Biological soil conditioner with reduced rates of chemical fertilization improves soil functionality and enhances rice production in vegetable-rice rotation

Soil is an essential source of nutrients for crop growth, but excessive chemical fertilizer can lead to soil acidification and decreased sustainability. Organic fertilizer helps improve soil physicochemical properties and increase soil utilization efficiency. However, soil functionality and crop sustainability response to organic fertilizers need further research. In this study, multiple fertilizer practices (including different amounts of nitrogen fertilizer or soil conditioners, traditional organic fertilizer), various rice varieties, and other rotation systems were applied to test the effects of soil conditioners on crop yield and soil fertility. The results showed that crop yield sustainability and stability were significantly positively correlated with soil pH, EC value, and nitrogen (Pearson r > 0.5). In addition, improving soil quality was beneficial to increasing crop yield sustainability and stability (R2 > 0.5). Chemical fertilizers and soil conditioners can increase soil nutrient content and improve crop yield sustainability index (>0.8). Applying soil conditioners can enhance the activity of soil catalase and urease in paddy soil, especially in the 12 and 15 m3 ha−1 soil conditioner treatments due to soil microbial activity being affected by soil salinity and organic matter content. Soil conditioners increase the mass of Nitrospira species in soil, decompose nitrogen in the soil, and reduce soil nitrate and nitrite content, thereby improving soil pH and reducing the risk of soil acidification caused by excessive chemical fertilizer. Combining soil conditioners and chemical fertilizer (20 % less than traditional fertilization) can promote soil quality and fertility while improving crop yield sustainability and stability.