Influence of flooded and non-flooded conditions on methane efflux from two soils planted to rice

In a greenhouse study, CH₄ flux from alluvial and laterite soils planted to rice (cv. CR 749-20-2) was monitored under non-flooded and flooded conditions. CH₄ flux from continuously non-flooded pots was always lower than from pots maintained under flooded conditions. The cumulative CH₄ flux was 150 and 880 mg pot⁻¹ in laterite and 105 and 405 mg pot⁻¹ in alluvial soils under non-flooded and flooded conditions, respectively. While non-flooded conditions exhibited a single CH₄ peak at vegetative stage, flooded conditions showed additional peak at reproductive stage. CH₄ flux maxima was more intense under flooded conditions and persisted for a longer period during the reproductive stage than at the vegetative stage. Soil contents of Fe²⁺, readily mineralizable carbon (RMC) and ninhydrin reactive nitrogen (NRN) exhibited significant positive relationship with CH₄ flux. Among the plant characters, a significant negative relationship existed between CH₄ flux and α-naphthylamine oxidase activity of the root base under flooded condition and root tip under non-flooded conditions.