种植不同冬季作物对稻田甲烷、氧化亚氮排放和土壤微生物的影响

研究双季稻收获后填闲种植不同冬季作物在其生长季节内甲烷（CH4）和氧化亚氮（N2O）的排放特征,对合理利用冬闲稻田、发展冬季作物生产及合理评价不同种植模式具有重要意义。采用静态箱-气相色谱法对冬季免耕直播黑麦草、紫云英和冬闲的双季稻田中CH4和N2O排放及其相关微生物数量变化进行了分析。在冬季作物生长期,不同冬季作物稻田CH4和N2O排放通量均显著高于对照（冬闲）,CH4和N2O排放通量均表现为免耕直播黑麦草〉免耕直播紫云英〉冬闲;免耕直播黑麦草和紫云英处理稻田CH4排放量分别为2.28和1.07 g·m^-2,分别比对照增加241.92%和60.63%;N2O排放量分别为0.59和0.48 g·m^-2,分别比对照增加71.93%和40.06%;各处理稻田土壤产甲烷细菌、甲烷氧化细菌、硝化细菌及反硝化细菌的数量变化范围分别为0.33×10^2 163.37×10^2 cfu·g^-1、11.05×10^3~245.68×10^3 cfu·g^-1、3.21×10^3~178.26×10^3 cfu·g^-1和10.47×10^5~198.88×10^5 cfu·g-1,免耕直播黑麦草和紫云英处理稻田土壤产甲烷细菌、甲烷氧化细菌、硝化细菌和反硝化细菌的数量均显著高于冬闲,其中免耕直播黑麦草处理稻田土壤的产甲烷细菌、甲烷氧化细菌和硝化细菌数量显著高于免耕直播紫云英处理,而免耕直播紫云英处理稻田土壤反硝化细菌的数量则显著高于免耕直播黑麦草处理。研究结果显示,种植不同冬季作物能促进稻田生态系统中CH4和N2O的排放,而这两种气体的排放量与稻田土壤产甲烷细菌、甲烷氧化菌、硝化细菌和反硝化细菌数量变化密切相关。

Effects of different winter covering crops cultivation on methane and nitrous oxide emission fluxes and soil microorganism in double-cropping paddy field

Methane （CH4） and nitrous oxide （N2O） are two important trace gases, which are considered to have 15-30 and 150-200 times more radioactively active than CO2, respectively. It is well known that agricultural soils are the major sources of atmospheric CH4 and N2O. At present, the effect of different winter crops cultivations on CH4 and N2O emission fluxes from double-cropping paddy field is unclear. So the quantitative and possible mechanisms dependence of CH4 and N2O emission fluxes from double-cropping paddy field on different winter crops cultivation is still far from being understood. In the paper, the static chamber-gas chromatography （GC） technique with manual method was used to verify the effects of different winter crop treatments including no-tillage ryegrass （Lolium multiflorum L.） （T1）, no-tillage Chinese milk vetch （Astragalus sinicus L.） （T2） and fallow （CK） on CH4 and N2O emission from double-cropping paddy fields in subtropical regions of China and related microflora. The results showed that the flux and emission of CH4and N2O was varied with different winter crops cultivations in the order： T1〉T2〉CK, and the emission of CH4 and N2O from the two treatments during the whole growth stage was more significant than that of CK （P〈0.01）. T1 and T2 not only had the largest CH4emission （2.28 and 1.07 g·m-2） with increasing by 241.92% and 60.63%, but also had the largest N2O emission （0.59 and 0.48 g·m-2） with increasing 71.93% and 40.06% compared with CK. The results indicated that the abundance of methanogens, methanotrophs, nitrifying bacteria and denitrifying bacteria from the two treatments during the whole growth stage was more significant than that of CK. During the winter covering crops whole growth stage, the abundance of methanogens, methanotrophs, nitrifying bacteria, nitrifying bacteria was 0.33-163.37×102cfu·g-1, 11.05-245.68×103 cfu·g-1, 3.21-178.26×103cfu·g-1, 10.47-198.88×105 cfu·g-1, respectively. Moreover, the abundance of methano