Biochar decreases methanogenic archaea abundance and methane emissions in a flooded paddy soil

摘要

Biochar addition can reduce methane (CH_4) emissions from paddy soils while the mechanisms involved are not entirely clear. Here, we studied the effect of biochar addition on CH_4 emissions, and the abundance and community composition of methanogens and methanotrophs over two rice cultivation seasons. The experiment had the following five treatments: control (CI＜), chemical fertilizer application only (BCO), and 0.5% (w/w) (BC1), 1% (BC2), and 2% of biochar applied with chemical fertilizers (BC3). The season-wide CH_4 emissions were decreased (P ＜ 0.05) by 22.2-95.7% in biochar application compared with BCO in the two rice seasons (2017 and 2018). In 2017, biochar application decreased methanogenic archaea (mcrA) but increased methanotrophic bacteria (pmoA) abundances, and decreased the ratio of mcrA/pmoA, as compared with BCO (P＜ 0.05). In 2018, the abundance of mcrA was lower in BC2 and BC3 than in BCO (P＜ 0.05) but was not different between BCO and BC1, and the abundance of pmoA was lower in BC1, BC2 and BC3 than in BCO (P ＜ 0.05). The CH_4 emissions were positively related to abundances of the mcrA gene (P ＜ 0.01) but not to that of the pmoA gene in two rice seasons. Rice grain yield was increased by 62.2-94.1% in biochar addition treatments compared with BCO in the first year (P ＜ 0.01) and by 29.9-37.6% in BC2 and BC3 compared with BCO in the second year (P ＜ 0.05). Biochar application decreased CH_4 emissions by reducing methanogenic archaea abundance in the studied flooded paddy soil.