Split nitrogen application to soil improves maize agronomic performance and nitrogen use efficiency

Maize ( Zea mays L.) production requires substantial nitrogen (N) during the grain-filling reproductive stages. Therefore, splitting N fertilizer applications between planting and the early reproductive stage (R1) may improve maize growth and yield while reducing environmental N losses. This study evaluated the effects of split N applications on maize growth, yield, N use efficiency (NUE), and residual soil N over two contrasting seasons. Eight different split N applications, ranging from 100:0 to 50:50 (planting: R1), and two reduced rates (50% and 25% of the full rate) were tested for 2 years. In 2021, split applications did not impact aboveground biomass or grain yield, although delaying 50% of N to R1 reduced leaf area index (LAI) and chlorophyll content. However, upon the second application, all split-N treatments recovered with rapid N uptake during early reproductive growth stages. In 2022, under severe drought, overall maize growth declined. Moreover, reducing N application to 50% did not affect biomass or grain yield compared to full rates, but improved N uptake and agronomic efficiency while reducing residual soil nitrate. Further reduction of the N fertilizer rate to 25% significantly reduced maize growth and yield. These findings suggest that applying 50% of N at planting allows flexibility to adjust remaining applications based on water stress. The study showed that adaptive N strategies can maintain productivity, enhance NUE, and reduce environmental risk in dryland maize systems under variable climatic conditions.