Aplicação fracionada de nitrogênio sobre o desempenho produtivo e fisiológico do sorghum bicolor l.

Abstract

This study aimed to evaluate the effect of nitrogen fractionation on foliar N content, photosynthetic pigments, and grain yield in grain sorghum (Sorghum bicolor L.). The experiment was conducted at the Federal University of Mato Grosso do Sul campus in Chapadão do Sul (MS), during the second growing season of 2024, in a dystrophic Red Latosol with clayey texture. The experimental design was a randomized complete block design (RCBD) with six treatments: control (T1), a single fertilization at planting (T2), fertilization at planting + 1 topdressing (T3), fertilization at planting + 2 topdressings (T4), 1 topdressing (T5), 2 topdressings (T6), and four replications, totaling 24 plots. The nitrogen dose (urea) was applied in full at planting or fractionated into one and two topdressings. The variables analyzed included grain yield, leaf nitrogen content, total chlorophyll, and carotenoids. Analysis of variance, followed by Tukey's test at 5%, indicated significant differences between treatments, highlighting the higher yields in the split-dose fertilization management. Canonical discriminant and principal component (PCA) multivariate analyses showed a strong association between yield, leaf nitrogen, and total chlorophyll in the treatments with multiple topdressings, while the control showed greater carotenoid accumulation, indicating a photoprotective response. The heat map confirmed these patterns, showing a positive correlation between leaf nitrogen and yield and an inverse relationship with carotenoids. Splitting nitrogen fertilization increased nutrient use efficiency and favored the physiological balance of plants, resulting in higher grain sorghum yield performance under Cerrado conditions.