Fontes de nitrogênio na cultura do trigo: eficiência de uso e produtividade de grãos

Abstract

Nitrogen fertilization is essential for wheat production; however, a large proportion of the applied nitrogen may be lost through ammonia volatilization, particularly when urea is used. This study evaluated, over three growing seasons in southwestern Paraná, Brazil, five treatments: control (C), urea (UR), urea + NBPT (UR+NBPT), ammonium nitrate (AN), and ammonium nitrate at 70% of the recommended rate (AN70). Grain yield, NH₃ volatilization, nitrogen uptake and export, and nitrogen use efficiency were assessed. The experiment was conducted under field conditions at the Federal University of Technology – Paraná (UTFPR), Dois Vizinhos Campus, on a Red Oxisol. Ammonia volatilization was monitored using sponge collectors and quantified by distillation and titration. Over the three years of evaluation, grain yield was similar among treatments, with average values of 8.29, 7.14, 2.98, 3.90, and 2.66 Mg ha⁻¹ for UR, UR+NBPT, AN, AN70, and C, respectively. Urea and urea + NBPT also showed the highest nitrogen uptake, reaching 113.33 and 106.94 kg ha⁻¹, respectively, while nitrogen export reached 75.92 kg ha⁻¹. The greatest ammonia volatilization losses occurred in the urea-based treatments, especially during the first days after fertilizer application, with average losses of 8.29 kg N-NH₃ ha⁻¹ for UR and 7.14 kg N-NH₃ ha⁻¹ for UR+NBPT. Nitrogen use efficiency was highest for UR (35%) and lowest for AN (31%). It is concluded that, despite greater ammonia volatilization losses, urea showed the best overall agronomic performance, whereas ammonium nitrate exhibited lower efficiency under the evaluated conditions. These findings highlight the importance of considering not only fertilizer cost and nitrogen concentration but also its environmental behavior and agronomic efficiency, particularly in regions with variable climatic conditions such as southwestern Paraná, Brazil.