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Effects of Nitrogen Application Rate Using Dairy Manure and Defoliation Frequency on Dry Matter Yields, Nutritive Value, Ensiling Characteristics and Winter Survival of Pi300086 and Uf-1 Elephantgrasses

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Title:
Effects of Nitrogen Application Rate Using Dairy Manure and Defoliation Frequency on Dry Matter Yields, Nutritive Value, Ensiling Characteristics and Winter Survival of Pi300086 and Uf-1 Elephantgrasses
Creator:
Chapa, Suzgo C
Place of Publication:
[Gainesville, Fla.]
Florida
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University of Florida
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Language:
english
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1 online resource (135 p.)

Thesis/Dissertation Information

Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Animal Sciences
Committee Chair:
Staples, Charles R
Committee Members:
Sollenberger, Lynn E
Chikagwa-Malunga, Susan
Graduation Date:
12/15/2012

Subjects

Subjects / Keywords:
Agricultural seasons ( jstor )
Fertilization ( jstor )
Forage ( jstor )
Grasses ( jstor )
Harvesting seasons ( jstor )
Manure ( jstor )
Nitrogen ( jstor )
Nutrients ( jstor )
Plant nutrition ( jstor )
Plants ( jstor )
Animal Sciences -- Dissertations, Academic -- UF
elephantgrass -- manure
City of Gainesville ( local )
Genre:
bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Animal Sciences thesis, M.S.

Notes

Abstract:
A breeding line of elephantgrass (Pennisetum purpureum Schum.) called UF-1 and elephantgrass plant introduction PI300086 (PI3) were evaluated at the University of Florida Agronomy Forage Research Unit in Hague, Florida from March 2011 to April 2012 to assess effects of nitrogen application rate using dairy cow manure and defoliation frequency on dry matter (DM) yield, nutritive value, and ensiling characteristics.  In addition, survivability of plants post harvesting during below freezing conditions was assessed. Treatments (n = 12) were two elephantgrasses, PI300086 and UF-1, two defoliation intervals (6 and 9 wk), and three N fertilizer rates (0, 90 and 180 kg ha-1 yr-1) using dairy cow manure arranged in a 2 by 2 by 3 factorial design in a split plot arrangement  of a randomized complete block design. Treatments were replicated thrice (plots = 36). Seasonal yield of DM of UF-1 across harvesting intervals and N application rates was 20.8% greater than that of PI3 (8.9 vs. 7.4 Mg ha-1 yr-1, P  Yield of DM increased from 7.4 to 8.7 Mg ha-1 as the amount of N applied increased from 0 to 90 kg ha-1 (P -1 for plants fertilized with 180 kg of N ha-1.  Forage DM collected from harvests taken every 9 wk was greater than from 6-wk harvest intervals (9.6 vs. 6.8 Mg ha-1 yr-1, P  Yield of DM decreased with successive harvests for both 6- and 9-wk harvesting intervals.  Compared to PI3, entry UF-1 had greater concentration of CP (9.16 vs. 9.70%) and IVOMD (63.8 vs. 64.6%) when harvested at 6-wk intervals but only NDF concentration was different for the 9-wk harvests (66.7 vs. 65.5%), respectively.  The leaf to stem ratio favored PI3 over UF-1 (1.86 vs. 1.47 for 6-wk harvests and 1.06 vs. 0.91 for 9-wk harvests).  Entry UF-1 had more water soluble carbohydrates than PI 3 (3.67 vs. 3.13%, P  Rate of OM digestion in vitro was greater for UF-1 compared to PI3.  The 6-wk harvests had greater rate and extent of in vitro OM digestion compared to 9-wk harvests.  Efficiency of N uptake by plants from dairy cow manure was better when fertilized with 90 vs. 180 kg of N -1 yr-1 (24.4 vs. 9.8%).  Entry UF-1 had better persistence as it had very few dead plants after the 2011-2012 winter compared with PI3 (2 vs. 25%).  Results of the current study indicate that UF-1 is a better entry than PI3 for the subtropics because UF-1 recorded greater DM yields for the season regardless of harvesting interval and N-fertilization regime using dairy cow manure than PI3.  Additionally UF-1 displayed better cold tolerance and is more likely than PI3 to provide long-term stand survival. ( en )
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis:
Thesis (M.S.)--University of Florida, 2012.
Local:
Adviser: Staples, Charles R.
Statement of Responsibility:
by Suzgo C Chapa.

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UFRGP
Rights Management:
Copyright Chapa, Suzgo C. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
870309402 ( OCLC )
Classification:
LD1780 2012 ( lcc )

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1 EFFECTS OF NITROGEN APPLICATION RATE USING DAIRY MANURE AND DEFOLIATION FREQUENCY ON DRY MATTER YIELDS, NUTRITIVE VALUE, ENSILING CHARACTERISTICS AND WINTER SURVIVAL OF PI300086 AND UF 1 ELEPHANTGRASS ES By SUZGO CHARLES FRANCIS CHAPA A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF M ASTER OF SCIENCE UNIVERSITY OF FLORIDA 2012

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2 2012 Suzgo Charles Francis Chapa

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3 To my family

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4 ACKNOWLEDGMENTS I would like t o recognize and thank my major p rofessor Dr. C harles R. Staples for his advice and guidance that made this thesis possible. A big thank you goes to my Supervisory Committee members, Professor L ynn E. Sollenberger for his input in the planning and entire phase of the project and Dr. Suzan Chikagwa Malunga for her consistent follow ups in the implementation of the project. I would also like to give another big thank you to Dr. K en R. W oodard for his technical assistance during the field portion of the experiment. Also Dr. Jae Shin deserves a pat on the back for his work in the field and the processing and analyses of the samples. Eric Diepersloot and Jay Lemmerman, the farm managers for the University of Florida dairy farm are sincerely thanked for allowing me to collect manure from the farm. Many thanks go to Dwight for the machinery operations during seedbed preparation, harvesting and silage making. Many thanks go to colleagues at Florida, including Nick, Miriam Garcia, Joseph Hamie, Seth Jenkins Felix Makondi, Evandro Muniz, Chunala Njombwa, Oscar Queiroz, Juan Romero, Sergei Sennekov, Dan Wang, and Miquel Zarate for their assistance in crown splitting and plant ing of the eleph antgrass plots.Financial assistance for the research program was provided by USAID, Malawi govt / DAHLD/ DARS Mzuzu ADD and the Florida Milk Cooperative Milk Check Off Fund. Last but not least, I need to thank my family for being patient when I was away from them working towards my degree

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 LIST OF ABBREVIATIONS ................................ ................................ ........................... 11 ABSTRACT ................................ ................................ ................................ ................... 12 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 14 2 LITERATURE REVIEW ................................ ................................ .......................... 17 Potential of Elephantgrass ................................ ................................ ...................... 17 Morphological and Physiological Attributes of Elephantgrass .......................... 17 Effects of Management on Yield of Elephantgrass Fodder .............................. 20 Defoliation frequency ................................ ................................ ................. 20 Effect of fertilization on production of elephantgrass ................................ .. 24 Potential of Organic Amendments as Sources of Nutrients for Elephantgrass ....... 26 Effect of Increasing Amounts of Manure on Production of Elephantgrass ........ 26 Influence of Manure Application Methods on Availability of Organic Nutrients ................................ ................................ ................................ ........ 28 Nitrogen Mineralization ................................ ................................ ..................... 30 Nitrogen and Phosphorus Removal by Elephantgrass ................................ ..... 32 Nutritive Value, Ensiling, and Utilization of Elephantgrass ................................ ...... 36 Nutritive Value ................................ ................................ ................................ .. 36 Ensiling ................................ ................................ ................................ ............. 39 Utilization of Elephantgrass as a Ruminant Feed ................................ ............. 44 Utilization of Elephantgrass in Africa ................................ ................................ ...... 46 3 EFFECTS OF DAIRY MANURE APPLICATION AND DEFO LIATION FREQUENCY ON YIELD, NUTRITIVE VALUE, SIL A G E QUAL ITY AND WINTER SURVIVAL OF UF 1 AND PI300086 ELEPHANTGRASSES .................. 49 Background ................................ ................................ ................................ ............. 49 Materials and Methods ................................ ................................ ............................ 51 Locati on ................................ ................................ ................................ ............ 51 Treatments and Plant Management ................................ ................................ 52 Statistical Analyses ................................ ................................ .......................... 57 Results and Discussion ................................ ................................ ........................... 57 Harvesting plans and N applications ................................ ................................ 57

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6 Dry Matter Yields and Leaf to Stem Ratios ................................ ....................... 58 Total seasonal yields of forage DM ................................ ............................ 58 6 wk harvesting intervals ................................ ................................ ........... 60 9 wk harvesting intervals ................................ ................................ ........... 61 Chemical Composition of PI300086 and UF 1 Elephantgrasses Harvested every 6 Weeks ................................ ................................ .............................. 63 Chemical Composition of Pi300086 and U F 1 Elephantgrasses Harvested every 9 Weeks ................................ ................................ .............................. 65 Lag, Rate, and Extent of In Vitro Organic Matter Digestibility ........................... 67 Silage, Chemical Composition, and Digestibility ................................ ............... 68 Winter Survival ................................ ................................ ................................ 69 Efficiency of Nitrogen Uptake by Plants Fertilized with Dairy Cow Manure ...... 70 Summary ................................ ................................ ................................ ................ 70 LIST OF REFERENCES ................................ ................................ ............................. 124 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 135

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7 LIST OF TABLES Table page 3 1 Effect of N fertilization rate and harvest interval on seasonal dry matter (DM) yield of PI300086 and UF 1 elephantgrasses ................................ ..................... 73 3 2 Effect of N fertilization rate on dry matter yield and leaf to stem ratio of PI300086 and UF 1 elephantgrasses harvested a t 6 wk intervals ...................... 74 3 3 Effect of N fertilization rate on dry matter yield and leaf to stem ratio of PI300086 and UF 1 elephantgra sses harvested at 9 wk intervals ...................... 75 3 4 Effect of N fertilization rate on chemical composition of PI300086 and UF 1 elephantgrasse s harvested at 6 wk intervals ................................ ...................... 76 3 5 Effect of N fertilization rate on chemical composition of PI300086 and UF 1 elephantgrasses harvested at 9 wk intervals ................................ ...................... 77 3 6 Effect of N fertilization rate and harvesting interval on lag, rate, and extent of OM digestion of PI300086 and UF 1 elephantgrasses ................................ ....... 78 3 7 Effect of N fertilization rate and harvesting interval on water soluble carbohydrates of fresh forage and pH and organic acids of silage made usin g PI300086 and UF 1 elephantgrasses ................................ ................................ 79 3 8 Stand persistence of PI300086 and UF 1 during the winter of 2011 12 ............. 80 3 9 Efficiency of N uptake by PI300086 and UF 1 elephantgrasses harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 .................. 81

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8 LIST OF FIGURES Figure page 3 1 Monthly totals of rainfall and absolute minimum temperature at the University of Florida Agronomy Forage Research Unit during 2011 2012 and a 30 yr average ................................ ................................ ................................ ............ 82 3 2 Experim ental plot layout for one block ................................ .............................. 83 3 3 Total seasonal dry matter (DM) yield of PI3000 86 (PI3) and UF 1 elephantgrasses harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 (n = 3) ................................ ................................ .................. 84 3 4 Total seasonal dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrasses harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 (n = 3) ................................ ................................ .................. 85 3 5 Total seasonal dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrasses harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 (n = 3) ................................ ................................ .................. 86 3 6 Dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrasses w hen harvested at 6 wk intervals ................................ ................................ ............... 87 3 7 Leaf to stem ratio of PI300086 (PI3) and UF 1 elephantgrasses w hen harvested at 6 wk intervals ................................ ................................ ............... 88 3 8 Dry matter (DM) yield of PI3 and UF 1 elephantgrasses harvested 3 time s in a season at 6 wk intervals ................................ ................................ ................ 89 3 9 Leaf to stem ratio of PI3 and UF 1 elephantgrasses harvested 3 time s in a season at 6 wk intervals ................................ ................................ ..................... 90 3 10 Leaf to stem ratio of PI300086 (PI3) and UF 1 elephantgrasses harvested 3 time s in a season at 6 wk intervals ................................ ................................ ... 91 3 11 Dry matter yield of PI3 and UF 1 elephantgrasses harvested 3 times in a season at 6 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 ........ 92 3 12 Dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrasses w hen harvested at 9 wk intervals ................................ ................................ ............... 93 3 13 Dry matter (DM) yield of elephantgrass harvested 2 time s in a season at 9 wk intervals ................................ ................................ ................................ ....... 94 3 14 Leaf to stem ratio of PI300086 (PI3) and UF 1 elephantgrasses w hen harvested at 9 wk intervals ................................ ................................ ............... 95

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9 3 15 Leaf to stem ratio of elephantgrass harvested 2 time s in a season at 9 wk intervals ................................ ................................ ................................ ............ 96 3 16 Dry matter (DM) yield of PI3 and UF 1 elephantgrasses harvested 2 times in a season at 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 ..... 97 3 17 Leaf to stem ratio of elephantgrasses harvested 2 times in a season at 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 ................................ 98 3 18 Dry matter (DM) concentration of PI300086 (PI3) and UF 1 elephantgrasses harvested at 6 wk intervals ................................ ................................ ................. 99 3 19 Dry matter (DM) concentration of elephantgrasses harvested 3 times in a season at 6 wk intervals ................................ ................................ ................... 100 3 20 Organic matter (OM) concentration of elephantgrasses harvested 3 times in a season at 6 wk intervals ................................ ................................ ................ 101 3 21 Crude protein concentration of PI300086 and UF 1 elephantgrasses harvested at 6 wk intervals ................................ ................................ ............... 102 3 22 Crude protein (CP) concentration of elephantgrass harvested 3 times in a season at 6 wk intervals ................................ ................................ ................... 103 3 23 Neutral detergent fiber (NDF) concentration of elephantgrass harvested 3 times in as season at 6 wk intervals ................................ ................................ 104 3 24 Acid detergent fiber (ADF) concentration of elephantgrass harvested 3 times in a season at 6 wk intervals ................................ ................................ ............ 105 3 25 In vitro organic matter digestibility (IVOMD) of elephantgrass entries harvested at 6 wk intervals ................................ ................................ ............... 106 3 26 In vitro organic matter digestibility (IVOMD) of elephantgrass harvested 3 times in a season at 6 wk intervals ................................ ................................ ... 107 3 27 Dry matter (DM) concentration of PI300086 (PI3) and UF 1 elephantgrasses harvested at 9 wk intervals ................................ ................................ ............... 108 3 28 Dry matter (DM) concentration of two elephantgrasses harvested 2 times in a season at 9 wk intervals ................................ ................................ ................... 109 3 29 Crude protein (CP) concentration of two elephantgrasses fertilized with 0, 90, or 180 kg of N ha 1 yr 1 and harvested 2 times in a season at 9 wk intervals ..... 110 3 30 Neutral detergent fiber (NDF) concentration of PI300086 (PI3) and UF 1 elephantgrasses harvested at 9 wk intervals ................................ .................... 111

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10 3 31 Acid detergent fiber concentration of PI300086 and UF 1 elephantgrasses harvested at 6 wk intervals ................................ ................................ ............... 112 3 32 Acid detergent fiber (ADF) concentration of two elephantgrasses harvested 2 times in a season at 9 wk intervals ................................ ................................ ... 113 3 33 Acid detergent fiber concentration of PI300086 and UF 1 elephantgrasses fertilized with 0, 90, or 180 kg of N ha 1 yr 1 and harvest at 9 wk intervals ........ 114 3 34 In vitro organ ic matter digestibility of PI300086 and UF 1 elephantgrasses fertilized with 0, 90, or 180 kg of N ha 1 yr 1 and harvest at 9 wk intervals ..... 115 3 35 Organic matter digestion rate of PI300086 and UF 1 elephantgrasses ............ 116 3 36 Organic matter (OM) digestion rate of two elephantgrasses harvested at 6 or 9 wk intervals ................................ ................................ ................................ .... 117 3 37 Extent (96 h) of total organic matter digestion of elephantgrass harvested at 6 or 9 wk intervals ................................ ................................ ........................... 118 3 38 Exten t (96 h) of organic matter digestion of two elephantgrasses fertilized with 0, 90, or 180 kg of N ha 1 yr 1 and harvested at 6 or 9 wk intervals .......... 119 3 39 Water soluble carbohydrate concentration of PI300086 and UF 1 elephantgrasses prior to ensiling ................................ ................................ ...... 120 3 40 Water soluble carbohydrate concentration of two elephantgrasses harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 ............ 121 3 41 Silage pH of two elephantgrasses harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 ................................ ...................... 122 3 42 Concentration of acetic acid of two elephantgrass silages made with forage harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg o f N ha 1 yr 1 ................................ ................................ ................................ .................... 123

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11 LIST OF ABBREVIATION S AA Acetic acid ADF Acid detergent fiber ANR Apparent nitrogen recovery BA B utyric acid CP Crude Protein DM D ry matter DMI D ry matter intake FJLB F ermented juice of lactic acid bacteria IVDMD I n vitro dry matter digestibility IVOMD I n vitro organic matter digestibility LA L actic acid LAB L actic acid bacteria MBS M unicipal biosolids N Nitrogen NDF Neutral detergent fiber NFRV Nitrogen fertilizer replacement value OM Organic matter SP Splash plate TS Trailing shoe VFA Volatile fatty acids WSC Water soluble carbohydrates

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12 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Master of Science Degree EFFECTS OF NITROGEN APPLICATION RATE USING DAIRY MANURE AND DEFOLIATION FREQUENCY ON DRY MATTER YIELDS, NUTRITIVE VALUE, ENSILING CHARACTERISTICS AND WINTER SURVIVAL OF PI300086 AND UF 1 ELEPHANTGRASS ES By Suzgo Charles Francis Chapa December 2012 Chair: Charles R. Staples Major: Animal Sciences A breeding line of elephantgrass (Pennisetum purpureum Schum.) called UF 1 and elephantgrass plant introduction PI300086 (PI3) w ere evaluated at the University of Florida Agronomy Forage Research Unit in Hague, Florida from March 2011 to April 2012 to assess effects of nitrogen application rate using dairy cow manure and defoliat ion frequency on dry matter (DM) yield, nutritive value, and ensiling characteristics In addition, survivability of plants post harvesting during below freezing conditions was assessed. Treatments (n = 12) were two elephantgrass es PI300086 and UF 1, two defoliation intervals (6 and 9 wk), and three N fertilizer rates (0, 90 and 180 kg ha 1 yr 1 ) using dairy cow manure arranged in a 2 by 2 by 3 factorial design in a split plot arrangement of a randomized complete block design. Treatments were replicated thrice (plots = 36) Seasonal yield of DM of UF 1 across harvesting intervals and N application rates was 20.8% greater than that of PI3 (8.9 vs. 7.4 Mg ha 1 yr 1 P < 0.001). Yield of DM

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13 increased from 7.4 to 8.7 Mg ha 1 as the amount of N applied increa sed from 0 to 90 kg ha 1 ( P < 0.02) but DM yield increased no further plateauing at 8.4 Mg ha 1 for plants fertilized with 180 kg of N ha 1 Forage DM collected from harvests taken every 9 wk was greater than from 6 wk harvest intervals (9.6 vs. 6.8 Mg ha 1 yr 1 P < 0.001.) Yield of DM decreased with successive harvest s for both 6 and 9 wk harvesting intervals. Compared to PI3, entry UF 1 had greater concentration of CP (9.16 vs. 9.70%) and IVOMD (63.8 vs. 64.6%) when harvested at 6 wk intervals but only NDF concentration was different for the 9 wk harvests (66.7 vs. 65.5%) respectively. The leaf to stem ratio favored PI3 over UF 1 (1.86 vs. 1.47 for 6 wk harvests and 1.06 vs. 0.91 for 9 wk harvests). Entry UF 1 had more water soluble carbohydrates than PI 3 (3.67 vs. 3.13%, P < 0.001) but both made good quality silage based upon pH and lactic acid concentrations. R ate of OM digestion in vitro was greater for UF 1 compared to PI3. The 6 wk harvests had greater rate and extent of in vitro OM digest ion compared to 9 wk harvests. Efficiency of N uptake by plants from dairy cow manure was better when fertilized with 90 vs. 180 kg of N 1 yr 1 (24.4 vs. 9.8%) Entry UF 1 had better persistence as it had very few dead plants after the 2011 2012 winter compared with PI3 (2 vs. 25%). Results of the current study indicate that UF 1 is a better entry than PI3 for the subtropics because UF 1 recorded greater DM yields for the season regardless of harvesting interval and N fertilization regime using dairy co w manure than PI3. A dditionally UF 1 displayed better cold tolerance and is more likely than PI3 to provide long term stand survival.

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14 CHAPTER 1 INTRODUCTION Elephantgrass is a prolific warm season perennial bunchgrass that is characterized by high dry matter yields and sound nutritive value. It has promising potential as a forage for the dairy industry in warm climates around the world. Research on herbaceous plants in the tropics and subtropics have consistently reported tall elephantgrass to be the highest yielding or among the highest yielding C4 grasses with dry matter yields in the range of 20 to 52 Mg ha 1 yr 1 (Mtengeti et al., 200 1; Woodard and Prine, 1993a; Hsu et al., 1990; Bouton, 2002; Velez Santiago and Arroyo Aguilu, 1981; and Woodard and Sollenberger, 2008). To achieve these high dry matter yields of elephantgrass requires addition of a lot of nitrogen and phosphorus to soi ls. Obtaining high nutritive value is the greater challenge for elephantgrass. If it can be managed to produce large quantities of digestible nutrients, its value as a forage for milk production by dairy cows increases dramatically. Forages are needed to provide the effective fiber and a portion of the energy and protein required by high producing dairy cows. As forage quality increases, greater proportions are digested in the rumen which reduces gut fill and allows greater intake. Oba and Allen (1999) r eported a 0.17 kg increase in dry matter intake and 0.23 kg increase in milk yield for each one unit increase in forage NDF digestibility. Along with increased performance, diets based on high quality forage are associated with desirable ruminal fermentati on. Thus as forage quality increases and greater quantities are fed, total feed costs typically decline. One management strategy to improve nutrient density is to increase the defoliation frequency. It is certainly feasible to harvest three to four ti mes during the growing season. However, this frequent harvesting usually reduces seasonal yield of dry matter

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15 and can threaten the survivability of the plants during the winter season. Seeking to optimize yield with forage quality is always a goal of produce rs seeking to provide forages for supporting good animal performance. Research is continually seeking to develop new cultivars of forages including elephantgrasses that will provide significant improvements in yield, nutritive value, and survivability over traditional cultivars. A new elephantgrass initially called UF 1 has been identified as having potential for use as a forage or biofuel crop by scientists at the University of Florida. It has been propagated in nursery plots in order to supply plants fo r further evaluation. One of the traditional elephantgrasses is PI300086. It is high is that it has poor cold tolerance and poor survivability if intensively managed during the growing season (Woodard and Prine, 1991). Research will be carried out to determine if UF 1 can outperform PI300086 in measures of forage quantity, nutritive value, and winter survival under intensive management practices of frequent harvestin g. Due to the below freezing temperatures that occur regularly in the southeastern US, it becomes imperative to evaluate stand persistence of these two cultivars to ascertain their survivability in the region. Due to increasing costs of inorganic fertil izers to support forage production, it is important to assess alternative sources of nutrients for plants. Studies elsewhere have been done evaluating effects of inorganic nitrogen supply on elephantgrass yields and nutritive value (Valles de la Mora and F ernandez Rodiles, 1989) but effects of alternative N sources such as municpal biosolids have been evaluated recently (Costello et al., 2010).

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16 Use of home grown, high yielding accessions of elephantgrass using alternative sources of nitrogen would help re duce cost of milk production. Most Florida dairy farms are obligated to balance nitrogen input (feeds and fertilizers) and output (milk and animal wastes). Elephantgrass may be an excellent choice as a forage for utilizing nitrogen from animal wastes if high forage yield can be maintained under frequent harvesting management. However forage production based upon low input utilizing an alternative to inorganic nitrogen fertilizers necessitated this research. Information gathered from this study will help establish whether UF 1 can be an effective new cultivar as a forage for dairy farms using dairy cow manures as a source of plant nutrients. Therefore, the objective of this research is to evaluate effects of nitrogen application rate using dairy manure a s a nutrient source and defoliation frequency on dry matter yield, nutritive value, ensiling characteristics, and winter survival of PI300086 and UF 1 elephantgrasses.

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17 CHAPTER 2 LITERATURE REVIEW Potential of Elephantgrass Tropical grasses such as eleph antgrass (Pennisetum purpureum Schum ), because of their C4 carbon fixation pathway, are recognized widely for their potential to yield much biomass. In the subtropical and tropical areas of the world, elephantgrass has produced consistently the greatest or near the greatest dry matter (DM) with yields of 20 to 52 Mg ha 1 yr 1 (Mtengeti et al., 2001; Woodard and Prine, 1993a; Hsu et al., 1990; Bouton, 2002; Velez Santiago and Arroyo Aguilu, 1981; and Woodard and Sollenberger, 2008). Other common C4 grasse s such as rhodesgrass (Chloris gayana Kunth.) and guineagrass (Panicum maximum Jacq.) yielded 8 to 14 and 7 to 12 Mg ha 1 yr 1 respectively for example (FAO; http://www.fao.org/documents/en/detail/18546). Morphological and Physiological Attributes of Elep hantgrass Elephantgrass is a prolific bunchgrass, has large morphological variation characterized by natural cross pollination, and variability in growth responses to different environments which has contributed to differences within the species (Bogdan, 1 977; Skerman and Riveros, 1990). Plants in general can alter their morphology in order to both reduce the probability of future defoliation events and to better withstand them as they occur. This is achieved in certain species by altering leaf growth, ra te of tillering, and orientation of tillers and leaves in positions that are less likely to be harvested, i.e. favoring horizontal and lower growth (Nelson, 2000). Elephantgrass is a cross pollinated species that sets little seed. This low seed set is pa rtially due to self incompatibility and the fact that a single genotype or clone may occupy a large area. Genotypes do not breed true from seed. Therefore, cultivars of

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18 elephantgrass are all propagated vegetatively. Vegetative propagation makes possible rapid multiplication and dissemination of superior germplasm, but it is more labor intensive and costly and can predispose clonal material to disease (Boonman, 1993). Woodard et al. (1985) reported that elephantgrass PI300086 was established more easily f rom stem cuttings than was dwarf Mott. They evaluated the effect of planting date, (dates starting 4 July and ending 8 January), planting orientation of stem cuttings em cutting and position of nodes on the cutting (i.e. 2, 3, 4, 6, or 12 node stem cuttings) from either the base or the apex of individual stalks and planting depth of two cultivars (i.e. PI 300086 at 5 10 15 and 20 cm depths and Mott dwarf at 2.5 7.5 and 12.5 cm depths) upon subsequent establishment. They indicated that establishment of dwarf elephantgrass was more difficult than tall types. They concluded that PI300086 stem cuttings should be planted in July and August or in the late fall, Nov ember and December, in North and Central Florida, avoiding intermediate planting dates from late September to early November that results in winter kill. Planting orientation did not affect initial emergence or winter survival. Shorter cuttings having 2 and 3 nodes resulted in the highest primary shoot counts compared to stalks with six and 12 nodes. With horizontal furrow planting, Mott elephantgrass was found to be particularly sensitive to planting depth, whereas this factor was less critical for tall PI 300086. Stem cuttings from the lower stalk (more mature) were superior as planting material to cuttings from the upper stalk (less mature) in tall cultivars. On the other hand, Sollenberger et al. (1990) determined that using undefoliated stems was t he best method for propagating dwarf Mott elephantgrass.

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19 Elephantgrass is adapted to various soil conditions. It can grow in soil of low fertility and in acidic to slightly alkaline soil, but it is better adapted to deep, well drained, fertile soils. It usually does not grow well in heavy clay soils and cannot tolerate soils that remain waterlogged for long periods of time. The species also has substantial drought tolerance owing to a deep fibrous root system, but also responds to irrigation (Hanna et al ., 2004). After 15 years of field trials conducted in Florida, Alabama, and Georgia, the northern limit for sustained survival and adequate elephantgrass yield was determined to be where temperatures do not drop below the range of 6 to 9C (Woodard and Sollenberger, 2008). Germplasm varies for cold tolerance making it possible to extend the use of this plant into the subtropics. Elephantgrass grows best in regions with a in rapid assimilation and formation of new tissues. Frost kills leaves and above ground stems, but unless the soil freezes, the underground parts will resume growth at the beginning of the spring. Accessions vary in their ability to retain leaves after frost. The elephantgrass nursery at Tifton, GA was rated for leaf retention in mid February after killing frosts in mid December of 18 C. On a rating scale, of 1 (com plete leaf retention) to 5 (no leaf retention), more than 30% of the clones had a rating of < 3. Most of these clones were dwarf or semi dwarf, but some were erect, robust types. Elephantgrass is a short day plant that flowers when day length is 11 h or l ess. At Tifton, GA less than 5% of accessions flowered during 11 h days (Sollenberger et al.,

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20 2004). However, there may be interaction between day length and temperature, and germplasms vary in response to day length. The temperature during forage growth plays a major role in the nutritive value of the forage. Lower digestibility at higher temperatures is the result of increasing proportion of cell wall, particularly the indigestible fraction (Buxton and Fales, 1994). Increased lignification may be respo nsible for this decrease. A higher environmental temperature also promotes more rapid metabolic activity, which decreases the pool size of metabolites in the cellular contents. Temperature has its greatest effect on plant development in promoting the accu mulation of structural matter (Van Soest, 1982). Effects of Management on Yield of Elephantgrass Fodder Defoliation f requency Defoliation impacts the physiological and morphological processes that occur in forage plants, strongly influencing production of biomass and nutritive value. Strategic defoliation management of forages relies on 2 principal factors, namely 1) defoliation frequency which refers to the time period between defoliation events and 2) intensity which refers to the proportion of the canop y removed at each event. These 2 principal factors have important effects on yields, nutritive value, and persistence of tropical grasses and thus should be managed properly. Woodard and Prine (1991) evaluated the effects of harvest frequency on yield, nu tritive value, and persistence of 4 tall genotypes (PI300086, Merkeron, N 43, and N 51) in the colder subtropics. Three genotypes (Merkeron, N 43, and N 51) did not differ in DM yield in the 3 year period. However, the 3 year mean DM yields (1986 to1988) were 24.3, 21.1, and 17.0 Mg ha 1 across genotypes for 1, 2, and 3 harvests per year,

PAGE 21

21 respectively. Genotype PI300086 did not differ from Merkeron, N 43, or N 51 in 1986 and 1987, but in 1988 it was inferior in yield when harvested multiple times. In Taiw an, 5 elephantgrass genotypes (7007, 7103, 7105, 7108, and cv. A146) were harvested throughout the year when the uppermost leaf collar was 1, 1.5, or 2 m above the soil surface (Hsu et al., 1990). Cutting intervals averaged 58, 68, and 88 d for the 3 treat ments, respectively. Averaged across cultivars and over two years, DM yields were 34, 41, and 52 Mg ha 1 yr 1 for the 1, 1.5, and 2 m treatments, respectively. In Kenya, tall elephantgrass fertilized with 200 kg of inorganic N ha 1 produced 8, 13, and 18 Mg of DM ha 1 when harvested every 6, 9, and 12 wk, respectively (Boonman, 1993). In Puerto Rico, 7 elephantgrasses were fertilized with 670 kg of N ha 1 yr 1 and harvested to a 5 cm stubble height during a 2 year period at 30, 45, and 60 day intervals (Velez Santiago and Arroyo Aguilu, 1981). Across entries, DM yields were 14.6, 26.8, and 48.9 Mg ha 1 for 30, 45, and 60 day harvesting intervals, respectively. In Florida, elephantgrass (PI300086) was fertilized with 330 kg of N ha 1 yr 1 and harvested at a 3 cm stubble height every 6, 8, 12, and 24 wk during a 24 wk period (Calhoun and Prine, 1985). Averaged across 2 yr, yield increased from approximately 20 Mg ha 1 yr 1 (6 wk treatment) to 40 Mg ha 1 yr 1 (24 wk treatment). Yield exhibited a quadrati c response to harvest frequency described as y (Mg ha 1 ) = 4.3 + 3.15x 0.07x2 (x = weeks). The high DM yields of elephantgrass have been explained based on a long linear growth phase. In Florida, this period lasted up to 190 days (Woodard et al., 1993 b). Calhoun and Prine (1985) reported a linear growth phase of DM accumulation for PI300086 to be approximately 170 days and a crop growth rate of 23 g m 2 1 d 1 Thus

PAGE 22

22 when growth is interrupted with harvesting multiple times per season, the reduction in a nnual forage yield is attributed in part to uncollected solar energy during periods between harvests. Consequently the more interruptions made during the season, the lower the forage yield. However, a precipitous drop in DM yield with increased harvest f requency may be caused by loss of whole plants when genotypes are intolerant to both multiple harvesting events and cooler subtropical weather. The drop in yield of PI300086 was linked to loss of stand that occurred during the 1987 1988 winter in Florida (Woodard and Prine, 1991). Wadi et al. (2004) determined the effects of harvesting interval and cutting stubble height on DM productivity and over wintering of 4 Pennisetums (napiergrass, kinggrass, hybrid napiergrass, and pearl millet). Harvests were at 60 and 90 day intervals at a stubble height of 30 cm. The DM yields (90 and 60 d intervals) were greatest at 90 day intervals for napiergrass (13.3 vs. 4.9 Mg ha 1 yr 1 ), hybrid (10.6 vs. 5.0 Mg ha 1 yr 1 ), kinggrass (10.6 vs. 4.6 Mg ha 1 yr 1 ), and pearl millet (6.1 vs. 3.7 Mg ha 1 yr 1 ). Due to large differences in nutritive value between leaves and stems, defoliation strategies should be designed to maximize leaf percentage or leaf DM harvested or consumed. Of course, plant survival must be maint ained. With tall ecotypes, the leaf/stem ratio decreased from 1 to 0.78 to 0.64 as height at cutting increased from 1 to 1.5 to 2 m, respectively (Hsu et al., 1990). In Puerto Rico, the leaf/stem ratio of 7 elephantgrasses averaged 0.71 when harvested ev ery 45 d and 0.59 when harvested every 60 d (Velez Santiago and Arroyo Aguilu, 1981). When Merkeron elephantgrass was harvested at 1.2, 2.5, 3.7, and 4.9 m of growth in Florida, leaf percentage (2 yr average) decreased from approximately 50% (1.2 m tall) to approximately 10% (4.9 m

PAGE 23

23 harvested every 5 wk to a15 cm stubble during 2 warm seasons in Florida and Georgia (William and Hanna, 1995), the leaf/stem ratio of dwarf and Merkeron averaged 8.3 and 2.2, stem length averaged 10 and 55 cm, and number of nodes averaged 4.7 and 6.7, respectively. Merkeron consistently produced at least twice as much DM as Mott and the leaf/stem ratio was correlated negatively with DM yield. Elephantgrass has poor persistence under some defoliation regimes, especially when multiple harvests are made to a short stubble height. Chaparro et al. (1995, 1996) and Kalmbacher and Martin (1999) working in the subtropics (Florida) reported poor persi stence of elephantgrass using such management practices. Harvesting elephantgrass every 3 wk to a 10 cm (Chaparro et al., 1995) or to a 15 cm stubble height (Kalmbacher and Martin, 1999) resulted in loss of stand over several years. This defoliation mana gement greatly reduced rhizome mass, rhizome N concentration, and concentration of nonstructural carbohydrates compared to treatments with longer rest periods or taller stubble heights (Chaparro et al., 1996). Elephantgrass was persistent when cut at 10 c m stubble heights if defoliation interval was 9 wk or longer (Chaparro et al., 1995). In addition persistence was excellent if stubble height increased from 34 to 46 cm for the 3 wk cutting frequency. In Puerto Rico, Velez Satiago and Arroyo Aguilu (1981 ) reported that survival of 7 tall elephantgrass cultivars was greatly reduced after the first year when plants were defoliated to a 5 cm stubble height every 30 d. Similar conclusions were drawn for tall elephantgrass in Florida when it was defoliated ev ery 6 wk at a 3 cm stubble height (Calhoun and Prine, 1985). Also in Florida, 4 tall elephantgrass genotypes were fertilized with 340 kg of N ha 1 yr 1 and harvested 1, 2, or

PAGE 24

24 3 times per year to stubble heights of 10 to 15 cm (Woodard and Prine, 1991). W hen cut 3 times per year, PI300086 plants did not persist, but persistence of Merkeron, N 43, and N 51 was not affected by harvest frequency. Based on experience in East Africa, Boonman (1993) indicated that elephantgrass could not survive frequent cuttin g or grazing, and its growth form dictates rigid resting periods. He observed that continuous defoliation deprived the crop of its main avenue of perenniation because much of the regrowth arose from slowly emerging basal shoots that sprouted from the fles hy rhizomes. Effect of fertilization on production of e lephantgrass Nitrogen fertilization management is an important aspect of forage production. Culminating from its central role in protein and photosynthetic enzyme synthesis, it is one of the most impo rtant nutrients required by plants. Due to this, it strongly impacts establishment success, biomass production, nutritive value, and stand persistence. Literature indicates that top dressing elephantgrass planting nurseries with N fertilizer increased est ablishment success, herbage DM yield, and herbage CP concentration. In Florida, a range of N:P:K rates from 0:0:0 to 450:50:90 kg ha 1 were Prine, 1990). Vigour scores of primary tillers recorded 5 wk after planting improved to the highest fertilizer rate 448 49 186 kg ha 1 of N P K It was suggested that the propagation quality of P. purpureum stems can be improved by applying high rates of fertilizer to nursery plan ts. Minimum annual fertilizer rates of 224:25:93 and 336:37:139 kg N:P:K ha 1 for Merkeron and Mott, respectively were recommended. Elephantgrass can produce more DM than most perennial tropical C4 grasses, but fertilizer and water are required to achieve this. Nutrient removal of high yielding

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25 grasses can be extensive. In the absence of fertilization, yields can be reduced greatly. yields by using 10 different co mbinations of N and P. They established that 120 and 60 kg ha 1 of N and P respectively gave maximum DM yield of 47 Mg ha 1 yr 1 This rate also gave the greatest number of leaves per tiller (7.2) and tillers per plant (23.7), longest stem length from b ase to top leaf collar (217.3 cm), most leaf area (349.2 cm2), and greatest concentration of crude protein (9.39% of DM). In the humid tropics of Mexico, Taiwan, a local ecotype of elephantgrass, was fertilized with inorganic N at rates of 0, 90, 180, an d 270 kg ha 1 yr 1 and cut 9 times during a 24 month experiment (Valles de la Mora and Fernandez Rodiles, 1989). Herbage yields increased from 19 Mg ha 1 (no N applied) to 29.6 Mg ha 1 (270 kg of N ha 1 yr 1 ). Under unfavorable conditions in Australia, 2 80 kg of N ha 1 appeared to be an economical rate for elephantgrass and produced more than 15 Mg of DM ha 1 and 1435 kg ha 1 of CP (Grof, 1969). In Kenya, elephantgrass yields increased from approximately 5 (no N applied) to 20 Mg DM ha 1 (800 kg of N ha 1 ) when harvested every 9 wk (Boonman, 1993). Herbage CP increased from 60 to 120 g kg 1 of DM for the same fertilization rates. Boonman (1993) also noted that approximately twice as much N fertilizer was needed to equalize yields when plants were under a cut and carry management system compared with a grazed pasture system. This was likely because high proportions of nutrients consumed are returned to the pasture in dung and urine under grazing. Other nutrients also must be provided to sustain high le vels of productivity. Elephantgrass is a luxury consumer of potassium. Potassium concentrations of tall

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26 types at Kawanda, Kenya ranged from 31 to 67 g kg 1 of DM (Foster, 1969). In East Africa, an elephantgrass DM yield of 12.5 Mg ha 1 removed 30 kg ha 1 of P (Boonman, 1993). It has been suggested that tropical grasses can acquire up to 30% of their annual P uptake from soil below a 30 cm depth. As a result, soil P results from the top 30 cm of soil may be somewhat misleading for P availability (Nye an d Foster, 1961). Association of grasses with vesicular arbuscular mycorrhizae (VAM) may enhance P uptake. Two VAM fungi were evaluated for their ability to provide P to tall elephantgrasses across a range of soil P additions from 0 to 200 mg of P kg 1 of soil (Hung et al., 1990). Mycorrhizal dependency decreased with P addition but growth was greater for plants inoculated with VAM fungi across P rates. Potential of Organic Amendments as Sources of Nutrients for Elephantgrass Effect of Increasing Amount s of Manure on Production o f Elephantgrass Castillo et al. (2010) reported that municipal biosolids (MBS), an organic amendment, can be an alternative to inorganic fertilizers as a source of N. Replacing 33% of N from inorganic fertilizer with N from MBS reduced elephantgrass biomass production 0 to 11%, so there is potential benefit to including MBS in a fertilization program for bioenergy crops, even in situations where MBS are limited to P based application rates. Nongrazing lactating dairy cows, dry c ows, and heifers fed stored feedstuffs excrete in manure approximately 179, 83 and 43 kg of N yr 1 respectively (Nennich et al., 2005). On commercial dairy farms, only 20 to 30% of dietary N fed to dairy animals is converted into milk (Jonker et al., 200 2) with the remaining feed N excreted in manure (feces and urine). Approximately three fourths of the N contained in urine is in the urea form, which is readily hydrolyzed into ammonia by urease enzymes in soil and feces. Loss of N from manure as ammonia not only reduces the fertilizer N

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27 value of manure, but it also can contribute to environmental problems. High losses of N through ammonia volatilization following application to land often makes livestock slurries less efficient as a source of N for plan ts than inorganic fertilizers (Schroder, 2005). A wide range of estimates for N efficiency of slurry are reported internationally in both legislative and agronomic advice instruments. For example, Danish regulations specify that the N fertilizer replacem ent value of cattle slurry (i.e. the amount of inorganic N fertilizer that can be replaced by slurry N) applied to grassland should be calculated as 0.70 kg of slurry N kg 1 of inorganic N (Grant, 2009). This compares with lower replacement values of 0.45 to 0.60 and 0.40 kg kg 1 in the Netherlands and Ireland, respectively (Schroder and Neeteson, 2008; Ireland 2009). Agronomic advice in the United Kingdom (DEFRA, 2006) proposes a net fertilizer replacement value (NFRV) of 0.05 to 0.50 kg/kg depending on the method and timing of manure application. Absorption of manure nutrients by plants is dependent on plant growth. Careful fertilization management is required to produce herbage of high quality. Sunusi et al. (1997) assessed yield and digestibility of elephantgrass under 3 cattle manure application rates (10, 250, and 490 Mg ha 1 yr 1 in 1993 and 0, 120, and 240 Mg ha 1 yr 1 in 1994) and 3 cutting regimes (1, 3, and 6 harvests per year). The average N% of the manure for both years was 1.91% on a DM basis. Total DM yield and in vitro DM digestibility (IVDMD) increased whereas concentration of NDF tended to decrease with increasing amount of manure applied. The DM yields for the high, medium, and low manure application rates were 14, 8, and 2.5 Mg ha 1 yr 1 (6 harvests per year), 27, 18, and 6.5 Mg ha 1 yr 1 (3 harvests per year), and 28, 25, and 12 Mg ha 1 yr 1 (1 harvest per

PAGE 28

28 year), respectively. The IVDMD coefficients tended to increase with increasing amount of manure applied irrespective of cutti ng frequency. For example, elephantgrass receiving the most vs. the least amount of manure had greater IVDMD when harvested 6 times per year (62.6 vs. 57.2%) and when harvested 1 time per year (56.1 vs. 50.8%). The IVDMD for the stem and shealth plant pa rts followed the same response to manure applications. Influence o f Manure Application Methods on Availability o f Organic Nutrients Nitrogen utilization and N losses depend on interactions among manure spreading technique, grass cover, weather, and soil properties (Misselbrook et al., 2002). The losses of ammonia following land application are affected by weather and soil conditions such as air and soil temperature, relative humidity, solar radiation, rainfall, and wind speed at the time of and after app lication of manure (Sommer et al., 1991; Moal et al., 1995; Brasschkat et al., 1997; Genermont and Celliar, 1997; Menzi et al., 1998; Sommer and Olesen, 2000; Sommer and Hutchings, 2001; Sogaard et al., 2002; Misselbrook et al., 2005). The low plant util ization of N from slurry commonly has been attributed to method and timing of application. It has been well established that a surface broadcast application of slurry, using a splash plate (SP) method for broadcast slurry application, can be accompanied b y high N losses through NH3 volatilization (Malgeryd, 1998; Mattila, 1998; Morken and Sakshaung, 1998; Smith et al., 2000; Misselbrook et al., 2002). In these comparative studies, NH 3 emissions were progressively reduced using low emission spreading techn iques such as band spreading, trailing shoe (TS; tilling manure into soil), and injection. Trailing shoe increased the ANR, NFRVN, and NFRVDM after 40 to 50d post application by 0.09, 0.10, and 0.10 kg kg 1 respectively

PAGE 29

29 than the SP method. Methods such a s injection are associated with root damage resulting in reduced yields and stand longevity (Larson, 1986). Band spreading of slurry with a trailing foot attachment, also known as sliding shoe, drag shoe, or sleigh foot, places the manure in a series of n arrow bands on the soil surface beneath the canopy of the grass sward at spacings of 20 to 50 cm. This reduces the surface area of the manure and minimizes exposure to wind turbulence, resulting in reductions in ammonia loss of > 40% compared with surface broadcast application (Svensson, 1994; Huijsmans et al., 2001) and grass yields similar to those from mineral fertilizer (Bittman et al., 1999; Carter et al., 2010). Applying manure in bands reduces the surface area of manure and placement below the gras s canopy provides protection from wind, resulting in less NH3 loss during the first 24 h after spreading. In addition, band placement directly on the soil surface below grass canopy may encourage infiltration of slurry into the soil which would further re duce volatilization (Huijsmans et al., 2001). Lalor et al. (2010) evaluated NFRV of cattle slurry and used TS and SP methods of applying slurry to grassland. They found that TS resulted in reduced emissions of ammonia compared to surface broadcasting. In addition, applying slurry during cool and wet weather reduced ammonia emissions. The NFRV calculation was based on apparent N recovery (ANR) of slurry N relative to mineral N fertilizer and also that NFRV DM was based on DM yield. Lalor et al. (2010) re ported that the greatest ammonia losses were within the first 24 30 h after application, with approximately 50% of total ammoniacal N lost in this manner. Also Lalor et al. (2010) noted that when slurry DM was lower, ammonia losses were reduced. With inc reased volatilization, nitrate

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30 leaching was low indicating tradeoff between ammonia emission and nitrate leaching. be lost from applied slurry. They further found that D M yield was increased by an additional 0.39 Mg ha 1 with the TS compared to the SP method for the first harvest. The additional DM yield effect for TS was smaller for cumulative harvests, being 0.22 Mg/ha, indicating a greater residual effect following ap plication using SP rather than TS. The interaction of site and application time had a significant effect over first harvest and so too over cumulative harvests. The N uptake in the first harvest was affected by slurry application, being 19.0 kg ha 1 grea ter following slurry application with the SP method compared to the control treatment with no mineral N fertilizer. The N uptake was increased by an additional 9.2 kg ha 1 by using TS compared with SP. The mean ANR over all sites and years was 0.25 and 0 .16 kg/kg with SP and was 0.34 and 0.25 kg/kg with TS in April and June, respectively. The NFRV N averaged over all sites and years were 0.30 and 0.14 kg/kg with SP and were 0.40 and 0.24 kg/kg with TS in April and June, respectively. The mean NFRV DM av eraged over all sites and years were 0.21 and 0.12 kg/kg with SP and were 0.30 and 0.22 kg/kg with TS in April and June, respectively. N itrogen M ineralization In N mineralization, organic N from decaying plant and animal residues (proteins, nucleic acids, amino sugars, and urea) is converted to ammonia (NH 3 ) and ammonium (NH 4 +). This process is also called ammonification. The available N from applied manure includes inorganic N (NO 3 N and NH 4 + N) plus organic N mineralized following application. Nutrient mineralization depends on temperature, soil moisture, soil properties, manure characteristics, and microbial activity. Mineralization of organic N is

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31 expected to be low for composted manure because much of the N is lost through volatilization during the process of composting. To effectively utilize nutrients in application rates. Mineralization is microbially driven. It is influenced by temperature, soil water, soil p H, soil properties and amendment composition (Bernal and Kirchmann, 1992). Mineralization of N increases with increasing temperature under conditions found in agricultural soils (Cassman and Munns, 1980; Eghball et al., 2002). Also mineralization is grea test when soil moisture is near field capacity and declines with soil drying (Cassman and Munns, 1980). Both NO 3 N and NH 4 + N in manure are available to plants immediately. Ammonium can be converted to ammonia and be lost to the atmosphere following appl ication. Thus manure should be managed to minimize ammonia loss after application. Mineralization of N, under both aerobic and anaerobic conditions, is mediated by the activities of nonspecific heterotrophic soil microorganisms (bacteria, fungi, and actin omycetes) that use the N for their metabolism (He et al., 2003). The microorganisms produce extracellular enzymes that can degrade proteins and non protein N to NH 4 + (Pierzynski et al., 2000). During the mineralization process, organic materials (e.g., p roteins, chitins, amino acids, amino sugars, and nucleic acids) are degraded initially to NH 4 + to produce the inorganic forms of N for subsequent N uptake by the plant. Immobilization is the reverse of mineralization. It is the conversion of inorganic N into organic N. Although both NO 3 and NH 4 + can be assimilated by microorganisms, immobilization occurs predominantly from the NH4+ pool when available (Jarvis et al., 1996). The mineralization of N and immobilization processes

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32 take place simultaneously in the soil, with the relative magnitudes determining whether the overall effect is net N mineralization or net N immobilization (Cabrera et al., 2005). Although biological transformations of N in soils are complex, mineralization largely depends on the q uantity and quality (composition) of OM and reflects the influence of the environment, principally temperature and moisture, on biological activity (Goncalves and Carlyle, 1994). If the amount of N present is larger than that required by the microbial bio mass, mineralization occurs with the release of inorganic N. This usually occurs at a C:N ratio of less than 20. If the amount of N present is equal to that required by the microbial biomass, there will be no net N mineralization. On the other hand, if the amount of N in the material is lower than that required by the microbial biomass, there will be immobilization (Cabrera et al., 2005). In immobilization of N, ammonia and nitrate are taken up by microbes and largely immobilized, or made unavailable to plants, depending on the C:N ratios. When N is abundant, both microbes and plants assimilate ammonia and nitrate. Nitrogen and Phosphorus Removal b y Elephantgrass Limited information is available regarding the recovery and loss of fertilizer nitrogen (N) applied to intensively managed tropical grass pastures. Martha et al., 2004 conducted an experiment to determine the fertilizer N recovery and ammonia volatilizati on loss in an elephant grass (Pennisetum purpureum, Schum.) pasture fertilized with 100 kg N ha 1 as urea or ammonium sulphate, labelled with 15N, in late summer or in mid autumn. Herbage mass was greatest and litter mass was lowest in late summer. The N concentration of herbage was greatest in autumn and the total N content in soil was lower in late summer than in mid autum reflecting the high N uptake capacity of the grass. Proportionately higher 15N recovery in litter mass was observed

PAGE 33

33 in autumn than in late summer and the 15N recovery in herbage was greater for ammonium sulphate fertilized pastures. Around 60% of the fertilizer 15N recovered was retained in soil and in non harvestable fractions of the plant. The NH 3 volatilization loss was greater in late summer and most of the N loss occurred soon after fertilizer application. Urea and ammonium sulphate fertilizers were equally effective in sustaining herbage DM yield in the short term. The 15N derived from fertilizer and recovered in herbage und er an intensively managed tropical elephantgrass pasture, irrespective of the source of N fertilizer, can be quite low in the short term. More than 60% of the 15N from urea and ammonium sulphate recovered in the soil pasture system was found in the soil a nd in non harvestable fractions of the plant (stubble plus root and litter). The N retained in these components will eventually become available to the system which will increase its potential to sustain new herbage growth. Castillo et al. (2010) fertili zed Merkeron and Chinese Cross elephantgrasses with 350 kg of N ha 1 yr 1 using changing proportions of ammonium nitrate and MBS (100:0, 67:33, 33:67, and 0:100). Removal of soil N by elephantgrasses decreased as the proportion of fertilizer as MBS increa sed (56, 52, 43, and 41%, respectively). Authors did not have a nonfertilized treatment so N uptake from fertilizer alone could not be calculated. In a second study by the same authors (Castillo et al., 2011), Chinese Cross elephantgrass was fertilized w ith 350 kg of N ha 1 yr 1 using either ammonium nitrate, MBS applied to the surface, or MBS incorporated into the soil. A fourth treatment was 700 kg of N ha 1 yr 1 from MBS incorporated into the soil. Removal of soil N was 56, 36, and 47% for N treatmen ts applied at 350 kg of N ha 1 yr 1 respectively and 24% for N applied at 700 kg of N ha 1 yr 1

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34 Phosphorus concentration in elephantgrass has been reported to range from 1 to 5 g kg 1 (Vicente Chandler et al., 1959; Gomide et al., 1969). Castillo et a l. (2010) reported that the P concentration in Chinese Cross and Merkeron cultivars ranged from 1.4 to 2.4 g kg 1 with greatest concentrations occurring in plants fertilized with the most P using MBS. Availability of P from animal manure may be high, app roximately 50%, as most of it is in organic form and becomes available after application (Herrera et al., 2010). At a DM yield of 12.5 Mg of elephantgrass ha 1 yr 1 Boonman (1993) reported that 30 kg of P ha 1 yr 1 were removed. de Geus (1973) indicated that 40 to 64 kg of P ha 1 yr 1 may be needed to match the removal of P in intensively zero grazed grasses. Nutrient removal is a function of DM yield and nutrient concentration within the plant. The DM yield of elephantgrass was lower when harvested mor e frequently; but because the grass was less mature, it contained a greater concentration of minerals and total nutrient removal was the same or larger than with less frequent harvests (Boonman, 1993). Removal of P from soil by elephantgrass was as high a s 136 ha 1 yr 1 (Gomide et al., 1969), however fertilization was 900 and 340 kg ha 1 yr 1 of N and P, respectively, well beyond what can be considered practical from economical and environmental perspectives. It has been suggested that elephantgrass has l ittle tendency for luxury consumption of P (Pant et al., 2004). Castillo et al. (2010) fertilized elephantgrass with MBS and inorganic fertilizer (ammonium nitrate) and applied the two in proportions of 0:100, 33:67, 67:33 and 100:0 to 2 different elephan tgrass cultivars, Chinese Cross and Merkeron. Only the total amounts of P applied by treatment and removed by elephantgrass across a 2 yr period were considered. Apparent removal of P in the 0%

PAGE 35

35 MBS treatment in which all P was applied using inorganic sou rces at a rate of 60 kg P ha 1 yr 1 was 717 and 690 g of P removed per kg of P applied by Chinese Cross and Merkeron, respectively. For the 33 and 100% MBS treatments, apparent P removal decreased from 638 to 268 g kg 1 of P applied to Chinese Cross and f rom 890 to 330 g of P kg 1 of P applied to Merkeron, respectively. Presently, soil test P concentrations are used as criteria to recommend P fertilization practices. When the soil P threshold is reached, P applications are not recommended or in some stat es may be prohibited (Pierzynski and Gehl, 2005). The soil test P threshold level is set based on readily available, agronomic soil P testing procedures. This means that once crop yield no longer increases in response to additional P input, no more P cou ld be applied. Castillo et al. (2010) fertilized Merkeron and Chinese Cross elephantgrasses with triple superphosphate (P2O5) at 60 kg of P ha 1 yr 1 or changing proportions of ammonium nitrate and MBS (100:0, 67:33, 33:67, and 0:100). The 100% inorganic fertilizer treatment contained triple superphosphate (P2O5) so that P was applied at 60 kg ha 1 yr 1 Organic P was applied at 39, 79, and 118 kg ha 1 yr 1 in 2007 and at 47, 95, 142 kg ha 1 yr 1 in 2008 for treatments 67:33, 33:67, and 0:100, respectively. Removal of P by elephantgrasses did not differ between years. Removal of soil P by elephantgrasses decreased as % MBS increased in the fertilizer, namely 77, 78, 74, and 30% for treatments 100:0, 67:33, 33:67, and 0:100, respectively. Auth ors did not have a nonfertilized treatment so N uptake from fertilizer alone could not be calculated. In a second study by the same authors (Castillo et al., 2011), Chinese Cross elephantgrass was fertilized with triple superphosphate (P2O5) at 60 kg of P ha 1 yr 1 or MBS at 118 and 142 kg of P ha 1 yr 1 in 2007 and 2008, respectively. A fourth

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36 treatment was MBS incorporated into the soil at 236 and 284 kg of ha 1 yr 1 in 2007 and 2008, respectively. Removal of soil P was 65, 26, and 35% in 2007 and 78, 27, and 35% in 2008 for P of inorganic, MBS surface, and MBS soil incorporated treatments, respectively. For the double P application rate treatment, 16% of applied P in 2007 and 20% of applied P in 2008 were removed by elephantgrass. Authors did not ha ve a nonfertilized treatment so N uptake from fertilizer alone could not be calculated. Nutritive Value, Ensiling, and Utilization of Elephantgrass N utritive V alue Nutritive value includes the nutrient composition, digestibility of nutrients, and nature o f digested products. It is often expressed using crude protein, in vitro DM (or organic matter) disappearance, neutral detergent fiber, acid detergent fiber, and/or lignin concentrations. Research has demonstrated that Mott dwarf elephantgrsss is high in quality in addition to being very productive (Sollenberger et al., 1989; Chaparro et al., 1995; Ruiz et al., 1992). Average daily gains of 0.97 kg d 1 were reported for cattle grazing Mott elephantgrass compared with 0.38 kg d 1 for cattle grazing bahiagr ass (Paspalum notatum Flugge) pastures (Sollenberger et al., 1987; Sollenberger and Jones, 1989). Flores et al. (1993) concluded that the greater forage quality of Mott elephantgrass compared to Pensacola bahiagrass resulted from greater intake of digesti ble organic matter. This was associated with less cell wall and greater digestibility of cell walls in Mott as a consequence of a smaller proportion of sclerenchyma fibers and less developed girder structure. Also, as reported by Mott (1984), there was n o forage quality deficit in summer for animals grazing dwarf elephantgrass. Further, Ruiz et al.

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37 (1992) reported that dwarf elephantgrass silage was able to substitute for corn silage with only a small decrease in milk yield. Castillo et al. (2010) found greater N concentration in elephantgrass harvested in 2007 compared to 2008 which was attributed to the shorter growing period before the first harvest in 2007 (67 d) than in 2008 (111 d). The shorter growing period was due to a severe spring drought, whi ch delayed onset of spring growth and application of MBS and inorganic fertilizer. This likely translated into less mature herbage harvested. The literature includes numerous examples of less mature elephantgrass herbage having greater N concentration (G omide et al., 1969; Woodard and Prine, 1991; Schank and Chynoweth, 1993). As plants grow they contain increasing proportions of structural and storage materials that are low in N, so the concentration of N in the plant declines with increasing maturity (G reenwood et al., 1991). Sunusi et al. (1997) reported elephantgrass shoot N concentration of 1.61, 1.15, and 0.57% for elephantgrass supplied with 490 Mg of cattle manure ha 1 yr 1 and defoliated 6, 3, and 1 times per year, respectively. When 250 tons of manure ha 1 yr 1 were applied, the shoot N concentrations were 1.41, 0.95, and 0.45% when defoliated 6, 3, and 1 times yr 1 respectively. When 10 tons of manure ha 1 yr 1 were applied the shoot N concentrations were 1.13, 0.79, and 0.33% when defoliated 6, 3, and 1 times yr 1 respectively. The NDF concentrations decreased with increasing application of manure. Ruiz et al. (1995) reported that silage made with Mott dwarf elephantgrass when compared with bermudagrass silage and sorghum silage, had a grea ter extent of digestion at 96 h for DM (68.2, 61.9, and 67.9%), NDF (65.5, 59.4, and 60.0%), and

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38 cellulose (70.0, 65.0, and 59.5%), respectively. Additionally, DM of dwarf elephantgrass had a faster rate of digestion than that from bermuda and sorghum sil ages. Spitaleri et al. (1995) harvested two pearl millet by elephantgrass hexaploid hybrid genotypes at 6 and 12 wk intervals. Silage made from 6 vs. 12 wk maturities had greater CP concentration (162 vs. 92 g kg 1 of DM) and IVOMD (60.8 vs. 53.5%). Har vesting management can influence nutritive value. Chaparro and Sollenberger (1997) sought to identify the optimum management practices for producing the best IVOMD coefficients by imposing 4 defoliation frequencies (3, 6, 9 and 12 wk intervals) and 4 stub ble heights (10, 22, 34, and 46 cm). They found that leaf blade IVOMD was affected primarily by defoliation frequency and IVOMD kept decreasing with increasing length of regrowth period. An interaction between cutting frequency and cutting height was de tected. Leaf blade IVOMD increased with increasing stubble height and IVOMD increased linearly with increasing defoliation frequency. Thus IVOMD decreased from 750 to 700 g kg 1 as defoliation frequency increased from 5 to 10 wk. Similar results were ob tained by Mislevy et al. (1989b) working with PI300086. Digestibility of OM was 653 g kg 1 when elephantgrass was harvested at a 1.2 m height but it decreased to 490 g kg 1 when plants were 4.9 m tall. Their explanation for increased OM digestibility of the shorter plants was due to more leaf blade and less stem. In situ DM digestibility of Pennisetum orientale revealed that digestibility differed when elephantgrass was cut every month vs. every 2 months (57.5% and 44.1%, respectively) and lag time diffe red (0.7 and 1.5 h, respectively) (Sarwar et al., 2006). However, authors found no differences in the rate (3.7% vs. 3.2% h 1 ) of digestion for elephantgrass cut every 1 vs. 2 months, respectively.

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39 Ensiling Woolford (1984) pointed out that lactic and ace tic acids are major components that are responsible for increased acidity of ensiled biomass. Butyric acid concentration and ammoniacal N expressed as a proportion of total N in silage indicate fermentation by Clostridia bacteria which is undesirable. In addition, products formed from this secondary fermentation negatively affect voluntary intake in ruminant animals (Wilkinson et al., 1976). Acetic acid concentrations increase during heterofermentative processes which are less efficient than homofermenta tive reactions in which only lactic acid is produced. However, acetic acid in silage can help prevent aerobic deterioration of silage. Storing elephantgrass as silage is more likely an option than storing as hay because silage requires only enough dry w eather to wilt the forage to a water concentration of approximately 250 to 300 g kg 1 However, high moisture, low water soluble carbohydrate (WSC) concentrations, low WSC/buffering capacity ratio, and extensive lignification may limit the success of maki ng silage using elephantgrass (Mannetje, 2000; Yahaya et al., 2004). The WSC concentration of elephantgrass in Florida ranged from 26 to 96 g kg 1 of DM across several harvesting regimes (Woodard et al., 1991), with concentrations nearly twice as great w hen forage was harvested 2 or 3 times per growing season as compared with one harvest. Likewise WSC concentration of elephantgrass by pearl millet crosses harvested every 6 or 12 wk was intermediate, averaging 52 g kg 1 of DM (Spitaleri et al., 1995). Hs u et al. (1990) suggested that the best compromise between DM yield and silage quality was to harvest tall elephantgrass when the uppermost leaf collar reached 1.5 to 2 m above soil level which should result in good sugar concentrations.

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40 Silveira et al. (1979) ensiled without wilting 4 genotypes of elephantgrass after a 62 d regrowth. After 150 d of storage, mean silage pH values and lactic acid concentrations varied from 4.1 to 4.4 and from 58 to 79 g kg 1 of DM, respectively. Ranges for mean concentrations of acetic and butyric acids were 27 to 59 and 0.1 to 0.3 g kg 1 of DM, respectively, whereas mean ammoniacal N concentrations ranged from 133 to 176 g kg 1 of total N. With elephantgrass ensiled at 9 to 10 wk of age, Vilela et al. (1983) reported mean silage pH of 3.9 and concentrations of lactic, acetic, and butyric acid concentrations of 15, 20, and 2.3 g kg 1 of DM, respectively. Mean ammoniacal N concentration was 173 g kg 1 of N. In Florida, Woo dard et al. (1991) evaluated silage characteristics of 3 elephantgrasses as affected by harvest frequency and genotype. Lactic acid was the major end product of fermentation in silages of PI300086, Merkeron, and Mott. Silage made from immature dwarf elep hantgrass had similar concentrations of lactic and acetic acids. Butyric acid was negligible in all silages. Concentrations of WSC in fresh herbage ranged from 26.2 to 83.7 g kg 1 of DM and increased with more frequent harvesting. Buffering capacity of fresh PI300086 herbage was exceptionally low and increased with frequent harvesting. Flieg scores for PI300086 and Merkeron ranged from 84 to 100 denoting very high quality silages. In Tanzania, Mtengeti et al. (2006) investigated the effect of wilting p rior to ensiling 8 wk regrowth elephantgrass on forage and silage quality. Wilting the cut forage for 1 day increased the % DM only slightly from 19.3 to 20.6% indicating that the uncrushed stems did not dry very quickly. After ensiling, the wilted forag e had greater concentrations (g kg 1 ) of CP (98 vs. 91) and greater IVDMD coefficients (545 vs. 524) but concentrations (g kg 1 ) of ash (13.8 vs. 14.2%), NDF (697 vs. 702), ADF (437 vs.

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41 433), and lactic acid (0.60 vs. 0.68) did not differ. By adding juice from crushed derinded sugarcane stems at 10% of forage wet weight, concentration (g kg 1 ) of lactic acid increased to 2.19 for unwilted and to 1.47 for wilted elephantgrass. Yahaya et al. (2004) also studied additives for improving elephantgrass silage. They evaluated the effectiveness of adding (5% w/v) fermented juice of lactic acid bacteria collected and grown from chopped elephantgrass (24.6% DM) and a commercial acetic acid powder on silage quality and in situ NDF degradability of the silage. Addin g lactic acid bacteria reduced pH from 5.45 to 4.33 and increased lactic acid concentration from 0.94 to 3.47% of OM. However the 72 h extent of the slowly digestible NDF fraction (49.0 vs. 53.7%) was not improved by adding lactic acid bacteria. Adding a cetic acid powder had no influence on silage quality or NDF digestibility. Clostridium bacteria responsible for spoiling silage are particularly sensitive to low water activity, thus wilted silage will stabilize at a less acidic pH than non wilted silage (Bates et al., 1989). Lavezzo et al. (1989) wilted 60 d old tall elephantgrass for 8 h and increased DM concentration from 139 to 218 g of DM kg 1 Wilting decreased buffering capacity due to respiration of organic acids to carbon dioxide and water, decre ased ammonia (NH 3 N as a proportion of total N), and increased digestibility. Intake of DM and digestible DM of elephantgrass silage by sheep were increased 42 and 44% by wilting compared with directly ensiled forage (Tosi et al., 1983). The longest wilt ing period reduced butyric acid and NH 3 N concentrations. Tuah and Okyere (1974) reported that it was necessary to wilt elephantgrass to DM concentrations of 250 to 300 g kg 1 in order to make good silage.

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42 Buffering capacity (resistance to change in pH d uring ensiling) of forage to be ensiled also can be an important determinant of silage quality. Playne and McDonald (1966) estimated that the ionic moiety, mainly organic acids of plant forage, contributes 68 80% to the buffering capacity whereas plant pr otein contributes up to 10 20%. Maize (Zea mays L.) has a low buffering capacity, approximately 20 cmol of NaOH kg 1 of DM. This characteristic along with its high WSC concentration explain why it is easy to ensile (Sollenberger et al., 2004). The buffe ring capacity of elephantgrass by pearl millet crosses was even lower than maize (Spitaleri et al., 1995), with greater buffering capacity for forage harvested at 6 vs. 12 wk of regrowth (150 vs. 10.3 cmol of NaOH kg 1 of DM). Similarly, buffering capacit y was greatest for PI300086 elephantgrass when harvested 3 times per growing season (11.2 cmol of NaOH kg 1 of DM) and least (5.2 cmol of NaOH kg 1 of DM) when harvested once (Woodard et al., 1991). These data suggest that the buffering capacity of elephant grass and its crosses with pearl millet is often low; thus the primary barriers to successful ensiling of elephantgrass are low WSC and high moisture. The pH of ensiled forage was less for 12 wk regrowth (3.76) than for 6 wk regrowth (3.99) likely due, in part, to greater buffering capacity for the more immature forage. Silage pH averaged 3.8 for the one cut system and 4.0 for the three cut system. Due to anticipated low concentrations of WSC of elephantgrass forage, a range of additives have been tested for improving fermentation and silage quality. Tall elephantgrass in Sri Lanka was ensiled with or without cassava (Manihot esculenta Crantz) tuber meal or coconut (Cocos nucifera L.) meal (50 g kg 1 of fresh forage) (Panditharatne et al., 1986). Additiv e increased DM concentration from 150 (control) to

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43 approximately 200 g kg 1 decreased silage pH, and increased lactic acid concentration. Addition of molasses (40 g kg 1 of fresh forage) to Mott dwarf elephantgrass in Brazil resulted in lower silage pH a nd NH 3 N concentrations compared to the control silage (Tosi et al., 1995). Additionally, Mtengeti et al. (2006) reported improvement in lactic acid concentrations and in vitro DM digestibility of unwilted and wilted elephantgrass silage pretreated with m olasses (added at 5% of forage) or with juice from derinded fresh sugarcane stems (added at 10 and 15% of forage wet weight). Jayasuriya and Siskandarajaii (1976) reported that adding maize grain prior to ensiling elephantgrass increased silage intake in sheep by 30% over control. The combination of adding fermentable substrate and inoculating with lactic acid producing bacteria improved fermentation resulting in lower pH and NH 3 concentration plus increased lactic acid over control (Tamada et al., 1999). Thus wilting and addition of fermentable substrate can improve the ensiling process for elephantgrass. However, Vendramini et al. (2010) evaluated fermenatation variables and nutritive values of 9 cultivars of warm season grasses wilted for 4 hours prio r to ensiling. Elephantgrass (Merkeron) harvested in summer had lowest lactic acid (0.1% of DM) of all grasses. During fall harvest, elephantgrass had less in vitro true OM digestibility (60 vs 65%) and greater lactic acid (1.5 vs 0.2%) and acetic acid ( 2.1 vs 0.2%) concentrations than bermudagrass. Authors concluded that microbial inoculation had no effect on the silage fermentation. Reports vary regarding optimal forage maturity for silage. Regrowth of 6 to 9 wk was found to be optimum for herbage pro duction and nutritive value (Mwakha, 1972; Butt et al.,1993). Longer periods (8 16 wk) have been suggested for elephantgrass intended for silage by Mwakha (1972) and Wilkinson (1983) whereas Ogwang and Mugerwa (1976) and

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44 Spitaleri et al. (1995) recommend ed 8 10 wk for hybrid Pennisetums. Manyawu et al. (2003) recommend 6 7 weeks for Pennisetums for silage. Utilization of Elephantgrass as a Ruminant Feed In the tropics, forage production is seasonal and in some production systems there is need for conserv ed forages such as hay, stockpiling or silage to provide feed for livestock throughout the year (Sollenberger et al., 2004). Brown and Chavalimu (1985) determined that elephantgrass preserved as hay and silage with equal efficiency, but the thick stems of elephantgrass and the difficulty of drying forages in the humid tropics in general greatly limit opportunities to make hay. Omaliko (1983) reported that elephantgrass gave the highest yields and maintained the highest concentration of CP of 3 tropical gr asses (stargrass, Cynodon nlemfuensis Vanderyst; guineagrass, Panicum maximum Jacq.; elephantgrass) stockpiled for 2 yr in Nigeria. Boonman (1993) recommended that elephantgrass be used to provide fodder primarily in the dry season to small holder systems in East Africa. He suggested that grass be cut and fertilized 2 months prior to the end of the rainy season. In addition, when plants reach 1 m in height in the dry season, the leaves should be stripped off for fodder while stems are left standing to pr oduce further crops of leaves. The potential of elephantgrass to support cattle live weight gains ranges from 300 to 1500 kg ha 1 yr 1 and depends on climatic conditions, amount of fertilization, and management practices (Blaser et al., 1942). In Florida average daily gains by cattle of 0.73 kg head 1 and gain per ha of 413 kg yr 1 were reported when tall elephantgrass was rotationally stocked and the sward was fertilized with 80 kg of N ha 1 yr 1 (Blaser et al., 1942). During the season of short days, steers were supplemented with 1.5 to 3 kg of DM d 1 of unprocessed chopped sugarcane (Saccharum officinarium L.) to which urea

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45 was added at 30 g kg 1 In Brazil, milk production was measured from crossbred cows grazing tall elephantgrass pastures every 30 45 d, stocked at 4.5 cows ha 1 and receiving 200 kg of N ha 1 yr 1 (Deresz et al., 2001). Average milk yields per cow were greater for the 30 d treatment and averaged 10.4 vs. 9.4 kg d 1 for cows on the 45 d rotation. In Florida excellent animal perform ance was obtained when Mott dwarf elephantgrass silage was substituted for maize silage in a total mixed ration for high producing dairy cows (Ruiz et al., 1992). These authors found in situ rates and extent of DM and cellulose digestion were greater for elephantgrass than maize silage, and there was only a small decrease in milk yield when Mott silage was substituted for maize silage. Cows fed dwarf elephantgrass silage or corn silage, which were higher quality forage sources based on greater rates and e xtents of fiber digestion, consumed more DM and produced more milk than cows fed sorghum silage or bermudagrass silage. These attributes made DMI of total mixed rations containing dwarf elephantgrass to be greater alongside corn silage than that containin g bermudagrass and sorghum silages. Lactating cows fed diets containing dwarf elephantgrass had increased DMI 19.8 vs. 18.9 kg d 1 DMI as percentage of BW (3.59 vs 3.44%) and intake of CP (3.52 vs. 3.47 kg d 1 ) compared with cows fed bermuda or sorghum silages. Dwarf and semi dwarf genotypes tend to maintain a leafy profile for most of the growing season, regardless of age of regrowth, and are better suited for grazing situations (Sollenberger and Jones, 1989; William and Hanna, 1995). Growing cattle g razing Mott (dwarf genotype) averaged almost 1 kg d 1 without supplementation (Sollenberger et al., 1987). Daily gains of cattle grazing Mott elephantgrass were twice

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46 those obtained by cattle grazing other warm season perennial grasses grown in Florida. T his was due to its relatively high proportion of leaf at all stages of maturity and high nutritional value of the leaves: that is, 140 and 135 g kg 1 of CP and 750 and 710 g kg 1 of digestible OM at 35 d and 70 d regrowth, respectively (Boddorff and Ocumpau gh, 1986). Organic matter digestibility and intake of Mott elephantgrass was greater than that of Pensacola bahiagrass (Flores et al. 1993). These improvements were associated with lesser percentage of sclerenchyma (1.6 vs. 5.4%) and greater percentage o f epidermis (32.8 vs. 25.9%) in the leaf cross section area of Mott elephantgrass compared with Pensacola bahiagrass. Therefore depending on cultivar height, dwarf or tall, utilization tended to differ. Dwarf or semi dwarf genotypes are eligible for grazi ng or cut and carry whereas tall cultivars are suited for silage making as well as cut and carry. Utilization of Elephantgrass in Africa In parts of Africa, elephantgrass is the main fodder used by smallholder dairy farmers. Elephantgrass is often quite ma ture and low in nutritive value when harvested in these primarily cut and carry systems (Kariuki et al., 2001). Tall elephantgrasses are used by small holder dairy farmers in Malawi in a cut and carry system. This is largely done on a zero grazing basis owing to fragmented grazing lands that are communally owned. Also Boonman (1993) reported that management of tall elephantgrass required considerable skill because of its rapid growth and upright growth habit. Utilization of improved warm season grasses such as elephantgrass is on a lower scale in Malawi because of difficulties associated with establishment and maintenance of improved pastures and a lack of appreciation of the value of improved forage by these smallholder farmers who have the largest impa ct on milk yield in Malawi (Kumwenda

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47 and Ngwira, 2003). Results from research stations in Africa show that elephantgrass can produce up to 50 Mg of DM ha 1 yr 1 with proper management (Ogwang and Mugerwa, 1976; Mtengeti et al., 2001). Elephantgrass has a prolific growth habit and, if well managed, could produce more forage than is currently experienced in Malawi. Greater yields could be harvested and preserved for feeding ruminants, dairy in particular, in order to regularize animal productivity througho ut the year. The tropical areas characterized by distinct wet and dry seasons harvest more ruminant feeds in the wet season followed by deficit yields in the dry season. Silage making appears to be the only way feasible to achieve this noble task both in the tropics and subtropical areas of the world because thick stems and relatively large herbage accumulation per cutting make their preservation as hay very difficult. However, farmers do not have sufficient information on the cutting management of the P ennisetums in Malawi. Information is required to optimize herbage yields, nutritive value, and the concentration of WSC in Pennisetums at the time of ensiling so that dairy farmers derive the benefits of growing elephantgrass. Lack of knowledge has resul ted in farmers feeding mature elephantgrass when nutritive value is low. Effects of stage of regrowth on the herbage yield and nutritive value of the Pennisetums are widely documented (Woodard and Prine, 1991; Spitaleri et al., 1995; Manyawu et al., 2003) In general, it is accepted that Pennisetum herbage yields increase and nutritive value declines with increasing maturity (Woodard and Prine, 1991; Spitaleri et al., 1995). uate to support livestock production because it will have low nutritive value (Gomide et al.,

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48 1969). Researchers vary in their recommendation for harvesting frequency. Regrowth of 6 to 9 wk was found to be optimum for herbage production and nutritive val ue (Mwakha, 1972). Longer periods (8 16 wk) have been suggested for elephantgrass intended for silage (Mwakha,1972; Wilkinson, 1983) whereas Ogwang and Mugerwa (1976) and Spitaleri et al. (1995) recommended 8 10 wk harvests for hybrid Pennisetums. Manya wu et al. (2003) recommended 6 7 weeks for Pennisetums for silage making.

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49 CHAPTER 3 EFFECTS OF DAIRY MAN URE APPLICATION AND DEFOLIATION FREQ UENCY ON YIELD, NUTRITIVE VAL UE, SIL AGE QUALITY AND WINTER SURVIVA L OF UF 1 AND PI300086 ELEPHAN TGRASSES Background Warm season grasses are the dominant forage crops used for livestock production in the southeastern United States (Vendramini et al., 2010). Research on herbaceous plants in the tropics and subtropics have consistently reported tall elephantgra ss to be the highest yielding or among the highest yielding C4 grasses with dry matter (DM) yields in the range of 20 to 50 Mg ha 1 yr 1 (Mtengeti et al., 2001; Woodard and Prine, 1993a; Hsu et al., 1990; Bouton, 2002; Velez Santiago and Arroyo Aguilu, 198 1, and Woodard and Sollenberger, 2008). Elephantgrasses that combine high DM yields and good nutritive value are potentially promising forages for the dairy industry around the world. Research is continually seeking to develop new cultivars of forages inc luding elephantgrasses that are significant improvements in yield, nutritive value, and survivability over traditional cultivars. One of the traditional tall elephantgrass types used in Florida is PI300086 (PI3) which is high yielding and of average nutri tive value. repeatedly during the growing season. A tall elephantgrass breeding line (UF 1) has been developed at the University of Florida and is being conside red for release as a cultivar. If UF 1 has better survivability under intensive harvesting practices and below freezing temperatures than PI3, it could be an improvement over PI3 as a forage for producting ruminants if yield and quality are not compromise d. High nutritive value is a major challenge for elephantgrass. If it can be managed to produce good quantities of digestible nutrients, its value as a forage for milk

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50 production by dairy cows increases dramatically. Forages are needed to provide the eff ective fiber and a portion of the energy and protein required by high producing dairy cows. As forage quality increases, greater proportions are digested in the rumen which reduces gut fill and allows greater intake. Oba and Allen (1999) reported a 0.17 kg increase in DM intake and 0.23 kg increase in milk yield for each one unit increase in forage NDF digestibility. Along with increased performance, diets containing better quality forage can contain a greater proportion of forage, are associated with de sirable health of the rumen, and reduce ration costs. Thus as forage quality increases and greater quantities are fed, total feed costs typically decline. Seeking to optimize forage quality with yield is always a goal in order to provide forages for supp orting good animal performance. One management strategy to improve nutrient density is to increase the defoliation frequency. It is usually feasible to harvest three to four times during the growing season in subtropical areas. However frequent harvestin g often reduces seasonal yield of DM of elephantgrass and can threaten plant survivability during the winter season (Woodard and Prine, 1991). Finding the "right" combination of forage quality, yield, and winter survival is an important goal for developin g new cultivars. Due to increasing costs of inorganic fertilizers to support forage production, it is imperative to effectively utilize alternative sources of nutrients for plants. Using alternative sources of locally produced N for fertilization would h elp reduce costs of milk production. Many studies have been done evaluating effects of increasing inorganic N supply on elephantgrass yields and nutritive value but effects of alternative N sources such as dairy manure N on yield and quality are somewhat lacking. Most Florida dairy

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51 farms are obligated to balance the N input (feeds and fertilizers) and output (milk and animal wastes). Thus efficient use of manure to produce forage is important. Elephantgrass may be an excellent choice as a forage for uti lizing N from animal wastes if high forage yields can be maintained under frequent harvesting management. The hypothesis was that UF 1 will yield more DM per hectare, be of better quality, and have better winter survival than PI3, that 6 wk harvesting in tervals will result in better forage nutritive value but lower yield than 9 wk harvesting intervals, and that increasing N fertilization will increase DM yield. Therefore, the objective of this research is to evaluate effects of N application rate using d airy manure nitrogen and defoliation frequency on DM yield, nutritive value, ensiling characteristics, and winter survival of UF 1 and PI3 elephantgrasses. Information gathered from this study will help establish whether UF 1 can be an effective new culti var as a forage for dairy farms using dairy cow manures as a source of plant nutrients. Materials and Methods Location A field experiment was conducted at the University of Florida Agronomy Forage Research Unit in Hague, Florida (290 461 North, 820 251 We st) from March 2011 to October 2011. The soil type at the experimental site is a somewhat poorly drained Chipley sand (Thermic, coated Aquic Quartzipsamments). Soil on the experimental site was sampled on April 5, 2011 using a soil corer to a 30 cm depth Results of the soil analyses were a soil pH of 6.3 and Mehlich extractable P, K, Mg, and Ca values of 71, 40, 29, and 448 ppm, respectively. Monthly rainfall totals and minimum temperatures during the experimental period and the last 30 yr (Figure 3 1) were obtained from

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52 http://climatecenter.fsu.edu/products services/data/1981 2010 normals/gainesville and http://fawn.ifas.ufl.edu/data/reports/?res. Treatments and Plant Management Treatments (n = 12) were the factorial combinations of two elephantgrasses, PI300086 and UF 1, two defoliation frequencies (6 and 9 wk intervals), and three N fertilizer rates using dairy manure (0, 90 and 180 kg ha 1 yr 1 arranged in a 2 by 2 by 3 factorial design. The longer defoliation interval (9 wk) was chosen to represen t a lenient defoliation management to allow for relative greater accumulation of forage DM and the shorter interval (6 wk) was chosen to optimize nutritive value. The manure N rate of 180 kg ha 1 was reflective of a low to moderate rate used in Florida and a rate of 90 kg ha 1 was reflective of recommended rates in Malawi. Each treatment was replicated three times in a split plot arrangement of a randomized complete block design. Combinations of N rate by regrowth interval were main plots and elephantgrass entry the subplot. Each main plot consisted of eight, 4 m rows (6 plants at 0.67 m spacing within the row) with a 1 m spacing between rows. Four rows of each entry comprised the subplot. The arrangement and dimensions of the main plots and subplots are shown in Figure 3 2. Elephantgrass UF 1 was planted on March 25, 2011 and PI300086 on March 29, 2011. Both were planted using rooted crown splits obtained from a nursery in Citra, FL. Three w eeks after planting, soil was tilled between rows to control weeds using a mechanized harrow. To help establish growth of elephantgrass, inorganic fertilizer was applied at a rate of 50 kg N ha 1 5.46 kg P ha 1 and 20.74 kg K ha 1 on April 22, 2011. All plots were staged on June 1, 2011 by clipping all plants to a 20 cm stubble height. Dairy cow manure was applied on June 3, 2011 at designated rates for each treatment.

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53 The day prior to fertilization with dairy cow manure, manure was transferred to 40 L plastic containers by shovel from the concrete floor of a free stall barn housing approximately 150 lactating Holstein cows fed the same diet. Efforts were made to only collect manure that appeared to be recently deposited. The manure was stored overnigh t in a room kept at a constant temperature of 4C. Representative samples of the manure (n = 3) were collected at the time of each scheduled fertilization and analyzed for N, P, and K (Livestock Waste testing Lab, Gainesville, FL). Prior to application, manure was weighed, mixed with water (3.5:1 weight to volume ratio) to create a slurry,and applied down the middles of each of 8 rows of elephantgrass (Figure 3 2). Manure was applied in split applications during the growing season because Calhoun and Pri ne (1985) indicated that split application of fertilizer led to better uniformity in yields. Laboratory analysis of N was used to adjust the amount of manure applied at each subsequent application. Concentration of N in manure averaged 0.36 0.05% (as i s basis; n = 12). Plants assigned to the 6 wk harvesting interval treatment were harvested on July 15, August 24, and October 5, 2011 whereas plants assigned to the 9 wk harvesting interval treatment were harvested on August 5 and October 5, 2011. All pla nts were harvested to a stubble height of 20 cm. The 20 cm stubble height was chosen because Hanna and Monson (1980) suggested that this stubble height at each harvest should allow optimal forage production when plants are harvested at approximately 6 wk intervals (or up to four times per season). Because plants assigned to the 6 wk harvesting interval treatment would typically be harvested 4 times per growing season, the amount of N to apply was targeted at 0, 22.5, and 45 kg ha 1 per application for the

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54 0, 90, and 180 kg of N ha 1 treatments, respectively. Likewise because plants assigned to the 9 wk harvesting interval treatment would typically be harvested 3 times per growing season, the amount of N to apply was targeted at 0, 30, and 60 kg ha 1 per ap plication for the 0, 90, and 180 kg of N ha 1 treatments, respectively. Because 2011 was the establishment year, only 3 harvests of the 6 wk treatment and 2 harvests of the 9 wk treatment were made so annual application rates were 0, 67.5, and 135 kg N h a 1 for the 6 wk treatment and 0, 60, and 120 kg N ha 1 for the 9 wk treatment. In order to determine yield, four interior plants from the third row of each subplot were harvested (area of 2.68 m2) and weighed immediately. From these plants, a minimum of 1 kg (as is) of representative forage was placed in a mesh bag and dried in a forced air oven at 550C to constant weight to determine % DM. The forage DM harvested for each subplot was determined by multiplying the % DM by the fresh weight yield and adjus ting the area of land occupied by the 4 plants to a hectare. In addition, 5 average tillers were selected from the 4 plants and hand separated into leaf and stem components. These components also were dried in a forced air oven at 600C to a constant weig ht to determine leaf to stem ratio (DM basis). After drying the whole plant material, samples were ground initially through a hammer mill. Subsequently a Wiley Mill (Arthur H. Thomas Co., Philadelphia, PA) was used to grind samples through a 4 mm and then a 1 mm screen. Samples were analyzed for DM (8 h at 1050C), organic matter (OM; 5120C overnight), NDF and ADF using an Ankom Fiber Analyzer (Ankom Technology, Macedon, NY; Van Soest et al., 1991), N (semi automated colorimetry [Hambleton, 1977] after dig estion using a modified aluminum block (Gallaher et al., 1975), and in vitro OM digestibility (IVOMD;

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55 Moore and Mott, 1974). Lag, rate, and extent of OM digestion were determined on samples composited within treatment but across harvest dates. Approximat ely 1.5 g of dried ground sample was placed into a 125 mL Erlenmeyer flask in triplicate. Flasks were inoculated with a mixture of artificial saliva and ruminal fluid collected from a ruminally fistulated cow fed a bermudagrass hay based diet (Moore and M ott, 1974) and incubated in an oven set to 39 C. Flasks were removed after 0, 6, 12, 18, 24, 30, 36, 48, and 96 h of incubation and OM remaining was determined. Lag time and rate of digestion of OM was computed with the equation of Mertens and Ely (1982) : R = D0e k(t L) + U when t > L and R = D0 + U when 0 < t < L, where R = OM residue (at t = time after incubation), U), K = digestion rate constant, L = discrete lag time, and U = indigestible fraction at 96 h of incubation. The nonlinear models procedure of SAS was utilized to estimate discrete lag time Growth of elephantgrass is seasonal with most of forage production occurring during summer and early fall months in the southeastern U.S. For this reason, it is necessary to conserve forage during the months of greater forage production for utilization du ring the winter or dry season in the tropics. Due to weather related limitations of rainfall and humidity, conserving elephantgrass as good quality hay is almost impossible but making silage requires just enough dry weather for wilting before before ensil ing. After removing the four plants from each subplot for yield

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56 measurements, the remaining plants from each subplot were clipped to a 20 cm stubble height using a brush cutter. From the July 15th harvest of the 6 wk treatment and the August 5th harvest of the 9 wk treatment, the plants were hand fed into a John Deere forage harvester resulting in particle sizes of approximately 2 to 3 cm suitable for ensiling. Chopped forage was placed into 150 liter capacity plastic containers double lined with 1.2 mm thick plastic bags (n = 36), pressed down with feet to remove oxygen, tied off, and stored inside a non air conditioned building. Concurrently, a representative sample from each subplot was placed into plastic bags, sealed, placed on ice, and frozen at 2 0 C. Upon thawing, samples were analyzed for water soluble carbohydrates (WSC) according to Ministry of Agriculture, Fisheries, and Food (1986). Silage containers were opened after 42 wk of ensiling. The upper 15 cm were discarded due to the presence of mold. A representative sample of approximately 2 kg was collected and mechanically pressed with sufficient force to produce a liquid which was collected, pH determined (Accumet model 15 pH meter, Fisher Scientific, Pittsburg, PA), and liquid frozen at 2 0 C. Upon thawing, liquid was centrifuged at 4 C and 21,500 g for 20 min and the supernatant was analyzed for organic acids (Muck and Dickerson ,1988) and an HPLC system (Hitachi, FL 7485, Tokyo, Japan) coupled to a UV detector (Spectroflow 757, ABI Ana lytical Kratos Division, Ramsey, NJ) set at 210 nm. Plant uptake of N was calculated using total N yield from all harvests. The N yield from the 0 N fertilization rate was subtracted from the N yield of plants harvested with the manure treated plots and d ivided by the total amount of N applied during the growing season and multiplied by 100 to determine efficiency of N uptake by plants fertilized with dairy cow manure.

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57 Finally, cool weather survival of cultivars under these management practices was quantif ied by describing every interior plant (n = 12) in all plots at establishment in 2011 and at the spring of 2012 after the winter season as thriving (> 2 leaves), greatly weakened (1 to 2 leaves), or dead (0 leaves). Survival was reported as the percentage of plants thriving from one spring to the next. Statistical Analyses Data were analyzed using the Mixed procedure of SAS (version 9.2; SAS institute, 1999). Entries, N fertilization rates, and harvesting intervals were fixed effects and blocks were random. Because the 6 wk and the 9 wk harvests did not have the same number of harvests (n = 3 and n = 2 respectively) data of yield, leaf to stem ratio, chemical composition, and IVOMD were analyzed within harvesting interval. For the 6 wk harvesting interval treatment, harvest number per year was tested using single degree of freedom orthogonal contrasts (linear and quadratic effects). In addition, single degree of freedom orthogonal contrasts (linear and quadratic) were used to test responses to the 3 N appl ication rates. Interactions of entry, N application rates, and harvest number were tested for the 6 wk and the 9 wk harvest interval treatments. For data in which harvest number was not a factor, namely total seasonal yield, silage measures, and digestion lag and rate of OM, the model included harvesting interval, N fertilization rate, cultivar and all interactions. All means presented are least square Results and Discussion Harvesting plans and N a pplications As explained earlier, the amount of N to be applied for the 90 kg of N rate treatment was 67.7 kg ha 1 for the 6 wk treatment and 60 kg ha 1 for the 9 wk treatment

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58 during this establishment year. The actual total amount of N:P:K in cow manure applied to the plots assigned to the 90 kg of N ha 1 treatment was 69.3:14.7:14.7 and 60.3:13.6:11.5 kg ha 1 for the 6 wk and 9 wk harvesting interval treatments, respectively. Therefore the amount of N applied slightly exceeded the targeted amount of 67. 5 and 60 kg of N ha 1 The actual total amount of N applied to the plots assigned the 180 kg of N ha 1 treatment was twice that of the 90 kg of N ha 1 treatment so these plots also received just slightly more than targeted. Dry Matter Yields and Leaf to S tem Ratios Tot al seasonal yields of forage DM Accumulated yield of DM of UF 1 was 20.8% greater than that of PI3 (8.9 vs. 7.4 Mg ha 1 yr 1 Table 3 1 and Figure 3 3). Since no interactions with cultivar were detected, this yield advantage of UF 1 over PI3 was true across both harvesting intervals and all 3 N fertilization rates. Yield of DM increased from 7.4 to 8.7 Mg ha 1 as the amount of N applied increased from 0 to 90 kg ha 1 but DM yield increased no further plateauing at 8.4 Mg ha 1 for plants fertilized with 180 kg of N ha 1 (quadratic effect of N fertilization rate, Table 3 1 and Figure 3 4). Greater yields with increasing amounts of N application were expected. Valles de la Mora and Fernandez Rodiles (1989) reported that herbage yields increased from 19 (no N applied) to 29.6 Mg ha 1 (270 kg of N ha 1 yr 1 ). In Kenya, elephantgrass yields increased from approximately 5 (no N applied) to 20 Mg of DM ha 1 (800 kg of N ha 1 ) when harvested every 9 wk (Boonman, 1993). Forage harve sted was greater for the 9 wk than the 6 wk harvesting intervals (9.6 vs. 6.8 Mg ha 1 yr 1 Table 3 1 and Figure 3 5). These yields were consistent across entries with UF 1 registering greater yields than PI3 when cut every 6 wk (7.7 vs. 5.8 kg

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59 ha 1 ) and every 9 wk (10.2 vs. 9.0 kg ha 1 ). The advantage from 9 wk harvest intervals could be attributed to the longer uninterrupted linear growth phase. In Florida, the linear growth phase has been reported to last up to 190 d (Woodard et al., 1993b). Seasona l yields in this study were relatively low. This reduction was likely due to 2011 being the establishment year and stands were still filling in when the growth period began, one fewer harvest for each of the harvesting interval treatments in the establish ment year therefore stems were less developed, a relatively low rate of N fertilization with an organic N source, and the lower than normal rainfall in 2011. The accumulated amount of rainfall during the 8 month establishment and growing period was 670 mm vs. the 30 yr average of 911 mm (Figure 3 1), likely reducing the DM yields of the forages. Yields of DM were decreased by the relatively short growth intervals interrupting light harvesting in the linear growth phase (Woodard and Prine, 1991). Thus whe n growth is interrupted because of harvesting multiple times per season, the reduction in annual forage yield occurs in part due to uncollected solar energy during recovery periods between harvests. Consequently, the more interruptions made during the sea son, the lower the forage yield. The same authors reported that yields decreased by 15 and 30% with 2 and 3 cuttings vs. 1 cutting per season among the tall genotypes. In the present study the DM yields were almost half those obtained by Castillo et al. (2010) possibly because of the differences in the N rate used, differences in the N concentration of the amendments used, and elephantgrass stands were fully established at the start of the trial. Entry PI3 DM did not differ from other tall genotypes in t he first year.

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60 6 wk harvesting intervals Mean DM yield across the 3 harvests for the 6 wk harvesting interval treatment was greater for UF 1 compared with PI3 (2.6 vs. 1.9 Mg ha 1 Table 3 2 and Figure 3 6). The greater yield by UF 1 was accompanied by a lower leaf to stem ratio (1.47 vs. 1.86, Table 3 2 and Figure 3 7). Thus the increased yield of UF 1 was due more to increased stem than to increased leaf. Although stem diameter was not measured, it appeared that the stems of UF 1 were thicker than t hose of PI3 thus accounting for the greater stem weight for UF 1. Yield of DM decreased linearly with increasing harvest number, with yields being 3.3, 2.3, and 1.3 Mg ha 1 for harvests 1, 2, and 3, respectively (Table 3 2 and Figure 3 8). Similar resu lts were reported by Calhoun and Prine (1985), Vincent Chandler et al. (1959), Vlez Santiago and Arroyo Aguil (1981), Woodard and Prine (1991), and Boonman (1993). This may be attributed partly to shorter days and reduced solar energy available to suppo rt plant growth and perhaps a reduction in plant vigor with repeated harvests. As with the entry effect, the decreasing DM yield with increasing harvest number was accompanied by increasing ratio of leaf to stem (1.12, 1.38, and 2.50 for harvest 1, 2, and 3, respectively; quadratic harvest effect, P < 0.001; Table 3 2 and Figure 3 9). This increase in leaf to stem ratio with increasing harvest number was greater for PI3 compared to UF 1 (entry by linear harvest number interaction, P = 0.02; Table 3 2 and Figure 3 14). The difference in leaf to stem ratio between the entries was 0.2 units at the first harvest but increased to 0.6 units by the third harvest (Figure 3 10). Yield of DM increased with increasing amount of N applied for each harvest except the first harvest (quadratic harvest by linear effect of N rate interaction, P = 0.04, Table 3 2 and Figure 3 11). Yield of DM from the first harvest was unaffected by rate of N

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61 applied. This was due most likely to the time lag following first manure applicat ion before N mineralization began. There also may have been a seasonal component to N release from manure. Municipal biological solids applied in summer resulted in 22% more mineralization than when applied in spring (Castillo et al., 2011). Mineralizati on in summer was greater due to higher temperatures and soil moisture. Soil microorganisms are mesophylic hence their optimal growth range is 25 to 37 C (Jarvis et al., 1996). Therefore mineralization is enhanced in warmer summer months. In order to mini mize volatilization of N that is rapid within 24 to 30 hours after application (Lalor et al., 2010), dairy manure was incorporated into the soil with a gas powered tiller within 1 hour after application. Similarly, in the present study, dairy manure was in corporated within 3 hours after application. Castillo et al. (2011) reported that elephantgrass fertilized with MBS had % greater yield if the MBS were soil incorporated vs. broadcast on the soil surface. Soil incorporation of organic amendments increase s NH4 N into the soil due to reduced NH3 volatilization and enhances mineralization. 9 wk harvesting intervals Similar to results of the 6 wk harvesting interval treatment, mean DM yield per harvest for the 9 wk treatment was about 10% greater for UF I co mpared to PI3 (5.0 vs. 4.5 Mg ha 1 P = 0.03, Table 3 3 and Figure 3 12). The greater yield of UF 1 over PI3 was true for both the first and second harvests as entry harvest number interaction was not significant. The yield from the first harvest was o ver twice that of the second harvest (6.4 vs. 3.0 Mg ha 1 P < 0.001, Table 3 3 and Figure 3 13. This greatly reduced DM yield for the second harvest is evidence of the suppression caused by the shorter days and cooler temperatures of the second 9 wk peri od compared with the first period.

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62 As expected, the leaf to stem ratio was greater for the treatment with the lower DM yield. This was true whether speaking of entries PI3 vs. UF 1 (1.06 vs. 0.91, P < 0.001, Table 3 3 and Figure 3 14) or of the second vs. first harvest (1.17 vs. 0.80, P < 0.001, Table 3 3 and Figure 3 15). The increase in leaf to stem ratio may be attributed to less stem elongation associated with a shorter regrowth interval or slower growth rate. These results are similar to what Hsu et al. (1990) reported after harvesting elephantgrass every 58, 68 and 88 d. Compared to other studies, however, Velez Santiago and Arroyo Aguilu (1981) found a lower leaf to stem ratio of 0.71 upon harvesting elephantgrass every 30 d to a 5 cm stubble heig ht. Sarwar et al. (2006) reported no difference in the leaf to stem ratio of elephantgrass cut every month or every 2 wk (1.33 and 1.34, respectively). In the present study there was a difference because of the relatively longer cutting interval that was being investigated. William and Hanna (1995) reported that PI3 registered a mean leaf to stem ratio of 2.1 from a 2 yr study conducted at Brooksville, FL and Tifton, GA where elephantgrass was defoliated every 5 wk. Their greater ratio was likely due to th e shorter regrowth periods compared to those in the current study. Increasing application of manure N from 0 to 90 kg ha 1 increased DM yield from 4.2 to 5.2 Mg ha 1 but no further increase in yield (4.9 Mg ha 1 ) occurred when 180 kg of N ha 1 was applied (quadratic effect of N application rate, P = 0.02, Table 3 3 and Figure 3 16). This decreasing rate of response of yield to increasing N rate application was evident for the 6 wk harvesting interval treatment as well (Figure 3 11). Possibly, more of the N applied is volatilized as NH 3 when more manure N was applied. This decreasing rate of return of yield to increasing N application rate needs further

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63 investigation. The leaf to stem ratio response to N application rate (Figure 3 17) was mediated by the DM yield response to N application rate (Figure 3 16), namely the leaf to stem ratio was greatest at the lowest DM yield. Chemical C o mposition of PI300086 and UF 1 Elephantgrasses Harvested every 6 W eeks The % DM of PI3 was slightly greater than that of UF 1 (18.2 vs. 17.2%, P < 0.001, Table 3 4 and Figure 3 18. Plants from first, second and third harvest had 15.6, 16.1, and 21.4% DM (quadratic effect of harvest, P < 0.001, Table 3 4 and Figure 3 19). These responses followed those of leaf to stem ratio s to elephantgrass entry and harvest number (Figures 3 7 and 3 8) suggesting that the stems contained more moisture than the leaves. Although the concentration of OM increased linearly from 94.0 to 94.3 to 94.5% with increasing harvest number (P < 0.001), the increase was only slight and probably not biologically important (Table 3 4 and Figure 3 20). This too could be a result of increasing leaf to stem ratio that arose as harvest number increased suggesting that leaf material contains slightly less mine ral than stem material. Entry UF 1 had a greater concentration of CP than PI3, (9.70 vs. 9.16%, P = 0.03, Table 3 4 and Figure 3 21). The first, second and third harvests had 8.38, 9.62 and 10.27% CP, respectively (linear effect, P < 0.001, Table 3 4 and Figure 3 22). This was likely due to increasing leaf to stem ratio with increasing harvest number and also enhanced uptake of N from dairy manure due to an expanding root system with age of the plants. Applying more N as manure did not affect the CP conce ntration of the plants. The additional nutrients apparently were used for growth (Figure 3 11) rather than changing CP concentration. The lack of CP response with increasing N rate is not

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64 consistent with some studies like that of Boonman (1993) who repor ted that herbage CP increased from 60 to 120 g kg 1 of DM when fertilization was increased from zero to 800 kg of N ha 1 Also Spitaleri et al. (1995) fertilized elephantgrass with 32 or 72 kg of N ha 1 and incorporated it in the soil by disking. Silage m ade from 6 wk regrowth had greater CP concentration than 12 wk regrowth (16.2 vs. 9.2% DM basis). Therefore, the lack of response of these elephantgrass entries to increasing N rate is unclear but it may be due to the relatively low N rates applied and th e use of an organic N source. Concentration of NDF ranged from 60.8 to 68.7% (DM basis, Table 3 4). The concentration of NDF in the current study was lower than that reported by Manyawu et al. (2003) of 75.9% NDF for samples harvested at 6 wk intervals. This may be due to the use of different elephantgrass entries in the two studies. Elephantgrass UF 1 tended to contain less NDF than did PI3 (63.5 vs. 64.1%, DM basis, P = 0.06, Table 3 4 and Figure 3 30). These results cannot be attributed to differences in leaf to stem ratio becau se UF 1 had a smaller ratio of leaf to stem (Figure 3 7) but a lower NDF concentration suggesting that the stem of UF 1 is lower in NDF than the stem of PI3. Concentration of NDF decreased by 4.2 percentage units from the first to second harvest whereas t he decrease in NDF concentration was only 1.8 percentage units from the second to the third harvest (quadratic effect, P = 0.001, Table 3 4 and Figure 3 23). Findings agree with Manyawu et al. (2003) who reported that NDF concentration increased with age being 75.9 and 78.5% when cut at 6 and 8 wk intervals, respectively. Decreasing concentration of NDF with increasing harvest number matched with decreasing DM yield (Figure 3 8) and increasing leaf to stem ratio (Figure 3 9). Similar to the NDF respons e, concentration of ADF was greatest for the first

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65 harvest (36.4%) and least for the third harvest (32.7%, DM basis; quadratic effect, P = 0.01; Table 3 4 and Figure 3 24). Despite having more stem material (Figure 3 6), UF 1 had a greater mean IVOMD coe fficient than PI3 (64.6 vs. 63.8%, P = 0.03, Table 3 4 and Figure 3 35). Plants from the third harvest had a better mean IVOMD value (64.9%) than those from the first 2 harvests (quadratic effect, P = 0.05, Table 3 4 and Figure 3 36). This pattern is co nsistent with that of ADF concentration (Figure 3 24) Because ADF has a greater concentration of lignin than does NDF and lignin is generally considered indigestible, IVOMD and ADF values should be related negatively. This IVOMD response due to harvest nu mber also appears to match with the leaf to stem ratio (Figure 3 9) although a greater increase in IVOMD values were expected for the third harvest since the leaf to stem ratio approximately doubled. Chemical Composition o f Pi300086 a nd UF 1 Elephantgrasses Harvested e very 9 Weeks Many of the treatment effects detected for the 6 wk harvesting interval were detected also for the 9 wk harvesting interval. Concentration of DM was less for UF 1 compared with PI3 (22.4 vs. 20.1%, P < 0.001, Tables 3 5 and Figure 3 27) and for the first compared to the last harvest (18.9 vs. 23.6%, P < 0.001, Table 3 5 and Figure 3 28). Concentration of OM ranged from 95.1 to 96.5% (Table 3 5) across treatments with treatment effect of entry and N rate being so sma ll and likely having little biological influence (Figures not shown). Although not tested against the 6 wk harvest, the mean CP concentration of the plants harvested at 9 wk intervals was 3 percentage units lower than plants harvested at 6 wk intervals ( 9.43 vs. 6.36%, DM basis). Much of the quadratic N fertilization rate

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66 by harvest number interaction effect on concentration of CP (P = 0.05, Figure 3 29) can be explained by a changing leaf to stem ratio. When N rate was 0 kg ha 1 CP concentration was g reater for the second compared to the first harvest (6.91 vs. 5.87%, DM basis) and the corresponding leaf to stem ratio was 1.32 vs. 0.82, respectively. The CP concentrations did not differ between harvests when fertilized with 90 or 180 kg ha 1 and the l eaf to stem ratios were closer, namely 0.8 vs. 1.1 for both 90 and 180 kg of N ha 1 rates (Figure 3 17). As with the 6 wk harvesting interval, PI3 had greater mean NDF concentration than UF 1 (66.7 vs. 65.5%, DM basis, P = 0.02, Table 3 5 and Figure 3 30) This is in spite of a greater leaf to stem ratio for PI3 (Figure 3 14). Concentration of NDF for the plants harvested at 6 wk intervals was 63.8% (DM basis). This lower value for the less mature plants agrees with Manyawu et al. (2003) who reported ND F values of 75.9 and 78.5% for plants harvested at 6 and 8 wk intervals, respectively. Concentration of ADF was slightly greater for UF 1 vs. PI3 (37.9 vs. 37.0%, Figure 3 31), for first vs. second harvest (38.4 vs. 36.5%, Figure 3 32), and for plants re ceiving the most N fertilizer (37.0, 37.2, and 38.1% for 0, 90, and 180 kg ha 1 respectively, Figure 3 33). Cultivar and harvest number effects are reflective of leaf to stem ratio with the greater leaf to stem ratios associated with lower ADF values. H owever, the increasing concentration of ADF with increasing addition of N fertilizer cannot be explained by changing leaf to stem ratio (no differences, Table 3 4) or yield (similar yields for plants fertilized with 90 or 180 kg of N ha 1 Table 3 4). Mea n IVOMD coefficient was 57.4% for plants harvested at 9 wk intervals which was lower than the mean of 64.2% for plants harvested at 6 wk intervals (Table 3 5).

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67 Unlike plants harvested at 6 wk intervals, IVOMD values did not reflect ADF patterns of 9 wk pl ants as IVOMD was not affected by cultivar or harvest number. Plants fertilized with 90 kg of N ha 1 had greater IVOMD than those receiving 0 or 180 kg of N ha 1 (56.9, 59.0, and 56.4% for 0, 90, and 180 kg of N ha 1 quadratic effect, P = 0.02, Figure 3 3 4). Findings concur with those of Vendramini et al. (2010) who reported lower true digestibility of Merkeron elephantgrass compared to 8 other C4 grasses (60 vs. 65%). Spitaleri et al. (1995) also reported that IVOMD decreased with age of elephantgrass, being 66.7 and 56.0% for 6 and 12 wk regrowth, respectively. Lag, Rate, and Extent of In Vitro Organic Matter Digestibility Lag time is defined as the time required for microbial digestion of feeds to begin. It usually occurs in vitro rather than in sit u. This may be because the microorganisms have been transferred from the rumen of the cow to the laboratory, mixed with artificial saliva, bubbled with CO2, and transferred to a substrate, and incubated. The shock of the procedures may contribute to the lag time observed in vitro. Lag time ranged from 8.5 to 10.6 h and was not affected by any treatment (Table 3 6). Digestion rate of OM was greater for UF 1 compared to PI 3 (0.035 vs. 0.033 h 1 P = 0.01,Table 3 6 and Figure 3 35) indicating that UF 1 wi ll create less fill in the rumen than PI3. Unexpectedly, the OM of plants harvested at 9 wk intervals had a faster digestion rate compared to those harvested at 6 wk intervals (0.036 vs. 0.032 h 1 P = 0.001,Table 3 6 and Figure 3 36). Normally the less mature plant is more digestible. This is illustrated in the 96 h IVOMD values of 65.5 vs. 57.8% for plants from the 6 and 9 wk intervals, respectively (P < 0.001, Figure 3 37). This improvement can be attributed to a greater leaf to stem ratio and great er CP concentration of the 6 wk compared to the 9 wk harvest interval.

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68 Fertilizing with more N did not affect extent of OM digestion of plants harvested at 6 wk intervals, but IVOMD values were lower for 9 wk interval plants when fertilized with 180 kg o f N ha 1 compared with 0 or 90 kg of N ha 1 (harvest interval by quadratic N rate interaction, P < 0.01, Table 3 6 and Figure 3 38). It is unclear why fertilizing with 180 kg of N ha 1 would reduce exent of OM digestion. Silage, Chemical Composition, and D igestibility Pre ensiled UF 1 contained more WSC compared to PI3 (3.67 vs. 3.12%, DM basis, P < 0.001, Table 3 7 and Figure 3 39. These WSC values are in the same range as reported by Woodard et al. (1991), Hsu (1990), and Mtengeti et al. (2006). Elepha ntgrass harvested every 6 wk contained greater concentrations of WSC than elephantgrass harvested every 9 wk (3.73% vs. 3.05%, P < 0.001, Table 3 7 and Figure 3 40) which is inverse of the pattern of NDF response. Silage pH values were quite low, < 4.0, indicative of good quali ty silage (Table 3 7). Silage made from 9 wk regrowth had a slightly more acidic pH, 3.62 vs. 3.71 (P < 0.01, Figure 3 41). This could be attributed to low buffering capacity compared to the 6 wk regrowth interval. In agreement w ith the low pH values, concentration of lactic acid was at the high end of the normal range, mean of 9.4% (DM basis). These results suggest a homolactic acid type of bacterial fermentation as they are within the normal pH range of 3 4. Mtengeti et al. (2 006) added juice from crushed derinded sugarcane stems at 10% of forage wet weight and found that concentration (g kg 1 ) of lactic acid increased to 2.19 for unwilted and to 1.47 for wilted elephantgrass. Yahaya et al. (2004) also studied additives for i m proving elephantgrass silage. They evaluated the effectiveness of adding (5% w/v) fermented juice of lactic acid bacteria collected and grown from chopped elephantgrass (24.6% DM) and a commercial acetic acid powder

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69 on silage quality. Adding lactic acid b acteria reduced pH from 5.45 to 4.33 and increased lactic acid concentration from 0.94 to 3.47% of OM. Concentration of acetic acid was greater for 6 than 9 wk elephantgrass (1.87 vs. 1.02%, DM basis, P = 0.02, Table 3 7 and Figure 3 42). The results are similar to Woodard et al. (1991) who found that acetic acid concentration generally increased as harvest frequency increased with concentrations ranging from 0.25 to 1.58% for PI 300086 and Merkeron. Winter Survival Woodard and Prine (1991) reported a decrease in yield of PI3 in the subsequent year due to loss of stand that occurred during winter. Similar loss of stand occurred in the present study (Table 3 8). The UF 1 entry exhibited superior winter survival over PI3. Only 4 of 216 UF 1 plants (1. 8%) died over the winter vs. 55 of 216 (25.4%) plants of PI3. Likewise 86.1% of UF 1 plants had > 2 shoots in the spring of 2012 compared with 38.4% of PI3 plants. The 86.1% was brought down by the 9 wk, 180 kg of N ha 1 treatment which only had 61.1% of plants with >2 shoots. Less robust plants of PI3 may be attributed to lower nonstructural carbohydrate content, less rhizome mass, and lower N concentration in storage organs. Persistence is among the important attributes to be considered when choosing forages in areas such as the subtropics which are often characterized by freezing temperatures in the winter season that might result in the elimination of an entire forage population. Thus cultivars of elephantgrass that persist throughout the winter are ideal as costs for sourcing seed and seedbed preparation are minimized.

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70 Efficiency of Nitrogen Uptake by Plants Fertilized w ith Dairy Cow Manure After correcting for plant N in plots receiving no fertilization, efficiency of N uptake ranged from 18.5 to 2 6.8% with an average value of 24.4% (Table 3 9). Plants were most efficient at N uptake when fertilized at a 90 kg of N ha 1 rate (Table 3 9). Fertilizing with 180 kg of N ha 1 resulted in an average N efficiency of 9.8%. Harvesting frequency nor entry seemed to affect N uptake. Greater DM yields recorded for 9 wk harvesting intervals were primarily responsible for the greater N uptake. Nutrient removal of high yielding stands can be very high. In the absence of fertilizer in East Africa, elephantgrass yields dropped rapidly starting in the second year after planting (Boonman, 1993). Because of reduced yields, Woodard and Prine (1990) recommended annual N P K fertilizer rates of 225 25 90 kg ha 1 for Merkeron, a tall cultivar. Also Mannetje (1992) summ arized that high yields and persistence of elephantgrass requires a rich supply of nutrients, especially when cut frequently. He suggested that nutrient removal per Mg of DM is 10 to 30 kg of N. Summary Entry UF 1 produced more DM during the season than P I3. In addition, 9 wk harvesting intervals consistently registered more DM yield than 6 wk harvests. Applying 90 vs. 0 kg of N ha 1 yr 1 increased DM yields but applying 180 kg of N ha 1 yr 1 did not increase yields beyond that produced by the 90 kg N rate. It can be concluded therefore, that UF 1 performed better than PI3 in terms of DM productivity, considering that at both defoliation frequencies, UF 1 produced more DM than PI3 and also produced more DM at all N fertilization rates than PI3. The lea f to stem ratio inversely followed DM yield. Namely, it was consistently greater in PI3 than in UF 1 in 6 wk (1.86 vs. 1.47) and in 9 wk harvesting intervals (1.06

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71 vs. 0.91), in last vs. first harvest of the season (2.50 vs. 1.12 for 6 wk harvests and 1.1 7 vs. 0.80 for 9 wk harvests), and when increased N fertilization rate increased yield. It increased linearly in both entries with increasing harvest number with PI3 increasing more than UF 1. Entry UF 1 contained less DM, less NDF, and a more rapidly di gestible OM in vitro than PI3 when harvested at either 6 or 9 wk intervals and contained more CP and digestible OM than PI3 when harvested at 6 wk intervals. As plants were harvested later in the growing season, the concentration of DM increased and ADF decreased for both harvesting intervals. Only the plants harvested every 6 wk had increased concentration of CP and digestible OM with the later harvest. Applying 0, 90, or 180 kg of N ha 1 did not influence concentration of CP but IVOMD of 9 wk plants was improved when 90 kg of N ha 1 were applied. Harvesting at 6 vs. 9 wk intervals improved extent of IVOMD from 57.8 to 65.5%. Fertilizing with 90 kg of N ha 1 yr 1 resulted in better N uptake from dairy cow manure than when a 180 kg rate was used. Gr eater DM yields were mainly responsible for the greater N uptake because CP concentration of the plants was not increased by increasing N fertilizer. Therefore, in this study, a modest fertilization regime (90 kg N ha 1 yr 1 ) was adequate for higher yields of UF 1 in the first year of harvest Although fresh UF 1 contained more WSC, both UF 1 and PI3 made excellent silage in 150 liter drums when directly ensiled without wilting based upon low pH values, high lactic acid concentrations, and low butyric acid concentrations. However high water concentration of the direct cut material (~20% DM) make it necessary to wilt prior to ensiling on a practical basis.

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72 For cold weather tolerance, UF 1 proved to be much better than PI3 as very few plants died (2 vs. 25%) after the 2011 to 2012 winter season. Results of the current study indicate that UF 1 is a better candidate for forage than PI3 for the subtropics because UF 1 recorded greater DM yields for the season regardless of harvesting interval and N fertilization regimes using dairy cow manure. In addition, it had a greater concentration of CP and the OM was more extensively and rapidly digested. Also UF 1 displayed good cold tolerance for long term survival.

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73 Table 3 1 Effect of N fertilization rate and harvest i nterval on seasonal dry matter (DM) yield of PI300086 and UF 1 elephantgrasses PI300086 UF 1 6 week harvests 9 week harvests 6 week harvests 9 week harvests Measure 0 kg of N h a 1 90 kg of N h a 1 180 kg of N h a 1 0 kg of N h a 1 90 kg of N h a 1 180 kg of N h a 1 0 kg of N h a 1 90 kg of N h a 1 180 kg of N h a 1 0 kg of N h a 1 90 kg of N h a 1 180 kg of N h a 1 SEM Yield, kg of DM h a 1 a 52 10 643 0 590 0 8000 93 90 951 0 728 0 770 0 816 0 924 0 112 80 100 30 497 a Effect of entry, P < 0.001. Effect of harvest frequency, P < 0.001. Effect of N fertilization rate quadratic, P = 0.02.

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74 Table 3 2 Effect of N fertilization rate on dry matter (DM) yield and leaf to stem ratio of PI300086 and UF 1 elephantgrasses harvested at 6 wk intervals PI300086 UF 1 Harvest number 0 kg of N h a 1 90 kg of N h a 1 180 kg of N h a 1 0 kg of N h a 1 90 kg of N h a 1 180 kg of N h a 1 SEM Yield, kg of DM h a 1 a 1 st 284 0 30 50 28 30 370 0 367 0 345 0 19 3 2 nd 1 500 2160 187 0 23 40 248 0 317 0 19 3 3 rd 8 70 12 30 120 0 125 0 155 0 15 40 19 3 Leaf:stem DM basis b 1 st 1.26 1.22 1.21 0.93 1.04 1.04 0.11 2 nd 1.70 1.44 1.56 1.30 1.13 1.13 0.11 3 rd 2.72 2.75 2.89 2.36 2.15 2.16 0.11 a Effect of entry, P < 0.001. Effect of harvest linear, P < 0.001. Effect of N rate linear, P = 0.02. Effect of harvest quadratic by N rate linear interaction, P = 0.04. b Effect of entry, P < 0.001. Effect of harvest quadratic, P < 0.001. Effect of cultivar by harvest linear i nteraction, P = 0.02.

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75 Tab l e 3 3 Effect of N fertilization rate on dry matter (DM) yield and leaf to stem ratio of PI300086 and UF 1 elephantgrasses harvested at 9 wk intervals PI300086 UF 1 Measure Harvest number 0 kg of N ha 1 90 kg of N ha 1 180 kg of N ha 1 0 kg of N ha 1 90 kg of N ha 1 180 kg of N ha 1 SEM Yield, kg of DM ha 1 a 1 st 53 80 651 0 64 80 559 0 79 10 677 0 399 2 nd 26 20 287 0 30 40 30 30 337 0 325 0 399 Leaf:stem DM basis b 1 st 0.91 0.85 0.89 0.73 0.69 0.71 0.05 2 nd 1.42 1.08 1.18 1.22 1.05 1.05 0.05 a Effect of entry, P = 0.03. Effect of harvest, P < 0.001. Effect of N rate quadratic, P = 0.02. Effect of harvest by N rate quadratic interaction, P = 0.07. b Effect of entry, P < 0.001. Effect of harvest, P < 0.001. Effect of N rate quadratic, P < 0.01. Effect of harvest by N rate linear interaction, P = 0.02.

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76 Table 3 4 Effect of N fertilization rate on chemical composition of PI300086 and UF 1 elephantgrass es harvested at 6 wk intervals PI300086 UF 1 Harvest number 0 kg N ha 1 90 kg N ha 1 180 kg N ha 1 0 kg N ha 1 90 kg N ha 1 180 kg N ha 1 SEM Dry 1 st 16.4 16.9 15.5 14.9 14.7 15.3 0.4 matter, a 2 nd 17.1 16.7 16.1 15.7 15.2 15.8 0.4 % 3 rd 21.7 21.7 21.7 21.3 21.0 20.9 0.4 O M, b % of DM 1 st 94.6 94.1 93.9 93.7 94.0 93.9 0.3 2 nd 94.0 94.7 94.2 94.3 94.2 94.3 0.3 3 rd 94.6 94.8 94.6 94.5 94.5 94.3 0.3 CP, c % of DM 1 st 8.2 8.2 8.6 7.7 9.3 8.3 0.5 2 nd 8.9 9.1 9.1 10.0 10.6 10.0 0.5 3 rd 9.7 10.4 10.2 10.5 10.6 10.2 0.5 NDF, d % of DM 1 st 66.9 67.8 68.7 66.6 66.2 67.1 0.7 2 nd 62.3 64.3 63.0 63.3 62.2 63.1 0.7 3 rd 61.4 61.2 61.6 60.9 60.8 61.6 0.7 ADF, e % of DM 1 st 36.3 36.1 37.1 36.3 35.9 36.4 0.5 2 nd 34.0 35.6 34.8 35.7 35.4 35.9 0.5 3 rd 32.4 32.4 32.6 32.9 32.7 33.1 0.5 IVOMD f % 1 st 64.7 63.4 62.6 63.5 65.4 64.5 0.8 2 nd 63.6 63.6 61.9 65.1 64.1 63.6 0.8 3 rd 63.9 64.6 65.5 65.5 65.2 64.9 0.8 a Effect of entry, P < 0.001; Effect of harvest quadratic, P < 0.001. b Effect of harvest linear, P < 0.01. c Effect of entry, P = 0.03; Effect of harvest linear, P = 0.001. d Effect of entry, P = 0.06; Effect of harvest quadratic, P = 0.001. e Effect of ha rvest quadratic, P = 0.01. f Effect of entry, P = 0.03; Effect of harvest quadratic, P = 0.05.

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77 Table 3 5 Effect of N fertilization rate on chemical composition of PI300086 and UF 1 elephantgrass es harvested at 9 wk intervals PI300086 UF 1 Harvest number 0 kg N ha 1 90 kg N ha 1 180 kg N ha 1 0 kg N ha 1 90 kg N ha 1 180 kg N ha 1 SEM Dry matter a 1 st 20.6 19.3 20.4 18.0 17.4 17.6 0.6 % 2 nd 25.1 24.2 24.7 22.7 22.0 22.7 0.6 O M, 1 st 95.5 95.2 95.7 95.4 95.4 95.5 0.3 % of DM b 2 nd 96.5 95.1 95.7 95.1 95.1 95.3 0.3 CP, c 1 st 5.9 6.8 5.8 5.9 6.2 6.4 0.4 % of DM 2 nd 6.4 5.8 6.4 7.4 6.5 6.6 0.4 NDF, d 1 st 67.9 65.6 67.3 66.3 65.0 65.8 0.8 % of DM 2 nd 66.2 66.1 66.8 64.2 65.3 66.5 0.8 ADF, e 1 st 37.6 37.8 38.6 38.9 38.3 39.4 0.5 % of DM 2 nd 35.5 35.6 36.8 36.0 37.0 37.7 0.5 IVOMD f 1 st 56.2 58.6 56.3 57.9 58.4 57.6 1.4 % 2 nd 55.0 60.2 54.9 58.7 58.7 56.9 1.4 a Effect of entry, P < 0.001. Effect of harvest, P < 0.001. Effect of N rate quadratic, P = 0.04. b Effect of entry, P = 0.05. Effect of N rate quadratic, P = 0.03. c Effect of N rate linear by harvest interaction, P = 0.05. d Effect of entry, P = 0.02 e Effect of entry, P = 0.01. Effect of N rate linear, P < 0.01. Effect of harvest, P < 0.001. f Effect of N rate quadratic, P = 0.02.

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78 Table 3 6 Effect of N fertilization rate and harvesting interval on lag, rate, and extent of OM digestion of P I300086 and UF 1 elephantgrasses PI300086 UF 1 Harvest frequency 0 kg N ha 1 90 kg N ha 1 180 kg N ha 1 0 kg N ha 1 90 kg N ha 1 180 kg N ha 1 SEM Lag, h 6 week 8.9 8.5 9.2 9.0 8.5 9.3 0.5 9 week 9.3 10.6 9.1 9.3 8.9 9.2 0.5 Digestion rate, a h 1 6 week 0.032 0.030 0.032 0.033 0.036 0.032 0.002 9 week 0.031 0.035 0.037 0.038 0.036 0.038 0.002 Extent of slowly degradable OM, b % 6 week 9 week 53.5 47.7 54.6 45.7 55.5 43.3 53.2 44.4 52.2 46.4 54.8 43.5 1.2 1.2 Extent of OM digestion, c % 6 week 9 week 65.5 58.3 65.2 58.5 65.9 55.5 65.3 57.9 64.8 59.4 65.9 56.9 0.7 0.7 a Effect of entries, P = 0.01. Effect of harvest interval, P = 0.001. b Effect of harvest interval, P < 0.001. Effect of harvest interval by N rate linear, P = 0.01. c Effect of harvest interval, P < 0.001. Effect of harvest interval by N rate quadratic, P < 0.01.

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79 Table 3 7 Effect of N fertilization rate and harvesting interval on w ater soluble carbohydrates (WSC) of fresh forage and pH and organic acids of silage made using PI300086 and UF 1 elephantgrasses PI300086 UF 1 Measure Harvest frequency 0 kg of N h a 1 90 kg of N h a 1 180 kg of N h a 1 0 kg of N h a 1 90 kg of N h a 1 180 kg of N h a 1 SEM WSC a 6 week 3.54 3.34 3.47 4.21 3.99 3.85 0.24 % of DM 9 week 2.73 2.88 2.73 3.27 3.09 3.57 0.24 pH b 6 week 3.81 3.76 3.78 3.68 3.68 3.74 0.07 9 week 3.5 9 3. 65 3. 5 7 3. 5 9 3. 63 3. 6 7 0.07 O rganic acids, % of DM Lactic acid 6 week 9.93 8.46 8.74 10.78 10.05 10.63 0.89 9 week 7.67 9.45 9.63 10.28 8.87 8.09 0.89 Acetic acid c 6 week 9 week 2.72 1.04 1.20 1.09 2.29 0.54 1.87 0.48 1.78 1.23 1.38 1.72 0.61 0.61 Butyric acid 6 week 9 week 0.80 0.04 0.62 0.56 0.10 0.00 0.00 0.06 1.52 0.36 0.09 1.20 0.51 0.51 a Effect of entry, P < 0.001. Effect of harvest frequency, P < 0.01. b Effect of harvest frequency, P < 0.001. c Effect of harvest frequency, P = 0.02.

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80 Table 3 8 Stand persistence of PI300086 and UF 1 during the winter of 2011 12 Entry Harvest interval N, kg ha 1 % dead a % weak b % robust c PI3 6 week 0 27.8 38.9 33.3 90 30.6 33.3 36.1 180 30.6 30.1 33.3 9 week 0 13.9 36.1 50 90 30.6 41.7 27.8 180 19.4 30.6 50 M ean 25.4% (55/216) 35.1% (76/216) 38.4% (83/216) UF 1 6 week 0 0 8.3 91.7 90 0 11.1 88.9 180 0 8.3 91.7 9 week 0 0 11.1 88.9 90 0 5.6 94.4 180 11.1 27.8 61.1 M ean 1.8% (4/216) 12.0% (26/216) 86.1% (186/216) a No green shoots. b 1 2 green shoots. c > 2 green shoots.

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81 T able 3 9 Efficiency of N uptake by PI300086 and UF 1 elephantgrasses harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 PI300086 UF 1 Harvest interval N fertilization rate, kg ha 1 yr 1 N applied, kg ha 1 N harvested, kg ha 1 Efficiency of N removal, % SD N harvested, kg ha 1 Efficiency of N removal, % SD 6 wk 0 0 7 3 10 5 90 69 9 1 2 6.6 4 .0 123 26.8 31.7 180 138 86 9.5 4.6 12 2 12.3 14.5 9 wk 0 0 7 7 99 90 60 8 8 1 8.5 26.8 114 25.7 2.4 180 120 9 2 1 2.5 7.5 105 5.1 16.0

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82 Figure 3 1 Monthly totals of rainfall and a bsolute minimum temperature at the University of Florida Agronomy Forage Research Unit during 2011 2012 and a 30 yr average. Data were t aken from http://climatecenter.fsu.edu/products services/data/1981 2010 normals/gainesville and http://fawn.ifas.ufl.edu/data/reports/?res

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83 Block 1 4m 4m 4m UF 1 0 kg of N h a 1 9 wk 3 m PI 3 90 kg of N h a 1 6 wk 3 m UF 1 180 kg of N ha 1 6 wk 3 m plot 1 plot 8 plot 9 8 m 8 m 8 m PI 3 UF 1 PI 3 plot 2 plot 7 plot 10 3m 3m 3m PI 3 180 k g of N ha 1 9 wk 3 m UF 1 0 kg of N ha 1 6 wk 3 m UF 1 90 kg of N ha 1 9 wk 3 m plot 3 plot 6 plot 11 8 m 8m 8 m UF 1 PI 3 PI 3 plot 4 plot 5 plot 12 Ma in plot : 8 m by 4 m = 32 m Su bplot : 4 m by 4 m = 16 m Row length : 4 m Number of plants per row : 6 Distance between plants in a row (planting stations) : 0.67 m Plant population main plot : 6 plants / row 8 rows = 48 Plant population subplot : 6 plants/row 4 rows = 24 Plant population/block : 6 main plots/block 48 = 288 Plant population for 3 blocks : 3 288 = 864 Plant population per cultivar = 864 for 2 cultivars = 432 Figure 3 2 Experimental plot layout for one block. Block was repeated three times

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84 Figure 3 3 Total seasonal dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrass es harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 (n = 3)

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85 Figure 3 4 Total seasonal dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrass es harvested at 6 or 9 wk interva ls and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 (n = 3)

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86 Figure 3 5 Total seasonal dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrass es harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 (n = 3)

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87 Figure 3 6 Dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrass es when harvested at 6 wk intervals Data are means across 3 replicates (n = 9) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

PAGE 88

88 Figure 3 7 Leaf to stem ratio of PI300086 (PI3) and UF 1 elephantgrasses when harvested at 6 wk intervals. Data are means across 3 replicates (n = 9) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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89 Figure 3 8 Dry matter (DM) yield of PI3 and UF 1 elephantgrass es harvested 3 times in a season at 6 wk intervals. Data are means across 3 replicates (n = 18) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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90 Figure 3 9 L eaf to stem ratio of PI3 and UF 1 elephantgrass es harvested 3 times in a season at 6 wk intervals. Data are means across 3 replicates (n = 18) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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91 Figure 3 10 Leaf to stem ratio of PI300086 (PI3) and UF 1 elephantgrasses harvested 3 times in a season at 6 wk intervals. Data are means across 3 replicates (n = 9) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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92 Figure 3 11 Dry matter (DM) yield of PI3 and UF 1 elephantgrass es harvested 3 times in a season at 6 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 Data are means across 3 replicates (n = 6) for each fertilization rat e and harvest.

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93 Figure 3 12 Dry matter (DM) yield of PI300086 (PI3) and UF 1 elephantgrasses when harvested at 9 wk intervals. Data are means across 3 replicates (n = 9) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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94 Figure 3 13 Dry matter (DM) yield of elephantgrass harvested 2 times in a season at 9 wk intervals. Data are means across 3 replicates (n = 18) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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95 Figure 3 14 Leaf to stem ratio of PI300086 (PI3) and UF 1 elephantgrasses when harvested at 9 wk intervals. Data are means across 3 replicates (n = 9) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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96 Figure 3 15 Leaf to stem ratio of elephantgrass harvest ed 2 times in a season at 9 wk intervals. Data are means across 3 replicates (n = 18) with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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97 Figure 3 16 Dry matter (DM) yield of PI3 and UF 1 elephantgrass es harvested 2 times in a season at 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 Data are means across 3 replicates (n = 6) for each fertilization rate.

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98 Figure 3 17 L eaf to stem ratio of elephantgrass es harvested 2 times in a season at 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 Data are means across 3 replicates (n = 18) for each fertilization rate.

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99 Figure 3 18 Dry matter (DM) concentration of PI300086 (PI3) and UF 1 elephantgrasses harvested at 6 wk intervals. Data are means across 3 replicates (n = 9) for each entry with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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100 Figure 3 19 Dry matter (DM) concentration of elephantgrass es harvested 3 times in a season at 6 wk intervals. Data are means across 3 replicates (n = 18) for each harvest with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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101 Figure 3 20 Organic matter (OM) concentration of elephantgrass es harvest ed 3 times in a season at 6 wk intervals. Data are means across 3 replicates (n = 18) for each harvest with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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102 Figure 3 21 Crude protein (CP) concentration of PI300086 (PI3) and UF 1 elephantgrasses harvested at 6 wk intervals. Data are means across 3 replicates (n = 9) for each entry with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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103 Figure 3 22 C rude protein (CP) concentration of elephantgrass harvested 3 times in a season at 6 wk intervals. Data are means across 3 replicates (n = 18) for each harvest with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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104 Figure 3 23 Neutral detergent fiber (NDF) concentration of elephantgrass harvested 3 times in as season at 6 wk intervals. Data are means across 3 replicates (n = 18) for each harvest with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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105 Figure 3 24 Acid detergent fiber (ADF) concentration of elephantgrass harvested 3 times in a season at 6 wk intervals. Data are means across 3 replicates (n = 18) for each harvest with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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106 Figure 3 25 In vitro organic matter digestibility (IVOMD) of elephantgra ss entries harvested at 6 wk intervals. Data are means across 3 replicates (n = 9) for each entry with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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107 Figure 3 26 In vitro organic matter digestibility (IVOMD) of elephantgrass harvested 3 times in a season at 6 wk intervals. Data are means across 3 replicates (n = 18) for each harvest with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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108 Figure 3 27 Dry matter (DM) concentration of PI300086 (PI3) and UF 1 elephantgrasses harvested at 9 wk intervals. Data are means across 3 replicates (n = 9) for each entry with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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109 Figure 3 28 D ry matter (DM) concentration of two elephantgrass es harvested 2 times in a season at 9 wk intervals. Data are means across 3 replicates (n = 18) for each harvest with plots fertiliz ed with 0, 90, or 180 kg N ha 1 yr 1

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110 Figure 3 29 Crude protein (CP) concentration of two elephantgrass es fertilized with 0, 90, or 180 kg of N ha 1 yr 1 and harvested 2 times in a season at 9 wk intervals. Data are means across 3 replicates (n = 6) for each fertilization rate.

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111 Figure 3 30 Neutral detergent fiber (NDF) concentration of PI300086 (PI3) and UF 1 elephantgrasses harv ested at 9 wk intervals. Data are means across 3 replicates (n = 9) for each entry with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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112 Figure 3 31 Acid detergent fiber (ADF) concentration of PI300086 (PI3) and UF 1 elephantgrasses harvested at 6 wk intervals. Data are means across 3 replicates (n = 9) for each entry with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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113 Figure 3 32 Acid detergent fiber (ADF) concentration of two elephantgrass es harvested 2 times in a season at 9 wk intervals. Data are means across 3 replicates (n = 18) for each harvest with plots fertilized with 0, 90, or 180 kg N ha 1 yr 1

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114 Figure 3 33 Acid detergent fiber (ADF) concentration of PI300086 (PI3) a nd UF 1 elephantgrasses fertilized with 0, 90, or 180 kg of N ha 1 yr 1 and harvest at 9 wk intervals. Data are means across 3 replicates (n = 6) for each fertilization rate.

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115 Figure 3 34 In v itro organic matter digestibility (IVOMD) of PI300086 (PI3) and UF 1 elephantgrasses fertilized with 0, 90, or 180 kg of N ha 1 yr 1 and harvest at 9 wk intervals. Data are means across 3 replicates (n = 3) for each elephantgrass entry and fertilization rate.

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116 Figure 3 35 Organic matter (OM) digestion rate of PI300086 (PI3) and UF 1 elephantgrasses Data are means across 3 replicates (n = 18) for each elephantgrass entry that was harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1

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117 Figure 3 36 Organic ma tter (OM) digestion rate of two elephantgrass es harvested at 6 or 9 wk intervals. Data are means across 3 replicates (n = 18) for each harvesting interval and fertilized with 0, 90, or 180 kg of N ha 1 yr 1

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118 Figure 3 37 E xtent (96 h) of total organic matter (OM) digestion of elephantgrass harvested at 6 or 9 wk intervals. Data are means across 3 replicates (n = 18) for each harvesting interval and fertilized with 0, 90, or 180 kg of N ha 1 yr 1

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119 Figure 3 38 Extent (96 h ) of organic matter (OM) digestion of two elephantgrass es fertilized with 0, 90, or 180 kg of N ha 1 yr 1 and harvested at 6 or 9 wk intervals. Data are means across 3 replicates (n = 6) for each harvesting interval and fertilized rate.

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120 Figure 3 39 Water soluble carbohydrate (WSC) concentration of PI300086 (PI3) and UF 1 elephantgras ses prior to ensiling. Data are means across 3 replicates (n = 18) for each elephantgrass entry that was harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1

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121 Figure 3 40 W ater soluble carbohydrate (WSC) concentration of two elephantgrass es harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 Data are means across 3 replicates (n = 18) for each harvesting int erval.

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122 Figure 3 41 S ilage pH of two elephantgrass es harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 Data are means across 3 replicates (n = 18) for each harvesting interval.

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123 Figure 3 42 Concentration of acetic acid of two elephantgrass silages made with forage harvested at 6 or 9 wk intervals and fertilized with 0, 90, or 180 kg of N ha 1 yr 1 Data are means across 3 replicates (n = 18) for each harvesting interval.

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124 LIST OF REFERENCES Ireland. Dept. of Environ., Heritage and Local Government The Stationery Office 2009. European Communities (Good Agricultural Practice for Protection of Waters) R e gulations. SI 101. Bates, D.B., W.E. Kunkle, C.G. Chambliss, and R.P. Cromwell. 1989. Effect of dry matter and additives on bermudagrass and rhizome peanut round bale silage. J. Prod. Agric. 2:91 96. Bernal, M.P., and H. Kirchmann. 1992. Carbon and nitrogen mineralization and ammonia volatilization from fresh, aerobically and anaerobically treated pig manure during incubation with soil. Biol. Fertil. Soils 13:135 141. Bittman, S., C.G. Kowalenko, D.E. Hunt, and O. Schmidt. 1999. Surface banded and broadcast dairy manure effects on tall fescue yield and nitrogen uptake. Agron. J. 91:826 833. Blaser, R.E., W.G. Kirk, and W.E. Stokes. 1942. Chemical composition and grazing value of na pier grass Pennisetum purpureum Schum. grown under grazing management. Agron. J. 34:167 174. Boddorff, D., and W. R. Ocumpaugh. 1986. Forage quality of Pearl millet*napier grass hybrids and dwarf napiergrass. Soil Crop Sci. Soc. Fla. Proc. 45:170 173. Bogd an, A.V. 1977. Tropical pasture and fodder crops. Tropical agriculture series. Longman Group Ltd., London, UK. Kluwer Academic Publishers, Netherlands. Bouton, J.H. 2002. Bioenergy crop breeding and production research in the Southeast. Final Report for 1996 to 2001. Technical Report. ORNL/SUB 02 19XSV810C/01.http://www.ornl.gov/~webworks/cppr/y2001/rpt/116284.pdf (verified 21 May 2010). Oak Ridge Natl. Lab., Oak Ridge, TN Braschkat, J., T. Mannheim, and H. Marschner. 1997. Estimation of ammonia losses after application of liquid cattle manure on grassland. Z. Pflanzenernaehr. Bodenkd. 160:117 123. Brown, D.L., and E. Chavalimu. 1985. Effects of ensiling or drying on five forage species in western Kenya: Zea mays (maize stover), Pennisetum purpureum (Pakistan napier grass), Pennisetum sp. (bana grass), Impomea batata (sweet potato vines) and Cajanus cajan (pigeon pea leaves). Anim. Feed Sci. Tech. 13:1 6. Butt, M.N., G.B. D onart, M.G. Southward, R.D. Pieper, and N. Mohammad. 1993. Effect of defoliation on plant growth of napier grass. Trop. Sci. 33:111 120.

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135 BIOGRAPHICAL SKETCH Suzgo Charles Chapa earned his Bachelor of Science degree in Animal Science from Bunda College of Agriculture, a constituent of the University of Malawi in 1998. After his graduation Suzgo joined an Agribusiness Development Project in Malawi working there for 4 years. From June 2002 to January 2003, he served as a secondary schoo l teacher with the Ministry of Education in Malawi. Starting in February 2003, Suzgo joined the Ministry of Agriculture and Food Security as a livestock development officer and continues servicing Malawi farmers with this position. In 2010 he was awarded a scholarship from the United States Agency for International Development (USAID) and left Malawi to pursue a M aster of S cience degree in animal sciences at the University of Florida under the guidance of Dr. Charles R. Staples. After graduation he plans o n applying all the knowledge and training he received during his time at the University of Florida to help improve the farming system in Malawi as a mean s to ensure food security.