Sustainable nitrogen management in maize using optical sensor: Assessing yield, economics, and environmental impact

Abstract

Conventional nitrogen (N) application across large irrigated maize field often leads to low N use efficiency (NUE) due to substantial spatial and temporal variations in N needs throughout the growing season. This study aimed to optimize N management and enhance NUE in maize using the GreenSeeker™ (GS™) optical sensor, calibrated in conjunction with Nutrient Expert® (NE®). Field experiments conducted from 2012 to 2014 established a strong relationship between In-Season Estimated Yield (INSEY) at key growth stages (V₂–V₁₉) and maize yield, with R² values from 0.70 to 0.79. Based on INSEY–yield relationships at V₇ and V₁₁, N management prescriptions were implemented between 2015 and 2019 in the Indo-Gangetic Plains. The most effective strategy, NE® + 2-GS™, involved a basal N application per NE® guidelines and two split applications guided by GS™ at V₇ and V₁₁. This approach improved grain yield by 22.4 %, enhanced agronomic efficiency (31.6 kg yield kg⁻¹ N applied), and increased NUE compared to state recommendations (SR). Additionally, NE® + 2-GS™ improved N energy use efficiency by 37.4 %, reduced greenhouse gas emissions by 21.0 %, and achieved a higher eco-efficiency index (0.19 US $ MJ⁻¹ and 1.03 US $ kg⁻¹) than SR. The carbon footprint on a yield scale (CFy) was reduced by 48.2 %, indicating a substantial decrease in CO₂ emissions per economic yield unit. These findings support NE® + 2-GS™ as a feasible and environmentally sustainable strategy for efficient N management in maize.