One-Time Sulfate Fertilization Slightly Changed the Bacterial Community and Largely Induced Organic Carbon...

Although sulfate fertilizers increase soil sulfur content, their impact on microbial communities and sulfur metabolism remains unclear. We hypothesized that sulfate supplementation affects microbial community abundance and sulfur metabolism, influencing sulfur compound levels. In laboratory settings, we supplemented bare soil with a sulfate solution and monitored 16S rRNA and internal transcribed spacer (ITS) gene expressions, sulfur metabolism-related compounds, and soil organic carbon for 30 days. Significant bacterial community-related alterations were observed upon 1 g kg^-1 potassium sulfate supplementation; however, fungal communities remained unchanged. Compared to the control, sulfate-treated soil significantly accumulated Acidobacteria by day 12 and Bacteroidetes and Verrucomicrobiota by day 30. No such differences were observed in fungal communities. Our 16SrRNA and ITS gene-related functional prediction analysis revealed that sulfate addition significantly increased sulfur transport-, assimilation-, and reduction-associated gene expressions in the soil, indicating increased microbial sulfate activity, primarily through assimilation pathways. Among sulfur compounds, sulfate addition significantly increased only sulfate levels, and even these values remained relatively stable. However, sulfate supplementation significantly induced soil organic carbon consumption, highlighting microbial sulfur cycling stability and sulfur-carbon co-metabolism. Null model analysis of the sequencing data indicated potentially stochastic process-dominated microbial community assembly within 30 days, unaffected by sulfate addition. Overall, sulfate-based fertilizers primarily alter bacterial community structure, allowing for metabolic balance establishment of the sulfur cycle within a certain range, while significantly increasing soil organic carbon consumption. Therefore, sulfate-based fertilizer application and soil organic carbon and pH monitoring must occur simultaneously to avoid excessive sulfate use, potentially leading to soil dysfunction.