Maize Management Practices and its Relationship with Nitrogen Indexes and Yield

Abstract

Nitrogen fertilization usually increases maize yields, but its impact varies with water availability and plant density. Nitrogen indexes like chlorophyll meter readings may help to predict yield variations. Still, their effect has not been studiedunder contrasting plant densities, hybrids, and water availability conditions. This study aimed to analyze: (i) maize yieldresponse to nitrogen fertilization across different planting densities and water conditions; (ii) the relationship betweennitrogen indexes and yield and its components; and (iii) the effect of hybrids differing in their prolificacy on the relationship between nitrogen indexes and yield. Two experiments (Exp A and Exp B) were conducted using nitrogen fertilizationrates and plant densities, Exp A focused on water conditions (irrigation vs. rainfed), while Exp B compared three maizehybrids. The chlorophyll meter readings were determined at different stages. Also, biomass, grain yield, and its components were assessed, and their nitrogen nutrition index was determined. Chlorophyll meter readings values were relativized to compare among the experiments to obtain nitrogen sufficiency index. Increased nitrogen availability consistentlyincreased yield on average by 2599 kg ha−1 across all plant densities. Changes in density affected nitrogen sufficiencyindicators similarly to nitrogen rate variations and water conditions. Higher densities correlated with a 15% lower chlorophyll meter readings value. Nitrogen sufficiency index at R4 proved the best predictor of yield variations (R2=0.52) andshowed a high correlation with nitrogen nutrition index (r=0.90). Despite hybrids presenting yield differences in optimaldensities, responses to nitrogen fertilization both in yield and its components were consistent across hybrids. Plant densityinduces variations in nitrogen sufficiency index of similar or greater magnitude than nitrogen rates towards. This trend isclearer at the end of the crop cycle that were reflected in similar trends in the nitrogen nutrition index at physiologicalmaturity. Future nitrogen diagnostic methodologies should consider plant density effects on maize response to fertilization.