Dual Effects of Soil Conditioners on Wheat Yield and Soil Properties in Southern Henan

Aimed at addressing the constraints of farmland soil acidification on soil health and crop productivity, this study investigated the comprehensive ameliorative effects of different soil conditioners on acidic soils in southern Henan Province and identified the optimal amendment strategy. Based on a continuous fixed-point field experiment conducted from 2023 to 2025, treatments including NB (nitrogen fertilizer + biochar), lime, and controls were established. Crop yield, biomass, yield components, soil pH, available phosphorus, available potassium, soil organic carbon, aggregate size distribution, and rhizosphere microbial communities were measured, and Spearman correlation analysis was employed to link soil properties with microbial taxa. The results indicated that the NB treatment exhibited the most pronounced comprehensive improvement: it achieved a yield of 8.38 t·ha⁻¹ (46.5% higher than the control), increased thousand-grain weight by 12.3%, raised soil pH by 15.8%, and significantly enhanced available phosphorus (~ 40%), available potassium (85.6%), and soil organic carbon (33.1%). The proportion of large and medium aggregates (0.25–2 mm) reached 19.06%, and fungal richness was notably increased, with key soil physicochemical indicators strongly correlated with specific microbial genera. The superior performance of NB is attributed to its multi-pathway synergistic regulation—chemical pH buffering, physical structure improvement, and biological stimulation—achieving comprehensive and stable amelioration. Biochar combined with nitrogen fertilizer (NB) is the optimal amendment strategy for acidic soils in southern Henan, providing scientific evidence for the application of organic carbon-based conditioners in the management of acidified farmland.