RICE-ECOSYSTEMS OF INDIA IN THE CONTEXT OF METHANE EMISSION

摘要

The rice land is linked to the climate change due to its methane emission potential. The systems of growing rice and associated soil and crop management practices that have evolved are varied and complex. However, from the methane emission point of view, water regime is a crucial parameter. According to IPCC guidelines the rice ecosystem need to be categorized into four strata for methane emission study. Ancillary data on rainfall, elevation, soil, command area/ irrigation statistics were used with remote sensing derived rice maps in GIS to categorise the rice lands into four strata as: irrigated, rain fed flood prone and rain fed drought prone and others. In-situ weekly measurements of methane emission from the representative ecosystems was collected and analysed using gas chromatography following the IPCC standards for three consecutive years; 2003, 2004 and 2005. This paper highlights the results of the study carried out to stratify the rice lands of India into different strata and methane emission pattern observed using in-situ measurements. Results showed that the major stratum emerged as the rainfed drought prone with 42.8 per cent of total rice lands (wet season) and found in many states. Rainfed flood prone accounted for around 9.6 per cent, mainly found in Assam, Bihar, WB, Orissa, AP. Irrigated stratum occupied 38.8 per cent during wet season. The irrigated intermittent category was prevalent in the northwestern regions in about 8.8 per cent of the area. The CH_(4) emission pattern of irrigated crop in dry season showed a steady increase in the beginning which peaks during flowering stage, decreasing gradually there after. The results were consistent for different varieties and across the years. The emission pattern of irrigated wet season crop showed two peaks. The emission pattern also showed the influence of crop variety as well as year (of observation).