Factors controlling diet patterns of methane emission via rice

Methane emissions from hooded rice grown under greenhouse conditions were m onitored using a closed chamber technique. The three rice cultivars showed similar diel emission patterns though the amplitudes differed. Variation in emissions (maximum emission rate) from the different cultivars ranged from 0.164-0.241 mg/pot/h at tillering stage, 0.714-2.334 mg/pot/h at heading s tage, 0.399-1.393 mg/pot/h at ripening stage. The methane emissions increas ed in the morning at accelerating rates, reached a maximum in the early aft ernoon, then decreased rapidly to constant rates during the night. The diel emission pattern was modeled using a Gaussian equation for daytime, and a constant for nocturnal emissions. Applying an Arrhenius equation, more than 90% of the diel variation of methane emissions could be predicted from soi l temperature fluctuations. The predictions improved by using a diffusion m odel based on soil temperature and dissolved methane concentrations in soil solution. Soil temperature and methane concentration in soil solution are the two major factors controlling diel methane emissions.