Diatomite Outcompetes Biochar for Reducing Methane Emissions in Rice Paddy Soil Through Shifts in Microbial Communities and Resource Stoichiometry

Abstract

Diatomite is useful in soil remediation and water purification. However, its impacts on methane (CH4) and nitrous oxide (N2O) emissions in paddy soils and the underlying mechanisms remain poorly understood. A pot experiment was set up with four treatments, including a non-amended control (CK), sole biochar (B), sole diatomite (D), and combined biochar–diatomite (BD) amendments, to compare their effects on CH4 and N2O emissions from paddy soil. Compared to CK, D and BD treatments reduced global warming potential (GWP) by 32.40% and 34.41%, respectively, significantly outperforming B treatment. All amendments reduced cumulative N2O emissions by 50.0−62.3%, with no significant variations observed among the amended treatments. CH4 was the primary contributor to GWP, and its emissions were most effectively reduced by diatomite. A random forest analysis found that the DOC/NO3−-N ratio had a high relative influence on CH4 emissions. B, D, and BD treatments significantly increased pmoA gene abundances by increasing redox potential and lowering the DOC/NO3−-N ratio. B treatment significantly reduced mcrA gene abundances, whereas D treatment exhibited no significant effect. All amended treatments altered the methanogenic community; only D and BD affected the methanotrophic community. Overall, diatomite outcompetes biochar for reducing the GWP of rice cultivation because it more potently suppresses CH4 emissions by improving soil aeration, favorably shifting microbial community structure and altering resource stoichiometry.