In‐Season Nitrogen Management to Increase Grain Yields in Maize Production

CORE IDEAS: Optimal N rate treatment increased the maize yield and improved dry matter production and N accumulation post‐silking. In‐season N management‐based post‐silking N management can synchronize soil N supply and plant N uptake. Assessing the performance of leaf and root characteristics in response to post‐silking N management. Post‐silking N accumulation positively correlates with maize (Zea mays L.) grain yield in production, but the effect of N management post‐silking is unclear. This study was to evaluate maize yield and physiological changes in response to in‐season nitrogen management (INM) with respect to post‐silking N fertilization of maize. Optimal nitrogen rates (ONR) were determined for INM by subtracting soil nitrate‐N content measured at the maize root layers from the target N value. Other treatments included a zero N (0N) post‐silking control with the same N application pre‐silking as ONR and excessive N treatment (Exc. N) with the same N application pre‐silking as ONR plus an additional application of 50% of the target N value post‐silking. The grain yield with ONR of the INM was 10.9 Mg ha⁻¹, 17% higher than the 9.3 Mg ha⁻¹ obtained with the 0N control post‐silking. The Exc. N treatment post‐silking did not increase maize yield, but resulted in a high residual soil Nₘᵢₙ after harvest. The high grain yield obtained with ONR showed markedly higher dry matter (DM) production and N accumulation post‐silking, with higher net photosynthesis and green leaf area than obtained with the 0N control post‐silking. Additional N application post‐silking also improved root development, as evidenced by the 18, 20, and 9% increase in root dry matter, root length, and root surface area densities for ONR compared to the 0N control. Results suggested that INM can synchronize soil N supply and plant N uptake throughout the growing season, thereby increasing maize grain yield.