EFFECT OF CULTIVAR DIFFERENCE (IR72, IR65598 AND DULAR) ON METHANE EMISSION

Cultivar characteristics that may influence cultivar differences in me thane emissions were investigated under greenhouse conditions. Methane emission rates were monitored by the closed chamber technique. Methan e emission rates differed significantly among the three rice cultivars grown in the greenhouse. Traditional rice cultivar 'Dular' had the hi ghest methane emission rates followed by improved modem cultivar 'IR72 ', while newly developed high-yielding plant type 'IR65598' had the lo west methane emission rates. Significant correlation between methane e mission rates and dissolved methane in soil solution indicated that th e differences in methane emission rates were determined by the differe nces in source strength of methanogenic materials. A high correlation was found between methane emission rates and root dry weight, and betw een root dry weight and total carbon released from roots. At a given p artial pressure of methane in soil, methane emission rate was also cor related with tiller number at tillering stage. Root airspace and root oxidation power differed among rice cultivars, but neither correlates with methane emission rates.