Biochar Enhances the Abundance of Microbial Functional Genes Involve in C, N, P, and S Cycling: A Quantitative Metagenomic Insight From Paddy Soil

ABSTRACT Although biochar application is regarded as a promising agronomic strategy to enhance soil functions, research employing quantitative techniques to evaluate its influence on microbial functional genes specifically in paddy soils is still scarce. The objective of this study was to quantify the abundance of microbial functional genes associated with carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycling over a 2‐year paddy field experiment after biochar application, employing a quantitative metagenomic sequencing with the spike‐in method. An increase in rice yield of 7.0% and 12.5% relative to the control was observed following biochar amendment over the 2 study years. The majority of soil microbial functional genes related to C, N, P, and S cycling exhibited higher abundances in soils amended with biochar. Notably, genes associated with the Wood‐Ljungdahl pathway, Calvin‐Benson‐Bassham cycle, and denitrification increased by 18.5%–197.4%, 25.9%–116.0%, and 5.1%–405.3% over 2 years. Gene responsible for P regulators increased approximately 10.5%–109.6%, while the assimilatory sulfate reduction process exhibited an increase of 12.7%–246.0%. Random forest highlighted key biogeochemical processes (e.g., C degradation, tricarboxylic acid cycle, and dissimilatory N reduction) as potential contributors to improving rice yields. Biochar amendment led to the formation of a more complex gene co‐occurrence network, as exposed by network analysis. Collectively, these findings underscore that biochar application may consequently enhance microbial functional capacity in paddy soils, fostering improved agroecosystem functions.