Effect of subsoiling on tillers, root density and nitrogen use efficiency of winter wheat in loessal soil

A 2-year field experiment was carried out in loessal soil in a semi-humid climate to research winter wheat (Triticum aestivum L.) growth and nitrogen use efficiency. The result showed that subsoiling increased root penetration and promoted deep soil water absorption, which resulted in high resilience to the adverse dry climate. Soil NO3--N residue throughout the profile was decreased but increased in rotary tillage. Grain yield was significantly increased by 21.9% and 11.3% in 2016 and 2017, respectively, mainly due to the significantly larger spikes per hectare and grains per spike. Nitrogen use efficiency was significantly improved by 26.7% in 2016 and 13.8% in 2017. For loessal soil in semi-humid climate, breaking the plough pan was necessary, and it was useful for the increase of grain yield and nitrogen use efficiency.