Because two carbon-based greenhouse gases, CH4 and CO2, can share a common soil carbon source, reduced emissions of one gas may enhance emissions of the other. The current study aimed to compare CH4 and CO2 emissions and identify some related mechanisms caused by biochar addition to paddy soils. Two soils of relatively high organic carbon (OC = 3.05%) and low OC (OC = 0.54%) were taken from two paddy fields, mixed with biochar at 0%, 2%, and 4%, submerged, and incubated in closed plastic jars for 53 days. On days 1, 4, 8, 13, 19, 26, 34, 43, and 53, gas from the jar’s headspace was measured for CH4 and CO2, and standing water in individual jars was measured for pH and EC. The results revealed that biochar reduced CH4 emissions by 13% and 74% while increasing CO2 emissions by 36% and 86% in high-OC and low-OC soil, respectively. Biochar had greater impacts on pH, EC, and greenhouse gas emissions in low-OC soil than in high-OC soil. The inverse relationship between CH4 emissions and pH and EC can be explained by biotic mechanisms, which suppressed microbial activities, lowing CH4 emissions. CO2 emissions were proportionally or non-significantly correlated with EC and pH depending on tested soils, which may be explained by abiotic processes. In summary, biochar addition can suppress CH4 emissions while increasing CO2 emissions via biotic and abiotic mechanisms, respectively, dependent on soil pH and EC changes, and biochar effects were stronger in low-OC soil than in high-OC soil.
ⓒ 2026 BICE | Biochar-based Integrated Circular Economy for Paddy Rice.
