The responsive alterations of soil microbial communities driven by continuous maize cropping (CC) and their assembly mechanisms constitute a fundamental scientific question for the sustainability of agricultural ecosystems. However, the assembly processes of microbial communities and their microecological effects under long-term CC remain poorly understood. We hypothesized that maize CC drives predictable shifts in microbial community assembly via increased deterministic selection. To address this, we established a short- to long-term CC gradient (1–25 years). We found that CC significantly altered microbial community structure, the relative abundance of dominant bacterial genera increased with CC years (CCY), whereas dominant fungal genera exhibited a declining trend. Co-occurrence network analysis revealed that long-term CC led to enhanced modularity in bacterial networks and a sharp decline in the proportion of negative correlations. Additionally, our findings reveal a transition from stochastic to heterogeneous selection-dominated processes over time, with microbial diversity metrics showing strong linear relationships with CC duration. This study elucidates how CC shapes convergent-divergent trajectories of microbial communities through heterogeneous selection pressures, providing theoretical support for guiding targeted soil microecological management.

Excessive chemical fertilizer and low N use efficiency constrain mulched drip irrigated maize production in China’s Hexi Oasis, while livestock manure is underutilized. Recycling biogas residue and slurry offers a solution, but optimal substitution ratios under reduced N remain unknown. We conducted a two year field experiment with two reduced N rates (15% and 30% relative to the conventional local rate of 360 kg N ha⁻¹) combined with biogas residue replacing basal N at rates of 25%, 50%, or 75% and biogas slurry replacing 50% of topdressed N. The best performing treatment (N₁25: 15% N reduction + 25% residue substitution) significantly increased LAI (11.77%), SPAD value (10.98%), dry matter (2.51%), leaf and stem N translocation (13.81% and 10.00%, respectively), leading to a 2.14% yield gain. NUE, ANUE, and PFPN improved by 27.4%, 19.5%, and 18.5%. Path analysis revealed that N₁25 enhanced canopy photosynthesis and dry matter translocation, increasing grain weight. These findings demonstrate that integrated N reduction with biogas substitutes enhances productivity and N efficiency while recycling organic waste. Therefore, under the present experimental conditions, N₁25 represents a promising strategy for simultaneously improving grain yield and nitrogen use efficiency; however, multisite and long term validation is warranted to substantiate its broader applicability.