The effect of water management based on soil redox potential on methane emission from two kinds of paddy soils in Japan

Paddy fields are major sources of the global methane (CH4) emission. Water management of paddy fields affects rice yield and CH4 emission. There is need for improvement in the management to achieve a balance between them. We suggest the water management based on soil redox potential (Eh), which was named Eh control. The effects of Eh control on rice yield and CH4 emission, and applicability to field conditions were considered by pot experiments. This study was carried out at a plastic film house in the Agricultural and Forestry Research Center, University of Tsukuba, Japan, in 2002. The effects of Eh control (EH) were compared with conventional management methods (continuous flooding [CF], midseason drainage [MD], and MD plus intermittent irrigation [IM]) for two kinds of soils. The drainage for Eh control, aim of which was not to reach -200 mV, was carried out when the soil Eh decreased to -150 mV. Then one or two days later, the soil was reflooded. The CH4 emissions of MD, IM, and EH were 64, 26, and 17% of CF, respectively. However, the order of brown rice yield was as follows: IM > MD > CF > EH. With the drainage for Eh control, soil Eh increased to higher than 400 mV several times, and this condition was maintained for up to one day. This excessive drying of the soil affected rice growth and yield of EH. To apply Eh control to field conditions, the upper limit of soil Eh must be controlled to avoid the excessive drying. Moreover, water demand of rice plants is necessary to be considered. (c) 2005 Elsevier B.V. All rights reserved.