Understanding Yield Response to Nitrogen to Achieve High Yield and High Nitrogen Use Efficiency in Rainfed Corn

Chinese farmers believe that more fertilizer and higher grain yields are synonymous. A better understanding of the relationship between corn (Zea mays L.) yields and N rate could help agronomists match fertilizer rates with plant requirements. The objective of this study is to evaluate corn yield response to applied N fertilizer and to understand the factors affecting yield response to N fertilizer by 737 on-farm experiments in northeastern China. Corn grain yield without applied N fertilizer averaged 7.6 Mg ha(-1). Increased yield for applied N fertilizer (IYN, the difference between maximum yield across all treatments and yield of the N-0 treatment) averaged 2.5 Mg ha(-1) and varied from 0 to 9.3 Mg ha(-1). Farmers' practices and corn hybrids resulted in large variability in IYN, whereas no changes in IYN occurred among years or soil types. Under the current cropping system, the maximum corn yield significantly increased and IYN decreased with increasing yield of the N-0 treatment, suggesting that increasing IYN with high yield of the N-0 treatment using integrated hybrids along with strategic management of crops, soils, and N is crucial for achieving high yields with a high N use efficiency (NUE).