Compost-induced changes in microbial community reinforce the ecosystem functioning of sandy loam soil in China

In China, the extensive distribution of sandy loam soils, which are often low in fertility, highlights the need for effective remediation strategies. Compost application has emerged as a promising approach for improving soil health and supporting ecological restoration. However, the relationship between compost-induced soil properties and microbial functioning remains elusive. We examined the intricate relationships among soil properties, microbial communities, and organic matter transformations in response to varying compost inputs (0, 15, 30, 45, and 60 t compost hm-2), examining how each level influenced soil dynamics and microbial interactions. The gradient compost input significantly decreased the bacterial richness but increased bacterial cohesion and community stability. The low-abundant taxa (relative abundance <0.1%) exhibited a sensitive response to varying levels of compost input along the gradient. Two fundamental soil properties, dissolved organic nitrogen and available potassium, demonstrated significant correlations with two core species, Spirillospora and Saccharomonospora (p < .01). The gradient compost input had a notable impact on the abundant Deinococcota, which was closely associated with the reduction of organic nitrogen. Moreover, the gradient compost input stimulated rare taxa to reply changes of soil microenvironment, enhanced organic carbon and nitrogen transformation via functional microbial groups, strengthened the interplay among microbes and soil properties. Importantly, soil treated with 30 t compost hm(-2) exhibited the most resilient bacterial community and soil functioning, suggesting that 30 t compost hm(-2) might be the optimal input quantity for remediating sandy loam soil. These findings highlight that the gradient compost input reinforces the relation between microbes and C-/N-metabolisms, and establish more stable microbial interconnections thus enhancing functional gains.