METHANE EMISSION FROM TWO DIFFERENT RICE ECOSYSTEMS ( AHU AND SALI ) AT LOWER BRAHMAPUTRA VALLEY ZONE OF NORTH EAST INDIA

Abstract

Monocropping of rice is practiced in Assam (situated at north east part of India) throughout the year in different agro-ecosystems (upland and lowland) primarily under rainfed conditions. The estimation of methane emission has been realized investigating high yielding rice varieties viz. Ranjit and Mahsuri, grown under two different agro-ecosystems at Lower Brahmaputra Valley Zone of Assam with sandy to sandy loam type of soil. Variety 'Ranjit' grown at monsoon ( Sali ) rice ecosystem at lowland rainfed condition showed higher seasonal integrated methane flux value compared to variety 'Mahsuri' grown at pre monsoon ( Ahu ) rice ecosystem. Both varieties showed two methane peaks, one at the active tillering stage and the second at the reproductive stage of the crop. The observed variation in methane emission peaks are contributed mainly by physiological characteristics of the rice plant such as leaf numbers, tiller numbers, plant height, root shoot biomass and leaf area index. Statistical analysis of these parameters showed a positive correlation with methane emission. These physiological parameters are in turn governed by plant genotypes and environment i.e., the field water availability and climatological factors (rainfall and temperature) during the growing season. While comparing the two ecosystems it was found that methane emission is significantly less from upland rainfed rice ecosystem and this ecosystem can be considered a suitable option for biological mitigation of methane from rice paddies.