Optimizing nitrogen fertilizer inputs and plant populations for greener wheat production with high yields and high efficiency in dryland areas

Abstract Bridging yield gaps in staple crops is widely reported as a highly efficient means for improving grain production. However, changes in production efficiency and the environmental footprint remain less investigated when narrowing these gaps. In this study, we collected data from 299 wheat plots on the Loess Plateau of China to identify changes in nitrogen efficiency, nutrient balance, and environmental risks when narrowing the yield gaps. The low-yielding (LY) and high-yielding (HY) plots had an average yield gap of 1936 kg ha–1 (33.5%) and nitrogen partial factor productivity gap of 10.3 kg kg–1 (30.1%) that were simultaneously narrowed under similar fertilizer inputs. Optimizing sowing date improved spikes per m2 (27.4%) and grains per head (12.9%), key measures to improving wheat grain yields. The high-yielding high-efficiency (HYHE) plots produced on average 43.0% and 14.6% higher nitrogen partial factor productivity and grain yield, respectively than the high-yielding low-efficiency (HYLE) plots. Appropriate nitrogen fertilizer inputs significantly enhanced nitrogen use efficiency and maintained grain yield on HY plots. Grain yield and nitrogen partial factor productivity gradually increased with year of cultivar release (1995–2019) (P