Straw application in paddy soil enhances methane production also from other carbon sources
Flooded rice fields are an important source of the greenhouse gas methane. Methane is produced from rice straw (RS), soil organic matter (SOM), and rice root organic carbon (ROC). Addition of RS is widely used for ameliorating soil fertility. However, this practice provides additional substrate for CH 4 production and results in increased CH 4 emission. Here, we found that decomposing RS is not only a substrate of CH 4 production, but in addition stimulates CH 4 production from SOM and ROC. Apart from accelerating the creation of reduced conditions in the soil environment, RS decomposition resulted in enhancement of SOM-derived CH 4 production. In particular, hydrogenotrophic methanogenesis from SOM-derived CO 2 was stimulated, presumably by H 2 released from RS decomposition. On the other hand, the enhancement of ROC-derived CH 4 production after RS application was probably caused by the significant increase of the abundance of methanogenic Archaea in the RS treatment compared with the untreated control. Our results show that traditional management of rice residues exerts a positive feedback on CH 4 production from rice fields, thus exacerbating its effect on the global CH 4 budget.