Assessment of Methane Emission and the Factors That Influence It, from Three Rice Varieties Commonly Cultivated in the State of Puducherry

Abstract

India being the world’s second largest cultivator of paddy, it is very important that the extent of the resulting methane emissions is estimated, and steps are taken to minimize these emissions. Peninsular India is a prime rice-producing region; however, no significant information is available on the contribution of this region to methane emissions, nor are there available studies that show the effect of cultivars, growth seasons, soil characteristics, etc., on methane emissions. As one of the attempts to cover this knowledge gap, emissions of methane from paddy fields, situated in four villages of Puducherry, India, involving three rice cultivars, three soil types and two growth seasons have been studied. All the fields had a continuously flooded pattern of irrigation with water supplied at a rate of 11,500–20,000 m3/ha. Whereas the cultivars ADT 39 and ADT 45 generated the highest methane flux during their reproductive phase, with lesser emission during the vegetative phase and much less during maturity, CO 45 exhibited copious methane emissions during the vegetative phase, with several orders of magnitude lesser emission during the reproductive and the maturity phases. These trends were independent of the location of the field and soil type, though the absolute and the relative values of the emissions varied from location to location. Irrespective of the cultivar, the quantities of methane emission increased linearly with soil temperature across the day but decreased exponentially as soil pH increased beyond 7.

Keywords

• rice
• methane
• cultivars
• flooded irrigation
• global warming