The effects of groundwater level, water regime and organic manure on methane emission were studied from imitation field with collector boxes. The results show that methane emission rate from larger quantity of green manure plot(HHS 2) is higher than that from normal quantity of green manure plot(HMS 1) during early rice vegetation period, while to late rice, the order is HMS 1>HHS 2. The methane emission rate from low water level plot(HHS 2) is higher than that from high water level plot(HHS 1) during early rice vegetation period, while to late rice, the order is HHS 1>HHS 2. The methane emiss...