Mechanisms of water and fertilizer reduction and conditioner addition on the biological characteristics of soil nutrient transformation and potato yield

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Over-irrigation and over-fertilization waste a lot of water and fertilizer nutrients, increasing cost and environmental pollution in semi-arid areas. Soil conditioner has multiple beneficial effects in agricultural production, but the effects of soil conditioner addition combined with water and fertilizer reduction on crop growth and yield are still unclear. In this study, the effects and mechanisms of conventional irrigation (6.23 × 103 m3/ha) and fertilization (N: 225 kg/ha; P2O5: 350 kg/ha; K2O: 400 kg/ha) (CK), 30 % water reduction combined with conditioner addition (RI), 30 % fertilizer reduction combined with conditioner addition (RF), and 30 % water reduction combined with 30 % fertilizer reduction and conditioner addition (RIF) on the soil nutrient transformation and potato yield were explored from the perspectives of soil microbial community and metabolome. The results showed that RI, RF, and RIF treatments all reduced soil total organic carbon (TOC) content, increased soil NO3−-N content, and changed the composition of soil bacterial community and rhizosphere soil metabolites. Specifically, RI and RIF treatments significantly reduced the Shannon index and Chao1 index of soil bacterial community and the quantity of metabolite types in rhizosphere soil. However, RF treatment increased the quantity of metabolite types in rhizosphere soil, especially the metabolites involved in the Alpha-Linolenic acid metabolism, Starch and sucrose metabolism and Biotin metabolism pathways. In addition, RI and RF treatments increased the phosphorus accumulation in plants while maintaining the yield compared with CK. The redundancy analysis and Mantel test found that soil TOC and NO3−-N content significantly affected soil differential bacterial genera, and the differential bacterial genera and differential abundant metabolites (DAMs) in rhizosphere regulated potato yield by affecting plant nutrient uptake and dry matter yield. The structural equation model and path effect analysis found that plant nutrient uptake was the main factor influencing potato yield. Soil NO3−-N content and differential bacterial genera directly affected plant nutrient uptake, and soil TOC and starch and sucrose metabolism indirectly affected plant nutrient uptake. This study will provide a technical reference for increasing potato yield, reducing potato planting costs, and achieving sustainable agricultural development.