Subsoiling Combine with Layered Nitrogen Application Optimizes Root Distribution and Improve Grain Yield and N Efficiency of Summer Maize

No-tillage of summer maize after the harvest of winter wheat is the primary agricultural practice on the North China Plain. However, prolonged no-tillage without deep tillage practices negatively impacts soil properties, which is detrimental to the growth and yield of summer maize. In this study, Xianyu 688 and Jifeng 2 were used as test maize materials, no-tillage and surface fertilizing with normal nitrogen (N) (BC240), no-tillage and surface fertilizing with N reduction (BC180), subsoiling layered fertilization with normal N (FC240) and subsoiling layered fertilization with N reduction (FC180)were designed, in order to assess root distribution, N utilization and grain yield of summer maize. In the two maize cultivars, the FC240 and FC180 treatments significantly reduced soil bulk density in the 10–50 cm depth soil layer compared to the other two treatments, and also increased total N content in the 20–50 cm depth soil layer. Compare BC 240 treatment, the FC240 treatment significantly increased root length in the 20–40 cm soil layer and root rap bleeding. Additionally, the FC240 and FC180 treatments enhanced dry matter and N accumulation, grain yield, N uptake efficiency and N fertilizer partial factor productivity. In various treatment, Xianyu 688 exhibited increased grain yield, N uptake efficiency and N fertilizer partial factor productivity compare with Jifeng 2. When employing a total N application level of 180–240 kg N/hm[sup.2], the synergistic improvement of summer maize grain yield and N efficiency can be achieved by incorporating subsoiling combined with layered nitrogen application.