Persistence of perennial grass crops is essential to their profitable management. Recently, orchardgrass producers in the Mid-Atlantic have reported a reduction in the persistence and regrowth vigor of their swards. The overall objective was to evaluate which factors play a major role in controlling the persistence of orchardgrass harvested for hay in the Mid-Atlantic. A survey of orchardgrass fields, growth chamber experiment, and field experiment were conducted to that end. The objectives were to: (1) assess soil fertility, management practices, disease status, and climate in relation to producer perceived stand persistence rating, orchardgrass biomass, and soil test thresholds in orchardgrass hayfields in 4 states, (2) examine the interactions of high temperature and low cutting height on the physiology and regrowth of orchardgrass in controlled environments, and (3) evaluate yield, composition, and size/density compensation-corrected productivity of orchardgrass and orchardgrass/alfalfa mixtures harvested to four cutting heights over three years. The survey of hayfields indicated that the sward age, soil organic matter, grazing, manure application, and historical average high temperature were main determinants of stand persistence score. In the growth chamber experiment, regrowth was significantly reduced by the 35°C treatment as compared to 20°C. Low cutting height significantly reduced regrowth in the cool temperature treatment, but no effect of cutting height was detected under heat stress. In the field experiment, yields were highest from plots cut to 5 cm, but orchardgrass cover in these plots thinned through the experiment. Tiller size and density measurements indicated that cutting heights of 10 cm or greater were able to achieve and maintain optimal leaf area while productivity was reduced for the 5 cm treatment. Overall, it is apparent that excessively low cutting heights are a major cause of reduced persistence in orchardgrass swards and that high temperature stress will limit regrowth. These factors likely interact with fertility and disease status, and together cause the premature loss of orchardgrass stands. Efforts should be made to communicate the importance of increased cutting height to producers. Breeding of orchardgrass resistant to fungal pathogens and heat stress may be required to sustain an orchardgrass hay industry in the Mid-Atlantic. / Ph. D.

Resumo: O experimento foi conduzido na UNESP - Campus de Botucatu, Faculdade de Medicina Veterinária e Zootecnia. O delineamento experimental foi em blocos ao acaso num arranjo fatorial com três cultivares de Brachiaria brizantha (Marandu, Xaraés e BRS Piatã) e duas alturas de resíduo (15 e 25 cm), no total de seis tratamentos com quatro repetições (parcelas de 20 m2). O período de avaliação foi de um ano (01/12/2007 a 10/12/2008), com a realização de oito cortes, sendo três na primavera, três no verão, um no outono e um no inverno. A produção de massa seca (MS) da Xaraés foi maior no verão e na primavera em relação à Marandu. No somatório do ano a produtividade de MS da Xaraés foi 27,07% superior à Marandu, alcançando valor elevado (20.023 kg/ha), o que demonstra o potencial de utilização deste genótipo, principalmente em sistemas de produção de bovinos de corte mais intensivos. A produção de MS da Piatã nas estações do ano foi semelhante à Marandu, totalizando 17.572 e 15.757 kg/ha, respectivamente. Os dados de produção indicam que a Piatã apresentou a melhor distribuição da forragem produzida ao longo do ano. A produção de forragem das cultivares foi maior na altura do resíduo de 15 cm no verão e inverno, e não diferiu nas alturas de manejo no outono e primavera, demonstrando exigências diferentes de manejo do capim ao longo do ano. Os resultados obtidos confirmam a recomendação e a importância da cultivar Piatã como alternativa de utilização e diversificação das pastagens nos sistemas produtivos. / Abstract: The experiment was conducted in the School of Veterinary Medicine and Animal Science of UNESP - Botucatu Campus. The experimental design was a complete randomized blocks in a factorial arrangement with three cultivars of Brachiaria brizantha (Marandu, Xaraés and BRS Piatã) and two stubble heights (15 and 25 cm), in the total six treatments with four replications (20 m² plots). The evaluation period was of one year (12/01/2007 to 12/10/2008) with eight cuts: three in the spring, three in the summer, one in the fall and one in the winter. The production of dry matter (DM) of Xaraés in summer and spring were higher than Marandu with a total of 27.07% higher DM than Marandu. The total DM production was 20,023 kg/ha, demonstrating the potential of use of the Xaraés cultivar, especially in more intensive systems of beef cattle production. DM production of Piatã in the seasons was similar to Marandu, totalizing 17,572 and 15,757 kg/ha, respectively. The production data indicate that Piatã cultivar had the best distribution of forage produced during the year. The forage production of cultivars was higher in the stubble height of 15 cm in summer and winter, and did not differ for two heights of management in the fall and spring, showing different requirements of grass management during the year. The results confirm the recommendation and the importance of Piatã cultivar as an alternative of use and diversification of pastures in the production systems. / Orientador: Ciniro Costa / Coorientador: Paulo Roberto de Lima Meirelles / Banca: Heraldo César Gonçalves / Banca: Roberto Antonio Rodella / Banca: Cacilda Borges do Valle / Banca: Valdo Rodrigues Hering / Doutor

3 pp. / “Summer slump” is a decline in growth of alfalfa usually beginning in July in areas where maximum daily temperature exceeds 100 °F, such as the low elevation deserts of Southwestern U.S (Fig. 1). In more temperate regions, there is a gradual decrease in alfalfa yield in successive harvests throughout the year, but the yield decline in the summer is not as sharp as in hot summer regions. The term summer slump has also been applied to reduction in growth of perennial cool season grasses such as tall fescue during the summer.

Due to recent climate change and energy consumption concerns, several markets have emerged for agricultural biomass in the province of Ontario, Canada. Understanding variation of residue nutrient concentrations across the province and the causal factors is crucial for determining the feasibility of crop residue use in Ontario. The purpose of this study was to survey variation of Ontario winter wheat, soybean and corn residue nutrient concentrations and removals, as well as to determine the effect of altering cutting height and delaying harvest on the nutrient concentrations and removals of these residues. It was found that across-site nutrient concentration and removal variation were greater than within-site concentration and removal variation, and that site-scale climatological events, such as precipitation, are largely responsible. Concentration and removals differed significantly by year. Variation of nutrient concentration and removal did not correlate with crop grain yield, or soil characteristics such as organic matter, pH or texture. A leaching treatment significantly reduced residue nutrient concentrations and removals, but had no significant effect on the variation among residue samples. Finally, concentrations and removals differed significantly with cutting height and harvested corn component, highlighting the importance of harvest method in the system nutrient balances. / Ontario Soil and Crop Improvement Association, Ontario Ministry of Agriculture Food and Rural Affairs, University of Guelph

Made available in DSpace on 2014-06-11T19:32:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-26Bitstream added on 2014-06-13T21:05:28Z : No. of bitstreams: 1 lupatini_gc_dr_botfmvz.pdf: 341308 bytes, checksum: df486ae1605629080494d4b067f0a6e2 (MD5) / Universidade Estadual Paulista (UNESP) / O experimento foi conduzido na UNESP – Campus de Botucatu, Faculdade de Medicina Veterinária e Zootecnia. O delineamento experimental foi em blocos ao acaso num arranjo fatorial com três cultivares de Brachiaria brizantha (Marandu, Xaraés e BRS Piatã) e duas alturas de resíduo (15 e 25 cm), no total de seis tratamentos com quatro repetições (parcelas de 20 m2). O período de avaliação foi de um ano (01/12/2007 a 10/12/2008), com a realização de oito cortes, sendo três na primavera, três no verão, um no outono e um no inverno. A produção de massa seca (MS) da Xaraés foi maior no verão e na primavera em relação à Marandu. No somatório do ano a produtividade de MS da Xaraés foi 27,07% superior à Marandu, alcançando valor elevado (20.023 kg/ha), o que demonstra o potencial de utilização deste genótipo, principalmente em sistemas de produção de bovinos de corte mais intensivos. A produção de MS da Piatã nas estações do ano foi semelhante à Marandu, totalizando 17.572 e 15.757 kg/ha, respectivamente. Os dados de produção indicam que a Piatã apresentou a melhor distribuição da forragem produzida ao longo do ano. A produção de forragem das cultivares foi maior na altura do resíduo de 15 cm no verão e inverno, e não diferiu nas alturas de manejo no outono e primavera, demonstrando exigências diferentes de manejo do capim ao longo do ano. Os resultados obtidos confirmam a recomendação e a importância da cultivar Piatã como alternativa de utilização e diversificação das pastagens nos sistemas produtivos. / The experiment was conducted in the School of Veterinary Medicine and Animal Science of UNESP - Botucatu Campus. The experimental design was a complete randomized blocks in a factorial arrangement with three cultivars of Brachiaria brizantha (Marandu, Xaraés and BRS Piatã) and two stubble heights (15 and 25 cm), in the total six treatments with four replications (20 m² plots). The evaluation period was of one year (12/01/2007 to 12/10/2008) with eight cuts: three in the spring, three in the summer, one in the fall and one in the winter. The production of dry matter (DM) of Xaraés in summer and spring were higher than Marandu with a total of 27.07% higher DM than Marandu. The total DM production was 20,023 kg/ha, demonstrating the potential of use of the Xaraés cultivar, especially in more intensive systems of beef cattle production. DM production of Piatã in the seasons was similar to Marandu, totalizing 17,572 and 15,757 kg/ha, respectively. The production data indicate that Piatã cultivar had the best distribution of forage produced during the year. The forage production of cultivars was higher in the stubble height of 15 cm in summer and winter, and did not differ for two heights of management in the fall and spring, showing different requirements of grass management during the year. The results confirm the recommendation and the importance of Piatã cultivar as an alternative of use and diversification of pastures in the production systems.