Resumo
Urea is the N source most widely used in pastures in Brazil. A significant amount of N is lost to the atmosphere by ammonia and nitrous oxide emissions and leached surface or ground water as nitrate contributing to environmental degradation such as the global warming or eutrophication. The loss of nitrogen by ammonia volatilization is a major factor for low efficiency of urea applied in soil surface. An alternative to reducing these losses is the use of urease inhibitors. The aim of this study was to investigate the effects of treating urea with urease inhibitor (NBPT N-(n-butyl) thiophosphoric acid triamide) on the dry biomass yield in pasture of Urochloa (syn. Brachiaria) brizantha Marandu to minimize NH3 volatilization. The study was performed at the Instituto de Zootecnia (IZ) at Nova Odessa, SP, Brazil, in a typic acrudox soil composed of sand (49.5%), clay (20.9%) and loam (29.6%). A randomized experimental design with three treatments and four replications was used. The treatments were: i) No N; ii) Urea; iii) Urea treated with urease inhibitor NBPT. The rate of N was 50 kg/ha applied to the surface of the soil. Measurements of NH3 volatilized were done by semiopen PVC chambers. Controls chambers were added to allow NH3 volatilized from unfertilised soil or contained in the air that swept over the soil surface. We evaluated the yield and plant height, SPAD value and N
O artigo não apresenta resumo em português.
Resumo
Historically, tillers have been considered detrimental to maize because they do not produce ears and may act as sinks competing for carbohydrates with the main stem. This work was carried out aiming to evaluate the effect of tiller removal on maize grain yield at different sowing dates. The experiment was set during the 2006/07 and 2008/09 growing seasons. A randomized complete block design disposed in split-plots was used. Two sowing dates were tested in the main plots: second half of October (recommended) and second half of December (late). Four tiller's fates were evaluated in the split-plots: tiller removal when the main stem had six expanded leaves (V6), nine expanded leaves (V9), fifteen expanded leaves (V15) and tiller maintenance until harvesting. Hybrid P30F53 was sowed at 55,000 plants ha-1, with a row spacing of 0.7m. The percentage of plants with tillers and the number of tillers per plant were higher when maize was sown in October than in December. There was no grain yield difference between treatments where tillers were preserved and those where they were removed at V6, V9 or V15, regardless of sowing date. Such behavior demonstrates that tillers are not sinks that compromise maize agronomic performance. Furthermore, tillers may contribute positively to grain yield when maize is sown in October.
Historicamente, os perfilhos têm sido considerados indesejáveis na cultura do milho, porque não produzem espigas e podem drenar fotoassimilados do colmo principal. Este trabalho foi desenvolvido objetivando avaliar o efeito do estádio de remoção dos perfilhos sobre o rendimento de grãos do milho, em duas épocas de semeadura. O experimento foi conduzido em Lages, SC, durante os anos agrícolas de 2006/07 e 2008/09. Utilizou-se o delineamento experimental em blocos casualizados, dispostos em parcelas subdivididas. Na parcela principal, foram testadas duas épocas de semeadura: segunda quinzena de outubro (recomendada) e segunda quinzena de dezembro (tardia). Nas subparcelas, foram avaliados quatro estádios de remoção dos perfilhos: colmo principal com seis (V6), nove (V9) e quinze folhas expandidas (V15) e testemunha com perfilhos mantidos até a colheita. Testou-se o híbrido P30F53, na densidade de 55.000 plantas ha-1 e espaçamento entrelinhas de 0,7m. A percentagem de plantas perfilhadas e o número de perfilhos por planta foram maiores nas semeaduras de outubro do que nas de dezembro. Não houve diferenças no rendimento de grãos do tratamento em que os perfilhos foram mantidos, em relação àqueles em que eles foram removidos em V6, V9 ou V15, independentemente da época de semeadura. Isso demonstra que os perfilhos não são drenos que comprometam o desempenho agronômico do milho. Além disso, eles podem contribuir para o rendimento de grãos nas semeaduras feitas em outubro.
Resumo
Historically, tillers have been considered detrimental to maize because they do not produce ears and may act as sinks competing for carbohydrates with the main stem. This work was carried out aiming to evaluate the effect of tiller removal on maize grain yield at different sowing dates. The experiment was set during the 2006/07 and 2008/09 growing seasons. A randomized complete block design disposed in split-plots was used. Two sowing dates were tested in the main plots: second half of October (recommended) and second half of December (late). Four tiller's fates were evaluated in the split-plots: tiller removal when the main stem had six expanded leaves (V6), nine expanded leaves (V9), fifteen expanded leaves (V15) and tiller maintenance until harvesting. Hybrid P30F53 was sowed at 55,000 plants ha-1, with a row spacing of 0.7m. The percentage of plants with tillers and the number of tillers per plant were higher when maize was sown in October than in December. There was no grain yield difference between treatments where tillers were preserved and those where they were removed at V6, V9 or V15, regardless of sowing date. Such behavior demonstrates that tillers are not sinks that compromise maize agronomic performance. Furthermore, tillers may contribute positively to grain yield when maize is sown in October.
Historicamente, os perfilhos têm sido considerados indesejáveis na cultura do milho, porque não produzem espigas e podem drenar fotoassimilados do colmo principal. Este trabalho foi desenvolvido objetivando avaliar o efeito do estádio de remoção dos perfilhos sobre o rendimento de grãos do milho, em duas épocas de semeadura. O experimento foi conduzido em Lages, SC, durante os anos agrícolas de 2006/07 e 2008/09. Utilizou-se o delineamento experimental em blocos casualizados, dispostos em parcelas subdivididas. Na parcela principal, foram testadas duas épocas de semeadura: segunda quinzena de outubro (recomendada) e segunda quinzena de dezembro (tardia). Nas subparcelas, foram avaliados quatro estádios de remoção dos perfilhos: colmo principal com seis (V6), nove (V9) e quinze folhas expandidas (V15) e testemunha com perfilhos mantidos até a colheita. Testou-se o híbrido P30F53, na densidade de 55.000 plantas ha-1 e espaçamento entrelinhas de 0,7m. A percentagem de plantas perfilhadas e o número de perfilhos por planta foram maiores nas semeaduras de outubro do que nas de dezembro. Não houve diferenças no rendimento de grãos do tratamento em que os perfilhos foram mantidos, em relação àqueles em que eles foram removidos em V6, V9 ou V15, independentemente da época de semeadura. Isso demonstra que os perfilhos não são drenos que comprometam o desempenho agronômico do milho. Além disso, eles podem contribuir para o rendimento de grãos nas semeaduras feitas em outubro.
Resumo
Urea is the N source most widely used in pastures in Brazil. A significant amount of N is lost to the atmosphere by ammonia and nitrous oxide emissions and leached surface or ground water as nitrate contributing to environmental degradation such as the global warming or eutrophication. The loss of nitrogen by ammonia volatilization is a major factor for low efficiency of urea applied in soil surface. An alternative to reducing these losses is the use of urease inhibitors. The aim of this study was to investigate the effects of treating urea with urease inhibitor (NBPT N-(n-butyl) thiophosphoric acid triamide) on the dry biomass yield in pasture of Urochloa (syn. Brachiaria) brizantha Marandu to minimize NH3 volatilization. The study was performed at the Instituto de Zootecnia (IZ) at Nova Odessa, SP, Brazil, in a typic acrudox soil composed of sand (49.5%), clay (20.9%) and loam (29.6%). A randomized experimental design with three treatments and four replications was used. The treatments were: i) No N; ii) Urea; iii) Urea treated with urease inhibitor NBPT. The rate of N was 50 kg/ha applied to the surface of the soil. Measurements of NH3 volatilized were done by semiopen PVC chambers. Controls chambers were added to allow NH3 volatilized from unfertilised soil or contained in the air that swept over the soil surface. We evaluated the yield and plant height, SPAD value and N
O artigo não apresenta resumo em português.