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 in southern Henan Province, this study investigated the comprehensive ameliorative effects of different soil conditioners 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), NL (nitrogen fertilizer + lime), NM (nitrogen fertilizer + microbial fertilizer), NC (nitrogen fertilizer + calcium magnesium fertilizer), and controls were established. Crop yield, biomass, yield components, soil pH, ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), available phosphorus (AP), available potassium (AK), soil organic carbon (SOC), aggregate size distribution, and rhizosphere bacterial and fungal communities were measured, and Spearman correlation analysis together was employed to link soil properties with microbial taxa and to reveal yield regulation pathways. The results indicated that the NB treatment exhibited the most pronounced comprehensive improvement: it achieved a grain 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% (from 3.49 to 4.04), and significantly increased soil NH₄⁺-N and NO₃⁻-N contents while maintaining stable available nitrogen supply, as well as significantly enhanced AP (40%), AK (85.6%), and SOC (33.1%). The proportion of macro- and meso- 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. Partial Least Squares Path Modeling (PLS-PM) further revealed that SOC exerted opposite regulatory effects on bacterial and fungal communities. The superior performance of NB is attributed to its multi pathway synergistic regulation—chemical pH buffering, physical structure improvement, nutrient retention especially for available nitrogen, 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 conditioners in the management of acidified farmland.