Effects of reduced nitrogen on the nifH-harboring soil microbiome in a soybean-maize strip intercropping system.

Introduction: Nitrogen (N) is a core limiting factor for crop growth, with approximately 50% of global food production relying on chemical N fertilizer inputs. However, excessive N application results in N use efficiency below 40%, and unabsorbed N triggers environmental problems. Maize-soybean relay strip intercropping (MSSI) enhances vertical resource partitioning, increases land productivity, and optimizes N utilization, but its effects on Methods: A 2-year field experiment was conducted in two soil textures (sandy loam in Wuji and medium loam in Gaocheng) including three cropping systems: monocropping maize, monocropping soybean, and MSSI. To further explore the underlying mechanism, an N gradient experiment with four fertilizer rates was established in Wuji. At the maturation stage, rhizosphere soil samples were collected, and q-PCR, enzyme activity assays, and high-throughput sequencing were used to analyze N cycle-related marker genes, enzyme activities, and Results: The MSSI system maintained maize yields comparable to monocropped maize, while soybean yields reached 60.1-69.6% of monocropped levels. MSSI significantly increased Discussion: Our results demonstrate that the MSSI system significantly alters soil N fertility and the community structure of