Effect of nitrogen fertilization on methane and carbon dioxide production potential in relation to labile carbon pools in tropical flooded rice soils in eastern India

In an incubation experiment with flooded rice soil fertilized with different N amounts and sampled at different rice stages, the methane (CH4) and carbon dioxide (CO2) production in relation to soil labile carbon (C) pools under two temperature (35 degrees C and 45 degrees C) and moisture (aerobic and submerged) regimes were investigated. The field treatments imposed in the wet season included unfertilized control and 40, 80 and 120kgha(-1)N fertilization. The production of CH4 was significantly higher (27%) under submerged compared to aerobic conditions, whereas CO2 production was significantly increased under aerobic by 21% compared to submerged conditions. The average labile C pools were significantly increased by 21% at the highest dose of N (120kgha(-1)) compared to control and was found highest at rice panicle initiation stage. But the grain yield had significantly responded only up to 80kgha(-1)N, although soil labile C as well as gaseous C emission was noticed to be highest at 120kgha(-1)N. Hence, 80kgN ha(-1) is a better option in the wet season at low land tropical flooded rice in eastern India for sustaining grain yield and minimizing potential emission of CO2 and CH4.