Microbiological Mechanisms of Sand‐Mixed Soil Improvement in Continuously Cropped Soil

ABSTRACT

Sand‐mix soil is a widely adopted method for soil improvement in agricultural production. However, beyond the evident enhancement of physical structure, the mechanisms by which sand‐mix soil promotes crop root growth by influencing soil physicochemical properties and microbial communities remain insufficiently understood. This study implemented sand‐mix soil treatment in tobacco‐growing regions suffering from soil degradation due to continuous cropping, examining its effects on tobacco root systems, soil physicochemical properties, the integrated fertility index, and bacterial community characteristics. Notably, sand‐mix soil significantly decreased the proportion of microaggregates while increasing the proportion of macroaggregates. Interestingly, despite reducing the absolute levels of key soil nutrients, it increased the integrated soil fertility index. Additionally, sand‐mix soil boosted microbial diversity, enhanced microbial network stability and resistance, and enriched potentially beneficial bacteria, such as Dokdonella , Dongia , Opitutus , Luteimonas , Arachidicoccus , and Taibaiella , which are associated with beneficial effects on plant growth. A structural equation model revealed that sand‐mix soil directly and indirectly promotes tobacco root growth by improving soil physical properties, balancing nutrient distribution, and modulating microbial community structure. This study systematically uncovers the micro‐ecological mechanisms underlying soil improvement and potential crop yield increases via sand‐mix soil, offering novel insights for the scientific application of this method in mitigating soil degradation, particularly in overcoming continuous cropping challenges.