Subsoiling combined with layered nitrogen application optimizes root distribution and increases summer maize grain yield

Background 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. Methods Xianyu 688 and Jifeng 2 were used as test materials, no-tillage and surface fertilizing with normal N (BC240), no-tillage and surface fertilizing with N reduction (BC180), subsoiling layered fertilization with normal N (FC240) were designed, and subsoiling layered fertilization with N reduction (FC180), assess root distribution, dry matter accumulation, N absorption and utilization, and grain yield of summer maize. Results The FC240 and FC180 treatments significantly reduced soil bulk density in the 10-50 cm depth soil layer compared to the BC240 and BC180 treatments, and also increased total N content in the 20-50 cm depth soil layer. Root length in the 20-40 cm soil layer significantly increased with the FC240 treatment, along with a notable increase in root exudates, which improved root vitality during later growth stages. Additionally, the FC240 and FC180 treatments enhanced plant dry matter accumulation, N accumulation, and grain yield. Xianyu 688 exhibited increased N uptake efficiency, N fertilizer partial factor productivity, and N harvest index, while Jifeng 2 showed increased N uptake efficiency and N fertilizer partial factor productivity. Conclusion It provided useful enlightenment for selecting suitable maize varieties, formulating effective management strategies and cultivating high N-efficient varieties under the condition of subsoiling combine with layered N application.