Decomposição de resíduos de milho submetido à duas épocas de aplicação de nitrogênio e cultivado após diferentes intensidades de pastejo em aveia preta

Abstract

The correct management of crop residues allows intensified production systems to maximize the nutrient cycling and reduce demand for external inputs. The straw produced by a culture become a source of nutrients for the next crop, with fast or slow nutrient releasing depending on the material. The crop-livestock systems are an interesting way to maximize land use when alternates between animal and plant production, without degrading the environment. The present study aimed to evaluate the effect of nitrogen fertilization management (200 kg N.ha-1, applied to the pasture or crop in coverage as urea 45%.N) on the corn straw decomposition rate grown in a crop-livestock system, and the influence of the pasture grazing intensities, prior to the corn (high and low sward height), influences in the decomposition process of corn straw. The experiment was laid out in a private farm, in the municipality of Abelardo Luz – SC (Brazil), from April to October 2014. For the assets it were randomly collected 5 straw samples in each treatment just after the corn harvest moment, using of a frame of 0.25 m2. It was sampled 20 grams of the dried material and distributed into nylon bags (litter bags) that were allotted to each respective paddock. Seven samples were taken in each treatment, evaluating a period of 182 days. The decomposition rate was calculated by weigh difference and the results were analyzed in Statigrafics at 5% significance level. The results were significant for both evaluated variables, although there was no interaction between factors, and when nitrogen was applied in the pasture the material decomposed faster in comparison to the residue that received nitrogen in the grain culture. The height of the grass prior to the corn crop influenced the rate of decomposition being high when the pasture was managed in a low height.