[Effects of stabilized N fertilizer combined with straw returning on rice yield and emission of N2O and CH4 in a paddy field]. / ç¨³å®šæ€§æ°®è‚¥é åˆç§¸ç§†è¿˜ç”°å¯¹æ°´ç¨»äº§é‡åŠN2O和CH4排放的影响.

Based on a two-year field experiment located at Shenyang Applied Ecological Experiment Station of Chinese Academy of Sciences, we examined the effects of stabilized N fertilizer combined with straw returning on rice yield and emission of N2O and CH4 in aquic brown soil. Six treatments were set up, i.e. control (CK), urea(U), urea+urease inhibitor+nitrification inhibitor (U+I), straw (S), straw+urea (S+U), straw+urea+ urease inhibitor+nitrification inhibitor (S+U+I). The results showed that urea application increased rice yield, cumulative N2O and CH4 emission, and global warming potential. The treatment of U+I significantly mitigated cumulative N2O emission. Returning rice straw to the field significantly increased cumulative N2O emission, cumulative CH4 emission, global warming potential, and greenhouse gas emission intensity. The S+U+I treatment had the highest rice yield and greenhouse gas emission intensity. U+I treatment had the the second highest rice yield and the lowest greenhouse gas emission intensity. Rice yield in the S treatment showed no significant difference with CK. Our results indicated that S+U+I and U+I are relatively better agricultural strategies compared with other treatments in paddy fields on aquic soil.

[Mass spectrometry assay for denitrifying enzyme activity measurement].

Nitrification inhibitors exert inhibition function in soil nitrification process (NH4(+)-N to NO3(-)-N) and are widely applied in order to improve N fertilizer use efficiency. Before the new nitrification inhibitor is used, its effects on denitrification process must be investigated and denitrifying enzyme activity (DEA) is an effective indicator to show this process. In the present paper, a mass spectrometery (MS) method was taken to measure the denitrifying enzyme activity in the new nitrification inhibitor 3, 4-dimethylpyrazole phosphate (DMPP) incubation system. The results showed that the method measured the concentration of N2O in the incubation system accurately and the concentration measured by MS had marked correlation with that measured by gas chromatogram (GC) (MS(N2O) = -0.45 + 1.03GC(N2O, R2 = 0.995). At the same time, enrichment of 15 N2O and 15 N2 was measured to discriminate the nitrate reductase and N2O reductase. Differed with traditional method, the enzymatic inhibitor-acetylene was not appended. The results showed that DMPP had no influence on the denitrifying enzyme activity and indicated that the denitrification process was not influenced by DMPP.