legume crops planted immediat ely prior to the corn. The third cropping history also included 2 legumes grown prior to the final sweet corn, but the residue from the first crop, sunn hemp, was not left on the field, which could explain why ear production and soil health was not as high. For our tests, the inorganic fertilizer, AN, ga ve best results as an N source for sweet corn grown in a no-till multiple cropping system The organic sources, lupine and vetch, could not compete with the inorganic N at th e rates applied. The or ganic sources cannot offer the same immediate supply of N that th e AN can provide. The legumes must begin to break down in order for N to become available, whereas with the chemical

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193 formulation, N is available for crops right away. In addition, not all of the N that organic mulches contain can become av ailable; in a previous study, only a portion of the total N contained in organic legume mulches were recovered by subsequent crops (Eylands, 1984). Legume mulches have been found to cont ribute up to 50% of their N contained to a following crop (Sullivan, 2003). Although in organic fertilizers might be more economical, organic fertilizers offer benefits that inorganic fertilizers cannot. Organic fertilizers can improve soil moisture conserva tion, soil organic matter, provide other plant mineral elements, and reduce erosion in addi tion to reducing the threat of chemical leaching. The highest rates of applied N of those tested, 240 and 180 kg ha-1, produced corn with the highest yields and best production. As the applied N rate increased, production of fancy (>15.2 cm) ears also incr eased, and the production of non-marketable (<10.6 cm) ears decreased. Economically, the lower of the 2 rates, 180 kg ha-1, would be preferable if the same results can be achieved as with the higher rate. Table 6-1. Analysis of vari ance for a split-split plot e xperimental design with main treatments in a CRD experimental design. Source of variation Description df Total (1) Total for overall experiment (5*3*3*5) = 225-1= 224 Total (2) Total cropping histories (5*3) = 15-1 = 14 Main (A) Cropping histories (3-1) = 2 Error a Error main treatment (a) 12 Total (3) Total nitrogen sources (5*3*3-1-14) = 30 Sub (B) Nitrogen so urces (3-1) = 2 A* B A* B (3-1)* (3-1) = 4 Error b Error sub treatment (b) 24 Total (4) Total nitrogen rates: Total (1)-Total (2)-Total (3) = 180 Sub-sub (C) Nitrogen rate (5-1) = 4 A* C A*C (3-1)*(5-1) = 8 B* C B*C (3-1)*(5-1) = 8 A* B* C A*B*C (3-1)*(3-1)*(5-1) = 16 Error c Error sub-sub treatment (c) 144

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194Table 6-2. Statistics key to treatment m eans and interactions in sweet corn for th ree cropping histories, three sources of nit rogen, and five nitrogen rates in 2003 and 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————————Number of ears, total, m-2—————————————————— 0 h*s*r h*s*r h*s*r H*R h*s*rh*s*rh*s*r H*R h*s*r h*s*rh*s*rH*R S*R S*R S*R R 60 h*s*r h*s*r h*s*r H*R h*s*rh*s*rh*s*r H*R h*s*r h*s*rh*s*rH*R S*R S*R S*R R 120 h*s*r h*s*r h*s*r H*R h*s*rh*s*rh*s*r H*R h*s*r h*s*rh*s*rH*R S*R S*R S*R R 180 h*s*r h*s*r h*s*r H*R h*s*rh*s*rh*s*r H*R h*s*r h*s*rh*s*rH*R S*R S*R S*R R 240 h*s*r h*s*r h*s*r H*R h*s*rh*s*rh*s*r H*R h*s*r h*s*rh*s*rH*R S*R S*R S*R R X H*S H*S H*S H*S H*S H*S H*S H*S H*S S S S X X H H H H (h) = Main treatments (Cropping history, 1 to 3) S (s) = Sub treatment (Nitrogen source, 1 to 3) R (r) = Sub-sub treatment (N itrogen rate, 1 to 5) H*S = Main treatment Sub treatment inte raction (Cropping histor y Nitrogen source) H*R = Main treatment Sub-sub treatment in teraction (Cropping hi story Nitrogen rate) S*R = Sub treatment sub-sub treatment in teraction (Nitrogen source Nitrogen rate) h*s*r = Main treatment sub treatment sub-sub treatment interacti on (Cropping history Nitrog en source Nitrogen rate) †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine, VT = vetch, AN = ammonium nitrate.

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195Table 6-3. Sweet corn ears (>15.2 cm in lengt h) produced for three cropping histories, three sources of nitrogen, and five nit rogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ——————————————————Number of ears >15.2 cm m-2—————————————————— 0 1.26 0.70 0.98 0.98 1.32 0.96 1.44 1.24 0.72 0.68 0.44 0.61 1.10 0.78 0.95 0.94 50 1.14 1.06 1.80 1.33 1.56 1.64 2.70 1.97 1.36 1.02 2.00 1.46 1.35 1.24 2.17 1.59 100 2.12 1.90 1.90 1.97 1.74 2.48 3.48 2.57 1.88 1.78 4.06 2.57 1.91 2.05 3.15 2.37 150 2.34 2.12 2.34 2.27 2.88 2.56 3.84 3.09 2.34 2.46 2.80 2.53 2.52 2.38 2.99 2.63 200 2.06 2.18 4.18 2.81 3.26 2.96 4.24 3.49 3.48 2.60 4.04 3.37 2.93 2.58 4.15 3.22 X 1.78 1.59 2.24 2.15 2.12 3.14 1.96 1.71 2.67 1.96 1.81 2.68 X X 1.87 2.47 2.11 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source x N rate (highlighted) was signi ficant at p<0.05. Differences among N sources within N rates were different at p< 0.05 with LSD = 0.78. Differences among N rates within N sources were different at p< 0.05 with LSD = 0.65.

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196Table 6-4. Sweet corn ears (12.7–15.2 cm in length) produced for three cropping historie s, three sources of nitrogen, and five nitrogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears, 12.7–15.2 cm m-2—————————————————— 0 1.06 1.04 1.12 1.07 0.64 0.90 1.22 0.92 0.88 1.16 1.02 1.020.86 1.03 1.12 1.00 50 1.40 1.22 1.02 1.21 1.42 0.90 1.24 1.19 1.64 1.30 1.06 1.331.49 1.14 1.11 1.24 100 1.32 1.42 1.24 1.33 1.68 1.10 1.54 1.44 1.54 1.56 1.42 1.511.51 1.36 1.40 1.42 150 1.48 2.00 1.98 1.82 1.48 1.30 1.36 1.38 1.42 1.42 1.74 1.531.46 1.57 1.69 1.58 200 1.88 1.58 1.28 1.58 1.26 1.76 1.84 1.62 1.00 1.54 1.60 1.381.38 1.63 1.57 1.53 X 1.43 1.45 1.33 1.30 1.19 1.44 1.30 1.40 1.37 1.34 1.35 1.38 X X 1.40 1.31 1.35 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N rate (highlighted ) significant at p< 0.05 with LSD = 0.22.

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197Table 6-5. Sweet corn ears (10.2–12.7 cm in length) produced for three cropping historie s, three sources of nitrogen, and five nitrogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears, 10.2–12.7 cm m-2———————————————— 0 0.94 0.68 1.14 0.92 0.84 1.04 1.12 1.00 1.70 1.22 0.70 1.21 1.16 0.98 0.99 1.04 50 1.28 0.94 0.68 0.97 1.22 1.08 1.20 1.17 0.74 1.16 0.96 0.95 1.08 1.06 0.95 1.03 100 1.14 1.14 1.14 1.14 0.86 1.18 0.90 0.98 1.12 1.04 1.08 1.08 1.04 1.12 1.04 1.07 150 0.96 1.04 1.00 1.00 0.90 1.28 0.68 0.95 0.68 0.70 0.82 0.73 0.85 1.01 0.83 0.90 250 1.38 0.94 0.70 1.01 1.00 1.06 1.02 1.03 0.66 0.76 0.74 0.72 1.01 0.92 0.82 0.92 X 1.14 0.95 0.93 0.96 1.13 0.98 0.98 0.98 0.86 1.03 1.02 0.93 X X 1.01 1.03 0.94 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate.

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198Table 6-6. Sweet corn ears (<10.2 cm in lengt h) produced for three cropping histories, three sources of nitrogen, and five nit rogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears, <10.2 cm, m-2———————————————— 0 1.72 1.60 1.70 1.67 1.30 2.06 1.60 1.65 1.36 1.72 1.44 1.51 1.46 1.79 1.58 1.61 50 1.36 1.30 0.60 1.09 2.60 3.02 1.36 2.33 0.94 1.88 1.18 1.33 1.63 2.07 1.05 1.58 150 0.82 0.42 0.98 0.74 1.48 1.00 0.88 1.12 0.36 0.92 0.68 0.65 0.89 0.78 0.85 0.84 100 0.82 0.90 0.86 0.86 1.54 1.36 1.12 1.34 0.42 0.78 0.40 0.53 0.93 1.01 0.79 0.91 250 0.62 0.68 0.56 0.62 1.00 0.58 0.70 0.76 0.86 1.10 0.54 0.83 0.83 0.79 0.60 0.74 X 1.07 0.98 0.94 1.58 1.60 1.13 0.79 1.28 0.85 1.15 1.29 0.97 X X 1.00 1.44 0.97 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 0.30. N source (highlighted) significant at p< 0.05 with LSD = 0.24. N rate (highlighted ) significant at p< 0.05 with LSD = 0.33.

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199Table 6-7. Total sweet corn ears produced for three cropping histories, three s ources of nitrogen, and five nitrogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears, total, m-2———————————————— 0 5.04 4.02 4.94 4.67 4.10 5.00 5.38 4.83 4.64 4.82 3.56 4.34 4.59 4.61 4.63 4.61 50 5.20 4.48 4.12 4.60 6.80 6.62 6.50 6.64 4.68 5.36 5.22 5.09 5.56 5.49 5.28 5.44 100 5.40 4.84 5.22 5.15 5.78 5.76 6.76 6.10 4.88 5.28 7.28 5.81 5.35 5.29 6.42 5.69 150 5.58 6.06 6.16 5.93 6.78 6.54 7.00 6.77 4.86 5.30 5.76 5.31 5.74 5.97 6.31 6.00 200 5.98 5.42 6.66 6.02 6.48 6.32 7.80 6.87 6.04 5.96 6.90 6.30 5.17 5.90 7.12 6.40 X 5.44 4.96 5.42 6.00 6.05 6.69 5.02 5.34 5.74 5.48 5.45 5.95 X X 5.28 6.24 5.37 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) signifi cant at p<0.05 with LSD = 0.40. Cropping history x N rate (highlighted) si gnificant at p<0.05. Differences among croppi ng histories within N rates were differ ent at p< 0.05 with LSD = 1.10. Differences among N rates within cropping historie s were different at p< 0.05 with LSD = 0.75.

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200Table 6-8. Sweet corn ear (>15.2 cm in lengt h) yield for three cropping histories, three sources of nitrogen, and five nitroge n rates in 2003, Gainesville, Florida. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears >15.2 cm) ———————————————— 0 305 153 233 230 342 253 407 334 141 137 84 121 262 181 241 228 50 488 240 438 389 391 419 725 512 256 235 426 306 379 298 530 402 100 388 414 483 428 471 640 916 676 405 387 884 559 421 480 761 554 150 636 521 600 586 694 687 1003 795 484 512 703 566 605 573 769 649 200 537 543 1082 721 828 665 1031 841 787 629 787 734 717 612 967 765 X 471 374 567 454 533 817 414 380 577 477 429 654 X X 471 632 457 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) was significant at p< 0.05 with LSD = 156. N rate (highlighted) was significant at p< 0.05 with LSD = 104.

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201Table 6-9. Sweet corn ear (12.7–15.2 cm in length) yield for three cropping histories, three sources of nitrogen, and five nit rogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears 12.7–15.2 cm) ———————————————— 0 162 144 176 161 112 175 224 171 118 168 128 137 130 162 176 156 50 211 183 163 186 277 167 228 224 232 215 166 204 240 188 186 205 100 221 178 192 197 290 189 260 246 231 226 218 225 247 197 223 223 150 235 334 314 294 273 237 260 257 226 207 256 230 245 259 277 260 200 275 250 218 247 224 323 342 296 150 227 244 207 216 267 268 250 X 221 218 213 235 218 263 191 208 202 216 215 226 X X 217 239 201 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N rates (highlighted) significant at p< 0.05 with LSD = 41.

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202Table 6-10. Sweet corn ear (10.2–12.7 cm in length) yield for three cropping histories, three sources of nitrogen, and five ni trogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears 10.2–12.7 cm) ———————————————— 0 108 66 139 104 112 146 148 135 196 134 75 135 138 115 121 125 50 149 99 67 105 158 148 156 154 211 144 111 155 173 130 111 138 150 122 125 123 124 121 174 115 137 139 114 115 122 127 138 118 127 100 99 123 113 111 110 168 96 125 63 71 86 73 91 120 98 103 200 143 97 89 110 126 129 140 132 76 87 74 79 115 104 101 107 X 124 102 106 125 153 131 137 110 92 129 122 110 X X 111 137 113 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate.

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203Table 6-11. Sweet corn ear (<10.2 cm in le ngth) yield for three croppi ng histories, three sources of nitrogen, and five nitrog en rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears <10.2 cm) ———————————————— 0 89 99 108 99 128 155 107 130 97 130 97 108 105 128 104 112 50 89 87 41 72 190 250 132 191 62 141 79 94 114 159 84 118 100 56 29 69 51 130 94 72 98 28 61 52 47 71 61 64 66 150 61 67 62 63 129 125 111 122 31 55 37 41 73 82 70 75 200 41 50 43 45 90 63 69 74 60 79 41 60 63 64 51 60 X 67 66 65 133 137 98 55 93 61 85 99 75 X X 66 123 70 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 18. Cropping history x N rate (hig hlighted) significant at p< 0.05. Differences among croppi ng histories within N rates were different at p< 0.05 with LSD = 41. Differences among N rates within cropping historie s were different at p< 0.05 with LSD = 42.

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204Table 6-12. Total sweet corn ea r yield for three cropping histories, three sour ces of nitrogen, and five nitrogen rates in 200 3. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears total) ———————————————— 0 663 461 656 593 693 728 887 770 551 569 384 501 636 586 642 621 50 937 609 709 572 1015 983 1241 1080 762 735 781 759 905 776 910 864 100 786 746 866 800 1011 1097 1364 1157 802 787 1268 852 866 877 1166 970 150 1031 1043 1088 1054 1205 1217 1471 1298 803 844 1082 910 1013 1035 1214 1087 200 995 941 1431 1123 1267 1180 1582 1343 1072 1021 1146 1080 1111 1048 1387 1182 X 882 760 950 1039 1042 1309 798 791 932 906 864 1064 X X 864 1130 840 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 306. N rate (highlighted ) significant at p< 0.05 with LSD = 105.

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205Table 6-13. Diagnostic leaf (5th leaf from top) area for three cr opping histories, three sources of ni trogen, and five nitrogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Fifth leaf area leaf-1 (cm2) ———————————————— 0 426 465 480 457 523 559 555 546 483 487 480 483 477 504 505 496 50 485 485 461 477 570 582 613 588 528 535 498 521 528 534 523 529 100 545 506 480 510 621 580 676 626 545 524 574 548 571 536 577 561 150 547 519 528 531 677 639 638 652 513 517 539 523 579 559 568 569 200 533 526 534 534 616 618 645 626 545 555 566 556 565 566 585 572 X 507 500 498 602 596 625 523 523 531 544 540 552 X X 502 608 526 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 59. N rate (highlighted ) significant at p< 0.05 with LSD = 23.

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206Table 6-14. Diagnostic leaf (5th leaf from top) weight for three cropping histories, three sources of nitrogen, and five nitrogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Fifth leaf dry weight leaf-1 (g) ———————————————— 0 14.4 16.1 16.4 15.6 18.8 19.0 18.8 18.9 17.6 16.5 16.8 17.0 16.9 17.2 17.3 17.1 50 17.0 16.6 16.3 16.6 19.9 20.6 22.3 20.9 18.1 18.5 17.6 18.1 18.3 18.6 18.7 18.5 100 18.5 17.7 17.3 17.8 21.8 20.7 22.4 21.6 18.7 18.5 20.7 19.3 19.6 19.0 20.1 19.6 150 19.0 17.8 18.6 18.5 22.5 22.8 23.4 22.9 18.2 18.5 19.3 18.7 19.9 19.7 20.4 20.0 200 19.8 19.4 19.2 19.5 21.9 21.8 23.3 22.3 18.4 20.0 20.4 19.6 20.1 20.4 21.0 20.5 X 17.7 17.5 17.6 21.0 21.0 22.0 18.2 18.4 19.0 19.0 19.0 19.5 X X 17.6 21.3 18.5 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 2.1. N rates (highlighted) significant at p< 0.05 with LSD = 0.9.

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207Table 6-15. Nitrogen concentr ation of diagnostic leaf (5th leaf from top) for three cropping hist ories, three sources of nitrogen, and five nitrogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————N concentration in fifth leaf (g kg-1) ———————————————— 0 16.2 16.9 17.2 16.8 14.7 15.6 14.9 15.1 16.1 14.1 16.6 15.6 15.715.5 16.3 15.8 60 17.4 17.3 19.7 18.1 16.7 15.4 18.8 17.0 18.1 16.0 19.2 17.8 17.416.2 19.2 17.6 120 19.8 21.2 22.0 21.0 18.3 18.1 21.6 19.3 19.6 20.9 23.1 21.2 19.220.0 22.2 20.5 180 21.4 20.4 22.7 21.5 20.9 19.6 23.7 21.4 21.4 24.0 22.3 22.6 21.321.3 22.9 21.8 240 21.8 21.8 25.0 22.9 21.0 21.0 23.1 21.7 23.7 22.5 23.1 23.1 22.221.8 23.7 22.6 X 19.3 19.5 21.3 18.3 17.9 20.4 19.8 19.5 20.9 19.119.0 20.9 X X 20.1 18.9 20.1 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 1.0. N rate (highlighted ) significant at p< 0.05 with LSD = 1.0.

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208Table 6-16. Phosphorus concentr ation of diagnostic leaf (5th leaf from top) for three cropping hist ories, three sources of nitrogen, and five nitrogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————P concentration in fifth leaf (g kg-1) ———————————————— 0 4.49 4.09 4.44 4.34 4.57 4.40 4.28 4.42 3.92 3.47 3.85 3.75 4.33 3.99 4.19 4.16 50 4.41 4.19 4.34 4.31 4.22 4.19 4.46 4.29 3.92 3.40 3.72 3.68 4.18 3.93 4.17 4.09 100 4.26 4.11 4.35 4.24 4.41 4.47 4.60 4.49 3.91 3.86 3.89 3.89 4.19 4.15 4.28 4.21 150 4.36 4.12 4.28 4.25 4.43 4.37 4.67 4.49 3.89 4.14 3.95 3.99 4.23 4.21 4.30 4.24 200 4.34 4.24 3.88 4.15 4.36 4.33 4.64 4.44 3.89 3.87 3.95 3.90 4.19 4.15 4.16 4.17 X 4.37 4.15 4.26 4.40 4.35 4.53 3.91 3.75 3.87 4.22 4.08 4.22 X X 4.26 4.43 3.84 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N sources (highlighted) significant at p< 0.05 with LSD = 0.23. Cropping history x N rate (h ighlighted) significant at p< 0.05. Differences among croppi ng histories within N rates were different at p< 0.05 with LSD = 0.33. Differences among N rate s within cropping hist ories different at p< 0.05 with LSD = 0.18.

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209Table 6-17. Potassium concentration of diagnostic leaf (5th leaf from top) for three cropping hist ories, three sources of nitrogen, and five nitrogen rates in 2003. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————K concentration in fifth leaf (g kg-1) ———————————————— 0 29.2 27.5 27.5 28.1 27.6 27.3 25.4 26.8 25.3 24.0 24.9 24.7 27.4 26.3 25.9 26.5 50 29.2 28.2 28.3 28.6 26.3 27.9 26.7 27.0 26.3 25.9 26.0 26.1 27.3 27.3 27.0 27.2 100 30.5 30.9 27.1 29.6 28.9 29.1 27.0 28.3 26.1 26.4 24.4 25.6 28.5 28.8 26.2 27.8 150 29.8 31.8 27.9 29.9 27.8 29.7 25.5 27.7 26.6 29.0 24.2 26.6 28.1 30.1 25.9 28.0 200 30.7 31.0 26.7 29.5 30.7 30.6 26.8 29.4 28.2 26.5 23.6 26.1 29.9 29.3 25.7 28.3 X 29.9 29.9 27.5 28.3 28.9 26.3 26.5 26.4 24.6 28.2 28.4 26.1 X X 29.1 27.8 25.8 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 1.1. N source x N rate (highl ighted) significant at p< 0.05. Differences among N sources w ithin N rates were different at p< 0.05 with LSD = 1.2. Differences among N rates within N sources were different at p< 0.05 with LSD = 0.05.

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210 Table 6-18. Soil analysis for three cropping hi stories and three nitrogen sources in 2003. N source History 1† History 2 History 3 X ————————Mineral concentration, mg kg-1———————— N Lupine 541 719 503 588 Vetch 494 715 491 567 Amm. Nitrate 473 661 491 542 X 503 699 495 Cropping history (highlighted) significant at p< 0.05 with LSD = 117. P Lupine 61 150 71 94 Vetch 48 156 79 94 Amm. Nitrate 56 154 57 89 X 55 153 69 Cropping history (highlighted) significant at p< 0.05 with LSD = 46. K Lupine 52 77 56 61 Vetch 55 79 53 62 Amm. Nitrate 43 65 48 52 X 50 73 52 Cropping history (highlighted) significant at p< 0.05 with LSD = 21. N source (highlighted) significant at p< 0.05 with LSD = 7. Ca Lupine 641 1710 1098 1150 Vetch 610 1734 1189 1178 Amm. Nitrate 727 1660 927 1105 X 660 1701 1071 Cropping history (highlighted) significant at p< 0.05 with LSD = 371. Mg Lupine 41 58 41 47 Vetch 40 58 41 46 Amm. Nitrate 38 58 40 45 X 40 58 41 Cropping history (highlighted) significant at p< 0.05 with LSD = 11. ——————————————pH————————————— Lupine 6.2 7.0 6.9 6.7 Vetch 6.3 7.0 7.0 6.8 Amm. Nitrate 6.5 7.0 6.8 6.8 X 6.3 7.0 6.9 Cropping history x N source (h ighlighted) significant at p< 0.05. Differences among cropping histories within N sources different at p< 0.05 with LSD = 0.28. Differences among N sources with croppi ng histories different at p< 0.05 with LSD = 0.20.

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211 Table 6-18. Continued. N source History 1† History 2 History 3 X —————————————OM, g kg-1——————————— Lupine 13.7 16.1 16.6 15.5 Vetch 14.0 17.1 16.5 15.9 Amm. Nitrate 13.6 17.6 16.0 15.7 X 13.8 16.9 16.4 Cropping history (highlighted) significant at p< 0.05 with LSD = 0.13. ———————————CEC, cmol kg-1——————————— Lupine 4.97 10.24 6.75 7.32 Vetch 4.53 10.18 7.10 7.27 Amm. Nitrate 5.25 9.97 5.98 7.07 X 4.92 10.13 6.61 Cropping history (highlighted) significant at p< 0.05 with LSD = 2.0. †History 1 = sweet corn/Austrian winter pe a/sweet corn/sweet corn/Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wi nter pea/sweet corn/lima bean /Austrian winter pea/sweet Corn. History 3 = sunn hemp/Austrian winter pea/ sweet corn/sunn hemp/Austrian winter pea/sweet corn.

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212Table 6-19. Sweet corn ears (>15.2 cm in le ngth) produced for three cropping histories, three sources of nitrogen, and five ni trogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears >15.2 cm m-2———————————————— 0 1.82 1.04 1.52 1.46 1.66 2.16 2.16 1.99 1.70 1.94 2.78 2.14 1.73 1.71 2.15 1.86 60 1.68 1.92 1.74 1.78 2.32 2.66 2.72 2.57 2.06 1.84 2.48 2.13 2.02 2.14 2.31 2.16 120 1.58 2.04 3.04 2.22 2.60 2.64 3.38 2.87 2.66 2.30 3.86 2.94 2.28 2.33 3.43 2.68 180 2.28 2.42 3.08 2.59 2.50 2.72 3.26 2.83 2.86 2.68 4.64 3.39 2.55 2.61 3.66 2.94 240 2.34 2.52 3.76 2.87 3.48 3.44 4.46 3.79 2.72 3.30 5.52 3.51 2.85 3.09 4.25 3.39 X 1.94 1.99 2.63 2.51 2.72 3.20 2.40 2.41 3.66 2.28 2.38 3.16 X X 2.19 2.81 2.82 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 0.36. N rate (highlighted ) significant at p< 0.05 with LSD = 0.34.

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213Table 6-20. Sweet corn ears (12.7–15.2 cm in length) produced for three cropping historie s, three sources of nitrogen, and fiv e nitrogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears, 12.7–15.2 cm m-2———————————————— 0 1.34 1.24 1.66 1.41 0.96 1.32 1.02 1.10 1.08 0.88 0.80 0.92 1.131.15 1.16 1.14 60 1.06 0.92 1.22 1.07 0.80 1.16 1.20 1.05 0.92 0.82 1.22 0.99 0.930.97 1.21 1.04 120 1.26 1.26 1.10 1.21 0.76 0.94 1.22 0.97 0.92 0.90 1.02 0.95 0.981.03 1.11 1.04 180 1.18 1.08 1.44 1.23 0.98 0.84 1.14 0.99 1.42 1.02 0.94 1.13 1.190.98 1.17 1.12 240 1.54 1.10 1.06 1.23 1.04 1.20 1.54 1.26 0.84 0.66 1.00 0.83 1.140.99 1.20 1.11 X 1.28 1.12 1.30 0.91 1.09 1.22 1.04 0.86 1.00 1.071.02 1.17 X X 1.23 1.08 0.96 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 0.20.

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214Table 6-21. Sweet corn ears (10.2–12.7 cm in length) produced for three cropping historie s, three sources of nitrogen, and fiv e nitrogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears, 10.2–12.7 cm, m-2———————————————— 0 0.98 0.86 0.90 0.91 0.62 0.78 0.96 0.79 0.62 0.82 0.70 0.71 0.740.82 0.85 0.80 60 0.64 0.84 0.84 0.77 0.76 0.46 0.68 0.63 0.52 0.86 0.84 0.74 0.640.72 0.79 0.71 120 0.74 0.76 0.88 0.79 0.58 0.74 0.70 0.67 0.70 0.50 0.48 0.56 0.670.67 0.68 0.68 180 0.66 0.52 0.38 0.52 0.62 0.70 0.70 0.67 1.02 0.64 0.46 0.71 0.770.62 0.51 0.63 240 0.78 0.74 0.74 0.75 0.50 0.74 0.72 0.65 0.28 0.60 0.60 0.49 0.520.69 0.69 0.63 X 0.76 0.74 0.75 0.62 0.68 0.75 0.63 0.68 0.62 0.670.70 0.71 X X 0.75 0.68 0.64 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate.

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215Table 6-22. Sweet corn ears (<10.2 cm in le ngth) produced for three cropping histories, three sources of nitrogen, and five ni trogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears, <10.2 cm, m-2———————————————— 0 1.30 1.36 1.50 1.39 1.80 1.28 1.18 1.42 1.64 1.96 1.78 1.79 1.58 1.53 1.49 1.53 60 1.56 1.40 1.10 1.35 1.08 1.20 1.16 1.15 1.66 1.86 0.94 1.49 1.43 1.49 1.07 1.33 120 1.14 1.44 0.92 1.17 0.90 0.52 0.56 0.66 1.54 1.78 0.76 1.36 1.19 1.25 0.75 1.06 180 0.26 1.06 0.86 0.73 0.74 0.96 0.70 0.80 0.98 1.14 0.44 0.85 0.66 1.05 0.67 0.79 240 0.50 0.84 0.90 0.75 0.70 0.86 0.68 0.75 1.32 0.80 0.34 0.82 0.84 0.83 0.64 0.77 X 0.95 1.22 1.06 1.04 0.96 0.86 1.43 1.51 0.85 1.14 1.23 0.92 X X 1.08 0.96 1.26 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 0.07.

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216Table 6-23. Total sweet corn ea rs produced for three cropping histories, three sources of nitrogen, a nd five nitrogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Number of ears, total, m-2———————————————— 0 5.42 4.50 5.60 5.17 5.06 5.56 5.34 5.32 5.08 5.58 6.06 5.57 5.19 5.21 5.67 5.36 60 4.98 5.04 4.92 4.98 4.94 5.48 5.80 5.41 5.20 5.40 5.46 5.35 5.04 5.31 5.39 5.25 120 4.72 5.52 5.94 5.39 4.82 4.82 5.88 5.17 5.84 5.46 6.12 5.81 5.13 5.27 5.98 5.46 180 4.40 5.10 5.74 5.08 4.78 5.24 5.78 5.27 6.32 5.42 6.50 6.08 5.17 5.25 6.01 5.48 240 5.14 5.22 6.50 5.62 5.72 6.24 7.42 6.46 5.12 5.36 6.46 5.65 5.33 5.61 6.79 5.91 X 4.93 7.08 5.74 5.06 5.47 6.04 5.51 5.44 6.12 5.17 5.33 5.97 X X 5.25 5.53 5.69 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 0.40. Cropping history x N rate (hig hlighted) significant at p< 0.05. Differences among crop ping histories within N rates different at p< 0.05 with LSD = 0.77. Differences among N ra tes within cropping histories different at p< 0.05 with LSD = 0.55.

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217Table 6-24. Sweet corn ear (>15.2 cm in le ngth) yield for three croppi ng histories, three sources of nitrogen, and five nitrog en rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears >15.2 cm) ———————————————— 0 474 216 364 351 404 504 514 474 438 435 553 475 439 385 477 433 60 396 423 431 417 560 648 664 624 523 433 605 520 493 501 567 520 120 367 497 732 532 639 674 811 708 697 592 1011766 568 588 851 669 180 580 560 564 568 692 741 787 740 727 702 1308913 666 668 887 740 240 453 605 911 565 937 932 1227 1032 705 882 1247645 699 806 1128 878 X 454 460 600 646 700 801 618 609 945 573 590 782 X X 504 716 724 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 96. N rate (highlighted ) significant at p< 0.05 with LSD = 105.

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218Table 6-25. Sweet corn ear (12.7–15.2 cm in length) yield for three cropping histories, three sources of nitrogen, and five ni trogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears 12.7–15.2 cm) ———————————————— 0 174 161 228 188 135 199 146 160 161 122 120 135 157 161 165 161 60 166 108 189 155 117 179 176 157 136 111 176 141 140 133 180 151 120 182 181 144 169 117 133 194 148 150 145 161 152 150 153 166 156 180 167 136 190 164 171 128 169 156 218 154 135 169 185 139 164 163 240 206 155 144 168 165 173 245 194 124 99 159 127 165 142 182 163 X 179 148 179 141 162 186 158 126 150 159 146 172 X X 169 163 145 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate.

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219Table 6-26. Sweet corn ear (10.2–12.7 cm in length) yield for three cropping histories, three sources of nitrogen, and five ni trogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears 10.2–12.7 cm) ———————————————— 0 102 90 85 92 66 97 97 87 74 86 79 80 81 91 87 86 60 157 79 80 105 87 50 73 70 60 96 98 85 101 75 84 86 120 136 266 83 162 64 76 83 74 82 58 52 64 94 133 73 100 180 65 47 41 51 59 82 76 72 118 73 52 81 81 68 57 68 240 68 74 74 72 56 88 86 77 33 67 63 54 52 76 75 68 X 106 111 73 66 79 83 73 76 69 82 89 75 X X 97 76 73 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate.

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220Table 6-27. Sweet corn ear (<10.2 cm in le ngth) yield for three croppi ng histories, three sources of nitrogen, and five nitrog en rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears <10.2 cm)———————————————— 0 80 62 90 77 119 91 72 94 88 133 118 113 96 95 93 95 60 87 86 63 79 63 85 83 77 117 121 65 101 89 98 71 86 120 77 87 52 72 62 37 40 46 98 130 63 97 79 85 52 72 180 35 66 50 51 48 64 49 54 68 83 32 61 51 71 44 55 240 28 59 51 46 56 71 44 57 99 59 22 60 61 63 39 54 X 61 72 61 69 70 57 94 105 60 75 82 60 X X 65 66 87 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 15. N rates (highlighted ) significant at p< 0.05 with LSD = 16.

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221Table 6-28. Total sweet corn ea r yield for three cropping histories, three sour ces of nitrogen, and five nitrogen rates in 200 4. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Ear weight, g m-2 (Ears total) ———————————————— 0 826 529 767 708 724 891 828 814 761 776 870 802 771 732 821 775 60 806 696 763 755 827 962 996 928 835 760 945 847 823 806 901 843 120 762 1031 1011 935 882 920 1128 977 1026 925 1287 1079 890 959 1142 997 180 847 809 845 834 969 1015 1081 1022 1132 1011 1528 1224 982 945 1151 1026 240 755 893 1179 942 1214 1263 1602 1360 962 1107 1491 1187 977 1088 1424 1163 X 800 792 913 923 1010 1127 943 916 1124 889 906 1088 X X 835 1020 1028 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. N source (highlighted) significant at p< 0.05 with LSD = 87. Cropping history x N rate (h ighlighted) significant at p< 0.05. Differences among crop ping histories within N rates different at p< 0.05 with LSD = 285. Differences among N ra tes within cropping histories different at p< 0.05 with LSD = 172.

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222Table 6-29. Diagnostic leaf (5th leaf from top) area for three cr opping histories, three sources of ni trogen, and five nitrogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Fifth leaf area leaf-1 (cm3) ———————————————— 0 574 395 408 459 445 484 477 469 461 476 527 488 493 452 471 472 60 475 415 465 452 481 524 501 502 521 513 523 519 492 484 497 491 120 443 521 482 482 508 514 506 509 525 513 539 526 492 516 509 506 180 505 482 484 490 547 537 481 521 543 528 549 540 531 516 505 517 240 474 513 470 486 550 631 528 536 532 536 557 542 519 527 518 521 X 494 465 462 506 518 499 517 513 539 506 499 500 X X 474 508 523 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 34. N rate (highlighted ) significant at p< 0.05 with LSD = 23.

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223Table 6-30. Diagnostic leaf (5th leaf from top) weight for three cropping histories, three sources of nitrogen, and five nitrogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————Fifth leaf dry weight leaf-1 (g) ———————————————— 0 13.1 11.4 11.6 12.1 12.9 14.9 14.2 14.0 12.7 15.0 16.8 14.9 13.0 13.8 14.2 13.6 60 13.5 12.4 14.9 13.6 14.6 16.2 16.2 15.7 15.8 16.2 16.9 16.3 14.6 14.9 16.0 15.2 120 13.6 16.6 14.4 14.8 16.5 16.2 16.7 16.5 16.7 16.7 18.0 17.1 15.6 16.5 16.4 16.1 180 15.2 15.6 15.0 15.3 17.4 18.1 16.8 17.5 17.0 18.3 18.1 17.8 16.5 17.3 16.7 16.8 240 15.7 15.3 14.3 15.1 18.3 18.1 17.4 18.0 17.8 18.7 18.8 18.5 17.3 17.4 16.9 17.2 X 14.2 14.2 14.0 16.0 16.7 16.3 16.0 17.0 17.7 15.4 16.0 16.0 X X 14.2 16.3 16.9 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 1.1. N rate (highlighted ) significant at p< 0.05 with LSD = 0.6.

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224Table 6-31. Nitrogen concentr ation of diagnostic leaf (5th leaf from top) for three cropping hist ories, three sources of nitrogen, and five nitrogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————N concentration in fifth leaf (g kg-1) ———————————————— 0 18.2 20.6 20.4 19.8 17.1 18.9 19.4 18.5 18.9 18.7 19.3 19.0 18.1 19.4 19.7 19.1 60 18.5 18.8 22.5 20.0 21.2 19.7 22.4 21.1 19.8 19.0 20.5 19.8 19.8 19.2 21.8 20.3 120 18.9 21.3 25.1 21.8 23.1 20.7 22.6 22.1 19.4 16.0 22.3 19.2 20.5 19.3 23.3 21.1 180 20.5 22.5 24.9 22.6 31.9 21.9 23.2 25.6 20.7 19.6 24.1 21.4 24.3 21.3 24.1 23.2 240 21.3 24.1 28.6 24.7 18.9 22.7 24.3 22.0 21.9 21.6 24.1 22.5 20.7 22.8 25.7 23.1 X 19.5 21.5 24.3 22.4 20.8 22.4 20.1 19.0 22.1 20.7 20.4 22.9 X X 21.8 21.9 20.4 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history x N source (h ighlighted) significant at p< 0.05. Differences among cr opping histories among N s ources different at p< 0.05 with LSD = 2.6. Differences among N sour ces within cropping histories different at p< 0.05 with LSD = 2.0. Cropping history x N rate (h ighlighted) significant at p< 0.05. Differences among crop ping histories within N rates different at p< 0.05 with LSD = 3.0. Differences among N rate s within cropping histories different at p< 0.05 with LSD = 2.5. N source x N rate (highl ighted) significant at p< 0.05. Differences among N sources within N rates different at p< 0.05 with LSD 2.5. Differences among N rates wi thin N sources different at p< 0.05 with LSD = 2.5.

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225Table 6-32. Phosphorus concentr ation of diagnostic leaf (5th leaf from top) for three cropping hist ories, three sources of nitrogen, and five nitrogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————P concentration in fifth leaf (g kg-1) ———————————————— 0 4.2 3.9 4.1 4.0 4.4 4.4 4.5 4.4 3.9 3.7 4.1 3.9 4.1 4.0 4.2 4.1 60 4.0 3.8 4.1 4.0 4.6 4.3 4.3 4.4 4.1 3.7 3.9 3.9 4.2 4.0 4.1 4.1 120 4.3 3.7 3.8 3.9 4.3 4.4 3.9 4.2 3.8 3.9 3.8 3.8 4.2 4.0 3.8 4.0 180 4.0 4.1 3.9 4.0 4.2 4.2 4.1 4.1 3.6 3.9 3.6 3.7 4.0 4.1 3.9 4.0 240 3.9 4.2 3.9 4.0 4.2 4.4 3.9 4.2 3.8 3.7 3.6 3.7 4.0 4.1 3.8 4.0 X 4.1 3.9 4.0 4.3 4.3 4.1 3.9 3.8 3.8 4.1 4.0 4.0 X X 4.0 4.3 3.8 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 0.03. N source x N rate (highl ighted) significant at p< 0.05. Differences among N sources within N rates different at p< 0.05 with LSD = 0.19. Differences among N ra tes within N sources different at p< 0.05 with LSD = 0.20.

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226Table 6-33. Potassium concentration of diagnostic leaf (5th leaf from top) for three cropping hist ories, three sources of nitrogen, and five nitrogen rates in 2004. Cropping history 1† Cropping hi story 2 Cropping history 3 Cropping history X ——N source—— ——N source—— ——N source—— ——N source—— N rate LP‡ VT AN X LP VT AN X LP VT AN X LP VT AN X Kg ha-1 ————————————————K concentration in fifth leaf (g kg-1) ———————————————— 0 24.4 25.5 27.5 25.8 28.6 30.5 31.0 30.0 23.6 24.1 26.3 24.6 25.5 26.7 28.3 26.8 60 25.5 28.3 29.6 27.8 33.0 32.3 32.7 32.7 26.8 26.4 27.2 26.8 28.4 29.0 29.9 29.1 120 28.4 27.2 29.7 28.5 33.7 33.9 28.0 31.9 27.7 27.4 26.1 27.0 29.9 29.5 27.9 29.1 180 29.0 33.1 29.5 30.5 34.1 30.9 28.5 31.2 27.4 33.0 25.8 28.7 30.2 32.4 27.9 30.1 240 31.3 32.1 27.5 30.3 37.3 36.5 27.5 33.8 30.6 30.8 23.8 28.4 33.0 33.1 26.3 30.8 X 27.7 29.2 28.8 33.3 32.8 29.5 27.2 28.3 25.8 29.4 30.1 28.1 X X 28.6 31.9 27.1 †History 1 = sweet corn/Austrian winter pea/sweet corn/sweet corn /Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wint er pea/sweet corn/lima bean/Aus trian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/sweet corn/sunn hemp/Austrian winter pea/sweet corn. ‡LP = lupine; VT = vetch; AN = ammonium nitrate. Cropping history (highlighted) significant at p< 0.05 with LSD = 0.8. N source x N rate (highl ighted) significant at p< 0.05. Differences among N sources within N rates different at p< 0.05 with LSD = 2.7. Differences among N ra tes within N sources different at p< 0.05 with LSD = 2.6.

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227 Table 6-34. Soil analysis for three cropping hi stories and three nitrogen sources in 2004. N source History 1† History 2 History 3 X ————————Mineral concentration, mg kg-1———————— N Lupine 468 754 548 590 Vetch 510 685 541 579 Amm. nitrate 469 670 557 565 X 483 703 548 Cropping history x N source (h ighlighted) significant at p< 0.05. Differences among cropping histories within N sources different at p< 0.05 with LSD = 120. Differences among N sources within cr opping histories different at p< 0.05 with LSD = 58. P Lupine 75 155 75 102 Vetch 74 161 66 100 Amm. nitrate 59 181 79 106 X 69 166 73 Cropping history x N source (h ighlighted) significant at p< 0.05. Differences among cropping histories within N sources different at p< 0.05 with LSD = 43. Differences among N sources within cr opping histories different at p< 0.05 with LSD = 24. K Lupine 47 50 45 47 Vetch 36 48 41 42 Amm. Nitrate 35 51 35 41 X 39 50 40 Ca Lupine 705 1501 870 1025 Vetch 733 1281 801 938 Amm. Nitrate 692 1963 930 1195 X 710 1582 867 Cropping history (highlighted) significant at p< 0.05 with LSD = 540. N source (highlighted) significant at p< 0.05 with LSD = 201. Ma Lupine 60 82 65 69 Vetch 53 87 61 67 Amm. Nitrate 53 91 63 69 X 55 87 63 Cropping history (highlighted) significant at p< 0.05 with LSD = 17. —————————————pH—————————————— Lupine 6.8 7.3 7.2 7.1 Vetch 6.8 7.3 7.2 7.1 Amm. Nitrate 7.0 7.2 7.4 7.2 X 6.9 7.3 7.3 Cropping history (highlighted) significant at p< 0.05 with LSD = 0.1. N source (highlighted) significant at p< 0.05 with LSD = <0.1.

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228 Table 6-34. Continued. N source History 1† History 2 History 3 X ——————————OM, g kg-1—————————————— Lupine 1.24 1.59 1.45 1.43 Vetch 1.30 1.67 1.51 1.49 Amm. Nitrate 1.21 1.81 1.48 1.50 X 1.25 1.69 1.48 Cropping history x N source (h ighlighted) significant at p< 0.05. Differences among cropping histories within N sources different at p< 0.05 with LSD = 0.15. Differences among N sources within cr opping histories different at p< 0.05 with LSD = 0.12. ———————————CEC, cmol kg-1——————————— Lupine 5.17 9.03 6.27 6.82 Vetch 5.06 7.98 5.77 6.27 Amm. Nitrate 4.73 11.63 6.46 7.61 X 4.99 9.55 6.17 Cropping history x N source (h ighlighted) significant at p< 0.05. Differences among cropping histories within N sources different at p< 0.05 with LSD = 3.2. Differences among N sources within cr opping histories different at p< 0.05 with LSD = 1.8. †History 1 = sweet corn/Austrian winter pe a/sweet corn/sweet corn/Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wi nter pea/sweet corn/lima bean /Austrian winter pea/sweet Corn. History 3 = sunn hemp/Austrian winter pea/ sweet corn/sunn hemp/Austrian winter pea/sweet corn.

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229 CHAPTER 7 PLANT-PARASITIC NEMATODE POPULA TION CHANGES ASSOCIATED WITH CROPPING HISTORIES Introduction One way in which sustainable agriculture can be achieved is by utilizing several available management practices that benefit the environment. Not only can the practice of multiple cropping benefit the environmen t in improving soil and crop fertility and many other aspects, it can also be a very e ffective tool in nematode management. The concept of a cropping system is particularly useful in nematode control because it includes not only crop rotation, but also other critical features that can affect nematode populations, such as continuous monocultu re, continuous cropping, non-crop periods, season, weeds, and spatial arrangement of cr ops (McSorley, 2001). Multiple cropping as a means of nematode control is also consid ered a viable option due to the decline of nematicide-based technologies as of late. Several plant-parasitic nematodes are serious and endemic problems in the production of many crops grown in the sout heastern United States (McSorley and Gallaher, 1991). Root-knot nematodes (Meloidogyne spp.) have been identified as the key nematode pests in many cropping systems in north and central Florida (McSorley and Gallaher, 1991). Multiple cropping can aid in reducing nematode numbers, while the limitations of a 1 cover crop rotation cycle ar e the resurgence of ne matode populations at the end of the subsequent crops prone to ne matode damage (McSorley, 1999). Nematode populations, particularly plant-parasitic nemat odes, will rise or fall in a site depending on

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230 the sequence of crops planted (McSorley a nd Gallaher, 1992). The design of cropping sequences that can minimize plant-parasitic nematode buildup and damage has received increased interest (McSorley and Gallah er, 1992; Noe, 1988) due to the success of rotating crops for the management of nematodes in the southeastern U.S. (Johnson, 1982). The rotation or sequence of crops in multip le cropping can determine the severity of nematode problems in subsequent crops. Some crops are good hosts to nematodes and can increase populations while others are pr oven suppressors a nd can bring numbers down. In order to plan effective and profita ble systems, it is very important that the effects of different crops, as well as cropping histories, on the population densities of plant-parasitic nematodes are determined. Corn (Zea mays L.) is an important grain and forage crop adapted to cropping systems in the southeast region of the U.S. (Gallaher and Horner, 1983), therefore its effect on nematode populations is very per tinent information. Cultivars of field, sweet, and tropical corn have been found to be good hosts for many different species of nematodes. In a study conducted in north Fl orida, plant-parasiti c nematode populations, including M. incognita (Kofoid & White) Chitwood and Pratylenchus spp., increased more than tenfold during the growth period of several corn cultivars (Gallaher et al., 1991). In another experiment that took place in Florida, populations of both M. incognita and Criconemella spp. nematodes increased greatly on summer crops of corn (McSorley and Gallaher, 1992). Corn, a lthough apparently tolerant of some M. incognita infection (McSorley and Gallaher, 1991), w ill increase rather than decrease nematode populations when used as a cover crop or rota tion crop (McSorley and Gallaher, 1992).

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231 Another crop that is well adapted for use in cropping systems in the South is cowpea (Vigna unguiculata [L.] Walp.). Cowpea has been shown to be an effective cover crop for plant-parasitic nematode mana gement (McSorley and Gallaher, 1992), but the effect depends on cowpea cultivar. Some cultivars of this legume are known to be suppressive to plant-parasiti c nematodes (‘Iron Clay’) while others have proven to be very susceptible to nematode damage (‘Wh ite Acre’). In a study conducted in north Florida, ‘Iron Clay’ performed as well as sunn hemp (Crotalaria juncea L.) and other summer crops in reducing M. incognita as compared to a corn crop (Wang et al., 2002a). During an experiment conducted in summer of 2001, ‘Iron Clay’ cowpea suppressed M. incognita to a level equal to that in fa llow soil (Wang et al., 2003). A field experiment conducted on sandy soils in Florida resulted in the lowest population densities of M. incognita following cultivars ‘California Bl ackeye #5’ and ‘Mississippi Silver’ (Gallaher and McSorely, 1993). If an appropr iate cultivar were selected, cowpea would be a very beneficial addition to a cropping system because of its nematode management properties, as well as its ability to improve available N. An additional legume that is often used in crop rotations is lima bean (Phaseolus lunatus L.). As a legume, lima bean can bring the benefit of N improvement to a cropping system, but the effect of this crop on nematode levels must also be taken into consideration. In a field test conduc ted in Florida, lima bean had very high population densities (average of 338 100 cm-3 of soil) of M. incognita at harvest compared to cowpea and turnip (Brassica rapa L.) (Wang et al., 2003). Similar findings from other studies support the conclusion that lima bean is very susceptible to M. incognita, which is the key nematode pest in Florida cropping systems.

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232 Sunn hemp is a legume that is receiving increased attention due to its efficient green manure properties, its ab ility to fix N, its rapid pr oduction of biomass, and its capabilities to suppress several different type s of plant-parasitic nematodes (Marshall, 2002; Wang et al ., 2002b). Suppression of pl ant-parasitic nematodes by Crotalaria spp. has been known for decades (Huang et al., 1981), but recently, several studies demonstrated that sunn hemp suppressed Meloidogyne spp. better than nematicides, because it continued to suppre ss the nematode population development after a host was planted (Wang et al., 2002b). In several studies conducted in Florid a, M. incognita populations were found to be lower by as much as 47% on vegetable crops fertilized with sunn hemp as opposed to those fertilized with ammonium nitrate (NH4NO3) (Marshall, 2002). Sunn hemp has proven to be a poor hos t to many important plant-parasitic nematodes, by producing an allelopathic co mpound that is toxic to nematodes and by enhancing nematode-antagonistic mi croorganisms (Wang et al., 2002b). Crotalaria spp., including sunn hemp, also contain monocro taline, which is a substance known to suppress root-knot and other plant-pa rasitic nematode infestations (Rodriguez-Kabana et al., 1992; Marshall, 2002 ). Sunn hemp would be an excellent candidate for plant-para sitic nematode control in cropping systems. In order to investigate th e effects of specified cropping histories on nematode communities, a 2-yr experiment was conducted at the University of Florida. Nematode populations were examined after several di fferent cropping histor ies were completed, each taking place over the course of 1 year. Our objective was to determine which cropping histories resulted in low nematode population densities. Our null hypothesis

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233 was that year and the various cropping histor ies would not have any effect on nematode populations. Materials and Methods This study took place from August 2002 to June 2004 in Gainesville, FL on a loamy siliceous semiactive hyperthermic Gr ossarenic Paleodults (USDA-NRCS, 2003). Nematode Populations Following Final Sweet Corn, 2003 and 2004 A split-plot experimental design was us ed to examine nematode populations following the final sweet corn crop of each year of the study. Main effects, analyzed as a completely randomized design (CRD), were 3 different multiple cropping histories (histories 1, 2, and 3) that were grown during th e first year of the te st and then repeated during the second. History 1 consisted of sw eet corn followed by Austrian winter pea (Pisum arvense L.), and then sweet corn in 2003, and the same multiple cropping sequence repeated in 2004. History 2 consis ted of cowpea followed by Austrian winter pea and then sweet corn in 2003, and lima bean followed by Austrian winter pea and then sweet corn in 2004. History 3 consisted of sunn hemp followed by Austrian winter pea followed by sweet corn in 2003, and the same multiple cropping sequence repeated again in 2004. The sub-effects were 3 different N sources [lupine (Lupinus angustifolius L.), vetch (Vicia villosa [L.] Roth), and ammoni um nitrate (AN)] used on the final sweet corn crop in the 3 cropping histories each year. Data from each year were analyzed by analysis of variance (ANOVA). Pi and Pf Nematode Populations for Final Sweet Corn, 2003 and 2004 A CRD was used to examine nematode popul ations directly before and after the final sweet corn crop for each year of the 2 yr study. This study examined populations of nematodes before (Pi) planting the sweet corn and at the end (Pf) of the sweet corn crop.

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234 The three cropping histories described above we re the treatments. Data from each year were analyzed separately by ANOVA. Pi and Pf Nematode Populations for Austrian Winter Pea, 2003 and 2004 A CRD was also used to examine Pi and Pf of nematodes associated with the Austrian winter pea crop for each year of the study. Cropping histories were again the treatments as described above. Data from each year were analyzed separately by ANOVA. Nematode Analysis Nematode population information was ascertai ned by collecting 6 soil cores (2.5 cm diameter x 20 cm deep) obtained from each subplot (history x N source test) or main plot (Pi/Pf studies on fina l sweet corn crop or Austrian winter pea crop) of the test area. The 6 soil cores comprising each sample were mixed, and nematodes were extracted from 100 cm3 of soil from each of the samples using a modified sieving and centrifugal-flotation method (Jenkins, 1964). Nematodes were identified and counted, and populations for each genus were s ubjected to statistical analysis. Statistical Analysis Nematode data was recorded in Quattr o Pro (Anonymous, 1987) spreadsheets and transferred to MSTAT 4.0 (Anonymous, 1985) for analysis of variance (ANOVA) with the appropriate model for the experimental design. Numbers were compared using ANOVA followed by mean separation using LS D (Gomez and Gomez, 1984). Analysis of variance tables giving brea kdown of df and level of si gnificance for each variable tested is given in Tables 7-1 to 7-3.

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235 Results Nematode Populations Following Final Sweet Corn, 2003 and 2004 When examining nematode populations following each year of the cropping history experiment on the final sweet corn, no in teractions between cropping history and N source occurred for any of the nematode popul ations in either 2003 or 2004 (Table 7-4). Statistical (p< 0.10 in 2003 and p< 0.05 in 2004) differences were found among cropping histories for root-knot (Meloidogyne spp.) nematodes, which were most abundant in history 2 and least in hist ory 3 in 2004, but no differences occurred among N sources (Table 7-4). No significant di fferences were found for spiral (Helicotylenchus spp.) populations in either 2003 or 2004 (Table 7-4). Stubby-root (Paratrichodorus spp.) numbers were highest in histor y 2 (significantly different at p< 0.05) in 2003, and in 2004, both cropping history an d N source affected (p< 0.05) stubby-root nematode numbers (Table 7-4). Lesion nematode (Pratylenchus spp.) numbers were highest (p< 0.05) in history 1 in both years but N source was not significantly di fferent in either 2003 or 2004 (Table 7-4). Ring nematode (Criconemella spp.) populations were consistently most abundant in cropping history 1, but were unaffected by N sources (Table 7-4) in both 2003 and 2004. Pi and Pf Nematode Populations for Final Sweet Corn, 2003 and 2004 When the Pi and Pf nematodes associated with the final sweet corn crop of 2003 and 2004 were examined, root knot did not display any significant (p< 0.05) differences among cropping histories for Pi but was significantly different (p< 0.10) for Pf in 2003 (Table 7-5). In 2004, both the populations prio r to and following the corn were greatest (p< 0.001) in cropping history two and least (p< 0.001) in history 3 (Table 7-5). The only significant (p< 0.05) differences among cr opping histories displaye d by spiral nematode

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236 populations for 2003 and 2004 were those prior to the sweet corn crop (p< 0.05) or following sweet corn crop (p< 0.10) in 2003 (Table 7-5). Stubby-root nematodes were most abundant (p< 0.05) in history 1 prior to planting sweet corn in 2003, but were most abundant (p< 0.05) in history 2 and least abundant (p< 0.05) in history 1 following sweet corn in both years (Table 7-5). Again, both lesion and ring nematode populations displayed significant (p< 0.05) differences among cropping histories prior to and following the sweet corn crop in both 2003 and 2004, with highest numbers consistently present in history 1 (Table 7-5). Pi and Pf Nematode Populations for Austrian Winter Pea, 2003 and 2004 During the examination of nematode populati ons directly prior to and following the Austrian winter pea crop in 2003 and 2004, root-knot nematode numbers differed (p< 0.05) among cropping histories prior to planting. They remained highest (p< 0.001) in cropping history 2, following harvest in 2004, bu t not in 2003 (Table 7-6). Spiral nematode populations prior to and following harvest were greatest (p< 0.05) in cropping history 1 in 2003, but no significant (p< 0.05) differences were found in 2004 (Table 7-6). Stubby root nematodes we re always greatest (p< 0.05) in cropping history 1 and least (p< 0.10) in cropping history 3, both prior to and after the Au strian winter pea crop (Table 7-6). Both lesion and ring nema tode populations were more abundant (p< 0.05) in cropping history 1 than in histories 2 and 3 both prior to and following the Austrian winter pea crop in 2003 and 2004 (Table 7-6). Discussion and Conclusion Of the nematodes sampled, root-knot was not only the most prevalent but is also known to be the most problematic. Meloidogyne spp. can cause major damage to almost any vegetable crop and are considered to be the key nematode pest in crop production.

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237 Root-knot nematodes are so widespread in tropical and subtropical crop production that frequently they are taken to represent “n ematodes” in general and other economically important species are often ove rlooked (Netscher, 1990). The hypothesis that year and cropping history would not affect nematode populations cannot be supported. The 2 different years did have an effect on nematode numbers. The 2 yr of cropping histories e ach had different influences. The cropping systems grown in 2004 had the influence of the same cropping histories from the year prior. The systems from 2003 did not have th is influence. When cropping histories were examined, history 3, the cropping system u tilizing sunn hemp, was found to decrease root-knot nematode populations drastica lly, especially in 2004, after the cropping histories had been grown successively for 2 yr. The data indicate that to gain optimum nematode control benefits from this crop, at least 2 successive years of sunn hemp should be planted. A single crop of this plant can reduce nematodes (Wang, 2002b), but was not found to have such great effect on the samp led populations in the current study. Spiral nematode populations tend to build up during the growth of field corn, and similar effects could be expected on sweet corn, but numbers proved inconsistent. Stubby root numbers had increased by the end of the second year possibly because the plants of the second year were healthier and coul d sustain higher numbers of ne matodes. Lesion nematodes were basically unaffected over both years and ring nematodes, which also tend to build up on corn crops, built up in history 1 (sweet corn) during both years. When the final sweet corn crop was exam ined, the strong effects of the cropping histories and specifically sweet corn, were again apparent. After 2004 and 2 yr of the cropping systems, sweet corn consistently increased root-knot nematode numbers,

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238 proving to be a good host. Populations of spiral and stubby root nematodes were inconsistent. Ring nematodes incr eased in 2003, but decreased in 2004. When the effect of the winter crop, Austri an winter pea, was examined, root-knot nematodes were again affected greatly by s unn hemp. The history including sunn hemp, history 3, was seen to result in the lowest numbers of root-knot nematodes in both 2003 and 2004. Austrian winter pea was also found to decrease nematode numbers, which is important information, since not many winter legumes are known to do so. History 1 had the highest nematode count s for almost every nematode sampled, again displaying the effect of sweet corn and it s ability to build up nematodes. Spiral and stubby root numbers were inc onsistent. Lesion and ring num bers were extremely low, except in cropping history 1, demonstrating the ability of sweet corn to increase these nematodes. In summary, year effects were inconsis tent while cropping hi story effects were consistent. Also, any effect of the various N sources proved inconsistent. Sunn hemp and Austrian winter pea were found to decrease the most important and damaging nematode, root-knot, while sweet corn was found to increase its numbers. Also, sunn hemp (summer/fall) and Austrian winter pea (winter) growing seasons encompass 2 different times in the year. This equates to both warm and cool season suppression, or 2 seasons of nematode control.

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239 Table 7-1. Nematodes following spring plante d sweet corn for three cropping histories and three nitrogen sources analysis of variance. Source of variation df 2003 2004 —————————Root-knot———————— Cropping history (CH) 2 + *** Error A 12— — N source (NS) 2 ns† ns CH x NS 4 ns ns Error B 24— — Total 44— — ————————Spiral———————— Cropping history (CH) 2 ns ns Error A 12— — N source (NS) 2 ns ns CH x NS 4 ns ns Error B 24— — Total 44— — ————————Stubby-root———————— Cropping history (CH) 2 *** Error A 12— — N source (NS) 2 ns *** CH x NS 4 ns ns Error B 24— — Total 44— — ————————Lesion———————— Cropping history (CH) 2 *** Error A 12— — N source (NS) 2 ns ns CH x NS 4 ns ns Error B 24— — Total 44— — ————————Ring———————— Cropping history (CH) 2 *** *** Error A 12— — N source (NS) 2 ns ns CH x NS 4 ns ns Error B 24— — Total 14— — + Significant at the 0.10 level. Significant at the 0.01 level. ** Significant at the 0.05 level. *** Significant at the 0.001 level. †ns = not significant.

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240 Table 7-2. Analysis of variance for nema todes prior to and following spring planted sweet corn for three cropping histories. 2003 2004 Source of variation df Pi‡ Pf Pi Pf ————————Root-knot———————— Cropping history 2 ns† + *** *** Error A 12— — — — Total 14 ————————Spiral———————— Cropping history 2 + ns ns Error A 12— — — — Total 14 ————————Stubby-root———————— Cropping history 2 *** + Error A 12— — — — Total 14 ————————Lesion———————— Cropping history 2 * *** *** Error A 12— — — — Total 14 ————————Ring———————— Cropping history 2 *** *** *** Error A 12— — — — Total 14 + Significant at the 0.10 level. Significant at the 0.01 level. ** Significant at the 0.05 level. *** Significant at the 0.001 level. †ns = not significant. ‡Pi = nematode population prior to planting of sweet corn. Pf = nematode population following harvest of sweet corn.

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241 Table 7-3. Analysis of variance for nemat odes prior to and following winter planted cover crop of Austrian winter p ea for three cropping histories. 2003 2004 Source of variation df Pi‡ Pf Pi Pf ————————Root-knot———————— Cropping history 2 *** ns† *** *** Error A 12— — — — Total 14— — — — ————————Spiral———————— Cropping history 2 *** + ns Error A 12— — — — Total 14— — — — ————————Stubby-root———————— Cropping history 2 ** ** + Error A 12— — — — Total 14— — — — ————————Lesion———————— Cropping history 2 ** *** *** Error A 12— — — — Total 14— — — — ————————Ring———————— Cropping history 2 *** *** *** Error A 12— — — — Total 14— — — — + Significant at the 0.10 level. Significant at the 0.01 level. ** Significant at the 0.05 level. *** Significant at the 0.001 level. †ns = not significant. ‡Pi = nematode population prior to pl anting of Austrian winter pea. Pf = nematode population following ha rvest of Austrian winter pea.

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242 Table 7-4. Nematodes following spring pl anted sweet corn crop for three cropping histories and three nitrogen sources. N 2003 2004 source —————Cropping history—————— —————Cropping history—————— 1 2 3 X 1 2 3 X ————————————Number of nematodes, 100 cm-3 soil——————————— Root-knot Lupine 891 394 672 652 ns† 234 300 57 197 ns Vetch 699 693 1367 920 214 372 56 214 AN 1167 619 907 898 243 401 56 233 X 919 a§ 567 b 982 a 230 b 357 a 56 c Spiral Lupine 48 9 1 19 ns 9 22 1 11 ns Vetch 46 41 3 30 11 9 2 7 AN 34 23 3 20 9 37 1 15 X 42 ns 24 2 9 ns 22 1 Stubby root Lupine 1 15 17 11 ns 8 8 12 9 y‡ Vetch 2 19 7 9 7 5 7 6 y AN 5 26 6 12 8 18 19 15 x X 3 b 20 a 10 b 7 b 11 a 13 a Lesion Lupine 23 0 0 8 ns 19 1 0 6 ns Vetch 3 0 0 1 18 0 1 6 AN 16 0 0 6 18 0 0 6 X 14 a 0 b 0 b 18 a 0 b 0 b Ring Lupine 64 25 19 36 ns 14 5 7 9 ns Vetch 88 14 19 41 16 3 5 8 AN 97 55 35 62 15 9 12 12 X 83 a 32 b 25 b 15 a 6 b 7 b †ns = not significant. ‡Values in columns among N sources not followed by the same letter (x,y,z) are significantly different (p< 0.05) according to LSD. §Values in rows among cropping histories not followed by th e same letter (a,b,c) are significantly different (p< 0.05) according to LSD. History 1 = sweet corn/Austrian winter pe a/sweet corn/sweet corn/Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wi nter pea/sweet corn/lima bean /Austrian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/ sweet corn/sunn hemp/Austrian winter pea/sweet corn.

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243 Table 7-5. Nematodes prior to and followi ng spring planted sweet corn crop for three cropping histories. Cropping 2003 2004 history Pi Pf Pi Pf ————Number of nematodes, 100 cm-3 soil————— Root-knot 1§ 8 919 a‡ 37 b 230 b 2 15 567 b 342 a 358 a 3 30 982 a 5 b 56 c ns† + *** *** Spiral 1 29 a 42 a 43 9 2 4 b 24 b 56 22 3 1 b 2 c 4 1 + ns ns Stubby root 1 13 a 3 b 23 a 7 b 2 2 b 20 a 24 a 11 a 3 2 b 10 a 7 b 12 a *** + Lesion 1 7 a 14 a 12 a 18 a 2 0 b 0 b 0 b 0 b 3 0 b 0 b 0 b 0 b * *** *** Ring 1 34 a 83 a 29 a 15 a 2 0 b 32 b 7 b 6 b 3 3 b 25 b 4 b 8 b *** *** ** + Significant at the 0.10 level. Significant at the 0.01 level. ** Significant at the 0.05 level. *** Significant at the 0.001 level. †ns = not significant. ‡Values in columns not followed by the same letter are significantly different according to LSD at the designated level of probability. §History 1 = sweet corn/Austrian winter pe a/sweet corn/sweet corn/Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wi nter pea/sweet corn/lima bean /Austrian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/ sweet corn/sunn hemp/Austrian winter pea/sweet corn. Pi = nematode population prior to planting of sweet corn. Pf = nematode population following harvest of sweet corn.

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244 Table 7-6. Nematodes prior to and followi ng winter planted cove r crop of Austrian winter pea for three cropping histories. Cropping 2003 2004 history Pi Pf Pi Pf ————Number of nematodes, 100 cm-3 soil———— Root-knot 1§ 62 a 8 239 b‡ 37 b 2 10 b 15 887 a 342 a 3 1 b 3 8 b 5 b ** ns† *** *** Spiral 1 45 a 29 a 59 a 43 2 1 b 4 b 22 b 56 3 1 b 1 b 3 b 4 *** + ns Stubby root 1 12 a 13 a 8 a 23 a 2 1 b 2 b 5 a 24 a 3 1 b 2 b 0 b 7 b ** ** + Lesion 1 21 a 7 a 44 a 12 a 2 1 b 0 b 0 b 0 b 3 1 b 0 b 0 b 0 b ** *** *** Ring 1 58 a 34 a 36 a 29 a 2 1 b 0 b 2 b 7 b 3 1 b 3 b 5 b 4 b *** *** *** + Significant at the 0.10 level. Significant at the 0.01 level. ** Significant at the 0.05 level. *** Significant at the 0.001 level. †ns = not significant. ‡Values in columns not followed by the same letter are significantly different according to LSD at the designated level of probability. §History 1 = sweet corn/Austrian winter pe a/sweet corn/sweet corn/Austrian winter pea/sweet corn. History 2 = cowpea/Austrian wi nter pea/sweet corn/lima bean /Austrian winter pea/sweet corn. History 3 = sunn hemp/Austrian winter pea/ sweet corn/sunn hemp/Austrian winter pea/sweet corn. Pi = nematode population prior to planting of sweet corn. Pf = nematode population following harvest of sweet corn.

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245 CHAPTER 8 SUMMARY The results of these experiments demonstrat e the need for more research regarding the use of no-tillage practices, the use of organic N sources, and multiple cropping using the appropriate crops. Utilizing multiple cr opping when the climate is conducive can be extremely beneficial, not only for a grower, but for the environment. These agricultural techniques all promote sustainable agriculture which can help to preserve and maintain natural resources and ensure their use by future generations. Valuable information was obtained on the crops tested and the conditions best for their production in no-till cropp ing systems in Florida. Two sweet corn varieties were found to be superior hybrid choices for fall pr oduction of sweet corn in central Florida, ‘Silver Queen’ and ‘8102R’. The management of N fertilizer (ammonium nitrate) for sweet corn should be split into at least 2 applications, in order to reduce the risk of leaching. The number of split applications should be economically based. For production in Florida as part of a cr opping system or for use as organic mulch, the cowpea variety ‘Iron Clay’ would make the strongest choice. This variety of cowpea has the capacity to provide extra N, P, and K for succeeding crops, when used in a system. ‘Iron Clay’ can also reduce infestations of the extremely harmful plant-parasitic nematode, M. incognita, which poses a problem in crop production in Florida. ‘California Blackeye #5’ is a variety of cowpea that would make a good candidate for a very different situation, that is one of consumption. Its high pod production and high pod

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246 mineral content make it most suitable as a food crop. The lima bean variety most suited for production, possibly as a food crop, in Florida is ‘Fordhook’. Sunn hemp would make an excellent choi ce for inclusion in a multiple cropping system in Florida. It can be harvested and ut ilized as a green manure in order to increase soil OM, add minerals, especially N, and s uppress nematodes. The portion of the sunn hemp not harvested could be maintained for continual clipping and production of mulch. The mulch could be used for weed control, soil moisture conservation, and the slow release of additional N and other minerals. No-till planted Austrian wint er pea performed well as a c over crop in all systems in this study. Its residue contributed a significan t quantity of minerals especially N, for subsequent crops. This legume also woul d aid in soil conservation and nematode population management. A previous history involving co wpea and Austrian winter pea appeared to be best suited for production of sweet co rn in a no-till multiple cropping system in Florida. The system including these 2 legumes prior to sweet corn produced the most, as well as largest, marketable ears and had the healthiest soil. Ammonium nitrate gave best results as an N source for sweet corn grown in a no-till multiple cropping system when compared with lupine and vetch. Alt hough inorganic fertilizers might be more economical, organic fertilizers offer benefits that inorganic fertilizers cannot. Organic fertilizers or mulches can be used to impr ove soil moisture conservation, increase soil organic matter, provide N and other plant minerals, reduce weed competition, and reduce erosion in addition to eliminating th e threat of chemical leaching.

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247 When nematode populations were examined after 2 yr of cropping systems had been produced, year effects were inconsis tent while cropping hi story effects were consistent. Sunn hemp and Austrian wint er pea were found to decrease the most important and damaging nematode, root-knot nematode, while sweet corn was found to increase its numbers. Als o, growing sunn hemp (summer/fa ll) and Austrian winter pea (winter) consecutively would encompass 2 diffe rent times in the year, which equates to both warm and cool season suppression, or 2 seas ons of nematode control. All of these cropping systems had very pos itive results. Much needed information was gathered on several different types of crops and the conditions necessary for the successful production of each within no-till cr opping systems. Several varieties were proven more appropriate than others and so me N management techniques were more efficient than others. Positive results such as these should encourage the use of no-tillage and multiple cropping and the continued i nvestigation of organic fertilizers.

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248 LIST OF REFERENCES Adams, F., and C.E. Evans. 1962. A rapid method for measuring lime requirement of red-yellow podzolic soils. Soil Sci. Soc. Am. J. 26:355-357. Aguiar, J., J. Ehlers, W. Graves, B. Ma tthews, P. Roberts, and V. Samons. 1999. Coachella Valley cover crop research. Bo tany and Plant Sci. Dept., Sustainable Agric. Res. and Educ. Prog. Uni v. of California, Riverside. Allison, F.E. 1965. Organic carbon. p. 367-1378. In C.A. Black, D.D. Evans, J.L.White, L.E. Ensminger, and F.E. Clark (e d.). Methods of Soil Analysis, Part II. Am. Soc. Agron., Madison, WI. Anderson, J.R., N.L. Hubbard, F.D. Shaw, and F.W. Smith. 1990. Managing winterannual legumes as N sources for no-tillage corn on sandy coastal plain soils. p. 104-107. In: Mueller, J.P. and M.G. Wagger (ed.). Proc. Southern Region Conserv. Tillage Conf., 1990. Raleigh, NC NCSU Special Bulletin 90-1. North Carolina State Univ., Raleigh. Anonymous. 1987. Manual for Quattro Pro, Ve r 4.0. Getting started. Borland Int’l., Inc. Scotts Valley, California. Anonymous. 1985. Users guide to MSTAT, Ver 4.0. [Online]. Available at http://www.msu.edu/~freed/mstatc.htm l (verified on 28 March 2005). Michigan State Univ., Lansing. Beck, D.L., M.P. Hagny, and J.L. Miller. 1998. Principles and practices of no-till systems. Abstract, Amer. Soc. Agron. 90: 289. Blade, S.F., S.V.R. Shetty, T. Terao, and B.B. Singh. 1997. Recent developments in cowpea cropping systems research. p. 114-128. In: B.B. Singh, D.R. Mohan Raj, K.E. Dashiell and L.E.N. Jackai (ed.). In t’l. Inst. of Tropical Agric. Ibadan, Nigeria. Brady, K., and E. Buckman. 1969. The nature and properties of soils. 7th ed. The Macmillan Company, New York, NY. Burnside, O.C., and J.H. Williams. 1968. Weed control methods for kinkaoil, kenaf, and crotalaria. Agron. J. 60:162-164. Campbell, C.A., and R.P. Zentner. 1993. Soil organic matter as influenced by crop rotations and fertiliz ation. Soil Sci. Soc. Am. J. 57:1034-1040.

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255 BIOGRAPHICAL SKETCH Kimberly A. Seaman was born 18 May 1980, to Jeffery and Karen Seaman, in Rochester Hills, MI. She graduated Columbia Academy Prepatory School (fourth in her class) in 1998. She then attended David Li pscomb University in Nashville, Tennessee, where she obtained a BS in Environmenta l Science in 2002. During her undergraduate studies she served as the university gree nhouse manager and interned with the urban forestry department of the Tennessee Environmental Protection Agency. In August 2002, she began an MS degree prog ram at the University of Florida in the Agronomy Department. She was placed on an USDA-CREES grant entitled ‘Effects of Management Practices on Pests, Pathogens and Beneficials in Soil Ecosystems’ and worked as a graduate research assistant. She is currently a member of the Gamma Sigma Delta Agricultural Honor Society, Crop Scien ce Society of Florida, and the American Society of Agronomy.