The Effects of Water Management Incorporating Intermittent Irrigation on Soil Redox Potential (Eh) , Greenhouse Gas Emission, and Water Saving.

Paddy field is a major source of CH₄ gas in the agriculture sector（IPCC, 2001）. Water management of paddy field is an important factor which influences the release of CH4, N2O. Anaerobic environment is developed in paddy soil by water flooding so that CH₄ is generated due to the activity of methane producer （anaerobes bacteria）. Previous study showed that Intermittent irrigation suppressed the release of methane. The various saturation of soil made by Intermittent irrigation, however, released more N₂O than did saturated soil made by Flooding irrigation. （Yan et al., 2000）. In order to suppress the emission of greenhouse gases from paddy fields, we investigate the effects of Intermittent irrigation on soil redox potential (Eh), in relation to gas flux of CH₄ and N₂O. We had known that the water management which incorporating Intermittent irrigation in early time was bad for rice yield. So our research focus on the water management which compounds Flooding and Intermittent irrigation （Compound）, which started Intermittent irrigation after the flooding processing of one month after transplantation. We investigated the water consumption during culturing period.

Experiments were carried out in the 6 lysimeters （NO.1-6）. NO.1,3,5 were Flooding District, and NO.2,4,6 were Compound district. Gas sampling was carried out once a week by closed-chamber method. Soil redox potential (Eh) at 10 cm depth in each plot was measured chronologically.

As a result, it was seen that differences in the value of Soil redox potential (Eh) made by a different water management influenced on gas emission. Water consumption of Compound during culturing period was successful in 25 % reduction than Flooding. There is a need to be more detailed investigation of the timing of CH₄ and N₂O emissions will increase.