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/hm2, the synergistic improvement of summer maize grain yield and N efficiency can be achieved by incorporating subsoiling combined with layered nitrogen application.