Pea–Oat Cover Crops Improve Ear Leaf Area, Grain Yield and Nitrogen Use Efficiency of Rainfed Maize Under Residual Nitrogen Fertilization

Improving nitrogen use efficiency while maintaining maize productivity under rainfed conditions is an important objective of sustainable crop management. This study evaluated the residual effects of mineral nitrogen fertilization and pea–oat cover crops on plant height, ear leaf area (ELA), grain yield, and nitrogen use efficiency (NUE) of maize (Zea mays L.). A field experiment was conducted using the maize hybrid Kneja 561 grown under continuous monoculture and monoculture following a pea–oat cover crop mixture incorporated into the soil during the previous season. Residual effects of ammonium nitrate and urea previously applied at rates of 60 and 120 kg N ha−1 were assessed. Cover crops significantly improved maize performance compared with continuous monoculture. Plant height increased by 5.72%, ear leaf area by 4.33%, grain yield by 16.5% as compared with continuous monoculture, and nitrogen use efficiency by 13.73%, indicating more efficient utilization of residual nitrogen. Analysis of variance showed significant effects of the cropping system and nitrogen fertilization on ear leaf area and nitrogen use efficiency, whereas their interaction was not significant. The results demonstrate that integrating pea–oat cover crops into maize production can enhance ear leaf development, improve the efficiency of residual nitrogen use, and increase grain yield under rainfed conditions, supporting the adoption of cover cropping as a sustainable agronomic practice.