Rice yield, carbon sequestration and methane emission potential in paddy soil with the application of rice straw compost and tillage reduction

Abstract

Paddy field is a source of methane, a greenhouse gas contributing to global warming. Soil preparationfor rice cultivation influences on organic matter decomposition and affects methane emission rate. The presentexperiment was conducted to investigate the impact of soil tillage with application of rice straw compost (C/N ratio26:1) on rice yield, carbon sequestration in terms of quantified soil-organic fractions and on potential methaneemission from paddy soil. Experiment was trialed on the second rice cropping during February to May, 2007. Theexperimental design was split plot in CRD, with and without rice straw compost as main plots while tillages andpuddling as subplots. Two tillages and puddling resulted in the increase in plant number per unit area, giving higheryield by 10-13% compared with rice stubble incorporation. Application of 350 kg of rice straw compost / raiincreased rice yield by 19 - 27 %. Puddling decreased both soil organic carbon (SOC) content and organic residue (OR) density. Dissolved organic carbon (DOC) in soil declined right after soil preparation and gradually reached itsmaximum when rice plants were 87 days old, which was consistent with a growth stage of producing root exudates.Reduced tillage and no puddling had contribution to carbon sequestration and methane emission mitigation. On theother hand, they could cause lower rice yield. However, rice straw compost could sustain yield in the case of tillagereduction. Organic residues fractionated from rice stubble contributed higher methane emission potential than thosefrom rice straw compost. Puddling stimulated decomposition of persistent organic residues, fractionated from ricestraw compost, to methane gas.