EFFECT OF CONTINUOUS AND ALTERNATE WATER REGIMES ON METHANE EFFLUX FROM RICE UNDER GREENHOUSE CONDITIONS

In a greenhouse study, the effect of moisture regimes (continuously fl ooded, continuously nonflooded, alternately flooded) on methane efflux from an alluvial soil planted to rice was studied using the closed ch amber method. Methane efflux was almost 10 times more pronounced under continuously flooded conditions than under continuously nonflooded co nditions. Intermittently flooded regimes (alternately flooded and nonf looded cycles of 40 or 20 days each) emitted distinctly less methane t han the continuously flooded system. A significant negative correlatio n was found between methane emission under different water regimes and rhizosphere redox potential. Extractable Fe2+, readily mineralizable carbon (RMC) and root biomass presented a significant positive correla tion with cumulative methane emission. The correlation of methane emis sion with other plant parameters and microbial biomass was not signifi cant. Our results further suggest the possibility of reduced methane e missions through appropriate water management in a rainfed rice ecosys tem.