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

Abstract

Straw incorporation, a common agricultural practice for improving soil quality in paddy soil, leads to the increase of methane (CH4) 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 CH4 emission in the paddy soil with straw incorporation. In this study, the low-temperature biochar (BC300) and high-temperature biochar (BC500 and BC700) were incubated with or without straw in soil. Soil CH4 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. When no straw was applied, low-temperature biochar decreased soil Eh, increased the abundances of methanogenic archaea, and thus promoted the emission of CH4, while high-temperature biochar had little effect on CH4 emission. When straw was applied, biochar inhibited CH4 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. The results indicated that CH4 emission was affected by both biochar type and straw application. Biochar could significantly decrease CH4 emission when straw was returned to paddy soil, and the decrease induced by high-temperature biochar was stronger than that of low-temperature biochar.