Decomposition and nitrogen release in areas with and without grazing and its influence on corn

Resumo

This study aimed to evaluate the dry matter decomposition and N release from black oat residues and dung from goats, as well as its influence on corn yield grown in succession under increasing levels of N applied in topdressing. At winter, treatments consisted of different levels of a dietary supplement corresponding to 0, 5, 10 and 15 g kg-1 of body weight of females, Boer goats grazing oat cv. IAPAR 61 and a treatment without grazing. During the winter period were evaluated: forage sward, mass and its forage production, stocking rate, animal live weight gain, content of mineral N in the soil. At the end of grazing period, dry matter decomposition rate and N release from black oat residual biomass and animal dung were evaluated. At summer, main plots were divided into sub-plots and N applied at increasing levels over the corn crop (0, 50, 100 and 150 kg ha-1 of N as urea). During this period, corn yield was evaluated. Grazed areas at winter under increasing levels of supplementation resulted in an increase of animal production and increased dry matter decomposition rate and N release from the pasture when compared to ungrazed areas. At the ungrazed areas, it was necessary to apply 150 kg ha-1 of N in sidedress to ensure the same corn yield obtained at the grazing treatments without N application.