Greenhouse gas emissions in double sequence pea-wheat rotation fields under different tillage conditions

This study analyzed the effects of different tillage conditions on greenhouse gas emissions of double sequence pea-wheat rotation fields during 2011. Three greenhouse gases (CO₂, N₂O and CH₄) emission were investigated under four tillage types conventional tillage without straw mulching (T), no-tillage without straw mulching (NT), conventional tillage with straw mulching (TS) and no-tillage with straw mulching (NTS). The carbon dioxide analyzer and static chamber-gas chromatographic techniques were used to continuously measure and analyze the greenhouse gases fluxes. The results showed that double sequence pea-wheat rotation fields served not only as source of atmospheric CO₂, N₂O, but also as sink of atmospheric CH₄. Compared with T, NT retarded CO₂ emission. The three conservation tillage methods of NTS, NT and TS reduced N₂O emission but significantly increased CH₄ absorption. CO₂ and N₂O fluxes were significantly correlated with topsoil temperature (R² = 0.92^** and 0.89^**), soil temperature at the 5 cm soil depth (R² = 0.95^** and 0.91^**) and soil temperature at the 10 cm soil depth (R² = 0.77^* and 0.62^*). CH₄ fluxes were uncorrelated with soil temperature at different soil depths. The correlation coefficients between CO₂ and soil water content, and CH₄ and soil water content at 0~5 cm soil layer were 0.69^* and 0.72^*, respectively. The correlation coefficient between CO₂ and soil water content at the 5~10 cm soil layer was 0.77^* and that between CH₄ and soil water content at the 5~10 cm soil layer was 0.64^*. CO₂, CH₄ fluxes were positively correlated with soil water content at the 10~30 cm soil layer. N₂O fluxes showed negative correlations with soil water content at different soil layers. The calculated global warming potential of the three greenhouse gases under the different tillage conditions showed that NT limited greenhouse gas flux, thereby reducing greenhouse effect.