Greenhouse gases emission from paddy soil during the fallow season with and without winter flooding in central Japan

Abstract

Many papers on measurements of greenhouse gases (GHGs) emission in rice paddies during a rice cropping season have been published. During a non-cropping season between Nov. and Apr., we investigated direct and indirect GHGs emissions in rice paddies. The indirect GHGs emission was evaluated as the amount of dissolved gases leaching from the paddy fields. Water management practices for the experiment were (1) continuous flooding (CF) and (2) non-flooding (NF). Although the direct CO2 emission in the CF treatment was remained nearly zero during the non-cropping period, direct CO2 emission in the NF treatment was continuously observed throughout the non-cropping period. The concentration of dissolved N2O in the NF treatment was below the detection limit of the instrument during the non-cropping period except immediately after the flooding and before the drainage. The concentration of dissolved N2O kept approximately 2 µg L−1 during the non-cropping period in the CF treatment. The direct CH4 emission and dissolved CH4 were not observed during the non-cropping period. Total gas emission in the NF treatment was 10 times as large as that in the CF treatment. Direct CO2 emission accounted for more than 90 % of the total emission in both treatments.