Volatilização de amônia de fontes nitrogenadas com eficiência aumentada em condições de pastagem
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Data
2017-12-07
Autores
Meirelles, Guilherme Constantino
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A pastagem tem se destacado como principal fonte de alimento para pecuária brasileira pela sua extensa área e baixo custo de produção. A aplicação de nitrogênio na pastagem está associada diretamente com o aumento de produção de matéria seca, bem como incremento na qualidade da forragem, contribuindo na manutenção da capacidade produtiva. O experimento foi realizado no campo experimental da Faculdade de Ciências Agrárias e Tecnológicas, Campus de Dracena, com o objetivo de avaliar fontes nitrogenadas convencionais e com eficiência aumentada na volatilização de amônia e seus efeitos na produção de pastagem de Urochloa decumbens (syn. Brachiaria decumbens). O delineamento experimental foi em blocos ao acaso com quatro repetições, em esquema fatorial 4x2+1. As parcelas constituíam de 4 fontes nitrogenadas (ureia, nitrato de amônia, ureia + NBPT, ureia + B e Cu), com duas doses de nitrogênio (100 e 200 kg ha-1), acrescido um tratamento sem adubação nitrogenada (controle). As doses nitrogenadas foram parceladas em 5 aplicações iguais (20 e 40 kg ha-1), sendo a primeira após o corte de uniformização e as demais após os cortes imediatamente subsequentes. A aplicação das fontes e doses de nitrogênio afetaram a produção acumulada de massa seca e lâminas foliares de capim decumbens no primeiro e segundo ano de condução do experimento. A quantidade de N, P, K, Ca, Mg e S absorvidos foi maior com o aumento das doses de nitrogênio na adubação. No primeiro ano o teor de proteína bruta do capim decumbens aumentou com a aplicação de nitrogênio no sistema, independente da fonte; Os teores de FDN e FDA não alteraram em função das fontes e doses nitrogenadas. No segundo ano aumentaram os teores de FDA e PB em função das doses de nitrogênio independente da fonte utilizada, e o teor de clorofila aumentou com doses maiores de N. A menor eficiência de uso do nitrogênio na produção de massa seca de capim decumbens foi com a utilização de ureia sem revestimento e as fontes nitrato de amônio, ureia + NBPT e ureia + B + Cu não apresentaram diferença significativa; Na avaliação isolada em cada corte a ureia apresentou maior volatilização em relação as fontes nitrato de amônio, ureia + NBPT e ureia + B + Cu; Na volatilização acumulada de amônia, em quatro avaliações, foi em ordem crescente nitrato de amônio = ureia + NBPT < ureia + B + Cu < ureia (sem revestimento). A maior volatilização de amônia ocorreu até o nono dia após a aplicação dos fertilizantes nitrogenados. No segundo ano na volatilização acumulativa ocorreu na seguinte ordem crescente de perdas de amônia nitrato de amônio < ureia + NBPT = ureia +B + Cu < ureia.
Pasture have been the main source of feed for livestock systems in extensive production systems. Nitrogen fertilization is an important management practice in forage systems because it usually increases forage accumulation, nutritive value and persistence of the pasture. The objective of this study was to evaluate the effects of different levels and sources of N fertilizer on ammonia volatilization, herbage accumulation and nutritive value Urochloa decumbens pasture (syn. Brachiaria decumbens). The study was conducted at the Sao Paulo State University - Campus Dracena in 2015 to 2017. The experimental design was in randomized blocks with four replicates, in a factorial scheme 4x2+1. The plots were composed of four nitrogen sources (urea, ammonium nitrate, urea + NBPT, urea + B + Cu) and two nitrogen doses (100 and 200 kg ha-1), plus a treatment without nitrogen (control). The nitrogen doses were divided in five equal applications (20 e 40 kg ha-1), the first one after the cut of uniformization and the others after the immediately subsequent cuts. The application of the different sources and nitrogen doses affected the accumulated dry mass production of the signal grass in the first and second year of the experiment. The application of the different sources and nitrogen levels affected the accumulated dry mass production of leaf blade. The amount of N, P, K, Ca, Mg and S absorbed was higher with increasing levels of nitrogen at fertilization. In the first year the crude protein (CP) content of the signal grass increased with the application of nitrogen in the system, regardless of the source; The concentration of neutral detergent fiber (NDF) and acid detergent fiber (ADF) did not change due to nitrogen sources and doses. In the second year, the levels of ADF and CP increased as a function of the doses of nitrogen independent of the source used and the chlorophyll content increased with greater levels of N. The lower efficiency of nitrogen use in dry mass production of signal grass was with the use of uncoated urea and the sources of ammonium nitrate, urea + NBPT and urea + B + Cu did not present significant difference; In the isolated evaluation in each section the urea presented greater volatilization in relation to the sources of ammonium nitrate, urea + NBPT and urea B + Cu; In the accumulated volatilization of ammonia, in four evaluations, it was in increasing order ammonium nitrate = urea + NBPT < urea + B + Cu < urea (without coating). The highest volatilization of ammonia occurred until the ninth day after the application of nitrogen fertilizers. In the second year in the cumulative volatilization occurred in the following increasing order of ammonia losses ammonium nitrate < urea + NBPT = urea + B + Cu < urea.
Pasture have been the main source of feed for livestock systems in extensive production systems. Nitrogen fertilization is an important management practice in forage systems because it usually increases forage accumulation, nutritive value and persistence of the pasture. The objective of this study was to evaluate the effects of different levels and sources of N fertilizer on ammonia volatilization, herbage accumulation and nutritive value Urochloa decumbens pasture (syn. Brachiaria decumbens). The study was conducted at the Sao Paulo State University - Campus Dracena in 2015 to 2017. The experimental design was in randomized blocks with four replicates, in a factorial scheme 4x2+1. The plots were composed of four nitrogen sources (urea, ammonium nitrate, urea + NBPT, urea + B + Cu) and two nitrogen doses (100 and 200 kg ha-1), plus a treatment without nitrogen (control). The nitrogen doses were divided in five equal applications (20 e 40 kg ha-1), the first one after the cut of uniformization and the others after the immediately subsequent cuts. The application of the different sources and nitrogen doses affected the accumulated dry mass production of the signal grass in the first and second year of the experiment. The application of the different sources and nitrogen levels affected the accumulated dry mass production of leaf blade. The amount of N, P, K, Ca, Mg and S absorbed was higher with increasing levels of nitrogen at fertilization. In the first year the crude protein (CP) content of the signal grass increased with the application of nitrogen in the system, regardless of the source; The concentration of neutral detergent fiber (NDF) and acid detergent fiber (ADF) did not change due to nitrogen sources and doses. In the second year, the levels of ADF and CP increased as a function of the doses of nitrogen independent of the source used and the chlorophyll content increased with greater levels of N. The lower efficiency of nitrogen use in dry mass production of signal grass was with the use of uncoated urea and the sources of ammonium nitrate, urea + NBPT and urea + B + Cu did not present significant difference; In the isolated evaluation in each section the urea presented greater volatilization in relation to the sources of ammonium nitrate, urea + NBPT and urea B + Cu; In the accumulated volatilization of ammonia, in four evaluations, it was in increasing order ammonium nitrate = urea + NBPT < urea + B + Cu < urea (without coating). The highest volatilization of ammonia occurred until the ninth day after the application of nitrogen fertilizers. In the second year in the cumulative volatilization occurred in the following increasing order of ammonia losses ammonium nitrate < urea + NBPT = urea + B + Cu < urea.
Descrição
Palavras-chave
Adubação, Capim decumbens, Inibidor de urease, Nitrogênio, Urochloa decumbens, Fertilizing, Signal grass, Urease inhibitors, Nitrogen, Urochloa decumbens