| Abstract:Taking the exogenous organic carbon directly flooding as a referance, indoor incubation method was designed to study the methane emission difference from paddy soil under flooded condition adding different exogenous organic carbon (pig manure, chicken manure and rice straw), and the dynamic correlation between methane emission and oxidizable organic carbon fraction by using potassium permanganate oxidation method to group oxidizable organic carbon. The study was aimed at defining the effect of exogenous organic carbon on methane emission from paddy soil and its mechanism. The main experimental results are as follows:(1) Exogenous organic carbon flooded incubation mixed with soil significantly increased methane emission. Besides, methane accumulation emission amount in the treatment of Soil+Ricestraw was respectively60.70%(P<0.01) and86.97%(P<0.01) higher than that in the treatment of Soil+Chicken-manure and Soil+Pig-manure. Methane emission from each treatment was concentrated in the first31days after the incubation.(2) The carbon amount in the form of methane emission from exogenous organic carbon (pig manure, chicken manure and rice straw) was accounted for1.23%～3.75%of the total carbon amount input, and was only0.09%from soil incubation alone.(3) After adding exogenous organic carbon in flooded soil, methane emissions fluxes were significantly correlated with soil Eh and temperature, respectively, but were not correled with soil pH due to little pH change by soil buffer effect.(4) In the exogenous organic carbon flooded incubation mixed with soil, significant or extremely significant correlation was existed only between the content of soil AOC16.7-3.33and AOC3.33in the most of monitoring time. Moreover, methane emissions fluxes were extremely significantly correlated with soil AOC16.7-3.33and AOC3.33, respectively. Stepwise regression analysis of the relation of methane emissions fluxes with oxidizable organic carbon fractions, environmental factors in the methane emission peak was showed that soil AOC3.33organic carbon and soil temperature were the main influencing factors related with methane emissions fluxes in the exogenous organic carbon flooded incubation mixed with soil, and the direct positive effect of AOC3.33organic carbon on methane emissions was larger and showed a highly significant correlation.(6) The overall conclusion:exogenous organic carbon significantly promoted methane emissions in paddy soil. The decomposition and transformation of AOC3.33oxidizable organic carbon in flooding reductive condition is the key factor to affect methane emissions. AOC3.33content of exogenous organic carbon can be used as indicator in the CH4emission characteristics index. |
