CULTIVAR VARIATION IN METHANE EFFLUX FROM TROPICAL RICE

Wide variation in CH4 flux was noticed among the ten rice cultivars gr own under uniform field conditions. Cumulative CH4 flux ranged from 4. 61 g m(-2) to 20.25 g m(-2). The rice cultivars could be ranked into t hree groups based on their CH4 flux potential. Rice cultivars could al so be arranged based on their peak CH4 emission occurring either at ve getative, reproductive or at both growth stages. Of the several variab les studied (root region redox potential, above- and underground bioma ss, grain and straw yield, duration of the crop, percent area occupied by the air space and root oxidase activity), only oxidase activity of the root tip exhibited a significant (negative) correlation with CH4 flux indicating an indirect effect of root oxidation potential on CH4 flux. Data presented in this study, demonstrate inherent variation in CH4 flux among different rice cultivars that can be used for developin g future mitigation options.