Effect of tillage pattern on soil greenhouse gases (CO₂, CH₄ and N₂O) fluxes in semi-arid temperate regions

Different tillage methods and crop rotations were experimented in Lijiabao Town of Dingxi City, Gansu Province and soil carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) fluxes measured using carbon dioxide analyzer and static chamber-gas chromatographic techniques. Analysis of the four tillage methods tillage without straw or plastic film mulching (T), no-tillage without straw or plastic film mulching (NT), no-tillage with straw mulching (NTS) and tillage with straw mulching (TS) showed that soils with spring wheat and pea were sources of atmospheric CO₂ and N₂O, sink of CH₄ during crop growth seasons. In spring wheat fields, the mean values of soil CO₂ flux (μmol·m^-2·s^-1) were 0.203 6, 0.221 2, 0.241 8 and 0.224 9 for T, NT, NTS and TS treatments, respectively. The mean values of soil CH₄ flux (mg·m^-2·h^-1) were -0.041 6, -0.078 0, -0.081 8 and -0.053 7 and those of soil N₂O flux (mg·m^-2·h^-1) were 0.089 1, 0.069 2, 0.046 1 and 0.065 6 for T, NT, NTS and TS treatments, respectively. In pea field, the mean values of soil CO₂ flux (μmol·m^-2·s^-1) were 0.273 6, 0.261 6, 0.218 1 and 0.236 0 for T, NT, NTS and TS treatments, respectively. The mean values of soil CH₄ flux (mg·m^-2·h^-1) were -0.055 0, -0.073 7, -0.066 2 and -0.054 5 and those for soil N₂O flux (mg·m^-2·h^-1) were 0.123 4, 0.084 7, 0.080 6 and 0.035 0, respectively. Compared with T, NT and TS, NTS retarded CO₂ and N₂O emission and enhanced CH₄ assimilation. Based on the study, NT, NTS and TS conservation tillage methods were efficient for retarding greenhouse gas emission. CO₂ fluxes increased with increasing soil moisture and temperature in spring wheat field, and CH₄ uptake fluxes increased with increasing soil moisture, but reduced with increasing soil temperature. A significant positive correlation was noted between CO₂ flux and soil moisture in pea field. Similarly, a significant positive correlation was observed between N₂O emission and soil temperature in pea and spring wheat fields.