Altura do capim marandu após aplicação de fontes e doses nitrogenadas

Abstract

Pastures play a crucial role in Brazilian livestock production, with Marandu grass (Brachiaria brizantha cv. Marandu) being one of the most valued grasses due to its high productivity and adaptability to different environmental conditions. This study aimed to evaluate the influence of nitrogen (N) sources and rates on the height of Marandu grass in its fourth year of cultivation. Two experiments were conducted for this purpose. In the first experiment, three N sources were assessed: urea (conventional and NBPT-coated) and ammonium nitrate, associated with sulfur (S), calcium (Ca), and magnesium (Mg). In the second experiment, the effect of six N rates, ranging from 0 to 300 kg ha⁻¹ of N, was evaluated. These were applied in five fractions of 60 kg ha⁻¹ of N, at intervals of 20 to 35 days after lowering the grass to 20 cm in height, using two N sources: urea and ammonium nitrate. For the first experiment, statistical analysis used the Scott-Knott method at a 5% significance level, and for the second experiment, regression models in a 2x6 factorial scheme were employed to identify the optimal rate for maximizing grass height. Both experiments were analyzed using the SISVAR statistical program. Results indicated that the highest average grass height across several evaluations was achieved with the application of ammonium nitrate associated with S at a rate of 120 kg ha⁻¹ of N, yielding an increase of up to 90.82% compared to the control. The highest recorded height of 48.25 cm was observed in the fourth evaluation with the application of 184.48 kg ha⁻¹ of N using ammonium nitrate. It is concluded that the use of ammonium nitrate associated with S is essential for optimizing Marandu grass growth. The results indicate significant increases in grass height, contributing to more efficient livestock production systems.