High-quantity straw combined with microbial fertilizer positively drives soil multifunctionality and fertility in degraded arid desert ecosystems

Combining straw incorporation with microbial fertilizer in soils has been widely recommended for improving soil function and productivity. However, the effects of high-quantity straw input and the introduction of microbial fertilizer on soil microbial diversity, functional attributes, and nutrient enhancement in degraded sandy soils are inadequately comprehended. Herein, we established a field trial with five treatments: low-quantity straw input (LS), high-quantity straw input (HS), low-quantity straw combined with microbial fertilizer (LSM), high-quantity straw combined with microbial fertilizer (HSM), and without straw and microbial fertilizer (Control). Results indicated that all amendment treatments had a positive impact on soil multifunctionality (SMF) and pivotal nutrient contents. Compared to the control, HSM increased the SMF, total nitrogen (TN), available nitrogen (AN) and available phosphorus (AP) by 205.56 %, 140.00 %, 133.58 %, and 100.00 %, respectively. Biomaterials input reduced fungal richness and bacterial β-diversity. A network analysis showed that the external disturbance promoted species competition and niche separation. Compared to the control, HS notably increased the abundance of functional genes associated with carbon (C) decomposition (by 10.30–64.62-fold), while downgrading the abundance of genes related to C fixation (by 0.75–0.97-fold). The abundance of denitrification-related genes involved in nirK and nirS underwent a notable 25.97-fold increase under HS, while HSM exhibited a 3.82-fold increase in nosZ abundance. Meanwhile, the introduction of microorganisms in HSM was beneficial for the release and stabilization of bioavailable N through upregulation of ureC (0.41-fold) and gdhA (0.21-fold) gene abundance. The best multiple regression model showed that functional attributes were better predictors of SMF than microbial diversity and specific phyla. In summary, our findings highlight that the introduction of high-quantity straw with microorganisms is a feasible pathway for improving SMF and soil fertility in degraded ecosystems.