接种蚯蚓对施加秸秆的旱作稻田N2O排放的影响

通过田间试验研究了秸秆不同施用方式下接种蚯蚓(威廉腔环蚓，Metaphire guillelmi)对水稻旱作土壤N2O排放通量的影响。结果显示施加秸秆和接种蚯蚓增加了N2O的排放量。在秸秆表施的情况下，接种蚯蚓处理显著提高了N2O的排放量，从12.54 kg/hm2提高到14.94 kg/hm2 (P<0.05)；但是在秸秆混施的情况下，接种蚯蚓处理未显著提高N2O的排放量。蚯蚓的存在使土壤NO3--N的含量显著提高，尤其是在混施秸秆的情况下。由于栽培期内NH4+-N变化幅度较小，不同处理NO3--N含量的变化决定了土壤矿质氮的分异。农田生态系统中蚯蚓对N2O排放的贡献主要体现在促进秸秆混入土壤，从而加快秸秆的分解和N2O的排放。

Influence of Earthworms on N2O Emissions in Aerobic Rice with Crop Residues

Earthworms play an important role in determining the greenhouse-gas balance of soils worldwide. A field experiment in aerobic rice was conducted to investigate the effects of crop residues and earthworm activities on soil properties and N2O emissions. A 120-day mesocosm experiment was set up in which crop residues were either incorporated or applied on top of the soil in the presence or absence of earthworm (Metaphire guillelmi). The results indicated that Metaphire guillelmi significantly enhanced soil N2O emissions. In the treatment with crop residues mulching, the cumulative emission amounts of N2O significantly increased from 12.54 to 14.94 kg/hm2 (P<0.05) in the presence of earthworm. However, if residues were incorporated into the soil, the earthworm effect disappeared. Soil mineral nitrogen was increased, and nitrogen mineralization was strengthened by earthworm activities. The level of NH4+-N in soil of different treatments remained at a very low level during the whole growing period of aerobic rice, while the variations of NO3--N content in soil was very high. The spatial-temporal variations of soil NO3--N had close relationships with soil mineral nitrogen level. The results of this study suggested that Metaphire guillelmi increased cumulative N2O emissions by affecting denitrifier community activity via incorporation of fresh residue into the soil and accelerating decomposition.