Nitrogen management in second-crop maize in Southwestern Goiás

ABSTRACT Nitrogen (N) fertilizer management is a key factor in the success of maize crops. The objective of this work was to evaluate the response of second-crop maize to N applied exclusively as topdressing or at planting + topdressing. Five experiments were conducted in areas in southwestern Goiás in 2019 and 2020 to evaluate N application rates of 0 and 30 kg ha-1 at planting, combined with five N rates applied as topdressing at the maize V3 stage over a total of 0, 75, 150, 225, and 300 kg ha-1. Dry matter production in the V6 or V9 stage and yield parameters at harvest were evaluated. N application did not affect the number of grain rows per ear but increased the number of grains per row and, particularly, grain weight. The crop responded positively to increases in the total N rate in 4 of the 5 experiments: in 1 of these experiments, N fertilizer application at planting contributed to an increase in the efficiency of topdressing fertilization, resulting in a higher maize yield with a lower total N rate; in the other 3, a positive maize response to N occurred when total N was applied as topdressing at V3. However, the highest mean maize grain yield (8,233 kg ha-1) was found in the trial that showed no response to N fertilizer application - probably due to the better chemical fertility conditions of the area combined with an adequate distribution of rainfall, considering the multiple factors involved in N application recommendations.