Methane flux from rice/wheat agroecosystem as affected by crop phenology, fertilization and water level

Methane flux was measured for a rice/wheat agroecosystem of Gangetic Plains, with and without application of chemical fertilizer and wheat straw (WS). Three treatments of control, fertilizer application and fertilizer + WS application, were established in a completely randomized block design and measurements were made for two consecutive years (1993 and 1994). CH₄ measurements during growth of the rice crop period showed that there were significant difference in flux rates during the two years. Maximum emission occurred at the time of anthesis and minimum at the seedling stage. The flux rates were significantly higher for fertilizer or fertilizer + WS treatments. The effects of the treatments were similar across phenological stages and years. In the subsequent wheat crop and fallow period, the soils consumed CH₄. There were significant differences in CH₄ uptake rates between the two years. Fertilizer treatments reduced CH₄ uptake in both the years. The results suggested that tropical agroecosystems may consume substantial amounts of CH₄ and that the methane output can be reduced by lowering the submergence level in rice paddies.