Case study on effects of water management and rice straw incorporation in rice fields on production, oxidation, and emission of methane during fallow and following rice seasons

To investigate production, oxidation, and emission of methane (CH4) in rice fields during the fallow and following rice seasons as affected by water management and rice straw incorporation in the fallow season, field and incubation experiments were carried out from November 2007 to November 2008. Four treatments, i.e. two water managements (flooded and drained) and two rates of rice straw application (0 and 4.8 t/ha), were laid out in a randomised block design. Results show that obvious CH4 production occurred in flooded fields in the late fallow season; consequently, fallow CH4 emission contributed 9.6-33.1% to the annual total emission. However, emission mainly occurred during the rice season. During the rice season, the mean CH4 production potential in flooded fields was 2.6-3.8 times that in drained fields, making the total CH4 emission 2.1-2.5 times that in drained fields. Rice straw incorporated in flooded fields significantly increased production and emission of CH4 during both the fallow and the following rice seasons (P < 0.05), but in drained fields, no significant effect was observed (P > 0.05). There was no significant difference in mean CH4 oxidation potential between the treatments (P > 0.05), indicating that water management and rice straw incorporation in the fallow season have little influence on CH4 oxidation during the fallow and following rice seasons. Based on the findings, water management and rice straw incorporation in the fallow season significantly affected CH4 emission during the fallow and the following rice seasons by influencing CH4 production rather than CH4 oxidation in fields.