Effect of cultivar difference ('IR72', 'IR65598' and 'Dular') on methane emission

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