Effects of biochar on CH4 emission with straw application on paddy soil

Purpose Straw incorporation, a common agricultural practice for improving soil quality in paddy soil, leads to the increase of methane (CH 4 ) emission. Application of biochar in soil is an attractive method to sequestrate carbon and reduce the emission of greenhouse gas. This study aimed at exploring the effect of biochar on CH 4 emission in the paddy soil with straw incorporation. Materials and methods In this study, the low-temperature biochar (BC300) and high-temperature biochar (BC500 and BC700) were incubated with or without straw in soil. Soil CH 4 fluxes were monitored during the whole period of laboratory incubation. Soil properties were measured, including pH, redox potential (Eh) and dissolved organic carbon (DOC). The abundance and composition of methanogenic archaeal and methanotrophic bacterial communities were analyzed by real-time quantitative PCR (qPCR) and high-throughput sequencing, respectively. Results and discussion When no straw was applied, low-temperature biochar decreased soil Eh, increased the abundances of methanogenic archaea, and thus promoted the emission of CH 4 , while high-temperature biochar had little effect on CH 4 emission. When straw was applied, biochar inhibited CH 4 emission by decreasing the content of available carbon for methanogenic archaea. The inhibition effect of high-temperature biochar was stronger than that of low-temperature biochar. Conclusions The results indicated that CH 4 emission was affected by both biochar type and straw application. Biochar could significantly decrease CH 4 emission when straw was returned to paddy soil, and the decrease induced by high-temperature biochar was stronger than that of low-temperature biochar.