The supply of nitrogen fertilizer in wheat to the highest environmental quality with satisfactory yield
The management of nitrogen in wheat based on biological and environmental indicators can ensure productivity with a reduction in environmental impact. The objective of the study was to develop a more sustainable management of nitrogen use in wheat, considering the dose as a fraction of the total supply based on an estimate of the maximum technical and economic efficiency, and expected grain yield, in systems of succession of high and reduced release of N-residual, during acceptable and unfavorable crop years. The study was conducted from 2012 to 2018, in Augusto Pestana, RS, Brazil. Two experiments were conducted in each agricultural year and in each rotation system (soybean/wheat and corn/wheat), one to quantify the biomass yield and the other to determine grain yield. The experimental design was a randomized block with four repetitions in a 5 x 3 factorial, for doses of N-fertilizer (0, 30, 60, 90, 120 kg ha-1) and ways of supplying the nutrient [full condition (100%) at the phenological stage V3 (third expanded leaf); fractionated (70%/30%) at phenological stage V3/V6 (third and sixth expanded leaf) and fractionated (70%/30%) at phenological stage V3/R1 (third expanded leaf and ear differentiation)], in the soybean/wheat and corn/wheat succession systems with high and reduced N-residual release, respectively. More efficient use of nitrogen was obtained based on wheat grain productivity when applied at the full dose at the third expanded leaf stage. The supply of the maximum dose of nitrogen with an expectation of 3 t ha-1 ensures satisfactory productivity with reduced nutrient losses to the environment, especially in unfavorable years for cultivation, regardless of the succession system.