Abstract

It is possible to increase nitrogen for wheat productivity by adjusting the single and fractionated dose based on the condition of the agricultural year. The objective of this work is to study the  highest  amount of nitrogen used for the production of wheat using single dose  or fractionation under favorable and unfavorable cultivation years. The study was conducted in  2012, 2013 and 2014 in Augusto Pestana, Rio Grande do Sul, Brazil. The experimental design was a randomized block in a 4 × 3 factorial scheme with four replications. It consists of N-fertilizer rates (0, 30, 60 and 120 kg ha^-1), forms of supply [single (100%), growth stage V₃ (third expanded sheet); fractionated (70%/30%) growth stage V₃/V₆ (third and sixth expanded sheet); fractionated (70%/30%) phonological stage V₃/E (third expanded leaf and early grain filling)]. In favorable, intermediate and unfavorable years, wheat cultivated with single dose of nitrogen is more effective than the grain fractionated, regardless of the succession system. Nitrogen use efficiency can be substantially reduced or increased in wheat based on  the condition of the year of cultivation and the use of the optimal dose of the nutrient may not necessarily express maximum grain yield with economic efficiency.

Key words: Triticum aestivum, relation C/N, meteorological condition, simulation.