Impact of rice straw addition and soil tillage on density of organic carbon components in paddy soil, the contribution of methane emission into atmosphere and global warming potential

Abstract

Rice production caused methane emissions from ricefields intothe atmosphere. This experiment aimedto elucidate the impact of soil tillage and rice straw addition on the density of organic carbon components in the paddy soil, the contribution of methane emission into the atmosphere and the global warming potential. The experiment was conducted in irrigated area during the second rice cropping season in 2008. Completely randomized design of 2x3factorial treatments with2levelsof rice straw addition; withand without rice straw addition, and3conditions of soil tillage;1)notillage,2) incorporation of rice stubble, and3) incorporation of rice stubble,harrowingandthen puddling. The total 6treatments were carried out with 3 replications. Using the Chainat 1 rice, the result found that soil tillage affected the density of organic carbon components in paddy soil. The increasing number of soil tillage accelerated the decomposition of rice straw and stubble leading to the decreasing density of total organic carbon (TOC) andeachcomponent, i.e., rice roots (RR),particulateorganic residue (POR) andsoilorganic carbon(SOC). The addition of 4 tons of rice straw per rai to paddy soil in one growing season had no effect on the accumulation of organiccarboninsoil. Theexperiment further revealedthat total methaneemission(TME) increased withincreasing number of soil tillage and ranged from 20.6 to 102.3 gCH4 m-2 equivalent to Global Warming Potential (GWP) of 129to642gCeqm-2 . Furthermore, stubble incorporating,harrowing and then puddling released higher TME by53% compared with no tillage while incorporation of 4 tons of rice straw per rai, harrowing and puddling released higher TME andGWPby65%compared with noricestraw and notillage.However, reduction of tillage and soil preparation with stubble incorporation under moist-soil condition alone could decrease methane emission and mitigate global warmingpotential (GWP) by 32% compared with notillage.