Effects of straw incorporation along with microbial inoculant on methane and nitrous oxide emissions from rice fields.

Abstract Incorporation of straw together with microbial inoculant (a microorganism agent, accelerating straw decomposition) is being increasingly adopted in rice cultivation, thus its effect on greenhouse gas (GHG) emissions merits serious attention. A 3-year field experiment was conducted from 2010 to 2012 to investigate combined effect of straw and microbial inoculant on methane (CH 4 ) and nitrous oxide (N 2 O) emissions, global warming potential (GWP) and greenhouse gas intensity (GHGI) in a rice field in Jurong, Jiangsu Province, China. The experiment was designed to have treatment NPK (N, P and K fertilizers only), treatment NPKS (NPK plus wheat straw), treatment NPKSR (NPKS plus Ruilaite microbial inoculant) and treatment NPKSJ (NPKS plus Jinkuizi microbial inoculant). Results show that compared to NPK, NPKS increased seasonal CH 4 emission by 280–1370%, while decreasing N 2 O emission by 7–13%. When compared with NPKS, NPKSR and NPKSJ increased seasonal CH 4 emission by 7–13% and 6–12%, respectively, whereas reduced N 2 O emission by 10–27% and 9–24%, respectively. The higher CH 4 emission could be attributed to the higher soil CH 4 production potential triggered by the combined application of straw and microbial inoculant, and the lower N 2 O emission to the decreased inorganic N content. As a whole, the benefit of lower N 2 O emission was completely offset by increased CH 4 emission, resulting in a higher GWP for NPKSR (5–12%) and NPKSJ (5–11%) relative to NPKS. Due to NPKSR and NPKSJ increased rice grain yield by 3–6% and 2–4% compared to NPKS, the GHGI values for NPKS, NPKSR and NPKSJ were comparable. These findings suggest that incorporating straw together with microbial inoculant would not influence the radiative forcing of rice production in the terms of per unit of rice grain yield relative to the incorporation of straw alone.