Differential responses of bacteria, fungi, and C, N, P functions to soil acidification in farmland: A meta-analysis

Agricultural ecosystems face the persistent threat of soil acidification resulting from long-term chemical fertilizer application; however, the dynamics of microbial communities and carbon (C), nitrogen (N), and phosphorus (P) cycling functions under varying acidification levels remain unclear. In this study, we employed a meta-analysis of 821 observations from 121 peer-reviewed articles to investigate the responses of farmland soil microbial communities to varying acidification levels. Our results revealed significant variations in soil microbial composition, diversity, and function in response to acidification. As soil pH decreased, bacterial and fungal diversity exhibited divergent trends. Specifically, compared to neutral pH, bacterial Shannon diversity declined significantly by 50.67%, while Chao1 diversity increased by 29.19% at pH 3.5-4.5 ( p < 0.05). The abundances of Zygomycota, Acidobacteria, Gemmatimonadetes, Actinobacteriota, and Verrucomicrobia showed the strongest correlations with soil acidification. Functionally, acidification suppressed C degradation and methane metabolism, enhanced N degradation and nitrification while reducing multiple nitrate-reduction pathways, and stimulated phosphate acquisition, solubilization, and mineralization. Partial least squares path modeling (PLS-PM) analysis indicated that soil acidification had significant negative effects on soil C, N, and P nutrient availability, bacterial α diversity, and C and N cycling functions. This study employed a meta-analysis approach to analyze changes in microbial diversity and function across varying degrees of acidification, providing strategies for managing acidified farmland soils. • Soil acidification negatively impacts bacterial diversity but not fungal diversity. • C fixation and amino acid metabolism processes remain stable with acidification. • Acidification significantly promotes nitrification and N fixation processes. • Acidification promotes phosphorus function cycling processes.