Enhancing nitrogen use efficiency of wheat through real-time SPAD-based N fertilization

Nitrogen (N) fertilization is critical for optimal wheat productivity, yet traditional application methods often lead to inefficiencies, economic losses and environmental pollution. Real-time monitoring of N through chlorophyll meter readings offers a promising approach. This method can optimize N use efficiency while maintaining yield potential. To investigate this approach, a field trial was established during the winter growing season of 2015-16. The study was conducted at the research station of Bihar Agricultural University, Sabour, Bihar, India. The experimental layout utilized a split-plot arrangement with fourteen treatment combinations, encompassing two soil plant analysis development (SPAD) measurement levels (42 and 44) across seven wheat genotypes (HD 2967, HD 2985, HI 1563, PBW 343, HW 1105, HD 3086 and Sabour Samriddhi), each treatment replicated thrice. Nitrogen management using SPAD threshold of 42 and 44 effectively preserved wheat cultivar growth and yield characteristics while reducing N fertilizer usage by 33 and 12 kg ha-1 respectively as compared to the state recommended dose of 120 kg N ha-1. Linear correlations between foliar N content and SPAD measurements at the crown root initiation (CRI) and tillering stages identified optimal SPAD values of 45.3 and 42.0 respectively, for maximizing grain yield. Economic analysis revealed that HD 2967 generated the highest profit margins and return ratios, with Sabour Samriddhi ranking second, both significantly outperforming PBW 343 in financial metrics. Thus, SPAD threshold of 42 proved most effective for maintaining wheat productivity and profitability through efficient N fertilizer management.