Abstract

The biomass productivity and wheat grains efficiency is determined by nitrogen dose adjustment (full or fractioned), environmental conditions, and cropping system. The aim of this study was to improve the efficiency of N-fertilizer usage on wheat to maximize the biomass productivity and grain yield by adjusting the full or fractioned nitrogen dose in favorable and unfavorable year conditions, in succession systems with high and reduced N-residual release. In this study, two experiments were conducted between 2012 and 2014. One was to quantify the biomass productivity rate and another to determine grain yield. The experimental design was a complete randomized block, with four replications, in a 4 × 3 factorial scheme to N fertilizer rates (0, 30, 60 and 120 kg ha^-1) and supply forms of the nutrient [full dose (100%) in the V₃ phenological stage (third expanded leaf); fractioned (70 and 30%) at the V₃ and V₆ phenological stages (third and sixth expanded leaf, respectively) and; fractionated (70 and 30%) at the V₃ and E phenological stages (third expanded leaf and early grain filling), ] respectively, in soybean/wheat and maize/wheat cultivation systems. The nitrogen supply in wheat through single dose or fraction indicates linear tendency over the productivity biomass daily rate-1 with the increase of N-fertilizer, regardless of a favorable and unfavorable year and system of a succession of the high and reduced N-residual release. However, in favorable years, the use of full dose on V₃ stage is indicated. In the maize/wheat system, the full dose at V₃ stage is more efficient, especially with higher doses of the nutrient. For grain yield, the N-fertilizer fractioning was adjusted in intermediate cropping years, while the full dose became suitable at the V₃ stage in favorable years. However, in unfavorable years, nitrogen investments should be minimized, regardless of the supply form and succession system.

Key words: Triticum aestivum L., succession system, optimization, regression.