Methane Emissions from Rice Fields of the Rostov Region

Abstract

On the example of the Rostov region, the results of measurements by the chamber method of methane fluxes into the atmosphere from rice fields are analyzed. In addition to measuring methane fluxes in the phases of “germination” and “full ripeness” of rice, concentrations of methane and hydrogen sulfide, Eh, pH, density and humidity were determined in the water of the rice check and various horizons of watered soils. The rate of methane flow into the atmosphere from the surface of the rice check varied in the range from 0.195 to 0.531 mg СН4/(m2 h) and in the “full ripeness” phase of rice was on average 2.1 times higher than in the “germination” phase. The rate of methane flow into the atmosphere from the surface of soils located between rice checks was on average 4.9–12.1 times lower than the rate of its flow from rice checks, varying within 0.034–0.045 mg СН4/(m2 h). It is shown that after watering rice checks in soils isolated by a layer of water, Eh values decrease and, as a consequence, there is an increase in methane concentrations in soils and its fluxes into the atmosphere. According to the assessment, the total methane emission by rice fields of the Rostov region approximately reaches 1.253 tons per day or 150 tons/year, which is 0.4–1.5% of the annual methane release by the soils of the Rostov region.