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On-Farm Composting of Horse Manure and Its Use as a Fertilizer for Common Forages in North Florida

Permanent Link: http://ufdc.ufl.edu/UFE0022142/00001

Material Information

Title: On-Farm Composting of Horse Manure and Its Use as a Fertilizer for Common Forages in North Florida
Physical Description: 1 online resource (213 p.)
Language: english
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: bahiagrass, bedding, compost, florigraze, horse, manure, nitrogen, pensacola, pscu, uf, urea, waste
Animal Sciences -- Dissertations, Academic -- UF
Genre: Animal Sciences thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: With decreasing land availability and increasing regulations for animal agriculture in the United States, disposal and utilization of horse manure is becoming a major concern. Composting may serve as a viable treatment option for horse manure prior to land application, yet research on the composting of horse stall materials (HSM) and its value as a fertilizer is limited. The objectives of this dissertation were: 1) to evaluate various rates and sources of nitrogen (N) amendment and their effects on the ease of composting horse manure mixed with hay or wood shavings bedding; and 2) to examine the performance of unprocessed and composted HSM on forage production in north Florida. To study these effects, two composting studies and five land application trials were conducted from 2005 to 2007. Farm-scale composting was conducted using a multiple-bin system under roof cover. HSM containing either wood shavings or hay bedding were amended with urea or slow-release nitrogen sources to achieve specific carbon:nitrogen (C:N) ratios ranging from 15 to 60:1 and composted for either 84 or 120 d. Composting reduced the total mass of HSM by 15-60%. Composting HSM containing wood shavings bedding, but not hay, resulted in temperatures high enough to destroy parasite eggs, pathogens, insect larvae and weed seeds. Manure mixed with wood shavings showed a greater degree of decomposition and nutrient stability after composting than HSM containing hay bedding. Slow-release N sources reduced the loss of N during composting, but did not enhance the rate or extent of decomposition compared to urea. Slow-release N sources did not sustain microbial populations for an extended time beyond that observed for urea-treated or unamended HSM. HSM amended with N had higher concentrations of soluble N in the form of NO3 and NH4. Soluble N can increase the value of compost as a fertilizer by providing plant available forms of N; however, if applied in excess, the potential for surface and groundwater pollution exists. More research is needed to determine an economically feasible and timely method of promoting decomposition of bedding in HSM to form a higher quality end product. Investigations of land application of HSM were conducted during the growing season in Gainesville, FL (2006) and Live Oak, FL (2007). Unprocessed (STALL) and composted (COMP) HSM were either surface applied onto or incorporated into soil of Coastal bermudagrass (Cynodon dactylon), Argentine bahiagrass (Paspalum notatum), Pensacola bahiagrass or Florigraze perennial peanut (Arachis glabrata) forages. Application rates ranged from 11,200 to 37,000 kg ha^1 STALL and 8,400 to 18,500 kg ha^1 COMP. Fertilization with STALL or COMP improved yields for bahiagrass and bermudagrass compared to unfertilized control. Yields of bahiagrass and perennial peanut were greater with STALL than COMP, but yields were comparable between the fertilizer sources for bermudagrass. Across all forages, soil ammonium-N (NH4) and nitrate-N (NO3) did not vary due to fertilization or fertilizer source and did not increase soil residual NH4 or NO3 levels. Application of STALL or COMP had no measurable effect on soil phosphorus. STALL provided a greater fertilizer response than COMP during a single season, but effects of repeated application require further study.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis: Thesis (Ph.D.)--University of Florida, 2008.
Local: Adviser: Warren, Lori.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-05-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022142:00001

Permanent Link: http://ufdc.ufl.edu/UFE0022142/00001

Material Information

Title: On-Farm Composting of Horse Manure and Its Use as a Fertilizer for Common Forages in North Florida
Physical Description: 1 online resource (213 p.)
Language: english
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: bahiagrass, bedding, compost, florigraze, horse, manure, nitrogen, pensacola, pscu, uf, urea, waste
Animal Sciences -- Dissertations, Academic -- UF
Genre: Animal Sciences thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: With decreasing land availability and increasing regulations for animal agriculture in the United States, disposal and utilization of horse manure is becoming a major concern. Composting may serve as a viable treatment option for horse manure prior to land application, yet research on the composting of horse stall materials (HSM) and its value as a fertilizer is limited. The objectives of this dissertation were: 1) to evaluate various rates and sources of nitrogen (N) amendment and their effects on the ease of composting horse manure mixed with hay or wood shavings bedding; and 2) to examine the performance of unprocessed and composted HSM on forage production in north Florida. To study these effects, two composting studies and five land application trials were conducted from 2005 to 2007. Farm-scale composting was conducted using a multiple-bin system under roof cover. HSM containing either wood shavings or hay bedding were amended with urea or slow-release nitrogen sources to achieve specific carbon:nitrogen (C:N) ratios ranging from 15 to 60:1 and composted for either 84 or 120 d. Composting reduced the total mass of HSM by 15-60%. Composting HSM containing wood shavings bedding, but not hay, resulted in temperatures high enough to destroy parasite eggs, pathogens, insect larvae and weed seeds. Manure mixed with wood shavings showed a greater degree of decomposition and nutrient stability after composting than HSM containing hay bedding. Slow-release N sources reduced the loss of N during composting, but did not enhance the rate or extent of decomposition compared to urea. Slow-release N sources did not sustain microbial populations for an extended time beyond that observed for urea-treated or unamended HSM. HSM amended with N had higher concentrations of soluble N in the form of NO3 and NH4. Soluble N can increase the value of compost as a fertilizer by providing plant available forms of N; however, if applied in excess, the potential for surface and groundwater pollution exists. More research is needed to determine an economically feasible and timely method of promoting decomposition of bedding in HSM to form a higher quality end product. Investigations of land application of HSM were conducted during the growing season in Gainesville, FL (2006) and Live Oak, FL (2007). Unprocessed (STALL) and composted (COMP) HSM were either surface applied onto or incorporated into soil of Coastal bermudagrass (Cynodon dactylon), Argentine bahiagrass (Paspalum notatum), Pensacola bahiagrass or Florigraze perennial peanut (Arachis glabrata) forages. Application rates ranged from 11,200 to 37,000 kg ha^1 STALL and 8,400 to 18,500 kg ha^1 COMP. Fertilization with STALL or COMP improved yields for bahiagrass and bermudagrass compared to unfertilized control. Yields of bahiagrass and perennial peanut were greater with STALL than COMP, but yields were comparable between the fertilizer sources for bermudagrass. Across all forages, soil ammonium-N (NH4) and nitrate-N (NO3) did not vary due to fertilization or fertilizer source and did not increase soil residual NH4 or NO3 levels. Application of STALL or COMP had no measurable effect on soil phosphorus. STALL provided a greater fertilizer response than COMP during a single season, but effects of repeated application require further study.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis: Thesis (Ph.D.)--University of Florida, 2008.
Local: Adviser: Warren, Lori.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-05-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022142:00001


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1 ON-FARM COMPOSTING OF HORSE MANURE AND ITS USE AS A FERTILIZER FOR COMMON FORAGES IN NORTH FLORIDA By SARAH COURTNEY DILLING A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2008

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2 2008 Sarah Courtney Dilling

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3 To my children, James and Alyson Dilling, and my husband, Brad, for their unconditional love and support. I could not have surviv ed graduate school without them.

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4 ACKNOWLEDGMENTS I would like to begin by thanki ng Dr. Lori K. W arren, my supervisory committee chair and an authentic advisor. Her guidance throughout the graduate program, beginning with the experimental planning and continui ng with data analysis and revi ew of the dissertation, has been greatly appreciated. Thanks also go to my ot her committee members, (S.H. TenBroeck, M.W. Clark, G.E. Fitzpatrick, C.L. Mackowiak, and R.A. Nordstedt) for their willingness to serve on my committee, their input during my program and for reviewing my dissertation. Financial support from the Florida Department of Agricultural and Consumer Services is greatly appreciated and made the PhD program possible. Thanks are also expressed to Dr. G.E. Dahl, department chair, Dr. J. Brendemuhl, assistant chair, and Joa nn Fischer, graduate coordinator, for the opportunity to study in the Department of Animal Science. Special thanks go to those who helped during the field and lab activities. That includes fellow graduate students Kelly Vineyard, Jerome Vickers, Drew Cotton, Meg Brew, and undergraduate students Analese Pe ters, Sarah White, and Sarah Simpson. Thanks go to the horse teaching unit staff, Charles (Ruff) Stephens, Ju stin Callaham, and Joel McQuagge, for their support and cooperation with the composting experiments. Also, thanks to the North Florida Research and Education Center Live Oak staff, Randi Randell, Lani Lei Davis, and Jerry Butler, for their cooperation with the forage expe riments. In the nutrition lab, thanks goes to Jan Kivipelto and Nancy Wilkinson for their vast kno wledge, support and assi stance in analysis of forage and compost. I am especially thankful to my family fo r their great support, e ducation, and friendship they provided to me in building my strength a nd character. Last but no t least, I am deeply grateful for the love and support of my husband, Brad, who gave me unconditional love and the strength and confidence to complete a doctorate program. Also, I would like to thank my two

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5 children, James and Alyson, for shedding light and ultimate happiness during my graduate program.

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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ........10 LIST OF FIGURES.......................................................................................................................12 ABSTRACT...................................................................................................................................14 CHAP TER 1 INTRODUCTION..................................................................................................................16 2 LITERATURE REVIEW.......................................................................................................19 Nutrient Management.............................................................................................................19 Regulation..................................................................................................................... ...19 Surface and Groundwater Contamination....................................................................... 20 Soil Accumulation of Nutrients.......................................................................................23 Air Pollution....................................................................................................................24 Nutrient Management in the Pasture Ecosystem ....................................................................24 Stocking Rate and Stocking Method............................................................................... 24 Florida Pasture Forages................................................................................................... 27 Fertilization of the Pasture Ecosystem............................................................................29 Nitrogen....................................................................................................................30 Phosphorus...............................................................................................................32 Potassium.................................................................................................................34 Horse Stall Materials as a Fertilizer Source .................................................................... 35 Production of horse stall materials........................................................................... 35 Nutrient availability in manure................................................................................ 36 Limitations of unprocesse d m anure as fertilizer...................................................... 39 Compost..................................................................................................................................42 History of Composting.................................................................................................... 43 Types of Composting......................................................................................................45 The Aerobic Composting Process................................................................................... 49 Factors Affecting Aerobic Composting........................................................................... 51 Aeration.................................................................................................................... 51 Moisture...................................................................................................................52 Nutrients...................................................................................................................52 Pile size and porosity of the material....................................................................... 53 Maturity and Stability of Aerobic Compost.................................................................... 53 Aerobic Composting as a Tool for Horse Manure Management.................................... 54 Compost as a Fertilizer S ource for Florida Forages ........................................................ 56 Summary.................................................................................................................................58

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7 3 ON-FARM COMPOSTING OF HORSE STALL MATERI ALS: EFFECT OF CARBON TO NITROGEN RA TIO AND BEDDING TYPE............................................... 60 Introduction................................................................................................................... ..........60 Materials and Methods...........................................................................................................62 Experimental Design....................................................................................................... 62 Data Collection and Analysis.......................................................................................... 63 Statistical Analyses.......................................................................................................... 65 Results.....................................................................................................................................66 Weather Conditions......................................................................................................... 66 Composting Temperatures and Effect of Season............................................................ 66 Material Mass and Organic Matter..................................................................................67 Nutrient Concentrations in Compost...............................................................................67 Conductivity and Total Dissolved Solids........................................................................68 Water Holding Capacity and Bulk Density..................................................................... 68 Mass Balance Estimates for Nutrients............................................................................. 68 Discussion...............................................................................................................................69 Conclusions.............................................................................................................................73 4 ON-FARM COMPOSTING OF HORSE STAL L MATERI ALS: EFFECT OF SLOWRELEASE NITROGEN AMENDMENTS............................................................................ 83 Introduction................................................................................................................... ..........83 Materials and Methods...........................................................................................................85 Experimental Design....................................................................................................... 85 Data Collection and Analyses......................................................................................... 87 Statistical Analyses.......................................................................................................... 89 Results.....................................................................................................................................89 Weather Conditions......................................................................................................... 89 Composting Temperatures and Effect of Season............................................................ 89 Physical Properties and Chemical Com position of Compost.......................................... 90 Mass Balance Estimates for Nutrients............................................................................. 91 Microbial Populations..................................................................................................... 91 Discussion...............................................................................................................................92 Conclusion..............................................................................................................................96 5 CHARACTERISTICS OF SOIL AND NE WLY ESTABLISHED BAHIAGRASS FORAGE IN RESPONSE TO SOIL INCORPORATION OF UNPROCESSED AND COMPOSTED HORSE STALL MATERIALS................................................................... 102 Introduction................................................................................................................... ........102 Materials and Methods.........................................................................................................105 Site Description.............................................................................................................105 Experimental Design..................................................................................................... 105 Data Collection and Analysis........................................................................................ 106 Statistical Analysis........................................................................................................ 108 Results...................................................................................................................................109

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8 Bioassay.........................................................................................................................109 Forage............................................................................................................................109 Soil.................................................................................................................................110 Discussion.............................................................................................................................111 Conclusions...........................................................................................................................113 6 EVALUATION OF UNPROCESSED AND COMPOSTED HORSE MANURE ON SOIL CHE MICAL PROPERTIES AND YIELD OF ESTABLISHED NORTH FLORIDA PASTURE.......................................................................................................... 118 Introduction................................................................................................................... ........118 Materials and Methods.........................................................................................................119 Site Description.............................................................................................................119 Experimental Design..................................................................................................... 119 Data Collection and Analysis........................................................................................ 120 Statistical Analysis........................................................................................................ 122 Results...................................................................................................................................123 Bioassay.........................................................................................................................123 Forage............................................................................................................................123 Soil.................................................................................................................................125 Discussion.............................................................................................................................126 Conclusions...........................................................................................................................128 7 EFFECTS OF UNPROCESSED AND CO MPOSTED HORSE STALL MATERI ALS ON SOIL CHEMICAL PROPERTIES AND YIELD OF NORTH FLORIDA FORAGES............................................................................................................................135 Introduction................................................................................................................... ........135 Materials and Methods.........................................................................................................137 Site Descriptions............................................................................................................137 Experimental Design..................................................................................................... 137 Experiment 1: Pensacola Bahiagrass...................................................................... 138 Experiment 2: Coastal Bermudagrass.................................................................... 138 Experiment 3: Florigraze Rhizoma Perennial Peanut............................................ 139 Data Collection and Analysis........................................................................................ 139 Statistical Analysis........................................................................................................ 141 Results...................................................................................................................................142 Weather Conditions....................................................................................................... 142 Bioassay.........................................................................................................................142 Experiment 1: Pensacola Bahiagrass............................................................................. 143 Experiment 2: Coastal Bermudagrass........................................................................... 146 Experiment 3: Florigra ze Perennial Peanut ................................................................... 149 Discussion.............................................................................................................................152 Conclusion............................................................................................................................155 8 IMPLICATIONS.................................................................................................................. 172

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9 APPENDIX A SUPPLEMENTAL DATA FOR COMP OSTING STUDY (CH 3) ..................................... 174 B SUPPLEMENTAL DATA FOR COMP OSTING STUDY (CH 4) ..................................... 181 C SUPPLEMENTAL DATA FOR LAND APPLICATION STUDY (CH 5) ........................ 189 D SUPPLEMENTAL DATA FOR LAND APPLICATION STUDIES (CH 7) .....................191 LIST OF REFERENCES.............................................................................................................194 BIOGRAPHICAL SKETCH.......................................................................................................213

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10 LIST OF TABLES Table page 3-1 Nitrogen, carbon, total phosphorus, soluble phosphorus, and potassium in horse stall materials before (day 0) and after 84 days of composting................................................. 80 3-2 Pore space, water holding capacity, b ulk density, pH, conductivity, and total dissolved solids in horse stall materials before (day 0) and after 84 days of composting..................................................................................................................... ....81 3-3 Mass balance estimates of nutrients afte r 84 days of com posting stall materials.............. 82 4-1 Total nitrogen, nitrate, ammonia, phosphor us and potassium in horse stall materials before (day 0) and after 120 days of composting.............................................................. 99 4-2 Mass balance estimates of nutrients afte r 120 days of com posting stall materials.......... 100 5-1 Dry matter yield, total nitrogen and to tal phosphorus concentration in Argentine bahiagrass in response to fertilizatio n with stall m aterial and compost........................... 116 5-2 Argentine bahiagrass plots soil chemical pr oper ties in response to fertilization with stall material and compost............................................................................................... 117 6-1 Dry matter yield, mean nitrogen and phosphorus concentration, and nitrogen and phosphorus rem oved by mixed bahiagrass forage in response to fe rtilization with stall material and compost............................................................................................... 133 6-2 Established pasture plots soil chemical pr operties in response to fertilization with stall m aterial and compost............................................................................................... 134 7-1 Pensacola bahiagrass forage dry matte r yield and tissue nitrogen and phosphorus concentrations in response to fertilization with st all m aterial and compost....................160 7-2 Pensacola bahiagrass plots soil chemical properties in response to fertilization with stall material and compost............................................................................................... 161 7-3 Pensacola bahiagrass effect of sampli ng interval on soil chemical properties in response to fertilization with stall m aterial and compost................................................. 162 7-4 Pensacola bahiagrass effect of sampli ng depth on soil chem ical properties in response to fertilization with stall material and compost................................................. 163 7-5 Coastal bermudagrass forage dry matte r yield and tissue nitrogen and phosphorus concentrations in response to fertilization with st all m aterial and compost....................164 7-6 Coastal bermudagrass plots soil chemical pr oper ties in response to fertilization with stall material and compost............................................................................................... 165

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11 7-7 Coastal bermudagrass plots sampling interv al on soil chem ical properties in response to fertilization with stal l material and compost................................................................ 166 7-8 Coastal bermudagrass plots effect of sa m pling depth on soil chemical properties in response to fertilization with stall material and compost................................................. 167 7-9 Florigraze perennial peanut forage d ry matter yield and tissue nitrogen and phosphorus concentrations in response to fertilization with stall material and compost........................................................................................................................ ....168 7-10 Florigraze perennial peanut soil chemical pr operties in respo nse to fertilization with stall material and compost............................................................................................... 169 7-11 Florigraze perennial peanut effect of samp ling interval on soil chem ical properties in response to fertilization with stall material and compost................................................. 170 7-12 Florigraze perennial peanut effect of sa m pling depth on soil chemical properties in response to fertilization with stall material and compost................................................. 171 A-1 Treatment schedule for composting of stall m aterials containing bermudagrass bedding or wood shavings bedding.................................................................................. 180 B-1 Treatment schedule for compost treat ed with urea nitrogen am endment or unamended.......................................................................................................................187 B-2 Neutral detergent fiber, acid detergent fiber, lignin, total carbon, and organic m atter in horse stall materials before (day 0) and after 120 day of composting......................... 188 C-1 Argentine bahiagrass dry matter yield, tissue nitrogen and phosphorus, nitrogen and phosphorus rem oved in response to fertilizat ion with stall material and compost.......... 189 C-2 Argentine bahiagrass soil chemical propertie s in response to fer tilization with stall m aterial and compost....................................................................................................... 190 D-1 Pensacola bahiagrass soil chemical propertie s by day in response to fertilization with stall m aterial and compost............................................................................................... 191 D-2 Coastal bermudagrass soil chemical prope rites by day in response to fertilization with stall m aterial and compost....................................................................................... 192 D-3 Florigraze perennial peanut soil chem ical properties by d ay in response to fertilization with stall material and compost.................................................................... 193

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12 LIST OF FIGURES Figure page 2-1 Nitrogen cycle in soil..................................................................................................... ....31 2-2 Phosphorus cycle in soil................................................................................................... ..33 2-3 Susceptibility of organic com pounds found in compost fe edstock to mineralization.......38 2-4 Flow diagram of the anaerobic composting process.......................................................... 47 2-5 Flow diagram of the aerobic composting process.............................................................. 48 2-6 Phases of composting as re lated to temperature and tim e.................................................50 3-1 Maximum temperature reached during th e com posting of horse stall materials containing bermudagrass hay bedding or wood shavings bedding.................................... 75 3-2 Number of cumulative thermal unit days while composting ho rse stall m aterials containing wood shavings bedding during 84 days...........................................................76 3-3 Effect of season on ambient temperature and mean compost temperature of pooled treatm ents containing wood shavings bedding during 84 days of composting................. 77 3-4 Reduction in dry matter mass after 84 days of composting in treatm ents containing bermudagrass hay bedding or wood shavings bedding......................................................78 3-5 Change in pH after 84 days of composting in treatm ents containing bermudagrass hay bedding or wood shavings bedding.............................................................................79 4-1 Number of cumulative thermal unit days while composting ho rse stall m aterials during 120 days..................................................................................................................97 4-2 Changes in microbial populations presen t in hors e stall mate rial during 120 d of composting..................................................................................................................... ....98 6-1 Dry matter yield (Mg ha-1) of mixed bahiagrass in res ponse to fertilization with inorganic fertilizer (INOR G), horse stall materials (STALL), N-amended stall materials (ACOMP), unamended composte d stall materials (UCOMP), ACOMP + INORG (MIX) or no fertilization (UNFERT). a,b,cWithin each day, treatment means with different letters differ (P<0.05)................................................................................ 130 6-2 Established pasture nitrogen concentration in response to fertilization with horse stall m aterial and compost....................................................................................................... 131 6-3 Established pasture phosphorus concentration in response to fertilization with horse stall m aterial and compost............................................................................................... 132

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13 7-1 Pensacola bahiagrass tissue nitrogen a nd phosphorus rem oved after fertilization with horse stall material and compost...................................................................................... 157 7-2 Coastal bermudagrass tissue nitrogen a nd phosphorus rem oved after fertilization with horse stall material and compost.............................................................................. 158 7-3 Florigraze perennial peanut tissue nitrogen and phosphorus removed after fertilization with horse stall m aterial and compost.......................................................... 159 A-1 WOOD-30 changes in mean temperature pr of ile over time within each replication during 84 days of composting.......................................................................................... 174 A-2 WOOD-60 changes in mean temperature pr of ile over time within each replication during 84 days of composting.......................................................................................... 175 A-4 WOOD-CON changes in mean temperature pro file over time within each replication during 84 days of composting.......................................................................................... 176 A-5 HAY-CON changes in mean temperature pr ofile over tim e within each replication during 84 days of composting.......................................................................................... 177 A-6 Changes in mean temperature profile ove r tim e within each pile of HAY-15 during 84 d composting trial....................................................................................................... 178 A-7 Wood treatments pH before (day 0) and after 84 days of composting. ...........................179 B-1 Control treatment changes in temperature profile over tim e within each replication during 120 days of composting........................................................................................ 181 B-2 Urea changes in temperature profile ove r tim e within each replication during 120 days of composting.......................................................................................................... 182 B-3 Urea formaldehyde changes in temperature profile over tim e with in each replication during 120 days of composting........................................................................................ 183 B-4 Polymer sulfur coated urea changes in tem perature profile over time within each replication during 120 days of composting...................................................................... 184 B-1 Microbial profile of aerobic and anaerobic bacterial and pseudom onas for treatments during composting of horse stall material for 120 days................................................... 185 B-2 Microbial profile of nitrogen-fixing, ac tinom ycetes and fungi for treatments during composting of horse stall material for 120 days.............................................................. 186

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14 Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy ON-FARM COMPOSTING OF HORSE MANURE AND ITS USE AS A FERTILIZER FOR COMMON FORAGES IN NORTH FLORIDA By Sarah Courtney Dilling May 2008 Chair: Lori K. Warren Major: Animal Science With decreasing land availability and increasi ng regulations for animal agriculture in the United States, disposal and utilization of horse manure is becoming a major concern. Composting may serve as a viable treatment op tion for horse manure prior to land application, yet research on the composting of horse stall materials (HSM) and its value as a fertilizer is limited. The objectives of this dissertation were: 1) to evaluate various rates and sources of nitrogen (N) amendment and their effects on th e ease of composting horse manure mixed with hay or wood shavings bedding; and 2) to examine the performance of unprocessed and composted HSM on forage production in north Flor ida. To study these effects, two composting studies and five land app lication trials were cond ucted from 2005 to 2007. Farm-scale composting was conducted using a mu ltiple-bin system under roof cover. HSM containing either wood shavings or hay beddi ng were amended with urea or slow-release nitrogen sources to achieve sp ecific carbon:nitrogen (C:N) ra tios ranging from 15 to 60:1 and composted for either 84 or 120 d. Composting reduced the total mass of HSM by 15-60%. Composting HSM containing wood shavings bedding, but not hay, resulted in temperatures high enough to destroy parasite eggs, pathogens, insect larvae and weed seeds. Manure mixed with

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15 wood shavings showed a greater degree of deco mposition and nutrient stab ility after composting than HSM containing hay bedding. Slow-releas e N sources reduced the loss of N during composting, but did not enhance the rate or exte nt of decomposition compared to urea. Slowrelease N sources did not sustain microbial populations for an extended time beyond that observed for urea-treated or unamended HSM. HS M amended with N had higher concentrations of soluble N in the form of NO3 and NH4. Soluble N can increase the value of compost as a fertilizer by providing plant availa ble forms of N; however, if applied in excess, the potential for surface and groundwater pollution exists. More resear ch is needed to determine an economically feasible and timely method of promoting deco mposition of bedding in HSM to form a higher quality end product. Investigations of land application of HSM were conducted during the growing season in Gainesville, FL (2006) and Live Oak, FL (2007). Unprocessed (STALL) and composted (COMP) HSM were either surface applied onto or incorporated into soil of Coastal bermudagrass (Cynodon dactylon ), Argentine bahiagrass ( Paspalum notatum ), Pensacola bahiagrass or Florigraze perennial peanut ( Arachis glabrata ) forages. Application rates ranged from 11,200 to 37,000 kg ha-1 STALL and 8,400 to 18,500 kg ha-1 COMP. Fertilization with STALL or COMP improved yields for bahiagrass and bermudagrass compared to unfertilized control. Yields of bahiagrass and perennial p eanut were greater with STALL than COMP, but yields were comparable between the fertilizer sources for bermudagrass. Across all forages, soil ammonium-N (NH4) and nitrate-N (NO3) did not vary due to fertiliza tion or fertilizer source and did not increase soil residual NH4 or NO3 levels. Application of STALL or COMP had no measurable effect on soil phosphorus. STALL provi ded a greater fertilizer response than COMP during a single season, but effects of re peated application require further study.

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16 CHAPTER 1 INTRODUCTION W ith decreasing land availability for an imal agriculture in the United States, disposal and utilization of horse manure is becoming a major concern. In 2005 it was estimated that 500,000 horses reside in Florida generating a total economic impact of $5 billion (AHCF, 2005). If it is estimated that half of the horses in Florida are stalle d, producing 11 Megagrams (Mg) of stall material (including feces and urine, bedding and uneaten feed), a total of 2.7 million Mg of material can be generated every year. Common disposal methods for stall materials have included stockpiling on unused land, dumping into ravines and sinkholes, hauling to landfills, burning, and use as soil amendments for croplan d (Ott et al., 2000). With increasing emphasis on the control of environmental pollution, many of the above opt ions are no longer available. Further, as available space for disposal of munici pal solid waste decreases, the ability to dispose of manure in landfills may beco me restricted or strictly limited (Swinker et al., 1998). Horse manure management is regulated by th e federal government, similar to that of the dairy and swine industries (USE PA, 2002). Soil concentrations of nitrogen (N) and phosphorus (P) where horses are kept may be evaluated, and when in excess, the owner may be penalized according to confined animal feeding operations (CAFO) and animal feeding operations (AFO) regulations (USEPA, 2002). Since the practice of hauling agricultu ral manure to landfills may be limited in the future, horse owners may have to manage horses manure on-site, and composting could be a viable treatment option. Composting is the biological decomposition of organic matter to a humus-like product under controlled, aerobi c conditions (Epstein, 1997). The composting process is a waste management method used prim arily to stabilize organi c wastes. The stabilized end product can be used as an amendment for so il or potting mixes and is less likely to leach nutrients to groundwater or be carried off with surface runoff (Fitzpatrick, 1998). Compost can

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17 improve the physical, chemical and biological properties of a soil (Rynk et al., 1992). Physical properties of soil improve mainly due to the high organic matter content of composts. Compost enhances soil structure, thereby increasi ng porosity, water holding capacity, and water infiltration. The chemical prope rties of soil are improved by providing cation exch ange capacity and acting as a source of micronutrients. Further, composts improve the biological properties of soils by creating a diverse microbi ological environment that can suppress plant diseases and nematodes (Rynk et al., 1992). Research on the composting of animal ma nures is extensive (Chiumenti et al., 2006; Shiraishi et al., 2006; Tang et al., 2005; Tiquia and Tam, 2001), part icularly in regard to cattle, poultry and swine manures. All of these manures are nitrogen-rich a nd high in moisture content, which provides optimal conditions for composti ng (Rynk et al., 1992). Inve stigations into the composting of horse manure and stall materi als are lacking. Although horse manure possesses the optimal carbon:nitrogen ratio (C:N) of 30:1, it is often accompanied by large amounts of carbon-rich bedding, thereby increasing the overall C:N to as high as 130:1 (Rynk et al., 1992). Currently, land application of unprocessed hor se manure is a common method of disposal (Cotton, D. personal communicatio n, 2008). At typical recommended st ocking rates, 1 hectare of pasture per mature horse weighing 500 kg (Cha mbliss et al., 2006b) is required for manure nutrients to remain at levels similar to crop demand in FL (NRC, 1993). When this much land is not available, nutrients are applied in excess, resulting in soil accumulation and increased risk of leaching or runoff into surface and groundwater. If properly managed or composted, use of manu re for forage production can be an effective way to address problems with manure disposal and its impacts on groundwater quality. Research related to yield, animal performance, and nutriti ve value of Florida forages is abundant in the

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18 literature (Beck, et al., 2007; So llenberger et al., 1988; Stanley a nd Rhoads, 2000; Wright et al., 2003); however, there is little information regard ing the application of composted horse stall materials on Florida pasture forages. Composting and land application of horse stall material may be us eful practices, yet little is known about the most efficient means to produce compost and the performance of compost as a fertilizer source. Objective 1: to evaluate various rates of nitrogen amendment to accelerate composting of carbon-rich horse stall material (Chapter 3 ); Objective 2: to examine the effect of bedding type on the composting of hor se stall materials (Chapter 3 ); Objective 3: to evaluate slow release nitrogen sources as amendments to enhance composting of horse stall materials (Chapter 4 ); Objective 4: to evaluate composted horse stall materials as a fertilizer source for a newly established bahiag rass pasture (Chapter 5 ); Objective 5: to evaluate composted horse stall materials as a slow-release ferti lizer source for established bahiag rass pastures (Chapters 6 and 7); Objective 6: to evaluate composted horse stall mate rial as a supplemental fertilizer for Florida forages under hay production (Chapter 7); Objective 7: to determine the effects of composted horse stall material on soil physical and chemical characteri stics (Chapters 5, 6 and 7). In order to accomplish these objectives, two 1-year on-farm composting experiments were conducted from 2005 through 2007. Forage and soil da ta from five comp ost land application studies were collected during 2006 and 2007 in north Florida.

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19 CHAPTER 2 LITERATURE REVIEW Nutrient Management Regulation In 2006, the United States Census Bureau reported that Floridas hum an population reached 18 million with a 6.5% increase from th e previous year (USCB, 2006). It has been projected that Floridas populat ion will reach 29 million by 2030 (USCB, 2006). This substantial growth in population will ultimately impact water allocation, affordability in housing, law enforcement/jails, and-the factor most pertinent to the agriculture industry land availability. Currently, agriculture encompasses half of Floridas total 34.5 million acres. The majority (75%) of Floridas population lives within 15 miles of the coastline, but this prime real estate has almost been exhausted and people are moving in land, causing rural encroa chment conflicts. In 2005, the American Horse Council Foundation estim ated that over 500,000 horses reside in Florida (AHCF, 2005). While the nu mbers of horses have steadily in creased, land availability for animal agriculture has decreased, causing a rang e of environmental concerns from nutrient management to nuisance complaints such as odors and flies. Agriculture operations can poten tially generate enormous amounts of manure which can be recycled to crops or pasture. However, these operations are limited in acreage for extensive manure distribution resulting in potential e nvironmental threats to surface and groundwater quality (Newton et al., 2003; Pa nt et al., 2004). The United St ates Environmental Protection Agency (EPA) estimates that there are 370,000 Animal Feeding Oper ations (AFOs) in the U.S., and of this number, 12,700 have large numbers of an imals and may be classified as Concentrated Animal Feeding Operations (CAFOs) (USEPA, 2 000). The EPA also reported that agricultural operations, including AFOs, are a significant sour ce of water pollution in the United States. The

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20 latest National Water Quality Inventory (USEPA, 2000) reported that agriculture (including crop production, pastures, rangeland, feedlots, animal holding areas, and other animal feeding operations) is the leading contributor to water quality impairments in the nations rivers and lakes, and the fifth leading contributor to water quality impairments in the nations estuaries. These findings indicate that AFOs (as well as grazing and range animals) are a significant environmental concern throughout the United States. Environmental concerns related to agricultural waste can be divided in to three categories, concerns related to the soil (accumulation of nutrients), the water (eutrophication), and the air (carbon dioxide and methane emissions and odor s) (Jongbloed and Lenis, 1998). The federal Clean Water Act (1977) mandates that states minimize non-point source pollution or pollution associated with runoff and erosion, much of this originating from agricultural lands (USEPA, 1999). Recent strategies to re duce agricultural sour ce pollution have been attempted though implementation of Total Maximum Daily Load (TMDL) programs and Best Management Practices. The state of Florida is developi ng nutrient budgeting stra tegies to minimize environmental pollution and producing best management practice (BMP) manuals to educate and inform the public of these strategies. Surface and Groundwater Contamination Water contamination problems associated with agriculture are becoming increasing societal and political concerns. Nutrients su ch as nitrogen and phosphorus found in manure, fertilizer and animal feeds pose a risk to surface and groundwater at relatively low levels (Sharpley et al., 1994; Parry, 1998). Until recently, nitrogen was the main nutrient source that was believed to cause surface and groundwater contamination. Nitrogen is genera lly applied as a fertilizer in the largest quantities since it is usually the li miting agent to growth and quality of plants. Nitrogen exists in

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21 soil as nitrite (NO2), nitrate (NO3), or ammonium nitrogen (NH4), or in organic forms within the soil organic matter fraction (e.g. protein, DNA). The most soluble ion of n itrogen is nitrate, which is also the most common form of nitrogen in synthetic or commercial fertilizers (Watschke et al., 2000). Nitrate i ons are repelled by the clay part icles in the soil and generally are not adsorbed within the soil matrix. Hence, as water moves through the soil, nitrate nitrogen generally moves freely with the water. Excess nitrogen in bodies of surface water from runoff (agricultural and storm water), acid rain, or resurfacing leached nitrogen causes algae populations to grow rapidly or to bloom (L apointe and Bedford, 2007). The decomposition of the algae consumes dissolved oxygen in the water. Dissolved oxygen in water is a major factor affecting the survival and productivity of a quatic animal in surface water, and decreased dissolved oxygen reduces the population of fish, clam s, crabs, oysters, and other animal life. An algae bloom and subsequent decrease in disso lved oxygen is known as eutrophication (Lapointe and Bedford, 2007). A major concern in the state of Florida with regard to nitrogen contamination is groundwater pollution. In the early 1990s, the EP A found nitrate contamination in many Florida drinking water wells. Some urban and rural we lls exceeded the nitrate maximum contaminant level (MCL), suggesting that agricultural and fertilizer ap plication practices might be contributing to increased nitrate levels in the groundwater (Parsons and Boman, 2006). Nitrate contamination of groundwater can also occur from septic tanks or over-fertilization of lawns (Hubbard and Sheridan, 1994). The Florida Departme nt of Agriculture and Consumer Services (FDACS) carried out a more detailed drinking wa ter well analysis throug hout the state. Out of the 3,949 drinking water wells sampled, 2,483 (63%) ha d detectable nitrate levels and 584 (15%) had nitrate levels above the MCL, which is 10 mg/L. (Parsons and Boman, 2006). When people,

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22 particularly young people, drink water with hi gh nitrogen contamination, a medical condition known as methemoglobinemia, can result, where nitrite replaces oxygen in hemoglobin. With increased levels of methemoglobin, oxygen levels in the blood decrease, resu lting in cyanosis or oxygen starvation (Hubbard et al., 2004). Most cases of methemoglobinemia occur after consuming water with high concentrations of nitrate-nitrogen. Infa nts are particularly susceptible, as are people who receive kidney dial ysis treatment (Follett and Follett, 2001). Other effects associated with elevated concentrations of nitrate-nitrogen in drinking water include respiratory infection, alteration of thyroid me tabolism, and cancers induced by conversion of nitrate-nitrogen to nitrogen-nitroso com pounds in the body (Follett and Follett, 2001). Phosphorus can be transported fr om fields or pastures into lakes or streams either as a component of erosion or within runoff water. Phosphorus that is dissolved in runoff water has a greater effect on water quality ( due to availability) than phosphor us that is attached to soil particles and transported to water bodies by erosion (Sharpley et al., 1996). Phosphorus is responsible for algal blooms in surface waters (Bush and Austin, 2001) and can cause eutrophication at levels as low as 0.01 to 0.035 mg/L (Mallin and Wheeler, 2000). In addition, the type of phosphorus used in fertilizer can in fluence the potential risk of water contamination. Highly soluble fertilizers, such as superphosphate present a greater short-term potential for phosphorus loss since they are easi ly dissolved and transported. In the long term, however, lesssoluble phosphorus, such as dica lcium phosphate, may pose a greater risk. This is because less soluble fertilizer remains on the soil surface and a ccumulates due to slow rates of mineralization. While considerable work has been conducted on the movement of phosphorus from soil to surface water by runoff and erosion, vertical m ovement of phosphorus has received little attention. Until recently, pollution of groundwater by fertilizer phosphorus was considered

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23 insignificant (Hesketh and Brookes, 2000); yet studies have shown in sandy soils, phosphorus will leach through the soil profile (Johnson et al., 2004; Sims et al., 1998; Whalen and Chang, 2001). Leaching of phosphorus has also been report ed in poorly drained soils high in organic matter (Sharpley et al., 1994) and regions w ith a long-term history of organic manure applications (Breeuwsma et al., 1995). Soil Accumulation of Nutrients Nitrogen saturation of soil m ay be defined as th e availability of amm onium and nitrate in excess of total combined plant and microbial nutritional demand. By this definition, nitrogen saturation can be determined simply by increase d leaching of nitrate or ammonium below the rooting zone (Skeffington and Wilson, 1988). Current fertilizer application guidelines for Florida forages are based on nitrogen requirements (Mylavarapu et al., 2007). Most animal manure has a lower nitrogen to phosphorus ratio than that needed by crops. Thus, manure applica tions based on crop nitrogen requirements tend to provide phosphorus in excess of crop phosphorus requirements (Intensive Livestock Operations Committee, 1995). With time, this over-applicatio n of phosphorus can result in accumulation in soils. Only a small portion of the total phosphorus in animal manures is readily available to plants. The majority of phosphorus is in the organic or non-labile form, which is strongly held to mineral particles or is combin ed in mineral compounds of low solubility, mainly iron and aluminum phosphates in acid or weathere d soils and calcium phosphates in calcareous soils (Mallarino and Schepers, 2005). Stable phosphor us is considered unavailable to plants in the short term, although it becomes available ove r time due to minerali zation. The long-term effect of phosphorus surplus will be gradual sa turation of the soil P-so rption capacity (Hooda et al., 2001). Intensive poultry and sw ine operations in the U.S. have been identified as causing

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24 excessive phosphorus accumulation in area soils, which consequently increased potential for phosphorus loss in runoff (Sims, 1993). Air Pollution Nuisance od ors can have detrimental effect s on property aesthetics and values, and the quality of life in communities s ubjected to them (Schiffman et al., 1995). In the last decade, a number of countries have reported an increase in odor-related complaints due to agricultural and food processing industries (Both, 2001; Mahin, 2001) As a result, these industries have been forced to control odor emissions, as well as toxic air pollutants. Globally, methane emissions from livestock manure represents 5 to 6% of total methane emissions (Hogan et al., 1991), and nitrogen gas represents 7% of total nitrogen gas emissions (Khalil and Rasmussen, 1992). Nitrogen can damage the environment in the form of ammonia and nitrous oxide (N2O). Ammonia has direct to xic effects on vegetation and vertebrates, when returned to soil and water by ra infall, disrupts ecosystems and l eads to eutrophication (Lapointe and Bedford, 2007). This presents a quandary: volatilization of nitrogen from nitrogen-rich manure is attractive to help balance manure nutrien t application with crop needs, but the process also can result in acid rain. Dramatic increases in the air concentration of ammonia in areas of intensive agriculture have been reported, and Eur opean studies indicate that animal agriculture accounts for 15 to 75% of total ammonia vol atilization (Hartung and Phillips, 1994). Nutrient Management in the Pasture Ecosystem Stocking Rate and Stocking Method Pasture m anagement involves a series of decisions by the farmer, and the ultimate goals are to obtain the most profitable result, main tain pasture persistence, and adherence to environmental regulations. Choice of pasture us e grazing or hay, pasture forage, animal class, stocking rate, stocking method, and fertilizatio n are important factors to consider for

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25 management of pastures (Sollenberger et al., 2002 ). The following section discusses a subset of these management decisions and how they are relate d to nutrient cycling in a pasture ecosystem. Stocking rate is the number of livestock that can be effectively grazed on a defined area of land. The rate will vary greatly depending on the t ype of livestock, the fertility of the land, and the climatic conditions. The stocking rate of horse s in Florida has traditionally been reported as two acres of productive pasture per horse (or 1 horse per hectar e) (Chambliss et al., 2006b), yet this estimate is unsupported scientif ically. The acreage per horse wi ll vary with pasture species and productivity, horse class, amount of grai n and other supplements fed, and grazing management. To determine the pastures carrying capacity based on forage production, pasture intake must be estimated. It has been suggested that a horse will consume or damage 3% of body weight on a dry matter basis per day while on pa sture (Warren, 2006). For an average horse with a body weight of 500 kg, this amount would be 15 kg DM/day (Warren, 2006). Common pasture forages in Florida include Pensacola bahiagrass ( Paspalum notatum ) and Coastal bermudagrass ( Cynodon dactylon ) which produce an average of 5,600 and 9,000 DM kg/hectare, respectively, during an average north Florida growing season (Twidwell et al ., 1998; Chambliss et al., 2006a). Based on this level of forage production and 3% of body weight as consumption, a hectare of bahiagrass will support two horses a nd a hectare of bermudagrass wi ll support four horses during the growing season. This calcula tion is in agreement with Chambliss et al. (2006b) who suggested the stocking rate of one horse per he ctare for Florida bahiag rass pastures with low productivity and two horses per hectare fo r more productive bahiagrass pasture. Although most stocking rate r ecommendations are currently based on forage productivity, stocking rates may be based on soil nutrient levels and future budgets. This strategy is referred to

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26 as nutrient budgeting, which focuses on recycling ma nure to land as fertili zer and only replacing nutrients when a loss occurs. Factors that dete rmine the environmental balance of nutrients requires knowledge of all inputs and exports within the system, such as nutrients excreted, rate of forage litter decomposition, potential nutrient re moval from plants, and acceptable losses of nutrients via volatilization, leaching, runoff, and/or erosion. Although, current fertilizer application guidelines for Florida forages are base d on nitrogen requirements (Mylavarapu et al., 2007). The balance between nitrogen and phosphorus can become skewed when using manure as a fertilizer source. Most manures are phosphorus -rich relative to nitrogen, largely because of relatively large losses of volatili zed ammonia, denitrif ication losses in soil under wet, anaerobic conditions, and the ability of many crops to luxury-consume much more nitrogen than phosphorus (Van Horn et al., 1996). Most soils bind phosphorus effec tively, yet in some areas of Florida, saturation levels are being reached, and phosphorus budge ts are required. In such cases, fertilizer recommendations are then based on phosphorus requirem ents instead of nitrogen. The stocking rate changes significantl y when based on phosphorus levels in soil. For example, on a north Florida Pensacola bahiagra ss pasture with soil tests indica ting already high levels of nonlabile phosphorus present, the stocking rate becomes one horse per two hectares (Chambliss et al., 2006b). When stocking rate recommendations are impractical, the stocking method becomes an important pasture management tool, along with soil testing, fertilization, and mowing. Stocking method, also referred to as grazing method, is a defined techni que of grazing management to achieve specific production (FGTC, 1991). Stocki ng methods can be separated into two main categories: rotational and con tinuous stocking. In continuous stocking, horses graze the same pasture for the entire growing s eason or year. In rotational stoc king, the pasture is divided into

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27 paddocks that are rotationally grazed in sequential order. The purpose of rotational stocking is to allow a period for forage regrowth without anim al interference; giving the forage time to reestablish the carbohydrate levels and leaf area needed for the plan t to reach the steeper part of the growth curve, thereby resulting in faster growth (Chambliss et al., 2006a). Reasons cited for use of rotational stocking over continuous stocki ng include superior plan t persistence (Holechek, 1988) and increased animal production (Blaser, 1986). In addition to affecting the foragelivestock system, stocking method also impacts nutrient cycling. In part icular, stocking method may affect nutrient cycling in the pasture through its impact on uniformity of manure distribution. Peterson and Gerrish (1996) suggested that short gr azing periods and high stocking rates promote a more uniform manure distributio n on the pasture than do other grazing methods. Yet when pastures are managed through mowing and harrowing, which are common practices on horse operations, manure can be mechanically distributed. Florida Pasture Forages The state of Florida currently has over one million hectares of improved pastures, with bahiagrass occupying over 75% of this land base (Adjei and Rechcigl, 2002). Bermudagrass and rhizoma (perennial) peanut are also common forage species in Florida, mostly under hay production. Bahiagrass is a warm-season perennial which can be grown throughout Florida and in the Coastal Plain and Gulf Coast regions of the southe rn United States. Bahiagrass is mostly used for grazing with some hay, sod and seed harveste d from pastures (Chambliss and Adjei, 2006). Bahiagrass is well adapted to the sandy soils of Florida, tolerate s low soil fertility, low pH, and intermittent flooded conditions and survives well during drought conditions (Chambliss and Adjei, 2006). In north Florida, more than 85% of the total bahiagrass annual production occurs from April through September, and shows little growth at temperatures below 15C (Mislevy

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28 and Everett, 1981; Mislevy, 1985). The root system of bahiagrass, once fully established, can recover up to 70% of applied nitrogen a nd absorb significant am ounts of phosphorus and potassium from the topsoil and subsoil, as well as recycled nutrients from manure under grazing conditions (Rechcigl et al., 1992). Bermudagrass is a sod-forming, warm-season perennial which can be grown in the uplands of North Florida and much of the southern United States, and is well suited for either grazing or hay production. Bermudagrass is best grown in fe rtile or fertilized sa nd and clay soils, and tolerates moist conditions but not poorly drained soils and low soil pH (Staples, 2003). In north Florida, the majority of the total annual bermudagrass production occurs from May through October. There are many varieties of bermuda grass grown in Florida including: Coastal, Suwannee, Coastcross-1, Callie, Alicia, Tifton 44, Tifton 78, Tifton 85, and Florakirk (Chambliss et al., 2006). Bermudagrass responds we ll to nitrogen fertiliz ation. Prine and Burton (1956) reported that yield and protein incr eased proportional to ni trogen fertilization. Rhizoma (perennial) peanut is a warm-season pe rennial legume that is grown extensively throughout Florida and in the south Gulf Coast states of the United States, and is almost exclusively used for hay production. Perennial peanut also has potential uses as pasture, creep grazing, silage, ornamental plantings, conservation cover, and living mulch (French et al., 2006). High yields of excellent quality forage can be produced from March through October in Florida when perennial peanut is grown in sandy soils that are moderate to well-drained (Andrae and Heusner, 2003). Perennial peanut is the only warm-season legume that effectively tolerates Floridas climate and soil conditions, with approximately 10,500 hectares planted in 2005 (French et al., 2006). Once established, perennial peanut develops a deep and extensive system of rhizomes and roots, which enable the plant to extract moisture and nutrients from a large

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29 volume of soil. Since perennial p eanut is a legume, it does not re quire nitrogen fertilization, but has been reported to respond to nitrogen thr ough higher yield and protei n (Valentim et al., 1988). Perennial peanut does require phosphorus and potassi um for growth. Potassium fertilization at 75 and 150 kg ha-yr-1 resulted in positive yield responses, but forage production was not increased by phosphorus fertilization (Mooso et al., 1995). Fertilization of the Pasture Ecosystem Fertilization is an im portant management tool that strongly influences nutrient cycling in pastures. Fertilization increases the amount of nutrients cycli ng within the soil-plant-animal system, acting as a catalyst in the main recycl ing process, particularly in low soil fertility environments. Fertilization increases the total plant biomass produced, and accelerates plant residue decomposition, thereby increasing the availability of nutri ents in those residues (Warman and Termeer, 2005; Cadisch et al., 1994; Gijsman et al., 1997). Fisher et al. (1997) recommended fertilizer be applied to pastures once every two years at half the rates used for establishment. These applications would only re place the loss of nutrients that would occur through net nutrient removal by grazing animals and replacement by excr etion. A completely balanced system may continue to have increases in so il nutrients from mineralization due to prior land application of manure. When fertilizing forages for hay production, the fertilizer requirements are significantly higher because plant biomass is frequently being removed. Generally this type of ecosystem is only receiving nutrients from fertilizer; therefor e, current recommendations are based solely on the nitrogen requirements of forage species (Myl avarapu et al., 2007). Yearly soil testing will aid in the determination of efficien t liming and fertilization cycles which, in turn, are necessary for maintaining productive pastures for grazing. Fertilizer should be custom mixed based on pasture soil analysis and should be reeval uated every application year.

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30 Nitrogen Nitrogen is the m ost important fertilizer co mponent for plant yield and quality and, as such, carries the greatest potenti al risk to the environment (Mengel et al., 2006). Nitrogen is an integral component of many essential plant compounds. Plants use nitrogen to form amino acids, and chlorophyll. A good supply of nitrogen stimulates root growth and development, as well as the uptake of other nutrients (Brady and Weil, 2 002). The quantity of nitrogen to be applied to crops depends on several factors including: soil organic matter, grass species, desired yield, geographical location, and form of nitrogen. Previous research with warm-season grasses has shown nitrogen fertilization to increase fora ge dry matter yield and nitrogen (or protein) concentration (Prine at Burton, 1956; Harvey et al., 1996; Caraballo et at ., 1997; Johnson et al., 2001). Although plants will take up either ammonium or nitrate forms of nitrogen, soil chemical and biological processes generally make nitrate the most prevalent form of nitrogen in the soil; thus, the majority of nitrogen taken up is usually in the form of nitrate (Figure 2-1). Recommendations for nitrogen fert ilization are not based on soil te sts, rather recommendations are based solely on nitrogen re quirements of the forage species (Mylavarapu et al., 2007).

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31 Figure 2-1. Flow diagram of the nitrogen cy cle in soil. This figure demonstrates the transformations of nitrogen as ammonia nitrogen (NH3), organic nitrogen (R-NH2), ammonium nitrogen (NH4), nitrate nitrogen (NO3) and nitrogen gas (N2O) within soil and atmosphere. Manure Fertilize r Crop Residue NH4 NO3 R-NH2 Leaching N2 Fixation (by legume forages) Mineralization Nitrification Immobilization NH3 N2O Denitrification Volatilization Runoff and Erosion Plant Uptake Plant Uptake NH3

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32 Phosphorus Phosphorus is an essential elem ent for ma ny plant processes such as photosynthesis, nitrogen fixation, flowering, seed production, an d maturation. Root growth, particularly development of lateral roots and fibrous rootle ts, is also encouraged by phosphorus (Brady and Weil, 2002). The use of fertilizers to apply phosphorus is a common practice. Plants will take up water soluble phosphorus (e.g. monocalcium phos phate and dicalcium phosphate) through the process of diffusion at the plant roots (Figure 2-2). Recommendations for phosphorus fertilizer vary with crop species, yield goa ls, and soil type. If soil phosphorus is below the optimal level, the amount of phosphate fertilizer recommended will permit a gradual buildup of the available phosphorus supply. If soil phosphorus is high, the amount of phosphate recommended will be less than the amount of phosphorus removed in the harvested portion of the crop, allowing some decrease in the soil test (Mengel, 1997). It ha s been reported that bahiagrass does not respond to additional phosphorus fertilizati on when growing on soil alrea dy high in phosphorus (McCaleb et al., 1966). Some Florida soils are naturally high in phosphorus and soil tests may deem them high or very high; therefore phosphorus fertilization may be unnecessary. Phosphate is mined in the state of Florida, which began in the late 180 0s. Currently there are two active mining areas in Florida known as the northern and southern pho sphate districts, where about 2000 hectares are mined each year (Brown, 2005).

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33 Figure 2-2. Flow diagram of the phosphorus cycle in soil Manure Fertilize r Crop Residue Runoff Absorbed P (inorganic) Available P Plant and microbial P (i) Leachin g Mineral P (unavailable) Adsorption Desorption Immobilization Mineralization Precipitation Weathering Crop Uptake

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34 Potassium Of all the essential elements, potassium is the third most likely, after nitrogen and phosphorus, to limit plant productivity. Potassium promotes root growth, plant maturity, disease resistance and cold hardiness (Sartain, 2007). Plants take up very large am ounts of potassium, often five to ten times as much as fo r phosphorus and about the same amount as for nitrogen (Brady and Weil, 2002). In addition plants will increase pot assium uptake as fertilizer application increases (Simonsson et al., 2007). For this reason, potassium is commonly applied to soils as fertilizer and is a component of most mixed fertilizers. The environmental fate of potassium has received less attention than that of nitrogen or phosphorus, mainly because it is not currently cla ssified as a pollutant. The biogeochemistry of the potassium cycle in pastures is simpler and faster than the nitrogen and phosphorus cycles, mainly because potassium is not part of any organic compound and the chemistry of potassium in tropical soils is almost solely based on cation exchange reactions and mineral weathering, rather than by microbiological processes. Soil is the main reservoir of potassium in tropical pasture ecosystems and has been found to be ve ry mobile and prone to leaching (Martin and Sparks, 1985). The forms of potassium in soil, in order of their availabi lity for leaching, are solution, exchangeable, non-exchangeable and mineral (Martin and Sparks, 1985; Sparks and Huang, 1985). Unlike nitrogen and phosphorus, potassium cau ses no off-site environmental problems when it leaves the soil system. It has not been found to be toxic and does not cause eutrophication in aquatic systems. As a result, the EPA does not currently consider potassium as a pollutant in surface and groundwater (USEPA, 1999). In Florida, potassium is considered somewhat mobile, thus it does not build up in the soil. As a result, th e amount of potassium

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35 recommended as fertilizer is base d on what the crop potassium requirements are for the growing season (Sartain, 2007). Horse Stall Materials as a Fertilizer Source The potential value of manure as a fertilizer source depends on the m ethod and rate of application, cropping system, amount of manure av ailable, manure composition, amount of land available for application, quantity of available so il nutrients and the fraction of manure nutrients that could become available to plants after mi neralization (Newton et al., 2003; Eghball et al., 1997). Management of livestock manure applied to soil is more complex than traditional inorganic fertilizer because the nu trient concentration of manure is extremely variable and not all nutrients are available immedi ately for plant uptake. Production of horse stall materials There ar e an estimated 9.2 million horses residing in the United States, and of that, over 500,000 horses reside in the state of Florida ( AHCF, 2005). The average horse produces 14 kg of feces and 7 to 11 liters of urine per day (ASAE, 2005). Confinement of horses to stalls is a common husbandry practice. Bedding is often added on the stall floor to ab sorb urine and feces, as well as provide comfort to the horse. Much of the soiled bedding is removed along with manure when stalls are cleaned, resulting in approximately 20-25 kg manure (feces and urine) and 9 to 11 kg of bedding per day, along with smaller amounts of uneaten feed. Bedding materials make up a large portion of the volume of materials removed from horse stalls and may include straw, wood shavings, sawdust, grass ha y, peanut hulls, shredded paper and other locally available products. The most popul ar bedding in Florida is pine wood shavings (Cotton et al., 2006). Wood shavings are characterized by thei r high organic matter content, bulky nature, high absorption ability, and low nitrogen content (Ott et al., 2000). In this dissertation, stall material is defined as feces, urine, bedding material, and une aten feed. The typi cal stalled horse can

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36 produce 10,000 to 13,000 kg of stall material per year (Swinker et al., 1998). Dependant on diet, the average ton of horse manure will contain 8.6 kg of total nitrogen (N), 6.4 kg of available phosphoric acid (P2O5) and 16.3 kg of potash (K2O) (ASAE, 2005). Theref ore, per year the average horse will produce 77.5 kg of N, 57.1 kg P2O5 and 147 kg K2O from manure. In the horse, magnesium and micronutrient metals (Fe, Cu, Mn and Zn) are excreted primarily in the feces, while calcium, potassium and to a lesser extent sodium are excreted pr imarily in the urine. Nitrogen, phosphorus and sulfur are excreted bot h in feces and urine (Mathews et al., 1996; Hainze et al., 2004), with the relative proportion dependent on amounts in diet. Nutrient availability in manure Ani mals utilize only a portion of the nutrients ingested in thei r diet. The other source of nutrients in manure comes from nutrient recycling w ithin the animal (i.e., endogenous losses). For a non-mature, non-growing, non-lactating, non-pr egnant animal, endogenous losses resulting from tissue turnover can be signi ficant; thus, unutilized nutrie nts in manure are potentially available to plants upon land application (Hayne s and Williams, 1993). When nutrients, such as nitrogen, phosphorus and potassium, are excreted in feces or urine, they ar e either in the organic or inorganic form. Generally, th e inorganic water-soluble forms are more readily available to plants during the growing season compared to the less soluble organic fraction (Hainze et al., 2004). Yet, inorganic nutrients generally have a greater potential to pollute surface and groundwater, due to their enhanced m obility through the soil profile. When nutrients are excreted in organic fo rms, microorganisms within the soil must mineralize the nutrient into an inorganic form before it becomes available for plant uptake. Mineralization rates of nutrients in soil depend on several soil factors including microorganisms present, temperature, pH, oxygen concentration, so il type, C:N ratio, and th e specific type of organic matter present (Eghball, 2000). Figure 23 demonstrates the susceptibility of organic

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37 compounds to mineralization, with sugars minera lizing very rapidly and lignin being the most resistant to mineralization. The availability of nitrogen in hors e manure has been reported as 50% of the total manure nitrogen applied in the first year, which is similar to that for dairy manure, but less than swine manure (90%) and poultry manure (75%) (K idder, 2002; Eghball et al., 2001). While feces contain nitrogen predomin antly in the organic form, 60 to 70% of cow urine nitrogen and 70 to 80% of sheep urine nitr ogen is in the form of urea (Bellows, 2001). Urea in urine is soluble and therefor e immediately available for plan t uptake. The availability of phosphorus for plant uptake is slightly higher than nitrogen in most animal manure. Sharpley and Moyer (2000) reported that dairy cattle manure contains up to 90% available phosphorus because inorganic phosphorus constitutes 60 to 90% of total phosphorus in manure. By comparison, Hainze et al., (2004) reported that manure from yearling horses contained only 30-39% available phosphorus in manure, with the remaining phosphorus in organic forms that must be mineralized before becoming available for plant uptake. Excret ed potassium in urine is in the soluble form and has been reported as 100% plant available fo r all animal species (Eghball et al., 2001). This finding demonstrated that manure potassium can be used similar to inorgani c fertilizer potassium by plants. Since most nutrients are minerali zed slowly from manure, forage plants in the vicinity of manure piles will grow slowly for about two months following manure deposition (Haynes and Williams, 1993; Lory and Roberts, 2000). Howeve r, as mineralization of nutrients occurs, greater pasture regrowth and forage production occurs in the vicinity of manure and urine compared to other pasture areas without fertilization (Cid and Brizuela, 1998).

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38 Organic compound Susceptibility to Mineralization Sugars Starches, glycogen, pectin Fatty acids, glycerol, lipids, fats, phospholipids Amino acids Nucleic acids Very susceptible Protein Hemicellulose Cellulose Chitin Usually susceptible Aromatic and aliphatic compounds Lignocellulose Lignin Resistant Figure 2-3. The susceptibility of organi c compounds found in compost feedstock to mineralization (Epstein, 1997).

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39 Limitations of unprocessed manure as fertilizer Recycling n utrients present in horse stall mate rial by using as a fertilizer source may be a useful and practical tool for manure management Yet, there are certain limitations when using unprocessed manure as a fertilizer source that should be considered, such as land and seasonal constraints, potential for the sp reading of weed seeds and inte stinal parasites, fly and odor production, suppression of forage growth and the potential for contamination of surface and groundwater. Nutrients, such as nitrogen and phosphorus, in horse manure can negatively affect water quality when the number of grazing horses per land area exceeds the nitrogen fertility needs of the forages (Hubbard et al., 2004). In Florida, wh ere agricultural land is decreasing while the horse population is steadily incr easing, available land for applic ation of manure (from grazing animals or land application of stall bedding) at ag ronomic rates is a major constraint. It has been stated that in Florida, horse stocking rates can ra nge from 1-2 hectares required per horse to meet forage needs without additional accumulation of nutrients. Commonly, stocking rates are not taken under consideration when horses are stalled, because animals are not on pasture; yet, disposal of stall material is still necessary and is commonly land applied to forage crops. When stall materials are applied to land as a m eans of disposal and to provide fertilizer for pastures, certain inherent limitations exist, mostly due to the bedding. The most common bedding material used on Florida horse operations is pine wood shavi ngs (Cotton et al., 2006), which contain mostly carbon and very little nitrogen and phosphorus. Soil microorganisms require an optimal C:N ratio of 25-30:1 to perf orm biological processes, such as mineralization and nitrification (James, 2003). By itself, horse manure has an optimal C:N ratio of 30:1, yet when manure is accompanied by bedding, that rati o may increase to as high as 130:1 (Cotton et al., 2006). When the C:N ratio is above 30:1, so il microorganisms will not release inorganic

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40 nitrogen for plant uptake during decomposition. Instead, microorganisms supplement their nitrogen requirements from the soils inorganic nitrogen pool, thereby re ducing the availability of that pool to plants by the ac t of immobilization. It has been reported that when horse manure and wood shavings are applied to pastures, it can induce nitrogen de ficiency as a result of a C:N imbalance and growth of forage crops will be st unted (James, 2003). This deficiency is the result of soil microorganisms being more effective than plants at competing for nitrogen (Hodge et al., 2000). When pasture forage growth is stunted, the opportunity for weed seed germination and growth increases. Weed seeds can be transpor ted in hay, harvested gr ass seed, sod, and mowing equipment, or dispersed by wind, water, manure a nd wildlife (Sellers et al., 2006). Major et al. (2005) reported that poultry manure application on tropical pastures increased weed germination and composition when compared to inorganic fertil izer and compost. Horses kept on pasture will naturally distribute weed seeds in common feeding and high traffic areas, yet when stall material is land applied, weed seeds are distributed even ly across the pasture, potentially resulting in widespread germination. In addition to the widespread distribution of weed seeds, the potential for spreading intestinal parasites arises when horse stall material is land app lied. There are more than 150 types of internal parasites that are known to infect horses. From a practical standpoint, the most important ones are strongyles, ascarids, tapeworm s and bots. Each species of parasite has a specific life cycle, yet they all have a stage capabl e of living in the enviro nment or soil (Nielsen et al., 2007). Since all of the parasites pass out in the feces, controlling the manure is a very important step toward controlling the parasites in the hor se and soil. Lyons et al. (1999) advised not to land apply fresh horse manure on pastures util ized by horses in order to reduce the rate of

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41 infestation of parasites. If land application of fresh manure is necessary, options for reducing the parasite infestation exist. For ex ample, rotation of pastures for a time period of several months will disrupt parasite life cycles and reduce or k ill parasites. Alternating ruminants and horses on pastures can be beneficial because each animal eats larval parasites of the other host category, resulting in death of the ingest ed larvae. Pasture management strategies such as mowing and chain harrowing can also help expose larvae to dry air and sunlight (Lyons et al., 1999). Sunlight may kill or reduce parasite populations during Floridas summer months, but during winter months, it has been reported that the free-living stages of vari ous species of gastro-intestinal parasites can survive on pastur e (Drudge et al., 1958). Removal of manure from pastures has been another method of parasite control (Lyons et al., 1999). Finally, burying of manure by dung beetles can be beneficial in th e destruction of environmental st ages of parasites (Waller and Faedo, 1996). In Florida, where suburbanization of formerly rural areas is occurri ng, a rise in nuisance insect complaints is significant (Hogsette, 1993 ). Depending on the condition of the manure and the existing insect population, a pest outbreak re sulting from land application of manure may be an important liability. House flie s are an important pest of the horse industry and are frequently the cause of nuisance complaints. Once a nuisan ce pest outbreak enters the popular press, it effectively creates a negative investment clim ate for agriculture and the community. Horse manure may contain a large number of fly larvae and pupae and adult flies will emerge from the manure when land applied (Watson et al., 1998). It has been reported that spreading a thin layer of poultry manure on agricultural fields encour ages drying and reduces fly population (CalibeoHayes et al., 2005). However, because of the ball -like structure of horse manure, the manure is difficult to spread thin enough for adequate drying before adult flies can lay eggs.

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42 The primary environmental concern with regard to using horse manure as fertilizer for pastures is the potential for surface and groundwat er contamination. The presence of relatively mobile forms of nitrogen and phosphorus, as well organic matter, microbes, and other materials near the soil surface following horse manure applic ation can potentially d ecrease the quality of storm water runoff. This is particularly evident during the first post-ap plication runoff event. Studies such as those by Westerman et al. (1983), McLeod and Hegg (1984), and Edwards and Daniel (1993) indicate that runo ff from grassed areas treated with animal manures can contain elevated concentrations of nutrients, solids, and organic matter relative to untreated areas. When nutrients, such as nitrogen and phosphorus, exceed the loading rate for a body of water, eutrophication can occur. The plant available form s of these nutrients ap pear to be of most concern because of their potential for direct up take by aquatic vegetation and algae (Bushee et al., 1998). Management options such as the employment of vegetation buffer strips and incorporation of manure into soil as well as application timing ha ve been advocated for reducing pollution potential from pastures trea ted with manure (Young et al., 1980). Several management strategies have been disc ussed to counteract some of the limitations of using horse manure as fertilizer amendment for pastures. One management tool that has gained a renewed interest in the horse i ndustry is composting. Treating manure through composting could provide a means of reducing the environmental impact of horse manure by reducing the total volume of materi als, destroying parasites and weed seeds, and reducing runoff risk by stabilizing nutrients into organic forms. Furthermore, composting may enhance the value of stall materials, making it more attractive to end-users compared to unprocessed horse manure. Compost The subject of com posting can be subdivided into two major areas: the composting process and the compost product. For the purposes of this dissertation, the proc ess of composting has

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43 been defined as is the biological decompositi on of organic matter unde r controlled aerobic conditions (Epstein, 1997). The U.S. Composti ng Council (2000) has defined compost as, the product resulting from the controlled biological d ecomposition of organic matter that has been sanitized through the generation of h eat and stabilized to the point th at it is benefi cial to plant growth. Compost is an organic matter resource that has the unique ability to improve the chemical, physical, and biological ch aracteristics of soils or growing media, and it contains plant nutrients but is typically not char acterized as a fertilizer. History of Composting The first recorded use of com post, in the practice of placing manure on crops for the benefits of its high nitrogen content, was recorded in the Mesopotamian Valley on cuneiform tablets from the Akkadian Empire (Martin and Gershuny, 1992). The Tribes of Israel, the Greeks and the Romans all used composting practices (Fitzpatrick et al., 2005). Typically organic materials were piled and allowed to decompose for long periods of time producing compost. In Americas early history, Native Americans were known to use compost on their crops, as were the early European settlers. Ma ny New England farmers made compost as a recipe of ten parts livestock manure to one part fish, periodically turning their compost heaps until the fish disintegrated (Arner et al., 1995). American historical figures such as George Washington, Thomas Jefferson and James Madison were all known to be proponents of composting, boasting its importance for soil fertility (Arner et al., 1995). Work done in 1840 by a well-known German scientist, Justus von Liebig, proved that plants obtained nourishment from certain chemicals in solution. Liebig dismissed the significance of compost, because it was insol uble in water (van der Ploeg et al., 1999). Following this discover y, agricultural practices became increasingly focused on inorganic fertilizers. For farmers in many areas of the worl d, inorganic fertilizers replaced compost (Fitzpatrick et al., 2005). Sir Albert Howard, a British government agronomist

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44 in the Colonial service, went to India in 1905 and spent almost 30 years experimenting with organic gardening and farming. He found that the best compost consisted of three times as much plant matter as manure, with materials initially layered in a sandwich fashion, and then turned during decomposition (known as the Indore method and later as the Bangalore) (Howard, 1935). In 1943, Sir Albert Howard published the book, An Agriculture Testament, based on his work. The book renewed interest in organic methods of agriculture and earned him recognition as the modern day father of organic farming and garden ing. J. I. Rodale popularized Sir Alberts work and introduced American gardeners to the va lue of composting for improving soil quality (Martin and Gershuny, 1992). He established a farm ing research center in Pennsylvania and the monthly Organic Gardening magazine. In the Unite d States, very little research was conducted on composting in the 1950s and the only major experiments were conducted at the Richmond Station of the University of California under the leadership of Harold Gottas and Clarence Goulke (Epstein, 1997). In the 1960s the United States Public Health Service began two major research and demonstration projects on the compos ting of municipal solid waste with biosolids. One location was in Gainesville, Florida, and th e other in Johnson City, Tennessee (Breidenbach, 1971). Prior to the 1970s, there were very few co mmercial scale composti ng facilities, mainly due to very low tipping fees at landfills wh ich caused negative competition with composting facilities (Breidenbach, 1971). In 1972, the Clean Water Act enc ouraged composting of sewage sludge by establishing minimum treatment require ments for municipal wastewater and providing significant economic incentives (USEPA, 1999). A major boost to composting in the United States occurred following the formation of the Composting Council in 1990, which supported numerous composting research projects. As a result of the United States Environmental Protection Agency construction grants program emphasizing composting of biosolids, major

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45 European firms entered the American market in the in 1980s. The growth of biosolid composting facilities in the United States significantly incr eased and this trend continues today (Epstein, 1997). In the 1990s many states started banning ya rd wastes from landfills, brought on by the lack of landfill space near urban areas. As a result, the number of yard waste composting facilities has increased exponentially in the United States (Epstein, 1997). Todays trend for composting i nvolves municipal, agriculture and private use. Composting is a highly effective way of stab ilizing and reducing pathogens in biosolids, while diverting these resources from landfills, producing a high-quality soil amendment (Rynk et al., 1992). The EPA estimated the potential demand for compost to be over one billion cubic yards per year. The report describes nine markets for compost: agricu lture, silviculture, s od production, residential retail, nurseries, delivered t opsoil, landscaping, landfill cover, and surface mine reclamation (USEPA, 1998). In practice, compost is more commonly used by nurseries, landscapers, and soil blenders rather than for agri cultural purposes. Nevertheless, in its analysis, the EPA (1998) concluded that the demand for compost in agricultu re and silviculture alone could exceed current and potential supplies. Types of Composting Com posting may be carried out under anaer obic or aerobic conditions. In anaerobic composting, decomposition occurs where oxygen is absent or in limited supply. Using this method, anaerobic microorganisms dominate and develop gaseous compounds including methane, organic acids, hydrogen sulfide and othe r substances (Figure 2-4). In the absence of oxygen, these gases accumulate and are not meta bolized further. Many of these gases have strong odors and some present phytotoxicity. An aerobic composting occurs at relatively low temperatures and as a result, it leaves weed s eeds and pathogens intact (Mata-Alvarez, et al., 2000). Anaerobic composting has recently gained a renewed interest in th e agriculture industry.

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46 The gases produced by the anaerobic bacteria ar e commonly referred to as biogas and can be collected and used either as a di rect energy source or converted to electricity. At the same time, nutrients contained in the orga nic matter are conserved and mine ralized to more soluble forms (such as ammonium), thereby increasing the fert ilizer value of the material for crops. Manure represents a substantial bioe nergy resource if processed by anaerobic digestion. When considering biogas production from manure, the vol atile solids content of the material is as important as the total solids content since it represents the fraction of the solid material that may be transformed into biogas. Aerobic composting takes place in the presence of oxygen. Du ring this process, aerobic microorganisms break down organic matter and pr oduce carbon dioxide, ammonia, water, heat and compost-a relatively stable organic end product (Haug, 1993) (F igure 2-5). The heat generated during aerobic decomposition accelerates the breakdown of proteins, fats and complex carbohydrates such as cellulose and hemi-cellu lose. Moreover, this process destroys many microorganisms regarded as human and plant pat hogens, as well as weed seeds, provided it undergoes sufficiently high temperatures (Shi ralipour and McConnell, 1991). Although more nutrients are lost from the materials by aerobic composting, it is consider ed more efficient and useful than anaerobic composting for agricultural production. The remainde r of this dissertation, including all experimental chapters, will focus on aerobic composting, which is a more feasible method of composting on horse operations.

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47 Figure 2-4. Flow diagram of the an aerobic composting process (Haug, 1993). Anaerobic composting Heat Water Organic Matter CO2 H2S CH4 Undigested residue Water/nonrecyclables Biogas

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48 Figure 2-5. Flow diagram of the aerobic composting process (Haug, 1993). Microorganisms Organic matter Carbohydrates Sugars Proteins Fats Hemicellulose Cellulose Lignin Mineral matter Oxygen Water CO2 H2O NH3 volitization Compost Heat

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49 The Aerobic Composting Process The aerobic com posting process starts with th e formation of a pile sufficient enough to hold heat. Temperatures will rise rapidly to 70-80C within the first couple of days (Poincelot, 1975). During this temperature phase, mesophilic organisms multiply rapidly and break down the soluble and readily degradable compounds such as sugars and amino acids (Haug, 1993). These microorganisms generate heat via their own me tabolism and raise the temperature to a point where their own activities are suppressed. Therm ophilic fungi and several thermophilic bacteria continue the process, raising the pile temp erature to 65C or higher (Haug, 1993). This high temperature phase accelerates the breakdown of proteins, fats and complex carbohydrates like cellulose and hemicellulose from plant cells. Most of the plant/animal pathogens, weed seeds and nematodes are destroyed during this high temper ature phase (Shiralipour and McConnell, 1991). After most of the degrada tion has occurred, the temperat ure decreases, mesophilic microorganisms reemerge and the curing phase begins The start of this phase is identified when aeration no longer results in rehe ating of the pile. Eventually, the temperature declines to ambient temperature and the pile becomes more uniform and less biologically active, although mesophilic organisms recolonize the compost (P oincelot, 1975) (Figure 2-6). The material becomes dark brown to black in color and particle size is reduced to resemble a soil-like texture. In the process, the amount of humus increases, the ratio of carbon to nitrogen decreases, pH neutralizes, and the catio n exchange capacity of the material increases (Bernal et al., 1998).

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50 Figure 2-6. Phases of composting as relate d to temperature and time (Epstein, 1997). High rate composting Curing Thermophilic Temperatures Mesophilic Temperatures Time Temperature Stable and Mature Compost

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51 Factors Affecting Aerobic Composting The m ajor factors affecting the decompositi on of organic matter by microorganisms are oxygen and moisture (Rynk et al., 1992). Temperatur e is an important factor; however, it is the result of microbial activity. Other important f actors that could limit th e composting process are nutrient availability and pH. Nutrie nts, especially carbon and nitrogen, play an important role in the process as they are essential for microbial growth and activity (Eps tein, 1997). Carbon is the principal source of energy and nitrogen is needed for microbial prolifer ation. These factors will be discussed in more detail below. Aeration Aerobic composting requires an oxygen concentration of at least 5% th roughout the entire pile. Aeratio n provides a key source of oxygen a nd is indispensable for aerobic decomposition. Where the supply of oxygen is not sufficient, th e growth of aerobic microorganisms is limited, resulting in slower decomposition due to anaerobic bacteria pro liferation (Epstein, 1997). Proper pile aeration also removes excessive heat, water vapor and other gases trapped in the pile. Heat removal is particularly important in warm climates as the risk of overheating and fire is higher. There are four principal aeration methods used to provide oxygen during composting: active aeration, passive aeration, mechanical aeration and natural aer ation. Active aeration generally involves turni ng of the material with a bucket lo ader or special turning equipment (Larney et al., 2000). Turning schedules are t ypically based on pile temperature and oxygen concentrations. Passive aeration involves natural air convection generally through the use of pipes aligned vertically or horiz ontally within the pile, which pull in oxygen while ventilating gases generated from within the pile (Sylla et al., 2003). Mechanic al or forced aeration requires the use of blowers to generate air supply thr ough the pile (Solano et al ., 2001). Natural aeration

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52 occurs simply by diffusion and convection, which is governed by the exposed surfaces and their respective properties (B arrington et al., 2003). Moisture Adequate moistur e is essential for microbial activity. During composting a moisture content of 40-65% should be maintained (Rynk et al., 1992). If the pile is too dry, composting occurs more slowly. In contrast, if moisture content is above 65%, anae robic conditions develop, which will also hinder decomposition. In practice, it is advisable to start th e pile with moisture content of 50-60% and finish at about 30% moisture (Rynk et al., 1992). Nutrients Microorganism s require carbon, nitrogen, phosphorus and potassium as the primary nutrients. During composting, carbon and nitrogen are the most important nutrients affecting the process and the product. The optim al carbon:nitrogen ratio (C:N) of raw materials is between 25:1 to 30:1. At C:N ratios exceeding 50:1, the composting process slows due to depletion of available nitrogen, resulting in reduced cellula r growth (Bishop and Godfrey, 1983). A C:N ratio of less than 20:1 leads to underu tilization of nitrogen and th e excess may be lost to the atmosphere as ammonia or nitrous oxide, thereby generating problematic odors. When evaluating the carbon content of th e material to be composted, it is important to consider the availability of carbon to the microorganisms, and not just the total carbon content (Epstein, 1997; Figure 2-3). If a carbon source is unavailable to microorganisms, decomposition of materials will decrease. For example, if material has high a lignin content, which is highly resistant to microbial degradation, and star ting C:N ratio is not adjusted, decomposition will be hindered (Richard, 1996). Cappaert et al. ( 1975) found that the addition of mineral nitrogen fertilizer to hardwood bark, which is high in lignin, increased the rate of decomposition.

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53 pH Although th e natural buffering effect of the composting process lends itself to accepting material with a wide range of pH, the pH le vel should not exceed 8.0 (Jeris and Regan, 1973). At higher pH, more ammonia gas is ge nerated and may be lost to the atmosphere via volatilization. Pile size and porosity of the material The size of the pile is of great significance to composting. If the pile is too large, anaerobic zones occur near its cen ter, which slows the process in these zones. On the other hand, piles that are too small lose heat quickly and may not achieve a temperature high enough to evaporate moisture and kill pathogens and weed seeds (Rynk et al., 1992). The optimal size of the pile depends on parameters such as the phys ical properties of th e materials (e.g., porosity) and the method used to form the pile. While mo re porous materials allow bigger piles, heavy weights should not be put on top and materials shoul d be kept as loose as possible. Climate must also be factored in when considering effec tive pile size for composting. With a view to minimizing heat loss, larger piles are suitable for cold weather. However, in a warmer climate, the same piles may overheat and, in some extreme cases, catch fire (Riggle, 1996). Maturity and Stability of Aerobic Compost For compost to be safely used as a growing media, the principal requirement is its degree of stability or maturity, which implies stab le organic matter conten t and the absence of phytotoxic compounds and plant or animal pathogens (Bernal et al., 1998). Maturity and stability are two terms that are sometimes used interchangeab ly when referring to composts, yet they have slightly different meanings. Maturity is associat ed with plant growth pot ential or phytotoxicity (Iannotti et al., 1993), whereas stability is often related to the composts microbial activity (Eggen and Vethe, 2001). Immature composts ma y have high C:N ratios, high soluble salt concentrations, high concentra tions of organic acids and other phytotoxic compounds, high

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54 microbial activity, and high respiration rates (Jimenez and Garcia, 1989). Land application of immature compost can cause detrimental affects to plants and forage crops The negative effects of immature compost have been researched thor oughly and reported to caus e biological blockage of soil-available nitrogen by microbial populations (S carsbrook et al., 1969; Duggan, 1973). This may give rise to serious nitrogen deficiencies in the plant, an d consequently nitrogen starvation and growth-depression of crops (Bengtson and Cornette, 1973). The abundance of chemical and biological changes that occur during composting, and the range of methods suggested in the literature, has made it difficult to agree on met hods for the practical as sessment of maturity (Itavaara et al., 2002; Wang et al., 2004). Various parameters that have been used include C:N ratio of the finished product, water soluble car bon, cation exchange capaci ty, humus content, and respirometry (Garcia et al., 1992; Scaglia et al., 2000; Huang et al., 2001; Wu and Ma, 2002). Germination index, which is a measure of phytotoxi city, has been consider ed as a reliable, but indirect, quantification of compost maturity (Cunha Queda et al., 1996). Rigid control of compost maturity and product uniformity may lead to wider use of co mpost in the nursery industry. Commercial compost comp anies currently must monitor and manage their compost to consistently produce a uniform prod uct that can be successfully used for plants and crops (Klock and Fitzpatrick, 1999). Aerobic Composting as a Tool for Horse Manure Management There are a reported 9.2 m illion horses residing in the United States (AHCF, 2005). While the numbers of horses have st eadily increased, land availabilit y for animal agriculture has decreased, causing disposal or utilization of horse manure and soiled stall bedding to become a major concern. Horse owners have typically dispos ed of stall materials (manure plus bedding) by piling them on unused land, hauling them to la ndfills, burning them, or using them as soil amendments for pasture or cropland (NAHMS, 1998). With increasing emphasis on the control

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55 of environmental pollu tion, many of the above options are limited or no longer available. Another widespread management strategy is st ockpiling, where horse manure is piled to await disposal, hauling or spreading onto pastures (S weeten, 1996). In an equine manure management survey conducted by the University of Flor ida, (Cotton, D. personal communication, 2008). reported that approximately 80% of producers in cluded stockpiling in their manure management practices. A poorly managed manure pile can har bor intestinal parasite s, provide a breeding ground for flies and produce offensive odors (W arren and Sweet, 2003). Runoff from improperly stored manure can quickly become a potential environment contaminate as it carries soluble nutrients, pathogens and organic particles into the water cycle via surface runoff or by leaching into groundwater (Warren and Sweet, 2003). Land app lication of fresh manure can also generate large amounts of ammonia, carbon dioxide, methan e, and nitrous oxide, which potentially could be damaging to the environment (Yamulki, 2006). Treating stall materials through composting could provide a means of reducing the environmental impact of horse manure by reducing th e total volume of materials that need to be disposed of (Larney et al., 2000), destroying pa rasites and weed seeds (Romano et al., 2006; Larney et al., 2003; Larney and Blackshaw, 2003) decreasing odor production, compared to stockpiled manure (Li et al., 2007), producing a stor able end product for on and off farm use, and lowering nonpoint source pollution from horse fa rms (Michel et al., 2004). The stabilized end product can be used as a rich amendment for so il applications, such as agricultural cropland, landscape industry, or in nurse ry potting mixes (Lynch, 2004). The costs of the composting process can be offset by the value-added nature of compost (Michel et al., 2004). For example, compost enhances soil fertility, increases crop yields (Dick and McCoy, 1993) and reduces

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56 diseases caused by soilborne plant pathogens (Hoitink and Fahy, 1986; Hoitink and Boehm, 1999). There are some limitations to composting horse stall materials when compared to beef or poultry litter. One of the biggest obstacles in successfully compos ting horse stall materials is the high carbon content of bedding. By itself, horse manure is already near the ideal C:N of 25-30:1 needed to support microbial decomposition of orga nic materials. In contrast, the C:N of common beddings used in stalls ranges from 30:1 for st raw or hay to 950:1 for wood shavings (Warren and Sweet, 2003). When bedding is combined w ith manure, the C:N can often exceed 130:1 (Cotton et al., 2006). A high C:N in manure and bedding removed from horse stalls has been shown to slow the composting process (Swinker et al., 1998). This is thou ght to be due to the depletion of available nitrogen, with a subs equent reduction in mi crobial growth and decomposition of organic materials (Swinker et al., 1998). Amending horse stall materials with nitrogen may facilitate faster and mo re complete decomposition by supporting the microorganisms involved in composting. Another negative effect, caused by bedding is an increase in free air space, which may decrease pile temperatures, decomposition rate, and oxygen concentrations (Fraser and La u, 2000; McCartney et al., 2002). The type of bedding has also been found to influence compostability of horse stall material. Swinker et al. (1997) reported that sawdust bedding composted more readily than phone book paper or straw bedding. Straw was the least desirable composting material, while sawdust was the most consistent. However, Swinker et al. (1997) also stated that C:N ratios of all three materials were quite high, which decreased the rate of decomposition for each material. Compost as a Fertilizer So urce for Florida Forages Com post not only supplies nutrients needed to support forage production, it is also a valuable source of organic matter. Increasing soil organic matter improves soil structure,

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57 increases the water holding capacity or coarse-t extured sandy soils, improves drainage in finetextured clay soils, provides a source of slow release nutrients, reduces wind and water erosion, and promotes growth of earthworms and othe r beneficial soil orga nisms (Rynk et al., 1992). Furthermore, application of compost as a soil amendment reduces nitrogen leaching from the soil (Epstein, 1997). Therefore, ut ilization of compost could re duce the amount of commercial nitrogen fertilizer applied and decrease the potential for nitrate contamination of surface and groundwater (Diepeningen et al., 2006). The nitrogen content of a composted produc t depends on the feedstock and processing technology used to produce the compost. Si milar to unprocessed manure, the nitrogenphosphorus-potassium ratio of most animal manure derived compost is such that application to soils at a rate selected to satisfy the nitrogen requirements of forage might result in excess additions of phosphorus and potas sium. Therefore, meeting the forages phosphorus requirement first with compost and then supplementing wi th inorganic fertilizer to meet nitrogen requirements may be the optimal management strategy. The amount of compost to be applied to a par ticular soil depends on the composition of the compost, the forage crop grown, and environmen tal conditions (Eghball, 2000). An analysis of the compost to be applied is essential to m eet the requirements of forages prior to land application. The availability of nut rients in compost will depend mo stly on mineralization rates. Mineralization rates of nutrients in soil depend on several soil factors including microorganisms present, temperature, pH, oxygen concentrati on, soil type, C:N ratio, and organic matter (Eghball, 2000). Generally, 20-30% of the phosphorus (Hainze et al., 2004) and 80-90% of the potassium (Eghball et al., 2001) will be available from the compost during the first year after application. Calculating nitrogen availability is more complex than determining phosphorus and

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58 potassium availability. Most of the nitrogen in compost is organic, which is unavailable for uptake until soil microorganisms degrade the or ganic compounds through mineralization. The rate of nitrogen mineralization for beef cattle compost has been repo rted at 22% available nitrogen during the first year of application (Eghball and Po wer, 1999; Eghball, 2000). Horse manure has been reported as having a nitrogen mineralization rate varying from 20 to 50% (Maryland Cooperative Extension, 1993; Kidder, 2002), yet little data is available on nitrogen mineralization rates of compost made from horse manure. Many studies have demonstrated the positive effects of land application of compost generated from various manures on forage production, usually resu lting in yields that were comparable to those produced by inorganic ferti lizer (Catroux et al., 1981; Hornick et al., 1984; Davis et al., 1985; Warman and Termeer, 1996; Reid er et al., 2000; Tiffany et al., 2000). In the few instances where a negative response to com post application has been observed, either a high C:N ratio, excess metals, high soluble salts or ex tremely high application rates were responsible for the reduced yields or negative effects on soils or crops (Warman and Termeer, 2005). Summary The am ount of research that has been conducte d using horse stall material as the parent material for compost is limited. The research that has been conducted is primarily based on compostability of bedding that accompanies horse manure (Swinker et al., 1997; Ball et al., 2000; Airaksinen et al., 2001; Font anive et al., 2004) or the pa thogen reduction efficiency of composting horse stall materials (Romano et al., 2006). In addition, very little research has been published concerning the performa nce of unprocessed or composted horse stall material as a fertilizer source. A negative connotation exists in the horse industry when it comes to land application of stall material, mainly due to potential spreading of w eeds and pathogens onto pasture. Treating manure through composting coul d provide a means of reducing the negative

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59 environmental impact of horse manure by reducin g the total volume of materials, destroying parasites and weed seeds, and reducing runoff risk by stabilizing nutrients into organic forms.

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60 CHAPTER 3 ON-FARM COMPOSTING OF HORSE STALL MATERIALS: EFFECT OF CARBON TO NITROGEN RATIO AND BEDDING TYPE Introduction An estim ated 9.2 million horses reside in th e United States (AHCF, 2005). While the number of horses has steadily increased, land av ailability for animal agriculture has decreased. As a result, disposal and utiliz ation of horse manure and soiled stall bedding have become major concerns. Horse owners have typically disposed of stall materials (manure plus soiled bedding) by storing them on unused land, hauling them to landfills, burning them, or using them as soil amendments for pasture or cropland (NAHMS, 1998). With increasing emphasis on the control of environmental pollu tion, many of the above options are limited or no longer available. Another widespread management strategy is st ockpiling, where horse manure is accumulated to await later disposal, hauling or spreading onto pastures (Sweeten, 1996). A survey of equine breeding farms and training facilities in Florida found that 80% of producers included stockpiling in their manure management prac tices (Cotton, D. pers onal communication, 2008). A poorly managed manure pile can harbor intestinal parasites, provide a breeding ground for flies and produce offensive odors (Lyons et al., 1999; Ma jor et al., 2005; Watson et al., 1998). Runoff from improperly stored manure can quickly beco me a potential environment contaminate as it carries soluble nutrients, pathogens and organic particles into the water cycle via surface runoff or by leaching into groundwater (Yamulki, 2006) Land application of fresh manure can also generate large amounts of ammonia, carbon diox ide and nitrous oxide, which could further impact the environment (Yamulki, 2006). Trea ting manure through composting could provide a means of reducing the environmental impact of horse manure by reducing the total volume of materials, destroying parasites and weed seeds, and reducing runoff risk by stabilizing nutrients into organic forms.

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61 Compost is the product resulting from biol ogical decomposition of organic matter under controlled conditions, which has b een sanitized through the generati on of heat and stabilized to the point that is beneficial to plant growth (Thompson, 2001). Stabiliza tion includes the process of transforming inorganic soluble nutrients into organic insoluble forms, which are less likely to contaminate ground and surface water. The stabili zed compost can be used as amendment for soil applications, such as agricultural cropl and, landscaping, and nursery potting mixes (Lynch, 2004). Other benefits include a reduction in the volume of material (Larney et al., 2000), elimination of viable weed seeds (Larney and Blackshaw, 2003) and intest inal parasites (Larney et al., 2003), and decreased odor production, comp ared to stockpiled manure (Li et al., 2007). Horse manure is often mixed with bedding when removed from facilities where horses are stabled in barns. The high carbon content of bedding presents a unique challenge when composting horse manure that is usually not a limitation faced when composting other livestock manures. The optimal ratio of carbon to nitrogen (C:N) to support microbial decomposition of organic materials is 25-30:1 (Rynk et al., 1992). By itself, horse manure is already near the ideal C:N (ASAE, 2005). In contrast, the C:N of common beddings used in stalls ranges from 30:1 for straw or hay to 950:1 for wood shavings. When bedding is combined with manure, the C:N can often exceed 130:1 (Cotton et al., 2006). A high C: N in manure and bedding removed from horse stalls has been shown to slow the composting pr ocess (Swinker et al., 1998). This is thought to be due to the depletion of ava ilable nitrogen, with a subsequent reduction in microbial growth and decomposition of organic materials (Swinker et al., 1998). Amending horse stall materials with nitrogen may facilitate faster and mo re complete decomposition by supporting the microorganisms involved in composting. However, due to the varying amount of lignification in common horse beddings, it is unknown if all stall ma terials will respond to nitrogen amendment.

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62 The objective of this study was to evaluate various rates of nitrogen amendment and their effects on the ease of composting horse stall materials containing either pine wood shavings or bermudagrass hay bedding. The hypothesis was that the addition of nitrogen to horse stall materials would result in an increased rate of decomposition and improving the compost as a potential source of nutrients for fertilizer application. Materials and Methods Experimental Design Five treatm ents were used to evaluate the effects of bedding type and C:N on the composting of horse stall materials: 1) st all materials containing horse manure and wood shavings bedding that was not amended with ni trogen (WOOD-CON; C:N 85:1), 2) amended to a C:N of 60:1 (WOOD-60), or 3) amended to a C:N of 30:1 (WOOD-30) a nd 4) stall materials containing bermudagrass hay bedding that wa s not amended with nitrogen (HAY-CON; C:N 30:1) or 5) amended to a C:N of 15:1 (HAY-15). Urea served as the nitrogen amendment. All composting was performed in a concrete-based, 8-bin system (each bin measured 3 m x 3 m) housed under roof cover. Horse manure and bedd ing was removed daily from stalls, weighed, amassed in bin 1 over 14 d (amassing phase), ame nded with nitrogen (if appropriate), and moved by a front-end loader to bin 2 wher e it was started on trial (d 0). A new batch of stall materials would then be amassed in bin 1. In this manner, each batch of material was rotated from bin to bin every 14 d providing active aeration. When materials complete d the cycle in bin 8, they had been composted for 84 d. Three replicates of each treatment were performed with treatments randomly distributed throughout the trial period of December 2005-November 2006.

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63 The amount of urea needed to achieve the desi red C:N ratio for N-amended treatments was determined using the formula described by Fitzpatrick (1993): (Cstall) (Desired C:N)(Nstall) Ureaadd = ______________________________________ [Equation 3-1] (Nurea)(Desired C:N) (Curea) Where Ureaadd = kg urea to be added per one kg stall material; Cstall=kg carbon in 1 kg stall material; Nstall = kg nitrogen in 1 kg stall material; Curea=kg carbon in 1 kg urea; and Nurea=kg nitrogen in 1 kg urea. The carbon and nitrogen content of stall materials was determined from analyses performed on random samples obtained during the 14 d amassing phase prior to the start of composting. Compost temperature and oxygen c ontent were measured 3 d wk-1 and moisture content was adjusted as needed to maintain 50-60% moisture. Representative samples of stall materials were obtained prior to nitrogen amendment duri ng the amassing phase, when materials officially started on trial (d 0), and af ter 42 and 84 d of composting. Data Collection and Analysis Tem perature of compost was determined using a bi-metal dial thermometer with an 54.7 cm stem (Omega model B(-17-121C)-45.7cm). Temperature was determined by inserting thermometer 55 cm into center of pile, repeated in triplication and average temperature recorded. Moisture content was determined after forced-air drying in an oven at 60C until a constant weight was achieved. Organic matter (OM), pH, bul k density, pore space, water holding capacity (WHC), conductivity, tota l dissolved solids (TDS) and soluble phosphorus (Psol) of stall materials were determined using methods recommended by the U.S. Composting Council (Thompson, 2001). Soluble phosphorus was extracted by creating a 1:5 slurry of compost and deionized water. The 200mL sample is shaken at a rate of 180 excursions per minute for 20 minutes. The liquid is separated by centrifuge (at 8000 g for 15 minutes) and passed through a

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64 0.45 m membrane filter. The water soluble phosphor us content of the filtrate is quantified colorimetrically (PowerWave XS spectrophoto meter, Winooski, VT). Moisture content was determined after forced-air drying in an oven at 60C until a constant weight was achieved. Total nitrogen (N) and total carbon (C) analyses were performed with the Dumas combustion method (VarioMax N analyzer, Elementar Am ericas) (TMECC methods 04.02-D and 04.01-A (Thompson, 2002)). Total phosphorus (Ptot) was determined on samples that had been ashed prior to sulfuric acid digestion and then quantified colorimetrically (PowerWave XS spectrophotometer, Winooski, VT). Potassium (K ) concentration in samples was determined using atomic absorption spectrometry (Perkin-Elmer Corp, Norwalk, CT). Organic matter (OM) was determined after heating samples for 12 h in a muffle furnace at 550C (TMECC method 03.02-A (Thompson, 2002)). The pH was determined on a slurry prepared with stall materials and dionized water according to AOAC me thod 973.04 using a Thermo Orion Posi-pHIo SympHony Electrode and Thermo Orion 410-A meter (Thermo Fisher Scientific, Waltham, MA). Neutral detergent fiber (NDF), acid deterg ent fiber (ADF) and lignin concentrations were determined using the ANKOM A200 filter bag technique (AOAC 973.18(B-D)). Ambient temperature and rainfall was recorded weekly from the Alachua Florida Automated Weather Network. Nutrient data obtained from composted ma terials were transformed using mass balance estimates to determine net loss/gain of nutrients Total mass balance estimates for each nutrient (i.e., C, N, Ptot, Psol, K, NDF, ADF, and lignin) were dete rmined using the formula described by Larney et al. (2006): Mass balance (%) = 1 ((Nutrientfconc x DMfmass)/(Nutrienticonc x DMimass))*100 [Equation 3-2]

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65 Where mass balance = the percent change in the specified nutrient; Nutrienticonc = the initial concentration (mg kg-1) of the nutrient; DMimass = the initial dry matter (kg) of the stall materials; Nutrientfconc = the final concentration (mg kg-1) of the nutrient; and DMfmass = the final dry matter (kg) of the composted stall materials. Loss of a nutrient is denoted by a positive mass balance value, while a gain in a nut rient has a negative value. Thermal unit days were determined using th e formula described by Ring et al. (1983): Thermal days = Temperaturecomp Temperaturethreshold [Equation 3-3] Where thermal days = the number of days where compost is at or above the specified temperature threshold; Temperaturecomp= temperature (C) of compost; Temperaturethreshold= specified temperature (C). Whenever, the Temperaturecomp= is less than the threshold, the thermal day is set equal to zero. Whenever, the Temperaturecomp= is greater than the threshold, the thermal day is set equal to one. Statistical Analyses Statistical analysis of each variable was performed as an ANOVA using the MIXED procedure of SAS (V. 9.1, SAS Inst., Inc., Cary, NC). Nutrient data we re transform ed by mass balance estimates to account for mass reduction using Equation 3-2. The treatments with wood shavings (WOOD-CON, WOOD-60 and WOOD-30) were further partitioned into seasons (summer: May September; winter: December April) to analyze for seasonal effects. The sources of variation included treatm ent, time and treatment x time interactions as fixed variables. The LSMEANS procedure was used to compare treatment means and separation of means was performed using PDIFF. Contrast analysis was performed to examine the overall effects of bedding (HAY vs. WOOD) and nitrogen amendmen t (30:1 + 60:1 vs. unamended). For all analyses, a P-value less than 0.05 was considered significant, whereas a P-value less than 0.10 was discussed as a trend. Data were presented as mean standard error (SE).

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66 Results Weather Conditions During the 44 wk trial period (December 2005 Nove mber 2006) in Gainesville, Florida, the mean daily air temperature ranged from 1.7 to 28.2C with an average temperature of 19.2C. For summer months (May September), mean daily air temperatures ranged from 17.2 to 27.5C and averaged 24.5C. For winter months (December April), mean daily air temperatures ranged from 1.7 to 23.1C and averaged 13.7C. Composting Temperatures and Effect of Season Mean com posting temperatures of all WOOD treatments were greater (P<0.0001) than all HAY treatments. Mean composting temperatures in WOOD treatments did not vary in response to N amendment, but HAY-15 had higher m ean temperatures (P<0.001) than HAY-CON. Maximum composting temperatures required to destroy pathogens and parasites (55 C) and weed seeds (63 C) (USDA, 2002) were reached within the first 2 wks of composting in all WOOD treatments, but not in HAY treatments (Figure 3-1). All WOOD treatments had significant thermal unit days above stated temperat ures required to dest roy parasites and weed seeds (Figure 3-2). Thermal unit days were not affected by N amendment. After 84 d of composting, all materials remained above ambient temperature, regardless of bedding or N amendment. However, composting in the su mmer generated higher mean temperatures (P<0.0001) compared to the winter months in treatments containing WOOD (Figure 3-3). The starting dates of treatments were randomly assigned in an effort to minimize effects of seasonal variation. However, mean composting temperatures did differ (P<0.05) between each of the three replications within each treatm ent due to seasonal variation.

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67 Material Mass and Organic Matter Com posting reduced the DM mass of stall materials by 14 to 57%, with larger mass reductions observed in treatments with ha y bedding compared to wood shaving bedding (P<0.05). HAY-CON demonstrated the greate st mass reduction, followed by HAY-15 and WOOD-30. WOOD-60 and WOOD-CON had the lowest reduction in mass after composting (P<0.01) (Figure 3-4). Composting reduced (P<0.01) the OM of stall materials 17 to 60% in all treatments, regardless of bedding type or N am endment. Within the hay bedding treatments, HAY-CON had a greater OM reduction than HAY-15 (P<0.0001) (Table 3-3). In contrast, the reduction in OM of stall mate rials containing wood shavings bedding was not affected by nitrogen amendment. Nutrient Concentrations in Compost The concentrations of N, C, Ptot, Psol, and K at d 0 (after N amendment), d 84, and the overall all treatment mean are presented in Tabl e 3-1. Overall, hay bedding treatments contained higher concentrations of N than those with wood shaving bedding (P<0.0001); this difference in N was maintained after 84 d of composting. The concentration of C averaged 435.2 g kg-1 and was not affected by bedding type, N amendm ent or composting. The concentration of Ptot, Psol, and K were not altered by composting. Treatment s with hay bedding had higher concentrations of Ptot (P<0.001), Psol (P<0.05), and K (P<0.001) compared to those with wood shavings (P<0.001), but were not affected by N amendment. The average concentration of NDF (678 g kg-1), ADF (351 g kg-1) and lignin (80.0.6 g kg-1) in HAY treatments were not affected by composting or N amendment. Mean concentrations of NDF (837 g kg-1), ADF (683 g kg1) and lignin (248.8 g kg-1) in WOOD treatments were not affected by composting or N amendment.

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68 pH, Conductivity, and Total Dissolved Solids The pH, conductivity, and TDS of sta ll materi als at d 0, d 84 and the overall treatment means are presented in Table 3-2. Prior to com posting, the average pH of stall material was 8.4.2 (Figure 3-5). After 84 d of composting, th e pH in WOOD treatments declined (P<0.001) to 6.65.2 (Figure 3-5). In cont rast, the pH of HAY treatme nts did not decrease after composting. Amendment with N had no effect on pH in either the WOOD or HAY treatments. WOOD-30 had increased (P<0.01) conductivity and TDS than WOOD-CON, WOOD-60 and HAY treatments. Mean conductivity was 0.7.05 and 0.6.04 ms cm-1; TDS was 0.34.03 and 0.28.02 ppt in WOOD and HAY treatments, respectively. Water Holding Capacity and Bulk Density Water holding capacity (WHC) wa s not affected by com posting or N amendment, but was influenced by bedding type. The WHC of WOOD treatments (21.7.02%) was higher (P<0.05) than that observed in HAY treatments (8.71.5 %). Pore space was greater (P<0.05) in HAY treatments (76.3%) than in WOOD treatments (56.4%) (Table 3-2). The mean bulk density of WOOD bedding treatments (0.2.02 gm ml-1), was higher (P<0.05) than HAY bedding treatments (0.08.001 gm ml-1). The bulk density of stall ma terials increased (P<0.05) in response to composting in all treatments. Mass Balance Estimates for Nutrients Mass balance of C, N, Ptot, Psol, K, NDF, ADF and lignin are pr esented in Table 3-3. The C content of stall materials was reduced 15-60% in response to composting (P<0.05), with a greater loss in of C in HAY treatments compared to WOOD treatments (P<0.01). The largest reduction in C was observed for HAY-CON, followed by HAY-15 and WOOD-30. The lowest loss of C was exhibited by WOOD-60 and WOOD-CON (P<0.05). More N was lost from HAY treatments than WOOD treatments (P<0.05). A loss of N was observed HAYCON, HAY-15 and WOOD-

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69 30 (P<0.05), but not WOOD-60 or WOODCON. A greater reduction in Ptot was observed in HAY-CON and WOOD-30 (P<0.01) compared to other treatments. The loss of Psol was greatest in unamended stall materials (HAY-CON and WOOD-CON) (P<0.01) and intermediate in HAY15 (P<0.01). Composting resulted in a reduction in K in all treatments (P<0.05), except HAY-15. The NDF and lignin concentrations of materials were reduced (P<0.05) during composting, with the largest reduction occurring in HAY-CON (P <0.05) followed by the highly amended stall materials (HAY-15 and WOOD-30). The ADF content of stall materials tended to be reduced (P<0.10) during composting, with a larger reduction (P<0.0001) in HAY than WOOD treatments. Discussion Results of the present study dem onstrated that horse manure mixed with wood shavings bedding, with or without nitrogen amendment, can reach temperatures required to destroy parasites (55 oC) and weed seeds (63 oC) within the first couple of weeks of composting (Figure 3-1). In contrast, stall material s containing hay bedding did not ach ieve temperatures sufficiently high enough to kill parasites or weed seeds. Similar observations in temperature profiles between dairy cattle and horse manure mixed with w ood shavings and hay/straw bedding have been reported by other researchers (Curtis et al., 2005 ; Michel et al., 2004; Romano et al., 2006). In the current study, the differences in temperature profiles between bedding types may be related to differences in free pore space (Table 3-2) and the initial resistance of hay to biodegradation. A greater proportion of free pore space in the hay treatments may have allowed for greater convective air flow through the pile leading to gr eater heat loss and a lower rate of temperature increase. During this study, the temperature of stall materials containing wood shavings was affected by seasonal ambient temperature, with temperatur es significantly lower in the winter compared

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70 to the summer months (Figure 3-3). The temperat ure of the WOOD stall materials dropped more quickly in the winter, but increa sed again during the latter stage of composting. Such an increase suggests that decomposition in the winter was incomplete within the 84 day composting period and that the stall materials might still be immatu re. By comparison, temperatures recorded in the summer followed a pattern ideal to the composti ng process (Tiquia et al., 1997; Crowford, 1983). In the summer, the temperatures of WOOD st all materials increased rapidly to 45-50C, remained at this level for 24-48 hours, then cont inued to rise to a maximum temperature of 6065C. These high temperatures persisted until th e active decomposition wa s over and, thereafter, slowly decreased. The material is considered to be mature if the declin ing temperature reaches ambient temperature (Rynk et al., 1992). After 84 days of composting, the temperatures of WOOD stall materials did not decr ease to ambient temperatures, suggesting a decreased rate of decomposition and more time needed to achieve maturity. In contrast to WOOD stall materials, those containing hay bedding did not follow idea l composting temperature profiles and ambient temperatures did not affect pile temperatures. Hay stall material temperatures peaked rapidly, but then quickly decreased and remained at ambien t temperatures for the majority of the 84 day composting period. Composting reduced the mass of stall materi als 14 to 57%, with a greater reduction observed in treatments that included hay bedding and optimally amended wood shavings (Figure 3-4). Similarly, Michel et al. (2004) reported that dairy manur e mixed with straw showed a greater reduction in volume compar ed to that mixed with sawdust. If stall materi al includes wood bedding, this study suggests that nitrogen amendment to attain a 30:1 C:N ratio will increase reduction of material mass by approximately 50% when compared to unamended wood stall

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71 materials. Such a reduction in mass may be bene ficial by reducing the am ount of material horse owners must dispose of or manage. Composts used as growing media should have a high degree of maturity and adequate physical and chemical properties, such as part icle size, porosity, wate r holding capacity, air capacity, electrical conductivity and pH. These factors may be mo re important than the nutrient composition of compost because nutrients can be supplemented by fertilizers (Garcia-Gomez et al., 2002). Prior to composting, the pH of stall materials was 8.4, which can be unmarketable to gardeners and nurseries; however, after 84 days of composting, the pH of stall materials containing wood bedding declined to 6.65, which is more desirable for most end users (Swinker et al., 1998) (Figure 3-5). Generally, composting will yield an end product with a stable pH usually near neutral, independent of starting material (BCAF, 1996). However, in contrast to treatments containing wood bedding, the pH of hay bedding treatments did not decrease after composting in the current study. Curtis et al. (2005) also observed no decline in pH after composting horse and dairy cattle manure-straw mixtures. Another common concern when using compost derived from manure is soluble salt leve l. An ideal range of soluble salts for salt sensitive crops and forage is 400 1,000 ppm (Fitzpatrick et al., 1998). If the soluble salt concentration is in excess of approximately 2,000 ppm, chlorosis, necrosis, and loss of productivity in salt sensitive crops and plants may occur (Fitzpatrick et al., 1998). During this study, all treatments were within an acceptable range (Table 3-2). Most of the soluble salts came from the horse manure and the bedding diluted some of these salts making the concentrations more suitable for plants. Carbon losses are associated with all fo rms of manure management, as microbial decomposition breaks down available carbon in manure and bedding material (Larney et al.,

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72 2006). In this study, composting resu lted in carbon losses of 15-60% (Table 3-1). The majority of carbon loss likely results from microbial breakdow n of polysaccharides as they constitute the majority of plant carbon and are comparatively more easily degradable than lignin. Evidence of this was observed in the current study, where th e loss of NDF and ADF from stall materials was greater than loss of lignin, and paralleled the loss of carbon dur ing composting (Table 3-3). A larger loss of fiber materials was observed in st all materials with hay bedding compared to wood shavings. The higher nitrogen content of thes e materials would positively support microbial growth, resulting in greater degrad ation of bedding fiber (Table 3-1). Nonetheless, much of the bedding remained in all treatments after 84 days of composting. The materials had stabilized in temperature, darkened in color and there appeared to be complete breakdo wn of fecal material, but the decomposition of bedding was minimal, regardless of bedding type. The greatest loss of nitrogen (27-40%) occurred in the treatments with the highest nitrogen concentration (attained naturally or via a high le vel of nitrogen amendment) (Table 3-3). This loss of likely resulted from volatilization of nitr ogen as ammonia. Urea can be rapidly converted to ammonia and volatilize into the atmosphere (C urtis et al., 2005). The rate of conversion is influenced by factors such as moisture content, temperature, pH and urease activity. All of these factors are optimized during composting, which can facilitate a greater loss of nitrogen as ammonia when materials are highly amended with urea (Parkinson et al., 2004). Michel et al. (2004) reported 8 to 26% loss in nitrogen for sawdust amended and 15 to 43% for straw amended dairy manure. Interestingly, an increas e of nitrogen was observed in the wood stall materials amended to a C:N of 60:1 as well as unamended wood materials. This increase, along with increases in total phosphor us and total potassium in othe r treatments, are difficult to

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73 explain, although other authors reported similar outcomes and unknown reasons for the increases when composting cattle manure and poultry litte r (Larney et al., 2006; Sommer and Dahl, 1999). Phosphorus and potassium losses are often thought to be low to negligible during composting (Sommer and Dahl, 1999). In the current study most phosphorus mass balance values were positive, suggesting loss of phos phorus during composting. Other research has demonstrated when composting cattle and poultry manner, a loss of phosphorus occurs. Larney et al. (2006), reported a total phosphorus loss of 47-60% while composting beef cattle feedlot manure. Sommer and Dahl (1999) reported a phosphorus loss of 10% after composting dairy manure. Michel et al., (2004) reported a 12 to 21% loss of phosphorus for sawdust amended and 1 to 38% loss for straw amended dairy manure. Phosphorus losses are generally attributed to runoff or leaching (Larney et al., 2006), yet this study was c onducted under roof, so phosphorus losses due to runoff and leaching would have b een minimal. The water soluble fraction of phosphorus is especially of concern due to its potential to pollute surface and groundwater (Mallin and Wheeler, 2000) decreased in al l treatments except those highly amended wood treatments. During composting, microorganisms utili ze available (soluble) nut rients as an energy source and to sustain a variety of biological processes. The d ecrease in soluble phosphorus indicates proliferation of micr obiological activation and ther efore decomposition of organic matter. Conclusions In the current study, the type of bedding appeared to have a greater influence than nitrogen am endment on the decomposition of horse stall material thr ough composting. Horse manure and wood shavings mixtures, with or without added n itrogen, showed a faster rate of decomposition and nutrient stability during 84 da ys of composting than stall materials containing hay bedding. Composting horse stall materials reduced th e DM mass by up to 57%, thereby reducing the

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74 amount of materials that horse owners must st ore or dispose of. In addition, composting for 84 days allowed conversion of water-s oluble nutrients into organic form s that are less likely to be carried away through surface runoff or leached in to groundwater. Finally, horse manure mixed with wood shavings was capable of reaching temperatures that were high enough to destroy parasite eggs, larvae and weed seeds. However, more research is needed to determine an economically feasible method to further decompose bedding in a timely manner to produce a higher quality end product.

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75 20 30 40 50 60 70 80 HAY-15HAY-CONWOOD-30WOOD-60WOOD-CONTemperature (C)ab b b a Figure 3-1. Maximum temperature (mean SE) reached during the composting of horse stall materials containing bermudagrass ha y bedding (HAY-CON and HAY-15) or wood shavings bedding (WOOD30, WOOD-60, WOOD-CON). The two dotted horizontal lines represent temperatures at which weed seeds (63C) and pathogens and parasites (55C) are destroyed. a,bTreatments with different lette rs are significantly different (P<0.05).

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76 0 5 10 15 20 25 30 WOOD-30 WOOD-60 WOOD-CONThermal Unit Days 63C 55C Figure 3-2. Number of cumulative thermal un it days (mean SE) horse stall materials containing wood shavings bedding remained above temperatures reported to kill weed seeds (63C) and pathogens/parasites (55 C) during 84 d of composting. Thermal unit days were not affected by nitrogen amendment prior to composting.

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77 0 10 20 30 40 50 60 701 7 1 3 1 9 2 5 3 1 3 7 4 3 4 9 5 5 6 1 6 7 7 3Temperature (C) Winter compost Summer compost Winter ambient Summer ambient Figure 3-3. Effect of season on ambient temper ature and mean compost temperature of pooled treatments containing wood shavings bedding during 84 d of composting. Season affected both ambient (P<0.0001) and mean compost (P<0.0001) temperatures.

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78 0 10 20 30 40 50 60 70 HAY-15HAY-CONWOOD-30WOOD-60WOOD-CONWeight Reduction (%)a c c a b Figure 3-4. Percent reduction in material mass (mean SE) after 84 d of composting in treatments containing bermudagrass hay bedding (HAY-CON and HAY-15) or wood shavings bedding (WOOD-CO N, WOOD-60 and WOOD-30). a,b,cTreatments with different letters are signif icantly different (P<0.05).

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79 0 1 2 3 4 5 6 7 8 9 10 HAY-15HAY-CONWOOD-30WOOD-60WOOD-CON d 0 d 42 d 84 b a aa a,b b a a b Figure 3-5. Change in pH (mean SE) after 84 d of composting in treatments containing bermudagrass hay bedding (HAY-CON and HAY-15) or wood shavings bedding (WOOD-CON, WOOD-60 and WOOD-30). a,bMeans within treatments with different letters are significantl y different (P<0.05).

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80 Table 3-1. Nitrogen (N), carbon (C), total phosphorus (Ptot), soluble phosphorus (Psol), and potassium (K) concentrations in stall materials containing bermudagrass bedding (HAY-15 and HAY-CON) or wood shavings bedding (WOOD-30, WOOD-60 and WOOD-CON) before (d 0) a nd after 84 d of composting. g kg-1 Treatment P-value Day HAY15 HAYCON WOOD-30 WOOD60 WOODCON SEM Trt Day N d 0 22.4a 17.2a,b 13.2a,b 6.32b 5.27b 2.1 0.0134 d 84 22.7a 21.7a 10.6b 7.23b 7.40b 2.0 0.0005 mean 22.6a 19.4a 11.9b 6.78b,c 6.33c 1.4 0.0001 NS C d 0 464.3 438.6 440.5 432.8 459.2 10.2 NS d 84 430.5 411.7 435.2 394.6 451.7 12.5 NS mean 447.4 425.2 437.8 413.7 455.4 8.2 NS NS Ptot d 0 2.18 4.03 2.01 1.43 2.11 0.37 NS d 84 3.91a 6.29a,b 2.11b 1.47b 2.20b 0.56 0.0132 mean 3.04b 5.16a 2.06b 1.45b 2.16b 0.34 0.0015 NS Psol d 0 0.21a,b 0.33a 0.17a,b 0.10b 0.14b 0.02 0.0114 d 84 0.29a,b 0.36a 0.22b,c 0.11c 0.11c 0.03 0.0004 mean 0.26b 0.35a 0.19b 0.11c 0.12c 0.02 0.0001 NS K d 0 9.59b 15.5a 3.87c 5.16b,c 4.00c 1.26 0.0001 d 84 16.5a 18.0a 3.44b 4.94b 3.43b 1.85 0.0001 mean 13.0b 16.8a 3.66c 5.05c 3.72c 1.11 0.0001 NS Standard error mean. a,b,c Means within a row with di fferent superscripts are significantly different (P<0.05).

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81 Table 3-2. Pore space, water holding capacity (WHC), bulk density, pH, conductivity, and total dissolved solids (TDS) in stall material s containing bermudagrass bedding (HAY-15 and HAY-CON) or wood shavings bedding (WOOD-30, WOOD-60 and WOODCON) before (d 0) and after 84 d of composting. Treatment P-value Day HAY15 HAYCON WOOD30 WOOD60 WOODCON SEM Trt Day Pore space d 0 84.9 87.2 81.5 78.1 78.9 1.6 NS % d 84 86.1 82.6 75.9 72.0 82.8 2.0 NS mean 85.5 84.9 78.7 75.1 80.8 1.3 NS NS WHC d 0 4.23 8.8 23.6 19.9 22.6 2.8 NS % d 84 12.6 9.2 19.9 17.9 20.6 2.5 NS mean 8.43b 9.0a,b 24.5a 18.9a,b 21.6a,b 1.9 0.0280NS Bulk density d 0 0.07a,b,y 0.05b,y 0.20a 0.20a 0.13a,b 0.05 0.0110 gm ml-1 d 84 0.13x 0.10x 0.28 0.25 0.19 0.02 NS mean 0.10b 0.08b 0.24a 0.23a,b 0.16b 0.02 0.00030.0153 pH d 0 8.7 8.2 8.8x 8.6x 7.9x 0.1 NS d 84 8.4a 8.0a 6.7b,y 6.7b,y 6.3b,y 0.3 0.0470 mean 8.5a 8.14a 7.7b 7.6b 7.1b 0.2 0.01230.0002 Conductivity d 0 0.45b 0.56a,b 1.15a 0.48b 0.56a,b 0.1 0.0173 ms cm-1 d 84 0.55 0.69 0.94 0.68 0.69 0.06 NS mean 0.50b 0.62b 1.05a 0.58b 0.62b 0.05 0.0041NS TDS d 0 0.22b 0.25b 0.58a 0.23b 0.30a,b 0.04 0.0114 ppt d 84 0.27 0.34 0.44 0.34 0.32 0.03 NS mean 0.25b 0.29b 0.52a 0.29b 0.31b 0.03 0.0053NS Standard error mean. a,b,c Means within a row with different superscripts are significantly different (P<0.05). x,y Means within a column with different supe rscripts are significantly different (P<0.05).

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82 Table 3-3. Mass balance estimates (%) of car bon (C), nitrogen (N), total phosphorus (Ptot), soluble phosphorus (Psol), potassium, neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin and organic matter (O M) in response to composting of stall materials containing bermudagrass bedding (HAY-15 and HAY-CON) or wood shavings bedding (WOOD-30, WO OD-60 and WOOD-CON) for 84 d. Treatment p-value % HAY15 HAYCON WOOD-30 WOOD60 WOODCON SEM Trt Bedding C 40.7b 60.0a 36.2b 22.4c 14.9c 5.0 0.0143 0.0064 N 41.5a 45.9a 26.7a -18.0b -27.3b 10.2 0.0408 0.0185 Ptot -6.4b 33.4a 45.7a 12.4b -19.5b 7.5 0.0065 NS Psol 21.8a 52.5b -30.9c -9.0c 55.9b 11.1 0.0015 0.1223 K -31.1b 49.3a 51.3a 12.9a 36.3a 10.1 0.0252 NS NDF 43.6b 64.4a 26.4b 18.3c 15.9c 5.7 0.0016 0.0002 ADF 43.1a 61.8a 21.7b 15.0b 14.9b 5.8 0.0018 0.0001 Lignin 26.6b 51.3a 28.6b 6.2c 4.8c 5.0 0.0044 0.0178 OM 38.2b 60.3a 38.7b 23.3b 16.8b 4.8 0.0126 0.0133 a,b,c Means within a row with different letters are signifi cantly different (P<0.05).Calculated as: 1-((Nutrient fconc x DMfmass)/ (Nutrient iconc x DM imass)) *100. Positive values represent loss, while negative values represent gain.Standard error mean. Bermudagrass hay bedding (HAY-15 and HAY-CON) vs Wood shavings bedding (WOOD-30, WOOD-60 and WOOD-CON).

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83 CHAPTER 4 ON-FARM COMPOSTING OF HORSE STAL L MATERI ALS: EFFECT OF SLOWRELEASE NITROGEN AMENDMENTS Introduction The decreas e in agricultural land availability and the increase in environmental regulations to protect waster quality has led to greater concern for the management of horse manure generated on farms and at boarding, racetrack and horseshow facilities. Current manure management practices on horse operations include stockpiling for disposal or land application of unprocessed materials ((Cotton, D. persona l communication, 2008); NAHMS, 1998). A poorly managed manure pile can harbor intestinal parasites, provide a breeding ground for flies and produce offensive odors (Yamulki, 2006). Runoff fr om improperly stored manure can quickly become a potential environmental contaminate as it carries soluble nutrients, pathogens and organic particles into the water cycle via surface runoff or by leaching into groundwater (Yamulki, 2006). Land application of fresh manure can also generate large amounts of ammonia, carbon dioxide, methane, and nitrous oxide, wh ich potentially could be damaging to the environment (Yamulki, 2006). Management of horse stall material (feces and urine, mixed with soiled bedding) could be a beneficial tool fo r the horse industry. Trea tment through composting could provide a means of reduc ing the environmental impact of horse manure by reducing the total volume of materials that ne ed to be disposed of, destroyi ng parasites and weed seeds, and reducing runoff risk by stabilizing nutrients into organic forms. One of the biggest obstacles in successfully composting horse stall materials, which is not generally encountered with other livestock manures, is the high carbon content of bedding. The optimal ratio of carbon to nitrogen (C:N) to support microbial decomposition of organic materials is 25-30:1 (Rynk et al., 1992). By itself, horse manure is already near the ideal C:N (ASAE, 2005). In contrast, the C:N of common be ddings used in stalls ranges from 30:1 for

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84 straw or hay to 950:1 for wood shavings. When bedding is combined with manure, the C:N can often exceed 130:1 (Cotton et al., 2006). A high C: N in manure and bedding removed from horse stalls has been shown to slow the composting pr ocess (Swinker et al., 1998). This is thought to be due to the depletion of ava ilable nitrogen, with a subsequent reduction in microbial growth and decomposition of organic materials (Swinker et al., 1998). Amending horse stall materials with nitrogen may facilitate faster and mo re complete decomposition by supporting the microorganisms involved in composting. Dilling and Warren (2007) reported the use of urea as a nitrogen amendment did not enhance decompos ition of horse stall materials over 84 d of composting. The authors speculated that the ra pid utilization of urea by microorganisms may have resulted in an exponential increase in microorganism populations without additional nutrient supply for continued population sustainability. The most common nitrogen amendment is urea mainly due to its low cost and high nitrogen content (46% N). Urea is extremely solu ble in water at high te mperatures and rapidly hydrolyses to ammonium. At hi gh temperatures under alkaline conditions the ammonium that makes up urea readily converts to ammonia and carbon dioxide, which can be lost through volatilization (Sartain an d Kruse, 2001). Dilling and Warren ( 2007) reported that nitrogen loss during composting was greatest in stall materials amended with urea at an optimal C:N ratio of 30:1. Slow release nitrogen sources such as pol ymer sulfur coated urea (PSCU) or urea formaldehyde (UF) may alleviate some of the negative affects found by Dilling and Warren (2007) while composting horse stall material. PSC U is manufactured by coating hot urea with molten sulfur and sealing with polyethylene oil. Nitrogen is released when the sealant is broken or by diffusion through pores in the coating. Thus the rate of release is dependent on the

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85 thickness of the coating or the sealant weight. PSCU is broken down by microorganisms, as well as chemical and mechanical action. The nitrogen in PSCU is released more readily in warm temperatures and dry soils (Schwab et al., 2005). The nitrogen product of a condensation reaction between urea and formaldehyde is UF. When used as fertilizer, approximately one third of the total nitrogen in UF is available in the first few weeks, another th ird in a few months, and the remaining portion in 1 to 2 years after land application (Kaempffe and Lunt, 1967). The nitrogen in UF is released primarily by microbial action. Fact ors affecting microbial activity, such as medium temperature, moisture, pH a nd aeration will affect nitrogen release (Kaempffe and Lunt, 1967). Conditions during composting include high temper ature, moisture and pH-all of which are optimal catalysts for the conversion of ammonium to ammonia and carbon dioxide. Therefore, the use of urea for composting horse stall materi als may not be the most efficient nitrogen source. The objective of this study was to evalua te the use of various slow release nitrogen sources as amendments and their ability to f acilitate composting of horse stall material containing pine wood shavings bedding. Use of sl ow release nitrogen s ources, such as PSCU and UF as an amendment for carbon-rich horse stal l materials may prolong mi crobial proliferation, thereby increasing the rate and ex tent of material decomposition. Materials and Methods Experimental Design To evaluate the effects o f slow-release ni trogen amendments on the composting of horse stall materials, the addition of 1) UREA (46-0-0), 2) PSCU (PolyS, Scotts, Marysville, Ohio; 37-0-0), or 3) UF (38-0-0) was compared to 4) a control treatment cons isting of unamended stall materials (CON). All composting was performed in a concrete-based, 8-bin system (each bin measuring 3 m x 3 m) housed unde r roof cover. Horse manure a nd pine shavings bedding was

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86 removed daily from stalls occupied by horses, weighed, and amassed in an assigned bin over a 7d period. After the 7-d amassing phase, materials we re amended with nitrogen to a C:N ratio of 25:1 (as needed), mixed with a front-end loader, and the trial initiated (d 0). A new batch of stall materials would then be amassed into a separate assigned bin. This schedule continued until 4 bins had been initiated. Active aeration was prov ided by mixing and/or m oving materials with a front end loader according to the following sche dule: At d 0-30, materials were mixed within their original bin every 7 d. At d 30-60, materials were moved to another randomly assigned bin at 14-d intervals. At d 60-120, materials were moved to another randomly assigned bin at 30-d intervals. When materials completed this sche dule, they had been composted for 120 d. Three replicates of each of the four treatments were performed, with treatments randomly distributed throughout the trial period of September 2006 through September 2007. Compost temperature and oxygen content were measured 3 d wk-1 and moisture content was adjusted as needed to maintain 50-60% moisture. Representative sample s of stall materials we re obtained at d 0, 30, 60, 90 and 120. The amount of urea, PSCU or UF needed to ach ieve the desired C:N ratio of (25:1) for nitrogen amended treatments was determined usi ng the formula described by Fitzpatrick (1993): (Cstall) (Desired C:N)(Nstall) Ureaadd = ______________________________________ [Equation 4-1] (Nurea)(Desired C:N) (Curea) Where Ureaadd = kg urea, PSCU or UF to be added per 1 kg stall material; Cstall=kg carbon in 1 kg stall material; Nstall = kg nitrogen in 1 kg stall material; Curea=kg carbon in 1 kg urea; and Nurea=kg nitrogen in 1 kg urea. The carbon and nitrogen content of stall materials were determined from analyses performed on random samples obtained during the 7-d amassing phase prior to the addition of nitrogen amendment.

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87 Data Collection and Analyses Tem perature of compost was determined using a bi-metal dial thermometer with an 54.7 cm stem (Omega model B(-17-121C)-45.7cm). Temperature was determined by inserting thermometer 55 cm into center of pile, repeated in triplication and average temperature recorded. Moisture content was determined after forced-air drying in an oven at 60C until a constant weight was achieved. Changes in the physical pr operties and chemical composition and of the stall materials were determined on samples obtained at d 0, 30, 60, 90 and 120 using standard analytical protocols recommended by th e US Composting Council (Thompson, 2002). In preparation for analysis, sub-samples of materi als were freeze dried a nd ground to 1 mm particle size. Moisture content was determined after forced-air drying in an oven at 60C until a constant weight was acheived. Total nitrog en (N) and total carbon (C) analyses were performed with the Dumas combustion method (VarioMax N analy zer, Elementar Americas) (TMECC methods 04.02-D and 04.01-A (Thompson, 2002)). Organic matter (OM) was determined after heating for 12 h in a muffle furnace at 550C (TMECC method 03.02-A (Thompson, 2002)). The pH was determined on a slurry prepared with stall materials and dionized water according to AOAC method 973.04 using a Thermo Orion Posi-pHIo SympHony Electrode an d Thermo Orion 410-A meter (Thermo Fisher Scientif ic, Waltham, MA). Nitrate (NO3) was determined by RQflex Reflectometer method (EMD Chemicals Inc., Ni trate in Waste Water, 1995, Gibbstown, NJ). Ammonia (NH3) was determined by distillation me thod (AOAC 941.04). Phosphorus (P) and potassium (K) were determined by acid extracti on and analysis by inductively coupled plasma radial spectrometry (Thermo IR IS Advantage HX, Thermo Fish er Scientific, Waltham, MA). The neutral detergent fiber ( NDF), acid detergent fiber ( ADF) and lignin content were determined using the ANKOM A200 filte r bag technique (AOAC 973.18(B-D)). The determination of pH, NO3, NH3, P, K, NDF, ADF and lignin was performed at Dairy One

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88 Laboratory, Ithaca, NY. Population densities of several microbial groups (aerobic, anaerobic, pseudomonas, nitrogen-fixing, ac tinomycetes, and fungi) were de termined at all 30-d sampling intervals by plate counts on semi-selective me dia (BBC Laboratories, Inc., Tempe, AZ). Ambient temperature and rainfall were recorded weekly from the Alachua Florida Automated Weather Network. Nutrient data from compost piles were tran sformed using mass balance estimates. Total mass balance estimates for each nutrient (i.e., N, NO3, NH3, P, K, NDF, ADF, lignin and C) were determined using the formula described by Larney et al. (2006): Mass balance (%) = 1 ((Nutrientfconc x DMfmass)/(Nutrienticonc x DMimass))*100 [Equation 4-2] Where mass balance = the percent change in the specified nutrient; Nutrienticonc = the initial concentration (mg kg-1) of the nutrient; DMimass = the initial dry matter (kg) of the stall materials; Nutrientfconc = the final concentration (mg kg-1) of the nutrient; and DMfmass = the final dry matter (kg) of the composted stall materials. Loss of a nutrient is denoted by a positive mass balance value, while a gain in a nut rient has a negative value. Thermal unit days were determined using th e formula described by Ring et al. (1983): Thermal days = Temperaturecomp Temperaturethreshold [Equation 4-3] Where thermal days = the number of days where compost is at or above the specified temperature threshold; Temperaturecomp= temperature (C) of compost; Temperaturethreshold= specified temperature (C). Whenever, the Temperaturecomp= is less than the threshold, the thermal day is set equal to zero. Whenever, the Temperaturecomp= is greater than the threshold, the thermal day is set equal to one.

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89 Statistical Analyses Statistical analysis of each variable was performed as an ANOVA using the MIXED procedure of SAS (V. 9.1, SAS Inst., Inc., Cary, NC). Nutrient data we re transform ed by mass balance estimates to account for mass reduction using the equation 4-2. The WOOD piles were further partitioned into seasons (summer: May September; winter: December April) to analyze for seasonal effects. The model incl uded treatment, time and treatment x time interactions as fixed variables. The LSMEANS procedure was used to compare treatment means and separation of means was performed using PDIFF. The effects of N amendment (CON vs. UREA, PSCU and UF) were determined by use of c ontrast analysis. Contra st analysis was also used to compare UREA vs. slow release nitroge n sources (PSCU and UF). Numbers of microbial populations were log-transformed (log10 CFU gdw-1) and analyzed by ANOVA as described above for other variables. For all analyses, a P-value less than 0.05 was considered significant, whereas P-values less than 0.10 wa s discussed as a trend. Data were presented as mean SE. Results Weather Conditions During the 52-wk trial period (September 2006 Septem ber 2007), the mean daily ambient temperature ranged from -7.2 to 35.5C with an average temperature of 19.3C. For summer months (May September), mean daily ambient temperatures ranged from 8.2 to 35.5C and averaged 24.3C. For winter months (December April), mean daily ambient temperatures ranged from -7.2 to 30.7C and averaged 14.9C. Composting Temperatures and Effect of Season Com posting temperatures differed by treatment (P<0.0001), with the highest mean temperature observed in CON (55.5C), followed by UREA (54.7C), PSCU (53.6C) and UF (52.6C). In most cases, maximum co mposting temperatures required to destroy

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90 pathogens and parasites (55C) and weed seeds (63C) (USDA, 2002) were reached within the first 2 wks of composting. However, two of the tw elve piles (one replicate for PSCU and UF) did not reach temperatures high enough to destroy weed seeds and pa rasites. With the exception of these two piles, all treatments had sufficient ther mal unit days above 55C for 3 d and 63C for 5 d to destroy pathogens and weed seeds (Figur e 4-1). Thermal unit days were affected by treatment (P<0.0001), with UF having the least nu mber of days above critical temperatures compared to CON, UREA and PSCU (P<0.001). Stall materials amended with UF experienced the fewest days above 55C (P<0.001) and mate rials amended with urea remained above 63C for more days (P<0.0001) compared to othe r treatments. After 120 d of composting, the temperature of materials remained above ambien t temperature, in all treatments. Across all treatments, composting conducted in the summer months generated higher mean temperatures (P<0.0001) compared to the winter months. Physical Properties and Chemical Composition of Compost Com posting reduced (P<0.01) the DM mass of stall materials by 25.0% and was not affected by N amendment. The OM of stall ma terials decreased (P<0.01) by 26.0% after 120 d of composting but was not affected by N amendm ent. The average concentration of NDF (854 g kg-1), ADF (705 g kg-1) and lignin (243 g kg-1) was not affected by N source or composting. At d 0 the pH of stall materials was not affected by N amendment (7.5.1). After 120 d of composting, the pH decr eased (P<0.0001) in treatments amended with N (PSCU, UF and UREA) (6.4.2) compared to CON (7.2.2). The concentrations of N, NO3, NH3, P and K at d 0 (after N amendment), d 120, and the overall all treatment mean are presented in Table 4-1. The concentration of N was greater (P<0.01) in treatments that received N amendment compared to CON and was not affected by composting. At d 0, there were no differences in NO3 concentration between treatments.

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91 However after 120 d of composting, treatme nts amended with N had increased NO3 concentrations compared to CON (P< 0.01). Unamended CON treatments had a NH3 concentration of 0 on d 0 and 120 d after composting. Overall, slow release N treatments had increased levels of NH3 when compared to UREA (P<0.0001) The average concentration of P (1.5.1 g kg-1) and K (5.6.4 g kg-1) was not affected by N source or composting. Mass Balance Estimates for Nutrients Mass balance of N, NO3, NH3, P, K, NDF, ADF, lignin and C are presented in Table 4-2. A reduction in N occurred in all N amended treatments with UREA having the largest loss compared to slow release N sources (P<0.01). A gain in N was measured in CON, however it was not significantly different than PSCU or UF. The largest gain in NO3 was observed for PSCU, followed by UREA and UF The lowest gain in NO3 was exhibited by CON. The materials amended with slow release N had a gain (P<0.05) in NH3. The largest gain was exhibited by PSCU followed by UF (P <0.01), however a reduction in NH3 (P<0.001) occurred in UREA. The source of N did not affect reducti on of P (37 %) and K (32 %) after 120 d of composting. The reduction of NDF tended (P<0.10) to be influenced by N amendment, with UREA having the lowest decrease. The ADF conten t of stall materials were reduced with CON having the highest reduction compared to N amende d treatments (P<0.01). A reduction of lignin occurred in UF and CON, yet a numerical increase was exhibited by PSCU and UREA. However, CON, PSCU and UREA were not signif icantly different from each other. Composting reduced (P<0.05) the C of stall materials, with UF having the largest reduction compared to CON, PSCU and UREA. Microbial Populations The changes in microbial populations pool ed across all treatme nts during 120 d of composting are presented in Figure 4-2. Number s of aerobic bacteria, anaerobic bacteria,

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92 pseudomonas, nitrogen-fixing bacteria, actinom ycetes, and fungi present during composting were similar in all treatments. The microbial population essentially followed the temperature curve, with the highest number of microbes observed at the start of composting (P<0.05). Aerobic, anaerobic, pseudomonas, and nitrogen -fixing bacteria decreased from d 0 to d 60 (P<0.05), then leveled off after 120 d of composting. Fungi numbers began to increase from d 60 to d 120 when pile temperatures were no l onger above 45C (P<0.05). Actinomycetes numbers remained constant throughout 120 d of composting. Discussion Results of the present study dem onstrated that horse stall materials containing wood bedding can reach temperatures required to destro y parasites and weed seeds within the first 2 weeks of composting. Similar findings have been reported by others (Dilling and Warren, 2007; Romano et al., 2006). During summer months, materials undergoing active composting generated significantly higher te mperatures than materials co mposted during winter months. Larney et al. (2000) found similar results w ith volume loss of beef feedlot manure after composting was increased during summer m onths compared to winter months. Materials amended with UREA were exposed to temperatures above 60C for a longer period of time compared to materials amende d with PSCU and UF (Fi gure 4-1). The nitrogen within UREA is immediately av ailable to microbes causing an explosion in growth and likely resulting in higher composting temperatures. Af ter approximately 60 days, unamended materials and those amended with UREA began to cool, suggesting that available nitrogen may have become a limiting factor for microbial activity. In contrast, materials amended with slow release urea (PSCU or UF) continued to experience in creases in temperature beyond day 60. Extended high temperatures suggest that microbial activity is prolonged compared to stall material amended with UREA or unamended materials. Com posted materials are cons idered to be mature

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93 if the declining temperature re aches ambient temperature (Rynk et al., 1992). In the current study, composting temperatures remained elevated above ambient temperatures in all treatments, suggesting that decomposition was incomplete and more time was needed to achieve maturity. On average, the DM mass of stall material s was reduced by 25% with composting, but was not affected by nitrogen amendment. A similar loss of mass after compos ting has been observed by other researchers (Dilling and Warren, 2007; Eghball et al., 1997; Romano et al., 2006; Rynk et al., 1992). A loss of total nitr ogen occurred during composting w ith a greater loss in materials amended with PSCU or UREA (Table 4-2). A gr eater loss of nitrogen from the urea treatment likely resulted from volatiliza tion of more readily availabl e nitrogen. Urea can be rapidly converted to ammonia, which then volatilizes into the atmosphere (Curtis et al., 2005). The rate of conversion of urea to ammonia is influenced by factors such as moisture content, temperature, pH and urease activity. Such conditions are at optimal levels during composting (Parkinson et al., 2004). Michel et al., (2004) reported nitrogen loss of 8 to 43% for dairy manure and straw bedding amended with urea. In c ontrast, slow release nitrogen sources, such as PSCU and UF, release nitrogen based on microbi al action. As a result, nitrogen is available as microorganisms are proliferating and able to utilize the nitrogen, causing lower vol atilization rates. Reducing the loss of nitrogen can increase the overall value of compost as a fertilizer by preserving added nitrogen. In addition, discouraging volatilization of nitrogen as ammonia will decrease potential atmospheric pollutants. The proportion of nitrate increased in respons e to composting, particularly in materials amended with PSCU and UF (Table 4-2). A rise in nitrate resulted from the nitrification of ammonia present when the materials began to cool (Mupondi et al., 2006). Ammonia was not present in unamended stall materials before or after 120 d of composting (Table 4-1). This

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94 finding is not surprising as the materials were not amended with nitroge n; further any residual ammonia from urine would likely have been vola tilized within hours of excretion by the horse (Pratt et al., 2000), leaving no re sidual ammonia by the time mate rials had been amassed for 7 days prior to the star t of composting. Compost amended with urea had a reduction in ammonia; while materials amended with slow release nitr ogen had a gain of ammonia after 120 days of composting (Table 4-2). The reduction of ammoni a in materials amended with urea was probably lost due to atmospheric volatilizat ion or converted to nitrate th rough nitrification. The gain of ammonia in materials amended with slow-releas e nitrogen demonstrates the breakdown of urea to ammonium carbonate and even tually to ammonia; yet cons ervation of ammonia occurred because of the slow release mechanism. Composting is a dynamic process carried out by a rapid succession of mixed microbial populations. The main groups of microorganism involved are bacteria, including actinomycetes, and fungi (Golueke, 1991). At the beginning of the composting process mesophilic bacteria predominate, but thermophilic bacteria take over and thermophilic fungi appear when the temperature increases to over 40C. When th e temperature exceeds 60C, microbial activity decreases dramatically, but afte r the compost has cooled mesoph ilic bacteria and actinomycetes again dominate (McKinley and Vestal, 1985; Stro m, 1985). During this study, the total aerobic bacteria, anaerobic bacteria and pseudomonas counts were highest at the beginning of composting (Figure 4-2). It is common for b acterial counts to be hi gh in the beginning of composting when using manure as a substrate (Ti quia et al., 2002). Because stall materials were amassed over a 7-day period prior to the start of composting, this may have permitted a rapid rise in microbial activity. In fact, pile temperatures had already reached th ermophilic levels by the time materials started on trial. The numbers of bacteria generally followed the temperature

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95 response which reached a peak of 55C within the first 2 weeks and then progressively decrease. de Bertoldi et al. (1983) reported that the total number of aerobic bacteria increased during the first 14 d of composting municipal waste to 109 CFU and steadily decreased thereafter 107 CFU. In the current study, aerobic ba cteria reached a level of 109 CFU, placing it within the maturity compost parameters set by the Organic Ag riculture Advisors (Binning, 2007). Anaerobic bacteria followed the same trend as aerobic b acteria, and remained in the desired range of aerobes:anaerobes at 10:1 or gr eater. When anaerobes are pres ent above this desired ratio, byproducts generated may be toxic to plant growth (de Bertoldi et al., 1983). Pseudomonads are important in nutrient cycling, as sisting plants with phosphorus av ailability, and some have been linked to the biological control of plant pathogens. Fungi and nitr ogen-fixing bacteria decreased until composting temperatures began to decrease then repopulated after day 60. Populations of free-living nitrogen-fixing bacteria will prolifer ate as the available nitrogen in the compost decreases (de Bertoldi et al., 1983) As a consequence, there is typically an inverse relationship between biologically available nitrogen in the compost and the concentr ation of free-living nitrogen-fixing bacteria. Fungi and actinomycetes play an important role in the decomposition of cellulose, lignin, and other more re sistant materials, despite being confined primarily to the outer layers of the compost pile and becoming active only during the latter part of the composting period. After 120 days of composting, fungi, actinomycetes, pseudomonads and nitrogen fixing bacteria were all within the optimal range fo r mature compost (Binning, 2007). The microbial population of aerobic bacteria, anaerobic bact eria, pseudomonas, nitrogen-fixing bacteria, actinomycetes, and fungi were similar in all tr eatments and did not appear to be altered by nitrogen amendment. Thus, there was no advantag e in population growth or duration that could be attributed to the use of slow re lease nitrogen sources as amendments.

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96 Conclusion The results from this study indicate that sl ow release nitrogen sour ces reduced the loss of nitrogen during composting of horse stall ma terial, but did not n ecessarily enhance the decomposition process compared to urea. Slow release nitrogen sources did not sustain thermophilic conditions any longer than the uname nded compost, as evidenced by a plateau of growth by day 60 in all treatments, which correlat ed with decreases in composting temperatures. Compost amended with nitrogen contained much higher concentrations of inorganic nitrogen (nitrate and ammonia), compared to the non-amended material. Nitrate and ammonia have the potential to pollute surface a nd groundwater if applied in excess of agrono mic rates onto pastures. At the same time nitrogen amended co mpost may increase the value of compost as a fertilizer, because nitrogen is in a plant availa ble form. In contrast, unamended compost contains mostly organic sources of nitrogen that must be mineralized before becoming available for plant uptake. The use of slow release nitrogen amendments may decr ease the risk of atmospheric pollution and increase the value of the composted horse stall material as a fertilizer source. However, more research is needed to determ ine an economically feasible method to further decompose carbon-rich horse stall materials and generate a higher quality end product.

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97 0 5 10 15 20 25 30 CONPSCUUFUREAThermal Unit Days 55C 63C a b a a a c b,c b Figure 4-1. Number of days (mean SE) horse stall materials remained above temperatures reported to kill parasites/pathogens (55C) and weed seeds (63C) during 120 d of composting. Within each temperature, tr eatments with different letters are significantly different (P<0.05).

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98 5 6 7 8 9 10 11 12 03 06 09 01 2 0log10 (CFU gdw-1) Aerobic Anaerobic Psedumonas N-fixing Actinomycetes Fungi Figure 4-2. Changes in microbial populations present in horse stall material during 120 d of composting. Data represents pooled means across all treatments.

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99 Table 4-1. Concentration (g kg-1, dry weight basis) of total N (N), nitrate (NO3), ammonia (NH3), phosphorus (P) and potassium (K) in horse stall materials before (d 0) and after 120 d of composting. Materials were tr eated with N amendment (PSCU, UF or UREA) or remained unamended (CON) prior to composting. g kg-1 Treatment P-value Day CON PSCU UF UREA SEMTrt Day Trt*Day N d 0 5.79b 11.03a 7.53b 15.78a 1.61 0.042 d 120 7.26b 15.84a 13.55a 10.07b 1.19 0.011 Mean 6.52a 13.44b 10.54b 12.93b 1.22 0.004 NS 0.018 NO3 d 0 0.35y 0.40y 0.43y 0.40y 0.04 NS d 120 1.10b,x 10.85a,x 10.43a,x 9.55a,x1.42 0.0043 Mean 0.73b 5.63a 5.43a 4.98a 0.56 0.00020.0001 0.0003 NH3 d 0 0 3.20y 4.00y 8.30 1.16 0.069 d 120 0d 32.1a,x 19.8b,x 4.20c 4.48 0.0033 Mean 0d 17.65a 11.88b 6.25c 1.86 0.00030.0002 0.0003 P d 0 6.27 5.57 5.43 6.67 0.33 NS d 120 5.63 5.17 5.17 4.93 0.45 NS Mean 5.95 5.37 5.30 5.80 0.62 NS NS NS K d 0 1.43 1.53 1.97 1.87 0.16 NS d 120 1.43 1.20 1.67 1.30 0.11 NS Mean 1.43 1.37 1.82 1.58 0.19 NS NS NS Standard error mean. a,b,c,d Within a row, means lacking a common superscript letter differ (P< 0.05). x,y Within a column, means lacking a common superscript letter differ (P<0.05).

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100 Table 4-2. Mass balance estimates of total nitrogen (N), nitrate-N (NO3), ammonia-N (NH3), phosphorus (P), potassium (K), neutral dete rgent fiber (NDF), acid detergent fiber (ADF), lignin and total carbon (C) in una mended horse stall materials (CON) or materials treated with nitrogen amendment (PSCU, UF or UREA) prior to composting for 120 d. Treatment (%) p-value CON PSCU UF UREA SEM Trt N -2.3b 4.4b 7.2b 56.25a 9.0 0.006 NO3 -113a -2654d -734b -1724c 370 0.001 NH3 0a -718c -257b 72.3a 118.5 0.001 P 31.4 31.8 46.0 46.4 4.6 NS K 49.4 35.1 62.7 38.0 6.1 NS NDF 31.1a 34.5a 60.4a 8.6b 8.3 0.10 ADF 44.0a 9.8b 17.9b 17.8b 4.7 0.03 Lignin 7.9b -11.8b 50.3a -12.6b 9.2 0.03 C 26.5b 24.5b 53.6a 38.2b 4.4 0.03 Calculated as: 1 ((Nutrient fconc x DMfmass)/ (Nutrient iconc x DM imass)) *100. Positive values represent loss, while negative values represent gain.Standard error mean. a,b,c Means within a row with different letters are significantly different (P<0.05).

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101 Table 4-3. The pH in unamended horse stall mate rials (CON) or materials treated with nitrogen amendment (PSCU, UF or UREA ) during composting for 120 d. Treatment p-value Day CON PSCU UF UREA SEM Trt Day Trt*Day pH d 0 7.1 7.5x 7.5x 7.8x 0.1 NS d 30 7.3 7.9x 7.4x 7.8x 0.1 NS d 60 7.1 6.8y 6.6y 6.9y 0.1 NS d 90 7.4 6.3y,z 6.3y 6.9y 0.2 0.091 d 120 7.2 6.1z 6.2y 6.8y 0.2 0.072 Mean 7.1 6.8 6.8 7.3 0.2 NS 0.0001 0.042 Standard error mean. x,y,z Within a column, means lacking a common superscript letter differ (P<0.05).

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102 CHAPTER 5 CHARACTERISTICS OF SOIL AND NEWLY ESTABLI SHED BAHIAGRASS FORAGE IN RESPONSE TO SOIL INCORPORATION OF UNPROCESSED AND COMPOSTED HORSE STALL MATERIALS Introduction Florida soils are generally sandy and low in organic m atter concentration (USDA, 2006). Such soils have a low nutrient and water reten tion capacity and low natural fertility. Therefore, fertilizers are commonly utilized in Florida to en hance soil fertility. Fertilization increases the total plant biomass produced, and accelerates plant residue deco mposition, thereby increasing the availability of nutrients from residues (W arman and Termeer, 2005; Cadisch et al., 1994; Gijsman et al., 1997). In pasture systems high dry matter yields require a large nutrient supply, and nitrogen (N) has been deemed as the most important nutrient contro lling grass productivity (Jarvis et al., 1995; Whitehead and Rais trick, 1990; Oliveira et al., 2001). Inorganic fertilizers are the most widely used source of nutrients to support plant growth, mainly due to high nitrogen content and, conseq uently, lower costs associated with storage, freight and utilization. The nutrien ts contained in inorganic fert ilizers (mainly N, phosphorus (P) and potassium (K)) are in forms that are readily available to plants; however, this also makes them a greater potential risk fo r surface and groundwater contam ination. In the early 1990s, the United States Environmental Protection Agency found nitrate contamination in many Florida drinking water wells. Some urban and rural we lls exceeded the nitrate maximum contaminant level (MCL), suggesting that agricultural and fertilizer ap plication practices might be contributing to increased nitrate levels in the groundwater (Parsons and Boman, 2006). The Florida Department of Agriculture and Consum er Services carried out a drinking water well analysis throughout the state a nd found that 63% of the 3,949 dri nking water wells sampled, had detectable nitrate levels and 15% ha d nitrate-N levels above the 10 mg L-1 MCL (Parsons and

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103 Boman, 2006). Nitrogen contaminat ion of groundwater and wells can cause a medical condition in people known as methemoglobinemia, whereby nitrite replaces oxygen in hemoglobin in the blood. With increased levels of methemoglobin, oxygen levels in the blood d ecrease, resulting in cyanosis, or oxygen starvation (Hubbard et al., 2 004). Leaching of P has also been reported in poorly drained soils high in organic matter (Sharpley et al., 1994) and regions with a long-term history of organic manure applicat ions (Breeuwsma et al., 1995). When nutrients, such as N and P, exceed the loading rate for a body of water, eutrophication can occur (Bushee et al., 1998). Up to 50% of the N in fertilizer can also be lost due to volatilizati on of ammonia, especially when high rates are applied to the surface of pastures (Whitehead and Raistrick, 1990; Primavesi et al., 2001; Martha, 2003). Loss of ammonia-N due to vol atilization is reduced by incorporation of fertilizer into the soil, when compared to surface applicati on (Martha et al., 2004). The addition of organic matte r has been found to enhance the overall ability of soil to retain both nutrients and water (Rynk et al., 1992). These are positive effects, both with regard to enhancing soil fertility and prot ecting groundwater resources from potential contaminants that might leach through the soil. The use of materials rich in organic matter, such as horse manure and compost as fertilizer has ga ined a renewed interest as a management tool for recycling nutrients. Yet, there are certain limitations when using fresh manure as a fertilizer source that should be considered, including la nd and seasonal constraints on a pplication, spreading of weed seeds and intestinal parasites, fly and odor production, suppression of fo rage growth and the potential for contamination of surface and groun dwater (James, 2003; Lyons et al., 1999; Major et al., 2005; Watson et al., 1998). Treating manure through composting could prov ide a means of reducing the environmental impact of horse manure by reducing the total volume of materials (Larney et al., 2000),

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104 destroying parasites and weed seeds (Romano et al., 2006; Larney et al., 2003; Larney and Blackshaw, 2003), reducing odor production compared to stockpiled manure (Li et al., 2007), and generating stabilized end product for onand off-farm use while lowering nonpoint source pollution from horse farms (Michel et al., 2004). Composted manure has successfully been used as a soil amendment for cropland, landscaping a nd gardening, and nursery potting mixes (Lynch, 2004). Composts have been found to enhance so il fertility, increase crop yields (Dick and McCoy, 1993) and reduce diseases caused by soilborne plant pathogens (Hoitink and Fahy, 1986; Hoitink and Boehm, 1999). Many studies have demonstrated a positive effect of land application of compost on forage, usually resulting in yields co mparable to those produced by inorganic fertilizer (Catroux et al., 1981; Hornick et al., 1984; Davis et al., 1985; Warman and Termeer, 1996; Reider et al., 2000 ; Tiffany et al., 2000). In the fe w instances where a negative response to compost application has been observed, reduced yields or negative effects on soils or crops have been attributed to high carbon to nitr ogen ratios (C:N), excess metals, high soluble salts, or extremely high application rates of the compost (Warman and Termeer, 2005). Utilization of compost could reduc e the amount of inorganic fertil izer needed without decreasing forage yield, and in turn, decrease the poten tial for nitrate contamination of surface and groundwater. Most investigations on the response of crops or pasture to compost application have utilized composts prepared fr om cattle, swine or poultry ma nures. The objective of this study was to compare the soil incorporation of unproce ssed and composted horse stall material on soil characteristics and establishment of Argentine bahiagrass ( Paspalum notatum ) in northern Florida.

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105 Materials and Methods Site Description A field study was conducted at the U niversity of Florida, Institute of Food and Agricultural Sciences, Horse Teaching Unit in Gainesville, Florida in 2006. A half hectare field was prepared by herbicide application followed by tilling to rem ove any existing plant biomass prior to this study. The soil type was a Millhopper (loamy, sili ceous, semiactive, hyperthermic Grossarenic Paleudult) (USDA, 2006). Experimental Design Four fertilizer treatm ents were examined for their effects on the establishment of Argentine bahiagrass ( Paspalum notatum ): inorganic fertilizer (INORG; %N-P-K of 16-4-8), unprocessed stall material (STALL; 0.6-0.1-0.3), semi-stabi lized stall material (SEMI; 1.0-0.2-0.4), and composted stall material (COMP; 1.2-0.2-0.4). Stall material consisted of horse manure and pine wood shavings bedding that had been removed duri ng routine stall cleaning and either stockpiled for 7 d (STALL) or amended with urea to achieve a C:N ratio of 30:1 and composted for either 42 d (SEMI) or 84 d (COMP) before use. The SE MI treatment was included to simulate shortterm stockpiling of stall material, which is comm only practiced on horse ope rations, prior to land applying manure on pastures (Cotton, D. pers onal communication, 2008). After preparation of the soil bed, treatments were land applied on 24 randomly assigned 36.5 m x 1.8 m plots, with 6 replications per treatment, in a complete random block design. Applicat ion rates were based on plant N requirements (112 kg N ha-1) for establishment of Argentine bahiagrass and were split into two applications, as recommended (Newma n et al., 2008). Organic fertilizers (STALL, SEMI and COMP) were applied at a rate of 112 kg N ha-1 prior to incorpor ation and seeding, then adjusted to balance approximated 50% mi neralization rates from organically bound N by supplementing 56 kg N ha-1 with inorganic fertilizer 30 d after germination. Dry matter

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106 application rate of STALL was 17.6 Mg ha-1 and COMP was 11.6 Mg ha-1 was incorporated to obtain recommended N rates. INORG was applied at an overall rate of 112 kg N ha-1 (34 kg N ha-1 initial application; 78 kg N ha-1 30 d after germination). All mate rials were incorporated into soil within 24 h afte r initial application. Bahiagrass was broadcast seeded at 34 kg ha-1 and covered with 2.5 cm of soil. Water towers were placed onsite to provide proper moisture for seedling germination. Mowing occurred after ev ery harvest and material was removed from plots. Data Collection and Analysis A biological assay was conducted on STALL, SEMI, and COMP prior to land application to evalu ate potential phytotoxicity. In vitro germination and root elonga tion tests were performed with compost extract using United States Composting Council method 05.05-B (Thompson, 2001). Germination rates of cucumber seeds subj ected to compost extract were compared to seeds exposed to deionized water. Compost extr acts were prepared from samples of STALL, SEMI, and COMP obtained within 24 h and oven-drie d to a constant weight Stall materials were mixed with deionized water in a 2:1 ratio (water: media, by weight ) and allowed to stand for 3 hr so that water could soak the media. The mixt ure was then filtered through Whatman #113 wet strengthened filter paper and the extracts collected. Whatman filter papers were placed in 9-cm petri dishes and moistened with 10 mL of compost extract. Ten cucumber ( Cucumis sativus ) seeds were placed in each dish. Three replicates of each dish were preformed for each of the STALL, SEMI and COMP stall materials. Deionized water served as the control. Petri dishes were placed in a lighted area with lids left on to maintain adequate humidity. The germination percentage was determined on d 3 and root elongation was measured on d 6. Germination (%), root length (%) and germination index was determined using the formulas described by Zucconi et al. (1981):

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107 Germination (%) = (Germinatedsample / Germinatedcontrol) *100 [Equation 5-1] Where Germination = the percentage of samp le seeds germinated in proportion to the control; where Germinatedsample= the average number of seed s germinated in the sample; Germinatedcontrol = the average number of seeds germinated in the control. Root length (%) = (Rootsample / Rootcontrol) *100 [Equation 5-2] Where Root length = the percentage of length of root in proportion to the control; where Rootsample = the average of root length in the sample; Rootcontrol = the average of root length in the control. Germination Index = (% Germination % Root Length)/100 [Equation 5-3] Soil samples were obtained at d 0 (prior to treatment), 30, 60 and 120. At each sampling interval, 20 soil cores were random ly collected within each plot at a depth to 15 cm using a stainless steel sampling probe. The cores within each plot were composited and oven dried at 65 C for 7 d. Soil was analyzed for ammonium-N (NH4), pH, organic matter (OM), cation exchange capacity (CEC) (calculation), and extr actable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). NH4-N was extracted from soils using a 1N KCl solution and analyzed spectrophotometrically (Markus et al., 1985; Dorich and Nelson, 1983). Soil pH was determined in a 1:2 soil:water extract of the soil using deionized water. Samples were stirred and allowed to equilibrate for a minimum of 30 minutes after adding the water. The pH was determined, using a hydrogen selective electrode (Schofield and Tayl or 1955). Soil organic matter (OM) was determined by loss-on ignition method (Magdoff et al., 1996). Double acid Mehlich I extraction was preformed to determine P, K, Ca, and Mg and analyzed by inductively coupled argon plasma (ICP) spectrometry (SRIEG, 1983) at all colle ction points. Soil analysis

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108 was performed by Agro Services International Laboratory (Orange City, FL) on a dry weight basis. Forage samples were collected by hand c lipping on d 30, 45, 60, 90 and 120. A 76 cm wire cable hoop (76 cm diameter) was rando mly placed in each plot and all forage material within the hoop was removed to a height of 10 cm. This procedur e was repeated in triplicate for each plot to determine dry matter. Plots were individually mowed and material was collected to obtain representative samples for tissue analysis. Forage samples were dr ied to a constant weight in a forced air oven at 65C to determine dry matter (DM) yield. Forage samp les were analyzed for total N with the Dumas combustion method (V arioMax N analyzer, Elementar Americas) (TMECC method 04.02-D (Thompson, 2002)). Total P wa s determined on samples that had been ashed prior to sulfuric acid digestion and then quantified colorimetrically (PowerWave XS spectrophotometer, Winooski, VT). Nutrient removal was determined using the formula described by Butler and Muir (2006): Nutrient removal (kg ha-1) = Nutrientconc Yield [Equation 5-4] Where nutrient removal = the amount of nutrient removed in relation to DM yield; Nutrientconc = the concentration of nutrient (kg kg-1); Yield = the DM yield of forage (kg ha-1). Crude protein (CP) was calculate d as % N 6.25 [Equation 5-5] Statistical Analysis Bioassay, forage and soil data were analy zed using the MIXE D procedure of SAS (V.9.1, SAS Inst., Inc., Cary, NC). Fertilizer treatment, time and treatment x time were included in the model as fixed variables and block was named as a random variable. Soil data obtained on d 0 was used as a covariate to account for residual soil nutri ent concentrations. C ontrast analysis was used to compare the performance of organic (STALL, SEMI, and COMP) vs. INORG fertilizers and composted (SEMI and COMP) vs. unpro cessed (STALL) fertilizers. The LSMEANS

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109 procedure was used to compare treatment mean s and separation of means was performed using Tukeys test. For all analyses, P-values less than 0.05 were cons idered significant, whereas Pvalues less than 0.10 were disc ussed as trends. Data are presented as mean SE, unless otherwise stated. Results Bioassay Germ ination rate of cucumber seeds was not affected by treatment with an average of 102%. Root length was inhibite d by COMP (43%) (P<0.05) but was similar between SEMI (136%) and STALL (121%). The Cucumber seed germination index was affected by compost extract prepared from COMP, STALL and SEMI The lowest germination index was observed for COMP (45%) (P<0.05) but was similar between SEMI (129%) and STALL (128%). The high germination index (>100%) noted for STALL a nd SEMI was due to a greater root length compared to that observed when seeds were exposed to deionized water. Forage Dry m atter yield, N and P concentrations at d 30 (after germination), 45, 60, 90 and 120, and the overall all treatment mean are presented in Table 5-1. During this 40 wk study (May to December 2006), mean daily ambient temperature ranged from 9 to 27C and averaged 23C. The highest temperatures were recorded in Augus t and the lowest in November. Total rainfall during the trial was 42 cm, which is below the average of 127 cm (Black, 2003). The majority of the rainfall occurred during June, July and August 2006. These unusually warm, dry conditions may have impacted the cumulative forage yield. Of the five harvests collected, the highest mean yield (1.36 0.07 Mg ha-1) was observed in September (P<0.0001). Forage dry matter yield was influenced the first 45 d after germination, wi th INORG having the highest mean yield and STALL the lowest yield (P<0.01). Incorporation of horse stall material into soil, whether

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110 unprocessed or composted, supported similar cumu lative forage yield to that observed with INORG. Cumulative forage yield over the 40 -wk experiment ranged from 3.3 to 3.9 Mg ha-1. Fertilizer source did not affect bahiagrass tissue N, which ranged from 20 to 25 g kg-1 or crude protein ranged from 12 to 19 %. The high est forage N and crude protein concentration, were observed during the month of July after 45 d of growth (P<0.0001) (Table 5-1). Tissue P was not affected by fertilizer so urce, but was affected by time. Th e lowest tissue P in bahiagrass was harvested during the month of July (3.7 0.2 g kg-1) (P<0.0001) but increased in August (4.3 0.05 g kg-1) and remained elevated throughout the remainder of this study. The amount of N and P removed, which is a function of tissue nutrien t concentration and dry matter yield, followed a similar trend to that of yield. Cumulative N (17 1.1 kg ha-1) and P (15 0.7 kg ha-1) removed by bahiagrass was not affected by fertilizer source (Figure 5-3), however as yield increased N and P removal increased as well. Soil Soil NH4-N, P, K, Ca, Mg, CEC, pH and OM at d 0 (prior to fertilization), d 30, 60 and 120, and the overall treatment mean are presented in Table 5-2. At d 0, prior to incorporation of fertilizer, no differences existed between pl ots in any of the soil measurements. Across treatments, soil NH4-N increased (P<0.0001) from 2.8.2 mg kg-1 at d 0 to 4.5.5 mg kg-1 at d 120. With the exception of K, fertil izer source had no effect on any soil measures. Soil pH, CEC, Ca, K and extractable P decreased (P<0.05) durin g the trial period. Soil OM decreased between d 0 and d 30 (P<0.0001) but by d 120 was not different than that observed pr ior to fertilization. Mean soil K was highest in STALL (P<0.05) and lowest in INORG (P<0.05), but similar between SEMI and COMP.

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111 Discussion The bioassay conducted using cucum ber seeds indicated that unprocessed and composted and partially composted horse stall materials did not contain toxic levels of nutrients or organic acids that would likely affect s eed germination or plant growth. The lowest germination index was observed with extract from composted stall materials. This fi nding varies from most reports, where unprocessed manure is usually cited as ha ving higher potential fo r phytotoxicity when compared to composted manure (Wu et al., 2000 ; Emino and Warman, 2004). Germination rates with stall material extracts did not differ from the deionized water contro l; rather the root length had the biggest influence on germination index. The shorter root length observed in composted stall material may have resulted from lower av ailability of organic nutrients in compost, compared to the more soluble forms available from unprocessed or partially composted materials. Incorporation of horse sta ll material into soil, whet her unprocessed or composted, supported similar cumulative forage yield to that observed with inorganic fertilizer (Table 5-1). However the rate of bahiagrass establishment fertilized with organic sources was decreased compared to inorganic fertilizer. However, afte r day 60, yield was similar between all fertilizer sources. Many studies have demonstrated the positive effect of land application of compost on forage yields, usually resulting in yields that were comparable to yields produced by inorganic fertilizer (Catroux et al., 1981; Tiffany et al., 2000; Warman and Termeer, 2005). Similar findings have been reported by Reider et al. ( 2000) when applying dairy manure compost to corn grain resulted in yields comparab le to inorganic fertilizer. Perenni al grass forage yield has also been found to respond similarly with inorganic fe rtilizer and dairy manure compost (Muir et al., 2001).

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112 Summer forages cut for hay often have insuffi cient crude protein for ruminant diets when inadequately fertilized with nitrogen (Ball et al., 1991). The crude pr otein concentration of bahiagrass fertilized with horse stal l material responded similarly to that fertilized with inorganic fertilizer, with an adequa te concentration (150 g kg-1) for a non-mature, non-growing, nonlactating, non-pregnant horse di et (NRC, 1989) (Figure 5-1). The amount of nitrogen and phosphorus removed, which is a function of tissue nutrient concentration and dry matter yield, followed a sim ilar trend to that of yield (Butler and Muir, 2006) (Figure 5-2). Apparent nutrient recovery ca nnot be determined because this study lacked an unfertilized control. Yet, soil ammonium-n itrogen concentrations at day 0 (prior to fertilization) were minimal, therefore the nitr ogen removed from bahiagrass was that supplied by fertilizer. Bahiagrass fertilized with inor ganic fertilizer at a rate of 112 kg N ha-1 removed approximately 95 kg N ha-1. However, bahiagrass fertilized with horse stall materi al at a rate of 168 kg N ha-1, removed 82 kg N ha-1. Bahiagrass fertilized with horse stall material removed half of the nitrogen, as a percent applied, when compared to inor ganic fertilizer. A 50% nitrogen mineralization rate was already balanced for prior to application of horse stall material, yet only approximately 25% of the nitrogen was recovered. Lower nitrogen recovery values indicate that not all the applied nitrogen from the unprocessed stall material or compost was available for plant uptake during the firs t year of application. During the course of the experiment, ammoni um-nitrogen was the only soil parameter to increase, most likely from mineraliza tion of organic nitrogen to plant available nitrogen by soil bacteria (Table 5-2). An increase in soil am monium-nitrogen was also reported by Butler and Muir (2006) after soil incorpor ation of dairy manure compost. In contrast, soil extractable phosphorus, potassium, calcium, and magnesium c oncentration decreased in the current study

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113 (Table 5-2). This finding is most likely due to ba hiagrass uptake of the nutrients, and removal of material after harvesting without reapplication of fer tilizer to account for loss. It has been reported that repeated application of manure w ill increase residual soil extractable phosphorus, during this study, mehlich-extractable phosphorus was not increased due to application of horse stall material. Although stall mate rials are high in organic matter, soil organic matter was not enhanced in response to incorporation of horse st all material. An increase in soil organic matter, with low organic matter levels, may require more th an one yearly application of compost or stall material, particularly on Floridas sandy soils (Butler and Muir, 2006; Ferreras et al., 2006). Conclusions Results of this study suggest th at the incorporation of unprocessed or com posted horse stall materials into soil can reduce or replace some of the use of inorganic fertilizers when establishing bahiagrass pastures without reduction in forage qual ity or production. In this study, unprocessed and composted horse stall material supported similar yield and crude protein as inorganic fertilizer. When app lied at agronomic rates composte d horse stall material could decrease the cost of manure disposal and purchas e of inorganic fertilizer, recycle nutrients and reduce environmental degradati on by stabilizing nutrients th at may threaten water quality. However, more research is needed to determine long term effects of repeated land applications, as well as the mineralization rates, of unprocessed and composted horse manure.

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114 0.0 5.0 10.0 15.0 20.0 25.0 7/10/067/28/068/10/069/5/0610/3/06 d 30d 45d 60d 90d 120 Crude protein (g kg-1) INORG STALL SEMI COMP Figure 5-1. Crude protein concentr ation of Argentine bahiagrass in response to fertilization with inorganic fertilizer (INORG), unprocessed st all materials (STALL), or stall materials composted for 42 d (SEMI) or 84 d (COMP). Fe rtilizer source had no effect on crude protein.

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115 0 20 40 60 80 100 120 INORGSTALLSEMICOMPNutrient Removed (kg ha-1) Nitrogen Phosphorus Figure 5-2. Nitrogen and Phosphorus removal (kg ha-1) by Argentine bahiagrass in response to fertilization with inorganic fertilizer (INORG), unprocessed stall materials (STALL), or stall materials composted for 42 d (SEMI) or 84 d (COMP). Fertilizer source had no effect on nitrogen and phosphorus removal.

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116 Table 5-1. Dry matter yield, to tal nitrogen (N) and total phos phorus (P) concentration in Argentine bahiagrass in response to fertili zation with inorganic fertilizer (INORG), unprocessed stall materials (STALL), or stal l materials composted for 42 d (SEMI) or 84 d (COMP). Treatments p-value Day INORG STALL SEMI COMP SEMTrt Week Trt*Day Yield 30 390.7a 95.8c 272.1a,b 219.9b,c 34.6 0.0001 (kg ha-1) 45 767.6a 527.4c 570.7b,c 719.8a,b 41.1 0.0041 60 825.2 590.5 646.3 697.5 51.3 NS 90 1426 1471 1283 1270 123.9 NS 120 529.3 693.4 533.5 588.9 66.4 NS Mean 787.8 675.7 661.2 699.3 35.4 NS 0.0001 NS Total 3943 3376 3308 3503 208 NS N 30 22.2 18.6 20.6 20.5 0.5 NS (g kg-1) 45 31.9 30.6 24.8 30.6 1.1 NS 60 26.9 25.1 24.9 24.7 0.7 NS 90 20.4 21.7 20.9 20.5 0.5 NS 120 21.9 25.3 22.2 24.4 0.6 NS Mean 24.7 24.2 23.4 24.1 0.9 NS 0.0001 NS P 30 3.90 3.54 3.63 3.86 0.13 NS (g kg-1) 45 4.41 4.14 4.49 4.64 0.10 NS 60 4.22 4.06 4.39 4.15 0.13 NS 90 4.31 4.31 4.18 4.27 0.11 NS 120 4.43 4.28 4.46 4.43 0.09 NS Mean 4.26 4.06 4.23 4.27 0.17 NS 0.0001 NS Standard error mean. a,b,c Means within a row with different lette rs are significantly different (P<0.05).

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117 Table 5-2. Soil Ammonium-nitrogen (NH4), Mehl ich-1 extractable phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) con centration and cation exchange capacity (CEC), pH, and organic matte r (OM) from Argentine bahiagrass plots in response to fertilization with inorganic fertilizer (INORG), unprocessed sta ll materials (STALL), or stall materials composted for 42 d (SEMI) or 84 d (COMP). Treatment p-value Day INORG STALLSEMI COMPSEMTrt Day Trt*Day NH4-N 0 2.83 3.00 2.83 2.67 0.14 NS mg kg-1 30 2.50 2.67 2.67 2.50 0.15 NS 60 3.33 2.67 2.83 3.00 0.13 NS 120 3.83 5.25 4.25 4.83 0.55 NS Mean 3.13 3.39 3.15 3.25 0.17 NS 0.0001 NS P 0 89.5 88.9 96.1 87.1 3.7 NS mg kg-1 30 84.07 100.4 100.1 93.6 3.2 NS 60 78.02 80.5 88.4 82.43 5.65 NS 120 84.52 86.3 86.6 73.55 3.50 NS Mean 84.0 89.1 92.8 84.2 2.1 NS 0.0173 NS K 0 116.8 130.8 131.4 113.3 4.5 NS mg kg-1 30 94.04b 194.9a 119.2b119.8b 10.8 0.0016 60 106.9 140.1 109.3 102.3 8.3 NS 120 86.46 101.7 93.5 84.9 7.1 NS Mean 101.1c 141.9a 113.3b105.1c 4.2 0.0001 0.0001 0.0001 Ca 0 1988 1911 1799 1781 76 NS mg kg-1 30 1862 2033 1706 1940 94 NS 60 1889 1964 1808 1710 116 NS 120 1703 1583 1499 1449 106 NS Mean 1861 1873 1703 1720 50 NS 0.0014 NS Mg 0 125.0 121.5 120.8 112.3 4.6 NS mg kg-1 30 114.8 141.6 118.8 129.6 6.7 NS 60 106.3 128.4 126.1 115.1 7.5 NS 120 107.6 116.7 105.1 102.2 7.5 NS Mean 113.4 127.0 117.7 114.8 3.4 0.0869 0.0193 NS CEC 0 12.5 12.3 11.5 11.2 0.5 NS meq 100ml-1 30 11.6 13.2 10.9 12.3 0.6 NS 60 11.7 12.5 11.5 11.0 0.7 NS 120 10.7 10.2 9.5 9.2 0.7 NS Mean 11.7 12.0 10.9 10.9 0.3 NS 0.0008 NS pH 0 7.10 7.08 7.08 7.05 0.03 NS 30 7.22 7.23 7.23 7.22 0.04 NS 60 6.87 6.95 7.01 6.87 0.06 NS 120 6.70 6.73 6.62 6.55 0.05 NS Mean 6.97 7.00 6.99 6.92 0.03 NS 0.0001 NS OM 0 32.67 32.0 29.5 26.0 1.8 NS g kg-1 30 23.5 27.3 25.0 25.0 1.5 NS 60 29.0 33.0 31.3 30.0 1.9 NS 120 32.5 29.5 29.2 35.7 2.4 NS Mean 29.4 30.5 28.8 29.2 0.9 NS 0.0062 NS Standard error mean. a,b,c Means within a row with different lette rs are significantly different (P<0.05).

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118 CHAPTER 6 EVALUATION OF UNPROCESSED AND COMPOSTED HORSE MANURE ON SOIL CHEMICAL PROP ERTIES AND YIELD OF ESTABLISHED NORTH FLORIDA PASTURE Introduction Spreading m anure and bedding removed from st alls onto pastures is a common method of manure disposal on horse farms ((Cotton, D. personal communication, 2008); NAHMS, 1998). Horse stall material has a high carbon to nitroge n ratio (C:N), due to carbon-rich bedding. Land application of materials with high C:N ratio has been found to create competition between microbes and pasture forage, thereby suppressi ng plant growth (Warman and Termeer, 2005). Composting reduces C:N ratio, ultimately reducing microbial competition, increasing organic matter (OM) and water holding capacity of sandy soils, thereby improving forage yield (Wei and Lu, 2005). In addition, organic nitrogen and phos phorus are mineralized slowly, which provide plants with a slow release of nutrients year-round. By comparison, the nutrients in inorganic fertilizers are immediately availa ble and quickly depleted due to plant uptake or environmental loss. Using compost as fertili zer potentially could reduce th e amount of commercial nitrogen fertilizer applied without decr easing forage yield, while decr easing the potential for nitrate surface and groundwater contamination. This study was preformed as preliminary eval uation of the surface application of horse stall material and its value as a fertilizer sour ce for an established mixed bahiagrass pasture in north Florida. Because the nitrogen content of st all materials is relatively low (see Chapters 3 and 4), the amount of material th at has to be land applied to m eet nitrogen requirements of mixed bahiagrass pasture can be substantial. Therefore, one objective of this pr eliminary study was to determine the effects of compost application on forage yield when app lied at rates to meet nitrogen requirements. A second objective was to compare the effects of unprocessed and composted horse stall materials on forage yield to determine if there was an advantage to

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119 composting these materials prior to land applying and to determine if either organic material performed as well as inorganic fertilizer. The final objective was to evaluate the impact of surface application of horse stall ma terials on soil characteristics. Materials and Methods Site Description A field study was conducted at the U niversity of Florida Institute of Food and Agricultural Sciences, Horse Teaching Unit in Gainesville, Florida in 2006. A 0.5 hectare (ha) plot was used within a 3 ha pasture. Prior to this study the past ure had received regular, repeated applications of horse stall material for over 10 years. Th e soil type was a Millhopper (loamy, siliceous, semiactive, hyperthermic Grossare nic Paleudult) (USDA, 2006). Experimental Design Six f ertilizer treatments were examined: inor ganic fertilizer (INORG; %N-P-K of 16-4-8), unprocessed stall material (STALL; 0.6-0.1-0.3), composted stall material amended with nitrogen (N) prior to compos ting (ACOMP; 1.0-0.2-0.4), composted stall material that was not amended with N (UCOMP; 0.8-0.2-0.4), a mixture of ACOMP + INORG (MIX) and no fertilizer (UNFERT). Stall material included horse manure and pine wood shavings bedding that had been removed during routine stall cleaning and either stockpiled for 7 d (STALL) or composted for 84 d (ACOMP, UCOMP) before land application. Application rates were based on N requirements for bahiagrass ( Paspalum notatum ) (Newman et al., 2008), adjusted to balance approximate mineralization rates of 50% (Kidder, 2002), from organically bound N. Surface applied to plots at a rate of 167 kg N ha-1 for STALL, ACOMP and UCOMP, 111 kg N ha-1 for INORG and a combination of (84 kg N ha-1 from ACOMP and 56 kg N ha-1 from INORG) for MIX. Dry matter application rate of STALL was 28 Mg ha-1, UCOMP was 21 Mg ha-1, ACOMP was 17 Mg ha-1 and MIX was 11 Mg ha-1 was surface applied to obtain reco mmended N rates. Each treatment

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120 was randomly applied in one row) to mimic how horse producers spr ead stall material on pastures with a manure spreader pulled behind a tractor) containing ten plots measuring 2 m x 3 m. Data Collection and Analysis A biological assay was conducted on ST ALL, UCOMP and ACOMP prior to land application to evaluate potential phytotoxicity. In vitro germination and root elongation tests were performed with compost extract using United States Composting Council method 05.05-B (Thompson, 2001). Germination rates of cucumber seeds subjected to compost extract were compared to seeds exposed to deionized water. Compost extracts were prepared from samples of STALL, SEMI, and COMP obtained within 24 h and oven-dried to a constant weight. Stall materials were mixed with deionized water in a 2:1 ratio (water: media, by weight) and allowed to stand for 3 hr so that water could soak the media. The mixture was then filtered through Whatman #113 filter paper and the extracts collect ed. Filter papers were placed in 9-cm petri dishes and wetted with 10 mL of compost extract. Ten cucumber s eeds were placed in each dish. Three replicates of each dish were used to test STALL, UCOMP and ACOMP stall materials. Deionized water served as the control. Petri dishes were placed in a lighted area with lids left on to prevent water loss. The percent of seeds that had germinated were determined on 3 d and root elongation was measured at 6 d. Germination (%), root length (%) and germination index was determined using the formulas described by Zucconi et al. (1981): Germination (%) = (Germinatedsample / Germinatedcontrol) *100 [Equation 6-1] Where Germination = the percentage of samp le seeds germinated in proportion to the control; where Germinatedsample= the average number of seed s germinated in the sample; Germinatedcontrol = the average number of seeds germinated in the control.

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121 Root length (%) = (Rootsample / Rootcontrol) *100 [Equation 6-2] Where Root length = the percentage of length of root in proportion to the control; where Rootsample = the average of root length in the sample; Rootcontrol = the average of root length in the control. Germination Index = (% Germination % Root Length)/100 [Equation 6-3] Soil samples were obtained at d 0 (prior to treatment), 30, 90 and 1 yr. At each sampling interval, 20 soil cores were random ly collected within each plot at a depth to 15 cm using a stainless steel sampling probe. The cores within each plot were composited and oven dried at 65 C for 7 d. Soil was analyzed for ammonium-N (NH4), pH, organic matter (OM), cation exchange capacity (CEC) (calculation), and extr actable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). NH4-N was extracted from soils using a 1N KCl solution and analyzed spectrophotometrically (Markus et al., 1985; Dorich and Nelson, 1983). Soil pH is determined in a 1:2 soil:water extract of the soil using deionized water. Samples were stirred and allowed to equilibrate for a minimum of 30 min after adding the water. The pH determination was made using a hydrogen sele ctive electrode (Schofield an d Taylor 1955). Soil OM was determined by loss-on ignition method (Magdoff et al., 1996). Double acid Mehlich I extraction was preformed to determine P, K, Ca, and Mg an d analyzed by inductively coupled argon plasma (ICP) spectrometry (SRIEG, 1983) at all collection points. Soil analysis was performed by Agro Services International Laboratory (Orange City, FL) on a dry weight basis. Forage samples were collected by hand clipping at 0 d (prior to fertilization), 20, 40, and 65 d. A 76 cm wire cable hoop (76 cm diameter) was randomly placed in each plot and all forage material within the hoop was removed to a height of 10 cm. This procedure was repeated in triplicate for each plot to determine dry matter. Plots were individually mowed and material was

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122 collected to obtain representative samples for tis sue analysis. Forage samples were dried to a constant weight in a forced air oven at 65C to determine dry matter. Forage samples were analyzed for total N with the Dumas combustion method (VarioMax N analyzer, Elementar Americas) (TMECC method 04.02-D (Thompson, 2002 )). Total P was determined on samples that had been ashed prior to sulfuric acid di gestion and then quantified colorimetrically (PowerWave XS spectrophotometer, Winooski, VT). Nutrient removal was determined using the formula described by Butler and Muir (2006): Nutrient removal (kg ha-1) = Nutrientconc Yield [Equation 5-4] Where nutrient removal = the amount of nutrient removed in relation to DM yield; Nutrientconc = the concentration of nutrient (kg kg-1); Yield = the DM yield of forage (kg ha-1). Crude protein (CP) was calculate d as % N 6.25 [Equation 5-5] Statistical Analysis Bioassay, forage and soil data were analy zed using the MIXE D procedure of SAS (V.9.1, SAS Inst., Inc., Cary, NC). Fertilizer treatment, time and treatment x time were included in the model as fixed variables. Soil and forage nutrient da ta obtained at d 0 were used as covariates to account for residual nutrient con centrations. If treatment di fferences existed in soil characteristics at d 0, data were normalized by subtracting d 0 values from values obtained at all subsequent sampling times. Contrast analyses were used to compared the performance of organic (STALL, UCOMP, and ACOMP) vs. inorganic (I NORG) fertilizers, composted (UCOMP and ACOMP) vs. unprocessed (STALL) fertilizers, and N-supplemented (MIX and ACOMP) vs. unamended (STALL and UCOMP) materials. The LSMEANS procedure was used to compare treatment means and separation of means was perfo rmed using Tukeys test. For all analyses, Pvalues less than 0.05 were consid ered significant, whereas P-valu es less than 0.10 were discussed as trends. Data were presented as mean SE unless otherwise stated.

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123 Results Bioassay Germ ination rate of cucumber seeds was not affected by treatment with an average of 102%. Root length was lower in deionized wate r control compared to treatments, thereby causing high root length percents. Seeds germ inated in STALL extract (111%) was reduced (P<0.05) compared to compost (ACOMP and UC OMP). Germination index of cucumber seeds was affected by compost extract prepared from STALL, UCOMP and ACOMP. The lowest germination index was observed for STALL (111%) (P<0.05), followed by ACOMP (136%) and UCOMP (169%) (P<0.05). Forage During the 16-wk study (July to October 2006), m ean daily ambient temperature ranged from 10 to 34C and averaged 24C. The highest temperatures were recorded in August and the lowest in October. Total rainfall during the tr ial was 28 cm, which was below the yearly average of 127 cm for this period (Black, 2003). The majo rity of the rainfall o ccurred during June, July and August. Of the three harvests collect ed, the highest mean yield (1.22 0.05 Mg ha-1) (P<0.0001) was observed 20 d after fer tilizer applicati on (Figure 6-1). Total forage yield for the season was affected by source of fertilizer (P<0.0001) (Table 6-1) Total forage dry mater (DM) yield was lowest in plots fertil ized with STALL (P<0.05) and inte rmediate for plots treated with INORG and ACOMP (P<0.05). The great est total DM yield was observe d in plots fertilized with UCOMP and MIX, as well as plots that receive d no fertilizer (UNFERT) (P<0.05). Overall, composted stall material gene rated higher total DM yield when compared to uncomposted material (P<0.0001). A trend (P<0.10) was observed for N-supplemented stall material to result in higher total DM yield compared to unamended materials.

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124 Fertilizer source appeared to affect N c oncentration of bahiagrass forage (P<0.0001). However, the N concentration of forage tissue was different (P<0.05) between plots prior to fertilization (at d 0). When d 0 tissue N concentra tion was included in the st atistical analysis as a covariate, an effect of fertilizer treatment was still present (P<0.0001) Tissue N concentration decreased (P<0.0001) from d 0 to d 20. After d 20, forage N concentration increased (P<0.001), regardless of fertilizer, for the remainder of the trial. At d 20, after fertilizer application, forage tissue N concentration was greatest in STALL, UCOMP, and ACOMP, and lowest in forage treated with INORG, MIX and unfertilized control (P<0.01). At d 40, forage tissue N concentration was highest in INORG, intermedia te in forage fertilized with STALL, MIX, UCOMP and ACOMP, and lowest in UNFERT forage (P<0.01). At d 65, forage tissue N concentration was highest in INORG, STALL, UCOMP, and MIX, and lowest in forage of ACOMP and UNFERT (P<0.01). Contra st analysis revealed that tissue N concentration was higher in forage fertilized with composted horse stall material compared to unprocessed material (P<0.01). Contrast analysis also revealed that N concentration was higher in forage fertilized with N-amended material compared to unamend ed stall material (P<0.0001).The forage CP, calculated from % N, followed the same trends of N concentration. Overall, CP ranged from 6 to 18%, during this trial, with an average of 11.5 0.1%, the greatest concen tration occurring during September (P<0.0001). Cumulative nitrogen removed by bahiagrass forage ranged from 37.5 to 24.4 g N kg-1 and was influenced by fertilizer source (P<0.005) (Table 6-1). The relative ranking of fertilizer treatments and their impact on forage mean N removal was MIX > UCOMP > UNFERT > ACOMP > INORG > STALL (Table 6-1). Overall, c ontrast analysis reveal ed plots treated with

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125 composted material had higher N removal than those fertilized with unprocessed stall material (P<0.0001). Forage P concentration was affected by source of fertilizer (P<0.0001) and day (P<0.0001). An overall increase in forage tissue P occurred between d 0 and d 65 (P<0.0001). Tissue P concentration was not diffe rent between plots prior to fer tilizer treatment (d 0). At d 20, after fertilizer application, forage tissue P c oncentration was highest in ACOMP and MIX and lowest in forage of unfertilized control (P<0.01).At d 40, forage P concentration was highest in ACOMP and lowest in STALL and UNFERT (P <0.001). At d 60, tissue P was highest in ACOMP and UCOMP and lowest in INORG (P<0.0001). Contrast anal ysis revealed that tissue P concentration was higher in forage fertilized with organic materials compared to inorganic fertilizer (P<0.05). Also, contrast analysis demonstrated, plots tr eated with composted material had higher tissue P than those fertilized with unprocessed stall material (P<0.0001). Cumulative P removed by bahiagrass forage ranged from 4.8 to 8.3 g P kg-1 and was influenced by fertilizer source (P<0.001) (Table 6-1). The effect of fertilizer treatment on mean forage P removed followed the same trends observed for mean N removal, where MIX > UCOMP > UNFERT > ACOMP > INORG > STA LL (Table 6-1). Contrast analysis demonstrated, plots treated with composted material had higher P removal than those fertilized with unprocessed stall material (P<0.0001). Soil The ef fects of fertilizer treatment on soil ch aracteristics are presented in Table 6-2. Differences in soil extractable P, Ca, Mg, CEC, pH and OM between plots were detected prior to fertilization treatment on d 0. As a result, d 0 values for these vari ables were used as a covariate to analyze the effect of fertilizer at all subsequent sampling times. Soil NH4 increased in response to fertilizer treatment (P<0.0001). The greatest increase was observed for UNFERT and

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126 ACOMP, a more moderate increa se in plots treated with UCOM P and INORG, and the smallest change observed when MIX and STALL were app lied as fertilizer (P<0 .01). Soil extractable P and K concentrations decreased during the study period, but were not aff ected by treatment. Soil Ca, Mg and CEC decreased over time and were a ffected by fertilizer treatment (P<0.05). Plots treated with unprocessed stall mate rial had a larger re duction in soil Ca, Mg and CEC compared to plots treated with compost (a mended or unamended) (P<0.01). Soil pH differed prior to fer tilizer treatment (d 0) (P<0.001), but was similar among plots 90 d after fertilizer application. After normalizing pH to account for differences at d 0, an effect of fertilizer treatment was obser ved (P<0.01). A larger decline in pH was observed with ACOMP (P<0.05) and no change in pH observed for MIX and UCOMP (P<0.05). Although soil OM was different before fertilizer application (P<0.01), normalization of the data to account for this variation continued to reveal an effect of treatment. Contrast an alysis demonstrated a difference in soil OM between plots treated with organi c fertilizer (P<0.01). In addition, soil OM was different between plots treated with unprocessed stall material (STALL) and composted material (UCOMP and ACOMP) (P<0.001). Discussion Inherent differences in forage com position a nd soil characteristics before fertilizers were applied make interpretation of results from this tr ial difficult (Table 6-2). In an effort to mimic method of land application of stall materials on horse farms, the experimental was not designed as a completely randomized block design; which could have elimin ated the pre-existing differences in forage and soil composition. Noneth eless, some key information can be gained from this experience. Forage yield appeared to be influenced by fertilizer treatme nt (Figure 6-1). Plots treated with unprocessed horse stall material produced the lowest total yield of forage. The nutrients

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127 within unprocessed stall material are in a form th at lend themselves to be ing more available for plant uptake compared to compos t, however, the lower yield rates observed may have been due to the high carbon-content of wood shavings be dding and the resulting high carbon:nitrogen ratio of the material, which can create out competiti on by soil microorganisms with forage roots for nitrogen uptake (Hodge et al., 2000 ). In addition, due to the relatively low concentration of nitrogen in unprocessed stall ma terial, application rates were higher compared to compost and other fertilizers. The application of a larger amount of stall materi al may have initially shaded the forage and slowed growth (James, 2003). Plots treated with compost that had either been amended with nitrogen prior to composting or not had similar dry matter yield compared to inorganic fertilizer. Land application of com post has been demonstrated to produce yields comparable to dry matter yields by inorganic fertilization (Catroux et al., 1981; Hornick et al., 1984; Davis et al., 1985; Warman and Termeer, 1996; Reider et al., 2000; Tiffany et al., 2000). Eghball and Power (1999b) found that cattle feedlot manure compos t, surface applied to corn grain, produced dry matter yield similar to that of inorganic fertilizer. The amount of nitrogen and phosphorus remove d by forage is a function of nutrient concentration and DM yield (Butler and Muir, 20 06). In the current study, removal of nitrogen and phosphorus by bahiagrass followed a similar trend to that of yield, where the lowest nitrogen and phosphorus removal was observed when unproce ssed stall materials were surface applied (Table 6-1). Fertilizer source also influenced crude protein and phosphorus concentration of forage biomass. Plots fertilized with unpro cessed and composted material had higher mean forage crude protein and phosphorus concentrations (Figure 63) than those treated with inorganic fertilizer. Similar results have been reported by Butler and Muir (2006) who found that organic nitrogen from composted dairy manure wa s taken up more effectively than inorganic

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128 nitrogen in tall wheatgrass. The increased phosphorus concentration in plant tissue of organically fertilized plots could be attributed to greater rates of phosphorus application, as an unbalance exists between the nitrogen and phosphorus in manur e and that needed by plants (Lynch et al., 2004). Although stall materials are high in organic matt er, soil organic matter was not enhanced in response to a single surface applic ation of horse stall material. An increase in soil OM may require more than one yearly application of com post, particularly on Flor idas sandy soils (Butler and Muir, 2006; Ferreras et al., 2006). The increa se in soil ammonium-nitrogen during the course of this trial most likely resulted from minera lization of organic nitr ogen to plant available nitrogen by soil bacteria. An increase in soil ammonium-nitrogen was also reported by Butler and Muir (2006) after so il incorporation of dairy manure compost. In the current study, soil phosphorus levels decreased duri ng the growing season and did not appear to be affected by fertilizer treatment. This finding suggests th at when unprocessed or composted horse stall materials are surface applied to pa stures at agronomic rates, the risk of soil phosphorus saturation is not necessarily different than would be observed with inorganic fertilizer. If forage tissue phosphorus concentration was higher with horse stall material, and more phosphorus was applied, but soil phosphorus wa s not altered, perhaps reac hing an equilibrium. Conclusions Results of th is study suggest that surface applic ation of composted horse stall materials at rates to meet forage nitrogen requirements can successfully support the growth of bahiagrass pasture. In contrast, surface application of unpro cessed (fresh) horse stall materials as the sole source of fertilizer may have limited value. In order to meet pasture nitrogen requirements, a large amount of stall material must be applied, resulting in shading of fo rage and a reduction in yield. In addition, the high carbon to nitrogen ratio of most stall materials may reduce nutrient

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129 uptake by plants as soil microbes immobilize plant nutrients. As a result, inorganic fertilizer sources (particularly nitrogen) will need to be included if unprocessed ho rse stall material is surface applied to pastures. Further research is needed to validate the findings of this preliminary study.

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130 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 8/7/2006 8/29/2006 9/26/2006 d 0-20 d 20-40 d 40-65 DM Yield (Mg ha-1) UNFERT INORG MIX STALL UCOMP ACOMPa a,b c b a,b a,b b b b b a a Figure 6-1. Dry matter yield (Mg ha-1) of mixed bahiagrass in res ponse to fertilization with inorganic fertilizer (INOR G), horse stall materials (STALL), N-amended stall materials (ACOMP), unamended composte d stall materials (UCOMP), ACOMP + INORG (MIX) or no fertilization (UNFERT). a,b,cWithin each day, treatment means with different letters differ (P<0.05).

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131 10 12 14 16 18 20 22 24 26 7/14/20068/7/20068/29/20069/26/2006 d 0 d 20 d 40 d 65 Nitrogen (g kg-1) UNFERT INORG STALL MIX UCOMP ACOMP Figure 6-2. Nitrogen concentration (g kg-1) of mixed bahiagrass in resp onses to fertilization with inorganic fertilizer (INOR G), horse stall materials (STALL), N-amended stall materials (ACOMP), unamended composte d stall materials (UCOMP), ACOMP + INORG (MIX) or no fertilization (UNFERT).

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132 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 7/14/20068/7/20068/29/20069/26/2006 d 0d 20d 40d 65 Total Phosphorus (g kg-1) CON INORG MIX STALL U-COMP A-COMP Figure 6-3. Phosphorus concentration (g kg-1) of mixed bahiagrass in response to fertilization with inorganic fertilizer (INORG), horse stall materials (STALL), N-amended stall materials (ACOMP), unamended composte d stall materials (UCOMP), ACOMP + INORG (MIX) or no fertilization (UNFERT).

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133 Table 6-1. Total dry matter (DM) yield, mean nitrogen (N) and phosphor us (P) concentration, and mean N and P removed by mixed bahiagrass forage in response to fertilization with inorganic fertilizer (INORG), horse stall materials (STALL), N-amended stall materials (ACOMP), unamended composte d stall materials (UCOMP), ACOMP + INORG (MIX) or no fertilization (UNFERT). DM Yield N N removed P P removed Treatment Mg ha-1 g kg-1 g kg-1 g kg-1 g kg-1 UNFERT 2.25x 17.8y,z 33.6x,y,z 3.43z 7.3x INORG 1.85y 19.1x 27.8y,z 3.53y,z 6.2x,y MIX 2.24x 18.6x,y 37.5x 3.68y 8.3x STALL 1.40z 17.7y,z 24.4z 3.56y,z 4.9y UCOMP 2.34x 17.5y,z 37.3x,y 3.68y 8.0x ACOMP 1.85y 19.9x 31.0x,y,z 3.87x 6.8x,y ANOVA SEM 0.10 0.2 2.3 0.01 0.5 Treatment 0.0001 0.0001 0.005 0.0001 0.0002 Trt*Day 0.0001 0.0001 0.0213 0.0001 Contrast 1 NS NS 0.0673 0.0198 NS Contrast 2 Contrast 3 0.0001 0.0991 0.0058 0.0001 0.0001 NS 0.0120 0.0124 0.0001 0.0361 Standard error mean. x,y,z Means within a column followed by different letters are significantly different (P<0.05). Contrast 1: organic (STALL, UCOMP, and ACOMP) vs. inorganic (INORG) fertilizers. Contrast 2: composted (UCOMP and ACOMP) vs. unpr ocessed (STALL) fertilizers. Contrast 3: N-supplemented (MIX and ACOMP) vs. unamended (STALL and UCOMP) materials.

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134 Table 6-2. Soil concentration of ammonia nitrogen (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg), cation exchange capacity (CEC), pH, and organic matter (OM)) in response to fertilization with inorganic fertilizer (INORG), horse stall materials (STALL), N-amended stall materials (ACOMP), unamended composted stall materials (U COMP), ACOMP + INORG (MIX) or no fertilization (UNFERT). UNFERT INORG STALL MIX UCOMP ACOMP Trt SEM NH4-N d0 2.4 2.7 2.3 2.2 2.2 2.2 NS 0.1 mg kg-1 d30 3.8 2.8 2.9 3.1 2.8 4.2 NS 0.3 d90 9.2a 8.2a,b 5.9b 5.9b 8.3a,b 8.9a 0.0008 0.3 Trt 5.1a 4.6a,b 3.7b 3.7b 4.4a,b 5.1a 0.0016 0.2 P d0 38 34 48 21 37 38 0.0505 2.5 mg kg-1 d30 30 32 35 21 20 36 0.0835 2.1 d90 33a 29a,b 29a,b 21b 22b 34a 0.0016 1.2 Diff -6 -5 -20 0 -16 -4 NS 2.4 K d0 55 56 71 53 63 65 NS 3.8 mg kg-1 d30 51 58 47 54 50 68 NS 2.4 d90 29 43 32 30 35 41 NS 1.9 Trt 44 53 50 45 49 58 NS 1.8 Ca d0 1058a,b 853a,b 1249a 504b 862a,b 1109a,b 0.0421 71 mg kg-1 d30 995a,b 900a,b 622a,b 547b 691a,b 1089a 0.0076 52 d90 543 713 567 518 583 691 NS 29 Diff -515a,b -140a,b -682b 15a -279a,b -418a,b 0.0239 66 Mg d0 49b 48b 66a 45b 54a,b 55a,b 0.0057 1.7 mg kg-1 d30 52a,b 54a,b 43b 56a 58a 63a 0.0008 1.4 d90 42b 48a,b 38b 39b 47a,b 55a 0.0006 1.3 Diff -6a 0a -28b -6a -7a -0.9a 0.0017 2.2 CEC d0 6.5a,b 5.4a,b 7.8a 3.4b 5.5a,b 6.9a,b 0.0386 0.1 meq 100g-1 d30 6.1a,b 5.7a,b 4.3a,b 3.7b 4.5a,b 6.7a 0.0094 0.3 d90 3.5 4.5 3.6 3.3 3.8 4.5 NS 0.2 Diff -3.0a,b -0.8a,b -4.2b 0.0a -1.7a,b -2.4a,b 0.0218 0.4 pH d0 6.8a,b,c 6.8a,b 7.1a 6.2c 6.5b,c 7.1a 0.0002 0.1 d30 6.8a,b,c 6.9a,b 6.4b,c 6.9b,c 6.3c 6.9a 0.0005 0.1 d90 6.1 6.4 6.4 6.4 6.4 6.2 NS 0.1 Diff -0.6a,b -0.4a,b -0.7a,b -0.1a -0.1a -0.9b 0.0017 0.1 OM d0 15.2a,b 9.0b 23.3a 9.1b 12.3a,b 19.5a,b 0.0037 1.3 g kg-1 d30 16.8a,b 15.2a,b 10.3b 11.9b 14.4a,b 19.6a 0.0029 0.7 d90 7.4a,b 8.1a,b 5.8b 6.8a,b 7.5a,b 10.6a 0.0214 0.4 Diff -7.8a,b -0.9a -17.5b -2.3a -4.8a -8.9a,b 0.0018 1.3 Standard error mean. Diff = Difference between d 90 and d 0 were cal culated where differences were detected prior to fertilizer treatment at d 0. a,b,cMeans within a row with different supe rscripts are significantly different (P<0.05).

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135 CHAPTER 7 EFFECTS OF UNPROCESSED AND COMPOSTED HORSE STALL MATERI ALS ON SOIL CHEMICAL PROPERTIES AND YIELD OF NORTH FLORIDA FORAGES Introduction Recycling n utrients present in horse stall materi al by using is as a fertilizer is a beneficial tool for manure management. Yet, there are certain limitations when using fresh manure as a fertilizer source that should be considered, including la nd and seasonal constraints on application, spreading of weed seeds and in testinal parasites, fly and odor production, suppression of forage growth due to the high carbon-content of beddi ng, and the potential for contamination of surface and groundwater (James, 2003; Lyons et al., 1999; Major et al., 2005; Watson et al., 1998). Nutrients, such as ni trogen (N) and phosphorus (P) in manure can negatively affect water quality when the numbe r of grazing animals per land area exceeds the N fertility needs of the forages (Hubbard et al., 200 4). In addition, the narrow N:P ratio in manure often results in excess loading of P when appl ication rates are based on crop N demands (Dao, 1999). The primary concern with regard to using hor se manure as an amendment for pastures is the environmental issues associated with su rface and groundwater contamination. The presence of relatively mobile N, P, organic matter (O M), microbes, and other materials near the soil surface following manure application can decrease the quality of runo ff, particularly for the first post-application runoff event. Studies such as those by Westerman et al. (1983), McLeod and Hegg (1984), and Edwards and Daniel, (1993) indi cate that runoff from grassed areas treated with animal manures can contain elevated concen trations of nutrients, so lids, and organic matter relative to untreated areas. When N and P ex ceed the loading rate for a body of water, eutrophication can occur. The plant available form s of these nutrients ap pear to be of most concern in the degradation of water quality becaus e of their potential for direct uptake by aquatic

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136 vegetation and algae (Bushee et al., 1998). Management options such as buffer strips, soil incorporation, and application timing have been advocated for reducing pollution potential from pastures treated with ma nure (Young et al., 1980). Several management strategies have been disc ussed to counteract some of the limitations of using horse manure as fertilizer amendment for pastures. One management tool that has gained a renewed interest in the horse i ndustry is composting. Treating manure through composting could provide a means of reducing th e environmental impact by reducing the total volume of materials (Larney et al., 2000), destroying parasites a nd weed seeds (Romano et al., 2006; Larney et al., 2003; Larney and Blacksh aw, 2003) and reduced odor production compared to stockpiled manure (Li et al., 2007). All while, producing a stor able end product for on and off farm use, and lowers nonpoint source pollution fr om agricultural farms (Michel et al., 2004). The stabilized end product can be used as a ri ch soil amendment for agricultural cropland, landscaping and gardening and nurse ry potting mixes (Lynch, 2004). Composts have been found to enhance soil fert ility, increase crop yields (Dick and McCoy, 1993) and reduce diseases caused by soilborne plant pathogens (Hoitink and Fahy, 1986; Hoitink and Boehm, 1999). Several studies have demonstrated that land application of compost on forage crops resulted in yields that were comparable to those yields produced by inorganic fertilizer (Catroux et al., 1981; Hornick et al., 1984; Davis et al., 1985; Warman and Termeer, 1996; Reider et al., 2000; Tiffany et al., 2000). Negative responses on forage yield and soil characteristics have been infrequently reported, and are generally attributed to using compost with a high C:N ratio, excess metals, high soluble salts or extremely high application rates (Warman and Termeer, 2005). Land application of compost could reduce the amount of commercial N fertilizer applied, thereby decrea sing the potential for nitrate surface and

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137 groundwater contamination (Diepeningen et al., 2006) However, little is known about the effects composted horse manure may have on forage yield. The objective of this study was to compar e the effects of unprocessed and composted horse stall material on soil chem ical properties and forage yi eld when surface applied to established plots of Coastal bermudagrass ( Cynodon dactylon (L.) Pers), Pensacola bahiagrass ( Paspalum notatum Flgge) and Florigraze perennial peanut ( Arachis glabrata Benth.) in North Florida. Materials and Methods Site Descriptions Field studies were conducted on established Coastal berm udagrass, Pensacola bahiagrass and Florigraze perennial peanut forage stands at the University of Florida, North Florida Research and Education Center near Suwannee Valley, Florida (N 30 18, W 82 54, elevation 47 m) in 2007. The soil type is a Blanton (loamy siliceous, semiactive, thermic Grossarenic Paleudult) (USDA, 2006). Experimental Design For each forage, twenty -four plots, (each 6 m x 6 m), were blocked and randomly assigned to one of four fertilizer treatments: 1) com posted horse stall material (COMP) (% N-P-K, 1.20.4-0.4), 2) unprocessed horse stal l material (STALL) (0.6-0.3-0.3) 3) inorganic fertilizer (INORG) or 4) an unfertilized control (UNFERT). Stall material included horse manure and pine wood shavings bedding that had been removed duri ng routine stall cleaning and either stockpiled for 7 d (STALL) or amended with urea to achieve a C:N ratio of 30:1 and composted for 120 d (COMP) before use. Initial INORG, COMP a nd STALL fertilizer tr eatments were surface applied by hand in May 2007.

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138 Experiment 1: Pensacola Bahiagrass Pensacola bahiagrass pasture was manage d as a medium N option grazed system, requiring fertilization rates of 112 kg N ha-1 applied as a single a pplication (Newman et al., 2008). The availability of nutrients from the orga nic fertilizers was estimated to be 50% the first season (Kidder, 2002). Therefore, STALL and CO MP were applied at a rate of 224 kg N ha-1. Dry matter application rate of STALL was 37 Mg ha-1 and COMP was 19 Mg ha-1. All fertilizer treatments were applied in a si ngle application in May 2007. Inorga nic fertilizer used for INORG treatment had a guaranteed % N-P-K analysis of 19-5-19 derived from diammonium phosphate, ammonium nitrate, muriate of potash, amm onium sulfate and dolomitic limestone and was applied at the recommended rate of 112 kg N-1. Bahiagrass samples were collected every 6 wk from July to November 2007 to a height of 10 cm and remaining biomass was mowed and removed from plots. Experiment 2: Coastal Bermudagrass Coastal bermudagrass p asture was managed for hay production with multiple harvests, requiring fertilization rates of 90 kg N ha-1 prior to the first harves t and an additional 90 kg N ha1 after each harvest, except the last in the fa ll (Newman et al., 2008). Th e fertilizer application rate for the INORG treatment followed these reco mmendations, with an initial application in May 2007. For STALL and COMP, an initial rate of 180 kg N ha-1 was applied in May 2007 based on an estimated first-season N availability of 50% (Kidder, 2002). Dry matter application rate of STALL was 29 Mg ha-1 and COMP was 15 Mg ha-1. After each harvest, inorganic fertilizer was applied to I NORG, STALL and COMP treatme nts at a rate of 90 kg N ha-1. The inorganic fertilizer used in this study had a guaranteed %N-P -K analysis of 19-5-19, derived from diammonium phosphate, ammonium nitrate, muriate of potash, ammonium sulfate and

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139 dolomitic limestone. Bermudagrass samples were co llected every 6 wk from July to November 2007 to a height of 10 cm and remaining biomass was mowed and removed from plots Experiment 3: Florigraze Rhi zoma Perennial Peanut Florigraze rhizome perennial peanut past ure was managed for hay production with multiple harvests, requiring fertilization rates of 33 kg P2O5 ha-1 before the first harvest and an additional 17 kg P2O5 ha-1 after each harvest, except the last in the fall (Newman et al., 2008). The fertilizer application rate for the INORG treatment followe d these recommendations, with an initial application in June 2007. For STALL and COMP, an initial rate of 67 kg P2O5 ha-1 was applied in June 2007 based on an estimated firs t-season N availability of 50% (Kidder, 2002). Dry matter application rate of STALL was 11 Mg ha-1 and COMP was 8 Mg ha-1. After each harvest, inorganic fertilizer was applied to I NORG, STALL and COMP treat ments at a rate of 17 kg P2O5 ha-1. The inorganic fertilizer used in this study had a guarant eed % N-P-K analysis of 37-28 derived from ammoniated phosphate, anhydrous ammonia, iron oxide, iron sulfate, manganese oxide, manganese sulfate, muriate of potash, normal super phosphate, sodium borate, sulfate of potash-magnesia, sulfuric acid, zinc oxi de and zinc sulfate. Perennial peanut samples were collected every 8 wk from August to Octo ber 2007 to a height of 10 cm and remaining biomass was mowed and removed from plots. Data Collection and Analysis A biological assay was conducted on STALL and COMP prior to land application to evaluate potential for phytotoxi city. Seedling em ergence and relative growth was performed using US Composting Council method 05.05-A (T hompson, 2001). Growing media was created from 50:50 blend of treatment (COMP or STALL) and No. 2 grade vermiculite. Pure vermiculite was included as negative control and soil-less potting media containing inor ganic fertilizer was included as a positive control. Two cucumber seed s were placed in each cell of a plastic seedling

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140 flat and the respective growing media was added. Materials were watered with deionized waster and then wrapped in a plastic bag. The plas tic wrapped seedling tr ay was placed under a florescent light fixture that prov ide 14 h continuous light and 10 h dark in a room maimtained at a temperature of approximately 27C. After 12 d, cucumber seedlings were evaluated for emergence, health and vigor of the cucumber s eedlings. The number of seedlings that had fully exposed hypocotyl and fully expanded cotyledo ns were counted and recorded for emergence evaluation. Healthy vigorous seedli ngs with height equal to or gr eater than the average seedling height or the positive control were counted and recorded. Soil samples were collected from all three fo rage sites in May 2007 to determine residual soil physical and chemical propertie s. Ten soil cores were randomly collected from at depths of 0 to15 cm and 15 to 30 cm each of the twenty-four plots and pooled for a total of 48 samples per forage site (24 plots x 2 depths). In additi on, soil samples were obtained at wk 6, 12, and 24 (Bahiagrass and Bermudagrass) and wk 8 and 16 (P erennial peanut). Soil samples were obtained using a stainless steel sampling probe. Samples we re air dried at 24C and analyzed for total N, nitrate-N (NO3-N), ammonium-N (NH4-N), pH, and cation exch ange capacity (CEC). Extractable P, potassium (K), calcium (Ca), and magnesium (Mg) were determined by double acid Mehlich I extract ion and analyzed on inductively coup led argon plasma (ICP) spectrometry. Sulfur (S), boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu) and OM were also determined by ICP spectrometry in samples obtai ned prior to fertiliza tion (May 2007) and at study conclusion (October/November 2007). So il samples were analyzed by Waters Agricultural Laboratory (Camilla, GA) on a dry weight basis. Bahiagrass and bermudagrass forage samples were hand collected at 6, 12, 18 and 24 wk after initial fertilizer ap plication. Perennial peanut was hand co llected at 8 and 16 wk after initial

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141 fertilizer application. A 76 cm wire cable hoop (76 cm diameter) was randomly placed in each plot and all forage material within the hoop was removed to a height of 10 cm. This procedure was repeated in triplicate for each plot to dete rmine dry matter. Plots were individually mowed and material was collected to obt ain representative samples for tissue analysis. Forage samples were dried to a constant weight in a forced air oven at 65C to determine dry matter. Forage samples were analyzed for total N with the Dumas combustion method (VarioMax N analyzer, Elementar Americas) (TMECC method 04.02-D (T hompson, 2002)). Total P was determined on samples that had been ashed prior to sulfuric acid digestion and then quantified colorimetrically (PowerWave XS spectrophotometer, Winooski, VT). Nutrient removal was determined using the formula described by Butler and Muir (2006): Nutrient removal (kg ha-1) = Nutrientconc Yield [Equation 7-1] Where nutrient removal = the amount of nutrien t removed in relation to total DM yield; Nutrientconc = the concentrati on of nutrient (kg kg-1); Yield = the DM yield of forage (kg ha-1). Crude protein (CP) was calculate d as % N 6.25 [Equation 7-2] Apparent recovery of N and P from fora ge tissue was calculated using the formula described by Lynch et al. (2004): ANR (%) = [(NremT NremU) / Nappl] 100 [Equation 7-3] Where apparent nutrient recovery (ANR) = the percentage of nutrient recovered by forage tissue in relation to the amount applied; NremT = nutrient removed by treatment (kg ha-1); NremU = nutrient removed by unfer tilized control (kg ha-1); Nappl = amount of nutrient applied (kg ha-1). Statistical Analysis Bioassay, forage and soil data were analy zed using the MIXE D procedure of SAS (V.9.1, SAS Inst., Inc., Cary, NC). Four treatments (UNFERT, INORG, STALL, and COMP) were assigned in a completely randomized block design w ith 6 blocks and 6 replications per treatment

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142 for a total of 24 plots. Treatment, week, dept h and treatment x week and treatment x depth interactions were included in the model as fixed effects and block was named as a random variable. Contrast analysis was performed to compare the effects of organic (STALL and COMP) vs. inorganic (INORG) fertilizer sources, fertilized (INORG, STALL and COMP) vs. unfertilized (UNFERT) treatments, and trea tment with organic (STALL and COMP) vs. no fertilizer (UNFERT). The LSMEANS procedure was used to compare treatment means and separation of means was performed using Tukeys test. For all analysis, P-values less than 0.05 were considered significant, wher eas P-values less than 0.10 were discussed as trends. Data were presented as mean SE, unless otherwise stated. Results Weather Conditions During the 24-wk experim ent (May to November 2007), mean daily ambieint temperature ranged from 14.5 to 27.6C and averaged 23.4C. Th e highest temperatures were recorded in August and the lowest in November. Total rainfa ll during the trial was 59.1 cm, which is below the 5-yr average of 84.4 cm during an equivalent 24-wk period. The majo rity of the rainfall occurred during June, July and August 2007. Bioassay Em ergence and relative growth of cucumber seedlings was not negatively affected by COMP or STALL. Percent emergence for COMP and STALL were both 100% when compared to the positive fertilizer control. Additionally, he alth and vigor of seedlings grown in COMP or STALL did not exhibit any relative differences compared to the fertilizer control. All cucumber seedlings were well formed, had un-deformed cotyledons and turgid hyp ocotyls with a length equal to or greater than the positive control.

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143 Experiment 1: Pensacola Bahiagrass Total DM yield and yield by harvest interval for Pensacola b ahiagrass are presented in Table 5-1. For fertilized plots, the average DM yield for each 6-wk harvest interval was 1,068 kg ha-1 and mean total yield over th e 24-wk study period was 3,550 kg ha-1. An overall effect of treatment (P<0.0001) was observed, whereby mean harvest yield was greatest for bahiagrass fertilized with INORG and STALL (P<0.05), inte rmediate for COMP (P<0.05) and lowest for UNFERT (P<0.01). Additionally, a significant treat ment x time interaction was detected for yield (P<0.0001). At the 6 wk harvest, DM yield from INORG was greater than STALL and COMP (P<0.05) and at 12 wk DM yield from both INORG and STALL were greater than COMP (P<0.05). There were no differences in yield between INORG, STALL and COMP at 18 and 24 wk. All fertilizer treatments (INORG, STA LL, COMP) resulted in greater DM yield than UNFERT at each harvesting interval (P<0.05), with the exception of wk 18 when yield did not differ among treatments. Contrast analysis of total yield revealed that bahiagrass responded to fertilization with higher yields co mpared to the unfertilized cont rol (P<0.0001), and total yield of inorganic fertilizer was higher compared to organic sources (STALL and COMP) (P<0.0001). Total DM yield from all harvests was greatest from plots fertilized with INORG and STALL (P<0.05), intermediate for COMP (P<0.05), and lowest for UNFERT (P<0.01). Over the 24-wk study, there was a significant effect of time (P<0 .0001) on yield of Pensacola bahiagrass, with yields generally being greatest at the wk 6 and 12 harvests (July and Aug), a significant decline at wk 18 (Sept), and a further decl ine at the wk 24 harvest (Nov). Tissue N and P concentrations of Pensacola bahiagrass are presented in Table 5-1. An overall effect of treatment was observed for tissue N (P<0.0001), whereby mean harvest tissue N was greater in plots fertilized with INORG or STALL (P<0.05) compared to COMP and UNFERT. Contrast analysis of tissue N revealed that bahiagrass did not respond to fertilization

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144 compared to the unfertilized c ontrol, or fertilization from organic compared to inorganic fertilizer. An effect of time (P<0.0001) and treat ment x time (P<0.0001) were also observed for tissue N concentration. Across treatme nts, tissue N concentration was elevated at the wk 6 (July) and wk 24 (Nov) harvests and lowest during th e wk 12 and 18 harvests (Aug and Sept). Tissue crude protein concentrations calculated from N concentrations followed the same treatment (P<0.0001), time (P<0.0001) and treatment x time (P <0.0001) patterns described above for tissue N. Mean harvest crude protein concentrati on was higher for INORG and STALL (each 7.6%) (P<0.05) and lower for COMP (6.7%) and UNFERT (6.6%). Total N removed by bahiagrass during the 24-wk study period was greatest when fertilized with INORG and STALL (P<0.05), intermediate with COMP (P< 0.05), and lowest in UNFERT (P<0.05) (Figure 5-1). An overall effect of treatment was observed for tissue P (P<0.0001), whereby mean harvest tissue P was greatest in plots fertilized with STALL (P <0.05), intermediate with UNFERT (P<0.05), and lowest for INORG and COMP (P<0.05) (Table 5-1). Contrast analys is of tissue P revealed that bahiagrass responded to organic fertilizer with higher tissue P compared to the inorganic fertilizer (P<0.0001). An effect of time (P<0.00 01) was observed for tissue P concentration, whereby tissue P generally increased thr oughout the 24-wk study period. Additionally, a treatment x time (P<0.001) interaction was dete cted, with some treatments experiencing no change (INORG, COMP) or a decline (STALL) in tissue P concentration from wk 6 to 12, followed by a subsequent increase at wk 18 and 24 above that observed at the 6 wk harvest. Total P removed by bahiagrass during the 24-wk study period was greatest when fertilized with STALL (P<0.05), followed by INORG (P<0.05), COMP (P<0.05), and lowest in UNFERT (P<0.05) (Figure 5-1).

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145 Treatment means of soil chemical properties of Pensacola bahiagrass plots are presented in Table 5-2. Fertilizer application, regardless of source, did not influe nce soil extractable TN, NO3-N, NH4-N, or Mg. Fertilizer source did have an effect on soil extractable P (P<0.05), K (P<0.0001) and Ca (P<0.01) concentrations. Mean so il extractable P concentr ation was greater in STALL compared to UNFERT (P<0.05), and mean soil K concentration was greater in STALL compared to all other fertilizer treatments (P< 0.05). Mean soil Ca concentration was greater in INORG compared to COMP (P<0.05). Mean so il CEC was higher in INORG compared to STALL, COMP or UNFERT (P<0.001). Fertilizer source did not affect soil pH or OM. Although time effects were observed for many of the soil chemical properties measured, no interactions of time x treatment were found, in dicating that soil properties changed similarly between fertilizer treatments over time. As a result, soil data for Pensacola bahiagrass were pooled across fertilizer treatments and are presen ted by sampling interval in Table 5-3. An effect of time was not detected for soil TN, but was observed for NO3-N (P<0.0001) and NH4-N (P<0.0001). Both soil NO3-N and NH4-N experienced a decline (P<0.05) from wk 0 (before fertilizer application) to wk 6. Soil NO3-N and NH4-N subsequently increased at wk 12 and 24 (P<0.05), but only NH4-N reached the same level observed prior to fertilizer application at wk 0. An effect of time was also detected for soil extractable P (P<0.001), Ca (P<0.05), Mg (P<0.01), S (P<0.0001), Zn (P<0.05), Mn (P<0.0001), Fe (P <0.01), and Cu (P<0.01) concentrations, but not K and B concentrations. In most cases, so il mineral levels decr eased in response to fertilization (wk 0 to 6) and re mained at steady concentrations through 24 wk. The exceptions to this pattern were soil Fe, whic h increased throughout the 24-wk study period, and soil Cu, which decreased from wk 0 to 6, but incr eased to pre-fertiliz ation concentrations by 24 wk. Soil pH did not change during the study period, but both CEC (P<0.05) and OM (P<0.05) decreased over

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146 time. The decline in CEC and OM did not necessarily appear to be an acute response to fertilization, but rather gr adually declined over 24 wk. No treatment x soil sampling depth interactions were observed in any of the soil chemical properties measured; therefore, soil data were pooled across all fertilizer treatments and sampling times and are presented in relation to sampling depth in Table 5-4. Soil NO3-N, K, Mg, Ca, S, Zn, Mn, CEC and pH were present in higher concen trations above 15 cm than in the lower depth profile (P<0.01). In contrast, soil extractable P and Fe were present at higher concentrations in soil below 15 cm (P<0.0001). Sampling depth had no effect on soil TN, NH4-N, B, Cu or OM. Experiment 2: Coastal Bermudagrass Total DM yield and yield by harvest interval for Coastal bermudagrass are presented in Table 5-5. F or fertilized plots, the average DM yield for each 6-wk harvest interval was 1,903 kg ha-1 and mean total yield over th e 24-wk study period was 7,611 kg ha-1. An overall effect of treatment (P<0.0001) was observed, whereby mean harvest yield was greatest for bahiagrass fertilized with INORG (P<0.05), intermediate for STALL and COMP (P<0.05), and lowest for UNFERT (P<0.01). Similarly, total DM yield from all harvests was greatest from plots fertilized with INORG (P<0.05), intermediate for STA LL and COMP (P<0.05), and lowest for UNFERT (P<0.01). Contrast analysis of total yield revealed that bermudagrass responded to fertilization with higher yields compared to the unfertilized control (P<0.0001), also total yield between use of inorganic fertilizer was higher compared to organic sources (STALL and COMP) (P<0.001). Over the 24-wk study, there was a significant e ffect of time (P<0.05) on yield of Coastal bermudagrass, with yields generally being greate st at the wk 6 and 12 ha rvests (July and Aug), followed by a progressive decline at wk 18 (Sep t) and wk 24 (Nov). A significant treatment x time interaction was not detected for DM yield. Nonetheless, separation of treatment means by time interval demonstrated that STALL and COMP performed similarly to each other and to

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147 INORG and UNFERT at the 6, 12 and 18 wk harvests At the 24-wk harvest, fertilization with STALL and COMP resulted in similar yield to INORG and were greater (P<0.05) than UNFERT. Tissue N and P concentrations of Coastal be rmudagrass are presented in Table 5-5. An overall effect of treatment was observed fo r tissue N (P<0.0001). Mean harvest tissue N was greatest in plots fertilized with INORG or STALL (P<0.05), intermediate in COMP (P<0.05), and lowest in UNFERT (P<0.05). Contrast analysis of tissue N revealed that bermudagrass responded to fertilization with higher tissue N compared to th e unfertilized control (P<0.0001), but there was no difference in tissue N between use of inorganic fert ilizer compared to organic sources (STALL and COMP) An effect of time (P<0.0001) was observed for tissue N concentration, but no treatment x time interaction was detected. Across treatments, tissue N concentration increased (P<0.0001) from an average of 14 g kg-1 at wk 6 to 19.8 g kg-1 at wk 24. Tissue crude protein concentrations calculated from N concentrations followed the same treatment (P<0.0001) and time (P<0.0001) patterns described above for tissue N. Mean harvest crude protein concentration was higher in INORG (18.7%), STALL (18.7%), and COMP (16.7%) (P<0.05) than UNFERT (14.3%). Tota l N removed by bermudagrass during the 24-wk study period was greater in INORG (P<0.05) co mpared to COMP and UNFERT (Figure 5-2). Total N removed in plots treated with STALL were similar to INORG and COMP, but greater than (P<0.05) than UNFERT (Figure 5-2). In co ntrast to N, tissue P concentration was not affected by fertilizer treatment (Table 5-5). Contrast analysis of tissue P revealed that bermudagrass responded to fertilization with higher tissue P compared to the unfertilized control (P<0.0001), but there was no difference in tissue P between use of inorganic fertilizer compared to organic sources (STALL and COMP) In addition, no effects of time or treatment x time were

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148 observed for bermudagrass P concentration. Howe ver, total P removed by bermudagrass during the 24-wk study period was affected by fertiliz er treatment (P<0.01). The application of fertilizer, regardless of source, resulted in a greater removal of P by bermudagrass compared to unfertilized control (P<0.05) (Figure 5-2). Treatment means of soil chemical properties of Coastal bermudagra ss plots are presented in Table 5-6. Fertilizer application, regardless of source, did not influe nce soil extractable TN, NO3-N, NH4-N, P or Ca. Fertilizer source did have an effect on soil K (P<0.001) and Mg (P<0.001) concentrations. Mean soil K concentr ation was greater in STALL compared to all other fertilizer treatments (P<0.05) Mean soil Mg concentration was greater in STALL compared to all other fertilizer treatment s (P<0.05). Mean soil pH was higher in STALL compared to INORG or COMP (P<0.01). Fertiliz er source did not affect soil OM or CEC. Although time effects were observed for many of the soil chemical properties measured, no interactions of time x treatment were found, in dicating that soil properties changed similarly between fertilizer treatments over time. As a result, soil data for Coastal bermudagrass plots were pooled across fertilizer treatments and are presen ted by sampling interval in Table 5-7. An effect of time (P<0.0001) was detected for soil TN, NO3-N and NH4-N. Soil TN declined from wk 0 to 6 (P<0.05), but then increased to pre -fertilization levels by wk 12. Soil NO3-N was lower (P<0.05) and soil NH4-N higher (P<0.05) at wk 6 and 12 compared to wk 0 and 24. An effect of time was also detected for soil extracta ble P (P<0.01), K (P<0.001), Ca (P<0.0001), Mg (P<0.0001), S (P<0.0001), Zn (P<0.0001), Mn (P<0.0001), Fe (P<0.05), and Cu (P<0.05) concentrations, but not B. In most cases, soil mineral levels decreased over the course of the 24wk study. The exceptions to this pattern were soil extractable P, which increased at wk 6 and 12, and soil Fe, which demonstrated a transient d ecrease at wk 6, followed by an increase to pre-

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149 fertilization levels by wk 12. Soil pH did not change during the st udy period, but both CEC (P<0.0001) and OM (P<0.05) decreased over time. No treatment x soil sampling depth interactions were observed in any of the soil chemical properties measured; therefore, soil data were pooled across all fertilizer treatments and sampling times and are presented in rela tion to sampling depth in Table 5-8. Soil TN, P, K, Mg, Ca, Zn, pH, CEC and OM were present in higher concentr ations above 15 cm than in the lower depth profile (P<0.001). Sampling depth had no effect on soil NO3-N, NH4-N, S, B, Mn, Fe or Cu. Experiment 3: Florigraze Perennial Peanut Total DM yield and yield by harvest interv al for Florigraze p erennial peanut are presented in Table 5-9. For fertilized plots, the average DM yield for each 8-wk harvest interval was 1,385 kg ha-1 and mean total yield over th e 16-wk study period was 3,019 kg ha-1. An overall effect of treatment (P<0.05) was observed, whereby mean harvest yield was greatest for perennial peanut fertilized w ith INORG (P<0.05) compared to STALL, COMP and UNFERT. Similarly, total DM yield from all harvests was greatest from plots fertilized with INORG (P<0.05) compared to STALL, COMP and UNFERT. No differences in mean or total DM yield were observed between STALL, COMP and UN FERT. Contrast analys is of total yield revealed that perennial peanut responded to fertilization with higher yields compared to the unfertilized control (P<0.0001), and inorganic fertilizer resulted in higher total yields than organic (STALL and COMP). Over the 16-wk study, there was a si gnificant effect of tim e (P<0.0001) on yield of Perennial peanut, with yields generally being gr eatest at the 8 wk harves t (August) compared to 16 wk (Oct). A significant treatment x time intera ction was not detected for DM yield, indicating forage production responded similarly over time for all fertilizer treatments. Tissue N and P concentrations of perennial p eanut are presented in Table 5-9. An overall effect of treatment was observed for tissue N (P<0.01). Mean harvest ti ssue N was greatest in

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150 plots fertilized with COMP or UNFERT (P<0.05) compared to INORG and STALL. Contrast analysis of tissue N revealed that perennial peanut responde d to fertilization with higher tissue N compared to the unfertilized control (P< 0.01) and organic fertilizer (STALL and COMP) resulted in higher tissue N than inorganic (P<0.01). An effect of time (P<0.01) was observed for tissue N concentration, but no treatment x time interaction was detected. Across treatments, tissue N concentration in creased (P<0.01) from an average of 24.9 g kg-1 at wk 8 to 26.9 g kg-1 at wk 16. Tissue crude protein concentrations calcul ated from N concentrations followed the same treatment (P<0.01) and time (P<0.01) patterns de scribed above for tissue N. Mean harvest crude protein concentration was hi gher in UNFERT (17%) and COMP (16.9%) compared to INORG (15.3%) and STALL (16%) (P<0.05). Total N re moved by perennial peanut during the 16-wk study period was greater in INORG (P<0.05) co mpared to COMP and UNFERT (Figure 5-3). Total N removed in plots treated with STALL did not differ from COMP, INORG or UNFERT, and total N removed by plots treated with CO MP was similar to STALL and UNFERT (Figure 5-3). An overall effect of treatment was obser ved for tissue P concentration (P<0.001), whereby mean harvest tissue P was greates t in plots receiving no fertili zer (UNFERT) (P<0.05) compared to INORG, STALL and COMP. Co ntrast analysis of tissue P revealed that perennial peanut responded to unfertilized control with higher tissu e P compared to the fertilized (P<0.0001) and organic fertilizer (STALL and COMP) resulted in higher tissue P than inorganic (P<0.0001). An effect of time was observed for perennial peanut P concentrati on (P<0.0001), but not a treatment x time interaction. Across treatments, tissue P decreased from the 8 wk to 16 wk harvest (P<0.0001). Total P removed by perennial peanut during the 24-wk study period followed a pattern similar to that observed for total N re moval (Figure 5-3). Total P removed was greater with application of INORG compared to COMP or UNFERT (P<0.05). Total P removed in plots

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151 treated with STALL did not differ from COMP INORG or UNFERT, a nd total P removed by plots treated with COMP was similar to STALL and UNFERT (Figure 5-3). Treatment means of soil chemical properties of perennial peanut pl ots are presented in Table 5-10. Fertilizer ap plication, regardless of source, did not influence soil extractable TN, NO3-N, NH4-N, Ca or Mg. Fertilizer source did have an effect on soil extr actable P (P<0.01) and K (P<0.0001) concentrations. Me an soil extractable P concen tration was lower in COMP compared to all other fertilizer treatments (P <0.05). Mean soil K concentration was lower in COMP and UNFERT compared to INORG and STALL (P<0.05). Fertilizer source did not affect soil pH, OM or CEC. Although time effects were observed for many of the soil chemical properties measured, no interactions of time x treatment were found, in dicating that soil properties changed similarly between fertilizer treatments over time. As a result, soil data for perennial peanut plots were pooled across fertilizer treatments and are pres ented by sampling interval in Table 5-10. An effect of time (P<0.0001) was detected for soil NO3-N and NH4-N, but not TN. Soil NO3-N was lower (P<0.05) and soil NH4-N higher (P<0.05) at wk 8 compared to wk 0 and wk 16. An effect of time was also detected for soil extractable P (P<0.05), K (P<0.0001), B (P<0.001), Mn (P<0.0001), Fe (P<0.0001), and Cu (P<0.0001) concen trations, but not Ca, Mg, S or Zn. Soil extractable P, S, and Mn decrease d and soil K, B, Fe and Cu incr eased over the course of the 16wk study. At wk 8, soil pH remained unchanged from wk 0, but decreased (P<0.05) at wk 16. Both CEC (P<0.001) and OM (P<0.0001) increased during the study period. No treatment x soil sampling depth interactions were observed in any of the soil chemical properties measured from perennial peanut plots; therefore, soil data were pooled across all fertilizer treatments and sampling times and are presented in relation to sampling depth in Table

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152 5-12. Soil TN, NH4-N, P, K, Mg, Ca, S, B, Mn, pH and CEC were present in higher concentrations above 15 cm than in the lower de pth profile (P<0.01). Only soil Zn was present in higher concentrations in the lower depth pr ofile (P<0.0001). Sampling depth had no effect on soil NO3-N, Fe, Cu or OM. Discussion Results from the bioassay indicated that unp rocessed and composted horse stall m aterials did not contain toxic levels of nutrients or or ganic acids that would affect cucumber seed emergence or plant health and vigor. This finding varies from most reports citing that unprocessed manure have higher potential for phyt oxicity when compared to processed manure (Wu et al., 2000; Emino and Warman, 2004). When surface applied to bahiagrass or bermuda grass, horse stall material and compost performed equally in regards to dry matter yield, but both generated lower yield than inorganic fertilizer during the first 6 weeks of growth (T able 7-1; Table 7-5). In bahiagrass, which only received a single application of fertilizer, unproc essed horse stall material produced similar dry matter yield as inorganic fertil izer from 6 to 12 weeks. By comparison, bermudagrass received supplemental inorganic fertilizer af ter every harvest, which was likel y responsible for the lack of difference in dry matter yield measured from 6 to 24 weeks between inorganic and organic (STALL and COMP) fertilizers (Tab le 7-5). Perennial peanut dry matter yield was not affected by fertilizer at the first harvest (week 8), yet fertilizer source di d appear to influence the second harvest (Table 7-9). Perenni al peanut plots fertilized with inor ganic fertilizer had the largest dry matter yield, followed by organic fertilizer (S TALL and COMP). Although dry matter yield in the second harvest was lower than that observed in the first, perennial pea nut plots treated with fertilizer did out perform the unfertilized control.

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153 The apparent nitrogen recovered from bahi agrass and bermudagrass fertilized with inorganic fertilizer averaged 30%, while orga nic sources (STALL and COMP) had much lower N recovery, averaging 14% (Figure 7-1; Figure 7-2). Motavalli et al. (1989) reported apparent N recoveries of forage as 19, 19 and 15% for dairy manure application rates of 53, 97 and 138 Mg ha-1 yr-1 (wet basis), respectively. Sullivan et al. (1997) reported cumulative annual apparent N recoveries of 17, 28, and 36% in harvested prai riegrass receiving dairy manure with varying application rates. In the current study the lowe r N recovery values observed for unprocessed and composted stall material were an indication that very little of the N applied was available for plant uptake during the first year of application. When calculating applicati on rates for horse stall materials in this study, a mineralization rate of 50% was chosen based on the warm climatic conditions and high annual rainfall in Florida, which have been shown to enhance decomposition of compost (Kidder, 2002). By comparison, a 20% mineralization rate of horse manure has been reported in cooler environments (UM, 1993). Du ring this study, the nitr ogen recovery from organic fertilizer suggests that available nitrogen from horse stal l materials is closer to 25% during the first growing season. Th erefore, the low rate of ava ilable nitrogen may limit land application of horse stall materi als and compost because of the sh eer volume of material that would have to be applied to meet forage nitrogen requirements. It could also be attributed, in part, to the dry climatic conditions at the expe riment site, dry conditions do not favor compost mineralization (Sikora and Szmidt, 2001). The dry conditions also impacted forage growt h. Additionally, more th an 85% of the total annual production of bahiagrass and bermudagrass occurs during the six warmest months (April through September) of the year, with very little growth as the temper ature drops (Mislevy and Everett, 1981). This explains the observed lowe r dry matter yield during the November harvest

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154 of bahiagrass and bermudagrass. A further reason might be the C:N of the compost, which was 40:1. It has been reported that compost should ha ve a C:N of 18 or less in order to prevent a competition between plant roots and soil micr oorganisms for N (Vogtmann et al., 1993). Soil ammonium-nitrogen and nitrate-nitrogen values remained unchanged in the upper 15 cm within all forage plots, regardless of fertiliz er source (Table 7-4; Table 7-8; Table 7-12). Soil residual ammonium-nitrogen and nitrate-nitrogen c oncentrations were also unchanged. Chang et al. (1991) reported that despite hi gh ammonium concentrations in cattle feedlot manure, repeated annual applications of the manure did not affect soil ammonium levels. Schlegel (1992) reported annual application of beef cattl e manure compost up to 16 Mg ha-1 had no effect on soil nitrate after 2 and 4 years. Xie and MacKenzie (1986 ) reported similar resu lts, showing no residual effects on soil nitrate from 2 years of beef cat tle compost applications when samples were collected in the following spring. Sanders on and Jones (1997) re ported soil nitrate increased with increasing manure application rate but nitrate concentrations be low 15 cm were not affected by manure treatment. These authors further reported that although nitrate levels in the soil increased, a maximum of only 7 mg kg-1 accumulated in the surface 15 cm of soil. It is not know if inorganic N changed below 15 cm due to le aching, but the drought conditions would have minimized the chance for leaching losses. In the current study, soil extracta ble phosphorus did not increase in response to application of unprocessed or composted stall material (Table 7-3; Table 7-7; Table 7-11). Evidence of prior manure application was apparent on the bahiagra ss plots where soil extractable phosphorus was significantly higher than that observed in the bermudagrass or pe rennial peanut plots. In fact, a swine production faci lity had been located near the bahiagrass field si te 10 years prior. The majority of the soil extractable phosphorus in the bahiagrass plots was located at the 15-30 cm in

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155 depth, compared to bermudagrass and peanut pl ots where phosphorus accumulated in 0-15 cm profile. A 7 year study conducted by Ferguson a nd Nienaber (2000) reported soil extractable phosphorus levels in the top 0.6 m increased significantly with application of beef feedlot manure or compost, but no evidence of phosphorus movement below that depth was observed. Similarly, Chang et al. (1991) found that increases in soil extractab le phosphorus were restricted to the upper 30 cm zone after 11 annual applicat ions of feedlot manure under irrigated, and under non-irrigated conditions. During this study, soil organic matter was not en hanced due to application of horse stall material, an increase in soil organic matter may require more than one yearly application of compost, particularly on Floridas sandy soils (Butler and Muir, 2006; Ferreras et al., 2006). Conclusion The surface application of eith er fresh or composted horse st all material to bahiagrass, bermudagrass and perennial peanut resulted in hi gher forage yield than th e unfertilized control. In many cases, one or both of these organic fert ilizers performed equall y as well as inorganic fertilizer. However, addtional f actors other than yield should be considered when using organic fertilizer sources for pasture or hay crop fer tilization. Application of unprocessed horse stall material may be disadvantageous due to the po tential to spread weed seeds and intestinal parasites, fly and odor production, suppression of forage growth and the potential for contamination of surface and groundwater (James, 2003; Lyons et al., 1999; Major et al., 2005; Watson et al., 1998). In contrast, composting horse stall materials prior to land application may aid in the destruction of weed s eeds and internal parasites, along with fly eggs and larvae (Lyons et al., 1999; Major et al., 2005; Watson et al., 19 98). Mineralization rate of compost made from horse stall materials is slow; therefore nutrients w ill continue to be supplied to forages for years after application. Ultimately, while unprocesse d horse stall material may have slightly

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156 outperformed compost in this study, use of comp ost has more benefits over manure when overall pasture management is considered.

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157 0 10 20 30 40 50 60 UNFERTINORGSTALLCOMPkg ha-1 removed Nitrogen removed Phosphorus removed c b a a d c ba Figure 7-1. Total nitrogen and phosphorus removed (kg ha-1) by Pensacola bahiagrass after application of inorganic fertilizer (IN ORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fe rtilizer (UNFERT). Treatments with different letters are significantly different (P<0.05).

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158 0 50 100 150 200 UNFERTINORGSTALLCOMPkg ha-1 removed Nitrogen removed Phosphorus removed b a aa c b a,b a Figure 7-2. Total nitrogen and phosphorus removed (kg ha-1) by Coastal bermudagrass after application of inorganic fertilizer (IN ORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fe rtilizer (UNFERT). Treatments with different letters are significantly different (P<0.05).

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159 0 20 40 60 80 100 UNFERTINORG STALL COMPkg ha-1 removed Nitrogen removed Phosphorus removed a a,b bb a,b bb a Figure 7-3. Total nitrogen and phosphorus removed (kg ha-1) by Florigraze perennial peanut after application of inorganic fertilizer (INORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fe rtilizer (UNFERT). Treatments with different letters are significantly different (P<0.05).

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160 Table 7-1. Forage dry matter (DM) yield and tissue nitrogen and phosphorus concentrations in Pensacola bahiagrass after application of inorganic fertilizer (INORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fertilizer (UNFERT). Treatments p-value Week UNFERT INORG STALL COMP SEM Trt Week Trt*Week DM Yield 6 636c,x 2066a,x 1397b,x 1375b,x 130 0.0001 (kg ha-1) 12 603b,x 1711a,y 1694a,x 1063b,x 111 0.0001 18 792x 627z 756y 718y 48 0.8686 24 122b,y 181a,b,z 250a,z 192a,b,z 13 0.0056 Mean 487c 1282a 1062a 860b 132 0.0001 0.0001 0.0001 Total 1624c 4062a 3718a 2869b 250 0.0001 Nitrogen 6 8.3c,x 13.4a,w 12.9a,x 10.6b,x 0.45 0.0001 (g kg-1) 12 9.6a,b,y 9.2a,b,x 10.1a,y 8.6b,y 0.20 0.0001 18 10.3y 11.4y 11.0y 10.1x 0.24 0.3092 24 14.1z 14.1z 14.1z 13.2z 0.18 0.1810 Mean 10.6 a 12.2 b 12.2 b 10.7 a 0.50 0.0001 0.0001 0.0001 Phosphorus 6 1.8b,x 1.8b,x 2.5a,x 1.7b,x 0.07 0.0001 (g kg-1) 12 2.2a,y 1.6b,x 1.3c,y 1.7b,x 0.07 0.0002 18 2.5y 2.6y 2.6x 2.4y 0.05 0.3895 24 2.7b,y 2.4b,y 3.2a,z 2.7b,z 0.07 0.0002 Mean 2.3b 2.0c 2.6a 2.1c 0.07 0.0001 0.0001 0.0002 Standard error mean. a,b,c Within a row, means lacking a common superscript differ (P< 0.05).w,x,y,z Within a column, means lacking a common superscript differ (P<0.05).

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161 Table 7-2. Mean soil chemical properties from Pensacola bahiagrass plot s after application of inorganic fertilizer (INORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fertilizer (UNFERT). Treatment P-value UNFERT INORG STALL COMP SEM Trt week TN 0.99 0.98 0.94 1.03 0.074 NS NS NO3-N 1.96 1.85 1.83 1.84 0.061 NS 0.0001 NH4-N 2.46 2.46 2.59 2.54 0.045 NS 0.0001 P 108.9b 114.9a,b 119.6a 116.2a,b 1.33 0.0284 0.0003 K 17.66b 20.08b 43.68a 20.62b 1.49 0.0001 NS Ca 449.7a,b 524.4a 404.68a,b 356.9b 17.6 0.0051 NS Mg 20.25 22.25 21.56 18.24 0.81 NS 0.0231 S 17.81 17.43 17.29 16.58 0.52 NS 0.0001 B 0.11 0.11 0.12 0.11 0.01 NS NS Zn 1.52 2.01 1.91 1.81 0.09 NS 0.0112 Mn 2.90 3.52 3.19 3.08 0.12 NS 0.0001 Fe 24.17a,b 22.50b 24.39a,b 27.29a 0.62 0.0210 0.0001 Cu 0.24 0.24 0.22 0.24 0.01 NS 0.0001 pH 5.8 5.8 5.8 5.6 0.01 NS NS OM 12.2 12.3 11.6 11.2 0.33 NS 0.0245 CEC 5.24b 5.88a 5.21b 5.11b 0.08 0.0003 0.0368 a,b,c Within a row, means lacking a common superscript differ (P< 0.05). Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) an d cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, OM (g kg-1), and CEC (meq 100g-1) data are expressed as mg kg-1. Standard error mean.

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162 Table 7-3. Effect of sampling inte rval on soil chemical properties of Pensacola bahiagrass plots. Data are pooled over all fertilizer treatments. Week SEM p-value 0 6 12 24 TN (g kg-1) 1.29 0.99 0.75 0.90 0.07 NS NO3-N 2.64a 0.92c 1.88b 2.04b 0.06 0.0001 NH4-N 2.65a 2.18b 2.57a 2.54a 0.04 0.0001 P 124.3a 111.1b 114.1b 110.2b 1.34 0.0002 K 25.77 30.54 22.26 23.47 1.50 NS Ca 511.2a 430.4b 396.0b 398.1b 17.6 0.0143 Mg 24.4a 20.65a,b 19.60a,b 17.63b 0.81 0.0023 S 20.2 a 14.32 b 0.52 0.0001 B 0.11 0.12 0.11 0.003 NS Zn 2.17a 1.69b 1.53b 0.09 0.0112 Mn 3.97a 3.33b 2.19c 0.13 0.0001 Fe 22.4b 25.9a,b 28.8a 0.62 0.0043 Cu 0.27a 0.17b 0.28a 0.007 0.0091 pH 5.84 5.72 5.78 5.75 0.04 NS CEC 5.52a 5.58a 5.08b 5.27a,b 0.08 0.0368 OM 12.6a 11.0b 0.33 0.0245 a,b,c Within a row, means lacking a common superscript differ (P< 0.05). Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) an d cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, CEC (meq 100g-1) and OM (g kg-1), data are expressed as mg kg-1. Standard error mean.

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163 Table 7-4. Effect of sampling depth on soil chemical properties of Pensacola bahiagrass plots. Data are pooled over all fertilizer treatments and sampling intervals. Soil Sampling Depth 0-15 cm 15-30 cm SEM P-value Total N 1.04 0.93 0.07 NS NO3-N 2.00 1.74 0.06 0.0019 NH4-N 2.54 2.42 0.04 NS P 109.9 119.9 1.33 0.0001 K 35.67 15.35 1.49 0.0001 Mg 27.02 14.13 0.81 0.0001 Ca 561.9 305.9 17.62 0.0001 S 18.47 16.08 0.52 0.0049 B 0.11 0.11 0.003 NS Zn 2.21 1.41 0.09 0.0001 Mn 3.49 2.86 0.13 0.0036 Fe 23.01 26.1 0.62 0.0001 Cu 0.24 0.22 0.007 NS pH 6.05 5.49 0.04 0.0001 CEC 5.89 4.82 0.08 0.0001 OM 12.0 11.6 0.34 NS Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) and cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, CEC (meq 100g-1) and OM (g kg-1), data are expressed as mg kg-1. Standard error mean.

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164 Table 7-5. Forage dry matter (DM) yield and tissue nitrogen and phosphorus concentrations in Coastal bermudagrass after application of inorganic fertilizer (INORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fertilizer (UNFERT). Treatment p-value Week UNFERT INORGSTALLCOMPSEMTrt Week Trt*Week DM Yield 6 755b 2622a,x 1520a,b 1161a,b 244 0.0315 (kg ha-1) 12 1108b 2415a,x 2103a,b 2240a,b 192 0.0336 18 798 2154 1868 2175 199 0.0837 24 287b 1654a,y 1344a 1582a 135 0.0001 Mean 721c 2211a 1708b 1789b 166 0.00010.0154 0.6375 Total 2762c 8844a 6833b 7157b 393 0.0001 Nitrogen 6 12.6x 15.8x 15.1x 12.6x 0.62 0.1507 (g kg-1) 12 14.9x 17.6x,y 18.1x 14.9y 0.65 0.1713 18 16.2y 20.1y 19.6y 17.9y 0.77 0.2818 24 13.8b,x 21.5a,y 22.4a,y 21.5a,z 0.74 0.0001 Mean 14.3c 18.7a 18.7a 16.7b 0.60 0.00010.0001 0.2674 Phosphorus 6 2.0 1.9 2.0 1.8 0.06 0.8088 (g kg-1) 12 2.1 1.7 1.8 1.8 0.07 0.2129 18 2.2 1.8 2.1 2.1 0.09 0.3743 24 2.0 1.9 2.0 1.8 0.06 0.4824 Mean 2.1 1.8 2.0 1.9 0.07 0.14560.3594 0.7971 Standard error mean. a,b,c Within a row, means lacking a common superscript differ (P< 0.05). w,x,y,z Within a column, means lacking a common superscript differ (P<0.05).

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165 Table 7-6. Mean soil chemical properties from Coastal bermudagrass plot s after application of inorganic fertilizer (INORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fertilizer (UNFERT). Treatment p-value UNFERT INORG STALL COMP SEM Trt Week TN 0.98 0.96 1.01 1.01 0.01 NS 0.0001 NO3-N 2.53 2.55 2.75 2.77 0.07 NS 0.0001 NH4-N 3.57 3.51 3.51 3.72 0.06 NS 0.0001 P 29.73 30.55 31.57 29.09 0.49 NS 0.0070 K 54.24 57.36 65.68 55.68 1.31 0.0005 0.0004 Ca 227.1b 233.9b 272.7a 225.1b 8.71 NS 0.0001 Mg 13.64b 12.61b 16.41a 13.11b 0.41 0.0002 0.0001 S 5.10 7.23 7.63 7.42 0.44 NS 0.0655 B 0.15a 0.12b 0.15a 0.15a 0.01 0.0113 0.0029 Zn 0.58 0.61 0.59 0.56 0.03 NS 0.0001 Mn 5.30 5.35 5.44 5.44 0.13 NS 0.0001 Fe 16.21 15.41 14.91 15.86 0.34 NS 0.0224 Cu 0.21 0.23 0.18 0.19 0.01 NS 0.0482 pH 5.6a,b 5.6b 5.7a 5.6b 0.02 0.0030 NS CEC 4.51 4.79 4.72 4.71 0.06 NS 0.0001 OM 12.54 12.70 12.65 12.99 0.21 NS 0.0240 Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) and cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, OM (g kg-1), and CEC (meq 100g-1) data are expressed as mg kg-1. Standard error mean. a,b,c Within a row, means lacking a common superscript letter differ (P< 0.05).

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166 Table 7-7. Effect of sampling inte rval on soil chemical properties of Coastal bermudagrass plots. Data are pooled over all fertilizer treatments. Week 0 6 12 24 SEM P-value Total N 0.99a 0.83b 1.07a 1.02a 0.01 0.0001 NO3-N 3.57a 2.29b 2.06b 2.91a 0.07 0.0001 NH4-N 3.07b 4.12a 4.21a 2.91b 0.06 0.0001 P 26.0a,b 29.29b 32.8a 28.8b 0.49 0.0070 K 71.9a 58.94a 60.1a 50.9b 1.3 0.0004 Ca 308.3a 233.6b 262.4a,b 169.8c 0.4 0.0001 Mg 16.5a,b 13.76b 16.3a,b 10.6c 8.7 0.0001 S 9.08a 7.65b 0.44 0.0001 B 0.15 0.12 0.15 0.01 NS Zn 0.95a 0.56a,b 0.39b 0.03 0.0001 Mn 6.17a 5.30a,b 4.39b 0.13 0.0001 Fe 16.7a 15.7b 16.7a 0.3 0.0224 Cu 0.40a 0.20b 0.16b 0.01 0.0482 pH 5.68 5.61 5.67 5.58 0.02 NS CEC 5.07a 4.84a 4.96a 4.19b 0.06 0.0001 OM 15.6a 12.3b 0.23 0.0208 Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) and cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, OM (g kg-1), and CEC (meq 100g-1) data are expressed as mg kg-1. Standard error mean. a,b,c Within a row, means lacking a common superscript differ (P< 0.05).

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167 Table 7-8. Effect of sampling depth on soil chemi cal properties of Coastal bermudagrass plots. Data are pooled over all fertilizer treatments and sampling intervals. Soil Sampling Depth 0-15 cm 15-30 cm SEM p-value Total N 1.06 0.89 0.01 0.0001 NO3-N 2.56 2.38 0.07 NS NH4-N 3.77 3.67 0.06 NS P 33.0 27.4 0.5 0.0001 K 66.1 48.4 1.3 0.0001 Mg 16.3 11.0 0.4 0.0001 Ca 267 183 8 0.0001 S 8.27 7.33 0.44 NS B 0.14 0.14 0.01 NS Zn 0.58 0.42 0.03 0.0041 Mn 5.24 4.61 0.13 NS Fe 15.7 16.82 0.34 NS Cu 0.20 0.19 0.01 NS pH 5.72 5.52 0.02 0.0001 CEC 4.91 4.45 0.06 0.0001 OM 13.8 11.5 0.20 0.0001 Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) and cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, OM (g kg-1), and CEC (meq 100g-1) data are expressed as mg kg-1. Standard error mean.

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168 Table 7-9. Properties of forage yield, nitrog en, crude protein (CP), carbon and phosphorus of week 8 and 16 from Florigraze perennial peanut with nutrien t application from inorganic fertilizer (INORG) horse stall material (S TALL), compost (COMP) or unfertilized (UNFERT). Treatment p-value Week UNFERT INORG STALL COMP SEMTrt Week Trt*Week DM Yield 8 2349x 2841x 2490x 2196x 128 NS (kg ha-1) 16 255c,y 838a,y 599b,y 509b,y 57 0.0004 Mean 1302a 1340b 1545a,b 1352a 143 0.0132 0.0001 NS Total 2603b 3679a 3089b 2704b 135 0.0001 Nitrogen 8 26.7a,x 23.2b,x 25.2a,b,x 26.4a,x 0.41 0.0042 (g ha-1) 16 27.7x 25.9y 26.0x 27.8x 0.51 NS Mean 27.2a 24.5b 25.6b 27.1a 0.05 0.0017 0.0061 NS Phosphorus 8 3.2a,x 2.9b,x 3.1a,b,x 3.0a,b,x 0.04 0.0052 (g kg-1) 16 2.9a,y 2.6b,y 2.7a,b,y 2.7a,b,y 0.05 0.0281 Mean 3.1a 2.7b 2.9b 2.8b 0.05 0.0002 0.0001 NS Standard error mean. a,b,c Within a row, means lacking a common superscript differ (P< 0.05). x,y Within a column, means lacking a common superscript differ (P<0.05).

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169 Table 7-10. Mean soil chemical properties from Florigraze perennial peanut plots after application of inorganic fertilizer (IN ORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fe rtilizer (UNFERT). Treatment p-value UNFERT INORG STALL COMP SEM Trt Week TN 1.05 1.09 1.09 1.08 0.02 NS NS NO3-N 4.71 3.63 3.63 3.76 0.25 NS 0.0001 NH4-N 3.91 4.01 4.40 4.09 0.15 NS 0.0143 P 26.3a 28.5a 27.2a 24.9b 0.6 0.0065 0.0390 K 15.6b 27.1a 24.8a 18.4b 1.2 0.0001 0.0001 Ca 196 204 202 200 5 NS 0.0456 Mg 20.5 24.8 23.4 21.3 1.1 NS NS S 16.33 18.45 18.83 17.31 0.63 NS NS B 0.11b 0.20a 0.14b 0.13b 0.01 0.0003 0.0005 Zn 0.85 0.93 0.83 0.75 0.05 NS NS Mn 4.73 5.23 5.0 4.79 0.16 NS 0.0001 Fe 14.48 13.88 14.1 14.0 0.22 NS 0.0001 Cu 0.15 0.13 0.15 0.13 0.00 NS 0.0001 pH 5.4 5.4 5.4 5.4 0.01 NS 0.0020 CEC 4.35 4.49 4.47 4.30 0.06 NS 0.0003 OM 15.2 14.0 14.9 14.2 0.4 NS 0.0001 Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) and cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, OM (g kg-1), and CEC (meq 100g-1) data are expressed as mg kg-1. Standard error mean. a,b,cWithin a row, means lacking a common superscript differ (P< 0.05).

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170 Table 7-11. Effect of sampling inte rval on soil chemical properties of Florigraze perennial peanut plots. Data are pooled over all fertilizer treatments. Week 0 8 16 SEM P-value Total N 1.12 1.07 1.05 0.02 NS NO3-N 5.69a 1.86c 4.26b 0.25 0.0001 NH4-N 3.82b 4.63a 3.86b 0.15 0.0135 P 27.8a 25.6b 26.7a,b 0.60 0.0351 K 19.3b 18.3b 26.9a 1.15 0.0001 Ca 213 205 185 1.01 NS Mg 23.9 23.1 20.5 5.69 NS S 18.6 16.8 0.64 NS B 0.12b 0.17a 0.01 0.0005 Zn 0.85 0.83 0.06 NS Mn 5.61a 4.35b 0.16 0.0001 Fe 12.6b 15.6a 0.22 0.0001 Cu 0.11b 0.17a 0.01 0.0001 pH 5.41a 5.43a 5.32b 0.01 0.0023 CEC 4.13b 4.64a 4.45a 0.06 0.0003 OM 12.8b 16.3a 0.01 0.0001 Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) and cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, OM (g kg-1), and CEC (meq 100g-1) data are expressed as mg kg-1. Standard error mean. a,b,c Within a row, means lacking a common superscript differ (P< 0.05).

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171 Table 7-12. Effect of sampling depth on soil chemical properties of Florigraze perennial peanut plots. Data are pooled over all fertil izer treatments and sampling intervals. Depth 0-15 cm 15-30 cm SEM p-value Total N 1.7 0.98 0.02 0.0001 NO3-N 3.96 3.90 0.25 NS NH4-N 4.99 3.21 0.15 0.0001 P 32.2 21.2 0.60 0.0001 K 29.1 13.8 1.15 0.0001 Mg 32.0 12.9 1.01 0.0001 Ca 239 165 5.69 0.0001 S 19.6 15.8 0.64 0.0023 B 0.18 0.12 0.01 0.0003 Zn 0.12 0.56 0.06 0.0001 Mn 6.04 3.93 0.16 0.0001 Fe 13.9 14.3 0.22 NS Cu 0.14 0.14 0.01 NS pH 5.44 5.34 0.01 0.0008 CEC 4.78 4.02 0.06 0.0003 OM 14.3 14.8 0.10 NS Nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), sulfur (S), boron (B), zinc (Zn), iron (Fe) copper (Cu), pH, organic matter (OM) and cation exchange capacity (CEC) with the exception of TN (g kg-1), pH, OM (g kg-1), and CEC (meq 100g-1) data are expressed as mg kg-1. Standard error mean.

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172 CHAPTER 8 IMPLICATIONS These stud ies demonstrated th at composting horse stall mate rial can be a beneficial management tool in the horse industry. Compos ting substantially reduces the volume of stall materials, thereby decreasing the amount of material to dispose of or land apply to pastures. Within the first 2 weeks of composting horse stal l materials, temperatures were elevated high enough to kill pathogens, parasites, and fly larvae and to inactiva te weed seeds. Nitrogen is commonly used to amend horse stall material pr ior to composting due to high carbon content in bedding, yet these studies indica ted that bedding type had a la rger influence on decomposition rates than nitrogen amendment. Horse manure a nd wood shavings mixtures, with or without added nitrogen, showed a greater degree of d ecomposition than hay bedding. Yet, nitrogen loss due to volatilization was increased when stall ma terials were amended with nitrogen. The use of slow-release nitrogen sources we re found to decrease loss of nitrogen, due to volatization, compared to urea nitrogen. The compost amended with nitrogen contained higher concentrations of soluble nitrogen, such as nitr ates and ammonium, compared to unamended materials. Nitrates and ammonium have the potential to pollute su rface and groundwater if applied in excess of agronomic rates onto pastures. At the same time, nitrogen amendm ent may increase the value of compost as a fertilizer, because the nitrogen is in a form readily available to plants. Results from land application st udies using horse stall material s as fertilizer suggest that unprocessed and composted stall material can reduce or replace the use of i norganic fertilizers in bahiagrass, bermudagrass and perenn ial peanut without reduction in forage quality or dry matter yield production. Composted horse stall material c ould decrease the cost of manure disposal and purchase of inorganic fertiliz er, recycle nutrients and redu ce environmental degradation by stabilizing nutrient that ma y threaten water quality. Duri ng this study, so il extractable

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173 phosphorus was not increased due to application from horse stall materials, which is a common concern when using organic sources as fertiliz ers. When organic materials are applied at agronomic rates, plants will absorb and utilize the majority of applied nitrogen and phosphorus. During this study, unprocessed horse stall materials outperforme d compost, yet the use of compost has more benefits over manure when overall pasture manage ment is considered. Application of unprocessed horse stall material ma y spread weed seeds and intestinal parasites, cause fly and odor production, and have the potential for contamination of surface and groundwater. Composting stall material prior to land application will correct some of the perturbations caused by unprocessed material.

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174 APPENDIX A SUPPLEMENTAL DATA FOR COMP OSTING STUDY (C H 3) 20 30 40 50 60 70 80 121416181Temperature (C) Pile 4 Pile 8 Pile 15 Average Figure A-1. Changes in mean temperature prof ile over time within each pile of WOOD-30 during 84d composting trial.

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175 20 30 40 50 60 70 80 12 14 16 1Temperature (C) Pile 2 Pile 12 Pile 14 Average Figure A-2. Changes in mean temperature prof ile over time within each pile of WOOD-60 during 84d composting trial.

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176 20 30 40 50 60 70 80 12 14 16 1Temperature (C) Pile 1 Pile 6 Pile 11 Average Figure A-4. Changes in mean temperature prof ile over time within each pile of WOOD-CON during 84d composting trial.

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177 20 30 40 50 60 12 14 16 1Temperature (C) Pile 3 Pile 7 Pile 13 Average Figure A-5. Changes in mean temperature prof ile over time within each pile of HAY-CON during 84d composting trial.

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178 20 30 40 50 60 12 14 16 1Temperature (C) Pile 5 Pile 10 Pile 16 Average Figure A-6. Changes in mean temperature profil e over time within each pile of HAY-15 during 84 d composting trial.

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179 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 WOOD-30 WOOD-60 WOOD-CONpH Initial Final Figure A-7. Mean pH of WOOD treatment s (WOOD-30, WOOD-60 and WOOD-CON) before and after 84 d of composting.

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180 Table A-1. Treatment schedule for composting of stall materials containing bermudagrass bedding (HAY-15 and HAY-CON) or wood shavings bedding (WOOD-30, WOOD60 and WOOD-CON). Pile number Treatment Start fill date Start trial date (d0) Mid trial date (d42) End trial date (d84) 1 WOOD-CON 11/21/2005 12/ 07/2005 1/18/2006 03/01/2006 2 WOOD-60 12/05/2005 12/21/2005 2/01/2006 03/15/2006 3 HAY-CON 01/02/2006 01/ 18/2006 3/01/2006 04/12/2006 4 WOOD-30 01/16/2006 02/01/2006 3/15/2006 04/26/2006 5 HAY-15 01/30/2006 02/15/2006 3/29/2006 05/10/2006 6 WOOD-CON 02/13/2006 03/ 01/2006 4/12/2006 05/24/2006 7 HAY-CON 02/27/2006 03/ 15/2006 4/26/2006 06/07/2006 8 WOOD-30 03/13/2006 03/29/2006 5/10/2006 06/21/2006 9 WOOD-30 03/27/2006 04/12/2006 5/24/2006 07/05/2006 10 HAY-15 04/10/2006 04/26/2006 6/07/2006 07/19/2006 11 WOOD-CON 04/24/2006 05/ 10/2006 6/21/2006 08/02/2006 12 WOOD-60 05/08/2006 05/24/2006 7/05/2006 08/16/2006 13 HAY-CON 05/22/2006 06/ 07/2006 7/19/2006 08/30/2006 14 WOOD-60 06/05/2006 06/21/2006 8/02/2006 09/13/2006 15 WOOD-30 06/19/2006 07/05/2006 8/16/2006 09/27/2006 16 HAY-15 07/03/2006 07/19/2006 8/30/2006 10/11/2006 Pile number 9 was removed from trial to be used for concurrent land application trial.

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181 APPENDIX B SUPPLEMENTAL DATA FOR COMP OSTING STUDY (C H 4) 40 45 50 55 60 65 70 12 65 17 61 0 1DayTemperature (C) Figure B-1. Changes in mean temperature profil e over time within each pile of CON during 120 d composting trial.

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182 40 45 50 55 60 65 70 75 12 65 17 61 0 1DayTemperature (C) Figure B-2. Changes in mean temperature profil e over time within each pile of UREA during 120 d composting trial.

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183 40 45 50 55 60 65 70 12 65 17 61 0 1DayTemperature (C) Figure B-3. Changes in mean temperature profile over time within each pile of UF during 120 d composting trial.

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184 40 45 50 55 60 65 70 12 65 17 61 0 1DayTemperature (C) Figure B-4. Changes in mean temperature profil e over time within each pile of PSCU during 120 d composting trial.

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185 0 4E+10 8E+10 1.2E+11 1.6E+11 0306090120Microorganisms (cfu) Aerobic Anaerobic Pseudumonas Figure B-1. Microbial profile of aerobic, anaerobic and pseudomonas for all treatments (CON, UREA, PSCU, and UF) during composting of horse stall material for 120 d.

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186 0 50000000 100000000 150000000 200000000 250000000 0306090120Microorganisms (cfu) N-fixing Actinomycetes Fungi Figure B-2. Microbial profile of N-fixing, actinomycetes and fungi for all treatments (CON, UREA, PSCU, and UF) during composting of horse stall material for 120 d.

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187 Table B-1. Treatment schedule for compost treat ed with nitrogen amendment (PSCU, UF, and UREA) or unamended (CON). Pile Amassing start date Start of trial (d 0) d 30 d 60 d 90 End of trial (d 120) Treatment 1 9/25/2006 10/02 10/3011/2712/251/22 Control 2 10/02/2006 10/09 11/0612/4 01/011/29 Urea 3 10/09/2006 10/16 11/1312/111/08 2/05 PSCU 4 10/16/2006 10/23 11/2012/181/15 2/12 UF 5 01/08/2007 1/22 2/19 3/19 4/16 5/14 Urea 6 01/15/2007 2/05 2/26 3/26 4/23 5/14 UF 7 01/22/2007 2/12 3/5 4/02 4/30 5/21 PSCU 8 01/29/2007 2/19 3/12 4/09 5/07 6/04 Control 9 4/16/2007 4/30 5/28 6/25 7/23 8/20 Control 10 4/23/2007 5/7 6/4 7/2 7/30 8/27 UF 11 4/30/2007 5/14 6/11 7/9 8/6 9/3 PSCU 12 5/07/2007 5/21 6/18 7/16 8/13 9/10 Urea

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188 Table B-2. Concentrations (%, dry weight basis) of neutral deterg ent fiber (NDF), acid detergent fiber (ADF), lignin, total carbon (C), and organic matter (OM) in horse stall materials before (d 0) and after 120 d of compos ting. Materials were ei ther treated with nitrogen amendment (PSCU, UF or UREA ) or remained unamended (CON) prior to composting. % Treatment P-value Day CON PSCU UF UREA SEM Trt Day Trt*Day NDF d 0 87.4 83.1 85.9 83.4 1.04 NS d 120 86.2a 85.8a 82.9b 88.5a 0.75 0.043 Mean 86.8 84.4 84.4 85.9 1.18 NS NS NS ADF d 0 71.3 67.4 65.9 63.5 1.35 NS d 120 74.6 74.5 72.0 74.4 0.57 NS Mean 72.9 70.9 68.9 68.9 1.34 NS NS NS Lignin d 0 24.1 20.8 21.9 21.5 0.60 NS d 120 27.9 26.5 22.3 29.2 1.17 NS Mean 25.9 23.6 22.1 25.3 1.18 NS NS NS C d 0 45.8 43.8 44.3 43.7 0.37 NS d 120 42.5 42.8 40.0 42.6 0.46 0.076 Mean 44.1 43.3 42.2 43.2 0.47 0.069 0.0001 0.062 OM d 0 96.3a,x 90.6b,x 93.5b,x 89.4b,x 1.04 0.024 d 120 89.3x 88.5x 83.6y 90.1x 1.19 NS Mean 92.8 89.5 88.5 89.7 1.32 NS 0.0034 0.049 a,b Means within a row with different lette rs are significantly different (P< 0.05).x,y Means within a column with different letters are signifi cantly different (P<0.05).

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189 APPENDIX C SUPPLEMENTAL DATA FOR LAND APPLICATION S TUDY (CH 5) Table C-1. Cumulative DM yiel d, mean nitrogen (N) and phosphorus (P) concentration, and mean N and P removed by Argentine bahiagra ss in response to fertilization with inorganic fertilizer (INORG), unprocessed st all materials (STALL), or stall materials composted for 42 d (SEMI) or 84 d (COMP). Cumulative Yield N N removed P P removed Treatment Mg ha-1 kg kg-1 g kg-1 kg kg-1 g kg-1 INORG 3.9 0.024 95.2 0.004 16.7 STALL 3.4 0.024 80.6 0.004 13.9 SEMI 3.3 0.025 82.2 0.004 13.8 COMP 3.5 0.023 81.9 0.004 15.1 ANOVA SEM 0.05 0.05 1.07 0.006 0.005 Treatment NS NS NS NS NS Day 0.0001 0.0001 0.0001 0.0001 0.0001 Trt*Day NS NS NS NS NS Contrast 1 0.0282 NS NS NS NS Contrast 2 NS NS NS NS NS Calculated as: Nutrientconc Yield. [Equation 5-4]. Contrast 1: Organic (STALL, SEMI and COMP) vs. inorganic (INORG) fertilizer sources. Contrast 2: Composted (SEMI and COMP) vs unprocessed (STALL ) fertilizer sources.

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190 Table C-2. Mean soil parameters (organic ma tter (OM), pH, cation exch ange capacity (CEC), Ammonia nitrogen (NH4), calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P) in response to fertiliza tion with inorganic fertilizer (INORG), unprocessed stall materials (STALL), or stal l materials composted for 42 d (SEMI) or 84 d (COMP). Soil Mehlich-1 Treatment OM pH CEC NH4 Ca Mg K P g kg-1 meg 100ml-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 INORG 29.4 6.9 11.6 3.1 1861 113 100z 84 STALL 30.4 7.0 12.0 3.4 1873 127 142x 89 SEMI 28.7 6.9 10.8 3.1 1703 118 113y 93 COMP 29.1 6.9 10.9 3.2 1720 115 105y 84 ANOVA SEM 1.83 0.03 0.45 0.14 76.7 4.6 4.4 3.6 Trt NS NS NS NS NS 0.086 0.0001 NS Day 0.0001 0.0001 0.0001 0.0001 0.00010.0001 0.0001 0.0001 Trt x Day NS NS NS NS NS NS 0.0001 NS Contrast 1 NS NS NS NS NS NS 0.0002 NS Contrast 2 NS NS 0.024 NS 0.04560.0335 0.0001 NS Contrast 1: Organic (STALL, SEMI and COMP ) vs. inorganic (INORG) fertilizer sources. Contrast 2: Composted (SEMI and COMP) vs. unproce ssed (STALL) fertilizer sources.

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191 APPENDIX D SUPPLEMENTAL DATA FOR LAND APPL ICATION S TUDIES (CH. 7) Table D-1. Mean soil chemical properties from Pensacola bahiagrass plots before (d0) and after application of inorganic fertilizer (IN ORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fe rtilizer (UNFERT). Treatment p-value week UNFERT INORG STALL COMP SEM Trt week TN 0 1.15 1.28 1.13 1.59 0.274 NS 6 0.95 0.99 1.03 1.00 0.272 NS 12 0.98 0.70 0.67 0.66 0.092 NS 24 0.88 0.93 0.91 0.88 0.021 NS Mean 0.99 0.98 0.94 1.03 0.074 NS NS NO3-N 0 2.82 2.63 2.50 2.61 0.118 NS 6 0.92 0.97 0.89 0.90 0.047 NS 12 2.06 1.77 1.85 1.85 0.083 NS 24 2.03 2.03 2.11 1.99 0.072 NS Mean 1.96 1.85 1.83 1.84 0.061 NS 0.0001 NH4-N 0 2.79 2.39 2.74 2.68 0.081 NS 6 1.95 2.19 2.22 2.33 0.097 NS 12 2.37 2.71 2.48 2.72 0.081 NS 24 2.26b,c 2.54b 2.91a 2.43b 0.085 0.0428 Mean 2.46 2.46 2.59 2.54 0.045 NS 0.0001 P 0 121.6 127.7 123.6 124.3 2.27 NS 6 105.2 110.1 117.9 111.3 2.36 NS 12 107.1 112.1 119.8 117.3 2.83 NS 24 101.9 109.9 116.9 112.1 2.76 NS Mean 108.9b 114.9a,b 119.6a 116.2a,b 1.33 0.0284 0.0003 K 0 23.29 27.21 25.38 27.21 2.38 NS 6 18.71 22.79 57.04 23.63 3.61 0.0001 12 13.00 12.65 46.93 16.47 3.15 0.0001 24 15.63 17.67 45.38 15.21 2.65 0.0001 Mean 17.66b 20.08b 43.68a 20.62b 1.49 0.0001 NS Ca 0 509.7 580.8 477.2 477.2 37.9 NS 6 452.7 534.4 429.7 304.7 37.3 NS 12 421.7 491.8 370.9 299.7 32.1 NS 24 414.8 490.6 340.9 345.9 31.6 NS Mean 449.7a,b 524.4a 404.68a,b 356.9b 17.6 0.0051 NS Mg 0 21.79 27.29 25.21 23.42 1.81 NS 6 21.12 22.08 22.58 16.79 1.68 NS 12 19.60 21.36 20.61 16.84 1.44 NS 24 18.50 18.25 17.83 15.92 1.38 NS Mean 20.25 22.25 21.56 18.24 0.81 NS 0.0231 Total nitrogen (TN), nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). With the exception of TN (g kg-1), data are expressed as mg kg-1. a,b,cWithin a row, means lacking a common superscript differ (P< 0.05).

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192 Table D-2. Mean soil chemical properties from Coastal bermuda plots be fore (d0) and after application of inorganic fertilizer (IN ORG), unprocessed horse stall material (STALL), composted horse stall material (COMP) or no fe rtilizer (UNFERT). Treatment p-value Week UNFERT INORG STALL COMP SEM Trt Week TN 0 1.01 1.03 1.09 1.04 0.02 NS 6 0.85 0.81 0.82 0.85 0.02 NS 12 1.05 1.01 1.12 1.10 0.03 NS 24 1.02 1.00 1.02 1.05 0.02 NS Mean 0.98 0.96 1.01 1.01 0.01 NS 0.0001 NO3 0 3.25 3.27 3.28 3.55 0.11 NS 6 2.04 2.04 2.73 2.39 0.17 NS 12 2.00 2.08 2.00 2.17 0.13 NS 24 2.84 2.82 2.99 2.97 0.10 NS Mean 2.53 2.55 2.75 2.77 0.07 NS 0.0001 NH4 0 3.24 2.82 3.08 3.16 0.10 NS 6 3.93 4.15 3.95 4.45 0.10 NS 12 4.09 4.14 4.18 4.41 0.10 NS 24 3.02 2.94 2.82 2.85 0.10 NS Mean 3.57 3.51 3.51 3.72 0.06 NS 0.0001 P 0 29.08 30.92 29.29 30.88 0.77 NS 6 29.27 29.20 31.95 26.77 0.81 NS 12 30.83 33.67 35.83 30.88 1.36 NS 24 29.75 28.41 29.21 27.88 0.75 NS Mean 29.73 30.55 31.57 29.09 0.49 NS 0.0070 K 0 61.67 60.12 64.17 66.25 3.14 NS 6 49.53b 58.11a,b 73.48a 54.65b 2.95 0.0023 12 58.21a,b 60.75a,b 67.92a 53.58b 2.08 0.0407 24 47.54b 50.46a,b 57.17a 48.25a,b 1.81 0.0381 Mean 54.24 57.36 65.68 55.68 1.31 0.0005 0.0004 Ca 0 241.6 290.8 311.1 328.5 19.2 NS 6 267.1 232.8 254.8 179.7 14.7 NS 12 248.0 245.4 336.5 219.9 19.3 NS 24 151.8 166.5 188.6 172.5 10.1 NS Mean 227.1 233.9 272.7 225.1 8.71 NS 0.0001 Mg 0 13.92 14.88 16.3 15.25 0.67 NS 6 14.56 12.59 15.50 12.42 0.68 NS 12 15.96a,b 13.79b 20.92a 14.58a,b 1.03 0.0250 24 10.12a,b 9.17b 12.88a 10.21a,b 0.62 0.0334 Mean 13.64 12.61 16.41 13.11 0.41 0.0002 0.0001 Total nitrogen (TN), nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). With the exception of TN (g kg-1), data are expressed as mg kg-1. a,b,c Within a row, means lacking a common superscript differ (P< 0.05).

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193 Table D-3. Mean soil chemical properties from Florigraze perennial peanut plots before (d0) and after application of inor ganic fertilizer (INORG), unpro cessed horse stall material (STALL), composted horse stall material (COMP) or no fe rtilizer (UNFERT). Treatment p-value Week UNFERT INORG STALL COMP SEM Trt Week TN 0 1.09 1.19 1.10 1.09 0.02 NS 12 1.05 1.01 1.12 1.10 0.03 NS 24 1.01 1.06 1.08 1.04 0.03 NS Mean 1.05 1.09 1.09 1.08 0.02 NS NS NO3 0 7.67 5.13 4.91 5.04 0.62 NS 12 1.86a,b 1.78a,b 2.06a 1.72b 0.05 0.0271 24 4.60 3.98 3.91 4.54 0.20 NS Mean 4.71 3.63 3.63 3.76 0.25 NS 0.0001 NH4 0 3.97 4.07 3.61 3.62 0.22 NS 12 4.23b 4.13b 4.86a,b 5.28a 0.19 0.0404 24 3.53 3.82 4.72 3.38 0.33 NS Mean 3.91 4.01 4.40 4.09 0.15 NS 0.0143 P 0 27.7 29.6 26.7 27.4 0.98 NS 12 24.9 26.7 27.2 23.5 0.98 NS 24 26.2 29.2 27.7 23.9 1.11 NS Mean 26.3a,b 28.5a 27.2a,b 24.9b 0.59 0.0065 0.0390 K 0 18.0 21.9 18.9 18.2 1.51 NS 12 13.9b 21.8a,b 24.2a 13.3b 1.64 0.0043 24 15.0c 37.7a 31.2a,b 23.7b,c 1.12 0.0002 Mean 15.6b 27.1a 24.8a 18.4b 1.15 0.0001 0.0001 Ca 0 199 222 207 222 8.95 NS 12 203 201 212 202 9.79 NS 24 186 190 188 175 10.5 NS Mean 196 204 202 200 5.69 NS 0.0456 Mg 0 22.6 26.5 22.3 24.1 1.65 NS 12 21.2 23.9 26.4 20.9 1.79 NS 24 17.8 23.8 21.6 19.8 1.79 NS Mean 20.5 24.8 23.4 21.3 1.01 NS NS Total nitrogen (TN), nitrate-N (NO3), ammonium-N (NH4), Mehlich extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). With the exception of TN (g kg-1), data are expressed as mg kg-1. a,b,cWithin a row, means lacking a common superscript differ (P< 0.05).

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BIOGRAPHICAL SKETCH Sarah Courtney Dilling was born in Glen C ove, New York, in 1979 to Robert and Susan Walsh. She moved to Pine Island, F lorida, in 1984 where she remained until 1996. Sarah attended and graduated from Venice High School in Venice, Florida (1997). She obtained a Bachelor of Science degree in environmental sc ience and policy from the University of South Florida (2001). Sarah took a year off between undergraduate and gr aduate school to work in an environmental laboratory as a chemist in Tamp a, Florida. In 2002, Sarah was accepted into a graduate program in animal science under Dr. S.H. TenBroeck at the University of Florida, and graduated with a Master of Science in 2004. Sa rah began a Ph.D. program in January 2005, in the Department of Animal Sciences at the University of Florida studying nutrient management and composting of horse stall material. After co mpletion of her program, Sarah will graduate with a Ph.D. majoring in animal science with a minor in soil and water science. Sarah plans on moving to South Florida and pursuing a caree r in the environmental science field.