CH₄ emission with differences in atmospheric CO₂ enrichment and rice cultivars in a Japanese paddy soil

Abstract

Abstract A pot experiment was conducted to investigate CH 4 emissions from a sandy paddy soil as influenced by rice cultivars and atmospheric CO 2 elevation. The experiment with two CO 2 levels, 370 μL L −1 (ambient) and 570 μL L −1 (elevated), was performed in a climatron, located at the National Institute for Agro‐Environmental Sciences, Tsukuba, Japan. Four rice cultivars were tested in this experiment, including IR65598, IR72, Dular and Koshihikari. Tiller number, root length and grain yield were clearly larger under elevated CO 2 than under ambient CO 2 . IR72 and Dular showed significantly higher tiller number, root length and grain yield than Koshihikari and IR65598. Average daily CH 4 fluxes under elevated CO 2 were significantly larger by 10.9–23.8% than those under ambient CO 2 , and varied with the cultivars in the sequence Dular ≧ IR72>IR65598 ≧ Koshihikari. Dissolved organic C (DOC) content in the soil was obviously higher under elevated CO 2 than under ambient CO 2 and differed among the cultivars, in the sequence IR72>Dular>Koshihikari>IR65598. The differences in average daily CH 4 fluxes between CO 2 levels and among the cultivars were related to different root exudation as DOC content, root length and tiller number. This study indicated that Koshihikari should be a potential cultivar for mitigating CH 4 emission and simultaneously keeping stable grain yield, because this cultivar emitted lowest CH 4 emission and produced medium grain yield.