Straw-derived bio-organic fertilizer enhanced ecosystem multifunctionality in acidic paddy by improving microbial community composition and functional diversity

Agricultural waste has tremendous potential for resource utilization. To promote sustainable straw utilization, a novel bio-organic fertilizer (BOF) was produced by combining rice straw and Bacillus methylotrophicus (YH-158) that can produce alkaline xylanase to accelerate straw decomposition. Based on a one-year micro-plot experiment with chemical fertilization as the control, this study assessed the effects of BOF application gradients (4, 6, and 8 t ha^-1) on EMF in acidic paddy soils through the quantification of 16 individual ecosystem functions, and explored the underlying mechanisms linking EMF to soil microbial communities. The results revealed a significant positive correlation between BOF application rates and EMF (R² = 0.734, P < 0.001). Compared to chemical fertilization alone, BOF treatments enhanced EMF by 68.16 %-93.44 %. BOF application increased soil pH and bacterial biomass, changed microbial community composition, and enhanced the intensity and Shannon's index of carbon metabolism. These indicators were significantly related to EMF, with carbon metabolism functional diversity (r = 0.826, P < 0.001) exhibiting the strongest relationship with EMF. Partial least squares path modeling showed that BOF improved EMF by altering microbial community composition (standardized coefficients = 0.468, P = 0.057) and functional diversity (standardized coefficients = 0.490, P < 0.05). Moreover, BOF promoted a shift toward a bacterial-dominated process through pH elevation. These findings suggested that straw-derived BOF application enhanced EMF by optimizing the composition and functional diversity of soil microbial communities. Specifically, high BOF inputs were more effective in enhancing EMF in acidic paddy fields.