Methane Flux from Indonesian Wetland Rice : the Effect of Water Management and Rice Variety

Abstract

Methane (CH,) is one of reactive greenhouse gases, its current concentration in atmosphere is increasing with a rate of about 12 + 1 ppbvlyr. An increase of 12 ppbv requires an excess of sources over sinks of 36 Tglyr. Roughly 70% of the total global emission of atmospheric methane (500 f 100 Tglyr) stems from anthropogenic sources mainly from anaerobic decay of organic matter in rice fields and enteric fermentation in ruminants, and about 30% stems from natural sources mainly frcm wetlands. Rice fields are considered as one of important sources of methane emissions into the atmosphere. Estimates of methane from this source show a wide range of 30 - 100 Tglyr with an average of about 60 Tglyr or around 18% of the total global methane emissions. There are large uncertainties about methane emission rates from wetland rice, these are due to the differences of agroclimatic condition and agricultural practices from one region to the others. Most studies on methane emission rates from rice fields are conducted in temperate regions, and practically no data are available from tropical regions. Those data obtained from temperate regions are used to extrapolate global methane emissions from rice fields.