Integrated Moldboard Ploughing and Organic–Inorganic Fertilization Enhances Maize Yield and Soil Fertility in a Semi-Arid Region of North China

To address soil degradation from long-term monoculture, rotary tillage, and excessive chemical fertilization in semi-arid regions of China, we conducted a three-year field experiment. We assessed the synergy of integrated management practices combined with both continuous and rotational tillage methods (including ploughing, rotary, moldboard ploughing) at varying tillage depths (10-15, 15-25, 25-35 cm) with different fertilization regimes (chemical vs. organic-inorganic). Among all treatments, the rotational tillage practice that integrates moldboard ploughing at 25-35 cm depth with organic-inorganic fertilization [1200 kg ha^-1 mature compost + 375 kg ha^-1 compound fertilizer (N:P₂O₅:K₂O = 15:15:15)] significantly reduces bulk density by 11.8% and increases total porosity by 17.9% in the 15-25 cm soil layer. This practice optimizes nutrient stratification, elevating available nitrogen and potassium in the shallow layer (10-15 cm) to 126.13 and 372.45 mg kg^-1, respectively, while boosting available phosphorus in the subsoil (25-35 cm) by 247.8%. Furthermore, it significantly enhances soil microbial activity, increasing populations of bacteria, actinomycetes, and fungi by 3.42 × 10⁵, 0.65 × 10⁵, and 2.40 × 10³ CFU g^-1, respectively, alongside a 49.4% rise in soil respiration. These synergistic improvements collectively promote stable maize yields (increasing by 1731.4 kg ha^-1) and high economic returns (net income increasing by 3301.6 CNY ha^-1). These findings support the promotion of integrated tillage-fertilization strategies to enhance maize productivity and soil ecological function in semi-arid regions.