Effect of Moisture Content on Carbon Dioxide Emission from the Soil of Rice Fields in Raozan, Bangladesh

Abstract

Emission of CO₂ from rice fields contributes to global warming. However, CO₂ emission from the soil of rice fields varies with moisture content (MC) during different stages of rice cultivation: submerged (MC≥ 70 per cent), moistened (40 per cent MC), and fallow (20 per cent ≥ MC). Therefore, this study focuses on the effect of MC on CO₂ emission from the soil of rice fields and investigates if average moisture conditions support high CO₂ emission from soil. The research was conducted in three locations in Raozan, Bangladesh. Samples were collected from top soil (0-30 cm), where different stages of rice cultivation were observed. Organic carbon percentage (OC percentage), microbial biomass carbon (MBC), pH, and electric conductivity (EC) of samples were also tested. Results of the study implied that the highest CO₂ emission occurred from submerged soil as a consequence of anaerobic fermentation that favored CO₂ emission due to pH and high OC percentage. Also, the methane oxidation occurred as the submerged samples were exposed to oxygen (O₂)during the sampling and experimental process. CO₂ emission was lowest in fallow soil because of dry conditions that led dehydration of microorganisms. Moistened soil had an intermediate CO₂ emission due to low OC percentage. Therefore, the study suggests that the dry conditions of soil result in the least amount of CO₂ emission; hence, intermittent irrigation methods should be applied in rice fields to minimize the CO₂ emission and water consumption.