Antecipação da adubação nitrogenada para a cultura do milho utilizando a braquiária como planta de cobertura

Abstract

The anticipation of nitrogen application in cultivation systems using cover crops to avoid nutrient losses in the soil profile, as well as increase the dry matter produced by cover crops, is an alternative to improve soil efficiency use of this nutrient. Nitrogen management is of great importance for the brachiaria-maize system, where N is traditionally applied at planting and covering in the main crop (maize). The aim of this work was to evaluate the efficiency of the anticipation of nitrogen fertilization for corn crop, using brachiaria as a predecessor crop. The experiment was conducted at the experimental field of the Federal University of Goiás / Jataí Regional, with a history of planting in succession soybean-corn/sorghum in the last 20 years, and emphasis on the content of Organic Matter of Soil that reaches 39.5 g kg-1. A randomized complete block design was used in a 5x2 + 1 factorial scheme with 4 replications. The first factor corresponded to five nitrogen rates: 0; 50; 100; 150 and 200 kg ha-1, using conventional urea as N source. The second factor was represented by the times of application of these nitrogen rates in the brachiaria cultivated as cover crops, being season 1: application of nitrogen 90 days before planting of corn and season 2: application of nitrogen 60 days before planting and an additional treatment with conventional nitrogen fertilization, represented by 150 kg ha-1 of nitrogen, unanticipated, applied to the corn crop, divided into planting and mulching fertilization. The following variables were evaluated in the brachiaria, 5 days before desiccation: dry matter, leaf nitrogen, normalized vegetation index and nitrogen release in the brachiaria straw. In maize were evaluated: normalized vegetation index, stalk diameter, activity of nitrate reductase enzyme, chlorophyll and nitrogen in leaves, plant height and cob insertion, components of grain yield and yield. With the exception of the 200 kg ha-1 rate of N applied 90 days before corn sowing, the antecipation of nitrogen fertilization for this crop, using braquiária as a cover plant, proved to be as efficient as conventional fertilization.