Effects of rice-straw and phosphorus application on production and emission of methane from tropical rice soil

Abstract

Rice-straw amendment increased methane production by 3-fold over that of unamended control. Application of P as single superphosphate at 100 μg (g soil)-1 inhibited methane (CH₄) production distinctly in flooded alluvial rice soil, in the absence more than in the presence of rice straw. CH₄ emission from rice plants (cv. IR72) from alluvial soil treated with single superphosphate as basal application, in the presence and absence of rice straw, and held under non-flooded and flooded conditions showed distinct variations. CH₄ emission from non-flooded soil amended with rice straw was high and almost similar to that of flooded soil without rice-straw amendment. The cumulative CH₄ efflux was highest (1041 mg pot^-1) in rice-straw-amended flooded soil. Appreciable methanogenic reactions in rice-straw-amended soils were evident under both flooded and non-flooded conditions. Rice-straw application substantially altered the balance between total aerobic and anaerobic microorganisms even in non-flooded soil. The mitigating effects of single-superphosphate application or low-moisture regime on CH₄ production and emission were almost nullified due to enhanced activities of methanogenic archaea in the presence of rice straw.