[Effects of Water Deficit on Greenhouse Gas Emission in Wheat Field in Different Periods].

Field experiments and static chamber-gas chromatography analysis were conducted in 2016-2017 to study the effects of deficit irrigation on CO ₂ , N ₂ O, and CH ₄ emissions from soils of winter wheat fields and to optimize irrigation management measures in the Guanzhong Plain of China. Three irrigation levels (full irrigation, 100%; medium water deficit, 80%; and severe water deficit, 60%) were set during the three important growth periods of winter wheat (overwintering, jointing to heading, and heading to filling periods), with 6 distinct treatments (CK, T1, T2, T3, T4, T5, in which CK treatment is full irrigation, and others are water deficit treatments). The dynamic characteristics of the emission fluxes of the three greenhouse gases were described. Crop yield, long-term net global warming potential (net GWP _L ), and seasonal net global warming potential (net GWP _S ) were used to comprehensively evaluate the influence of water deficit levels during different growth periods of wheat on economic and ecological issues in the Guanzhong Plain. The results showed that the CO ₂ and N ₂ O emission fluxes increased, with the highest values for CK treatment. The CH ₄ absorption fluxes decreased rapidly with increased irrigation, there was even indication of CH ₄ emissions during high irrigation treatment. Compared to CK treatment, T1, T2, T3, T4, and T5 CO ₂ emissions decreased significantly by 13.32%, 25.98%, 5.55%, 15.47%, and 17.52% ( P <0.05); and N ₂ O emissions decreased by 12.20%, 18.00%, 5.63%, 11.54%, and 13.53%( P <0.05), respectively. The total CH ₄ absorption significantly increased by 46.47%, 75.78%, 19.47%, 53.40%, and 62.33%( P <0.05), respectively. Net GWP _L for T1, T2, T3, T4, and T5 treatments were significantly reduced by 10.07%, 12.77%, 6.50%, 6.81%, and 11.53% ( P <0.05), respectively, in comparison with CK treatment. In addition to T3 treatment, net GWP _S of T1, T2, T4, and T5 treatments decreased significantly by 13.21%, 37.65%, 24.60%, and 19.86% ( P <0.05), respectively, compared with CK. Wheat yield at T1, T2, T3, T4, and T5 treatments reduced significantly by 12.56%, 32.53%, 2.25%, 20.93%, and 18.14% compared with CK treatment ( P <0.05). Even though wheat yield under T3 treatment was reduced by 2.25% compared with CK treatment, there was no significant difference ( P >0.05). In addition, there were highly significant ( P <0.01) positive partial correlations between CO ₂ , N ₂ O, and CH ₄ emission fluxes and soil WFPS. Therefore, deficient irrigation can significantly reduce greenhouse gas emissions in wheat fields, but there are varying degrees of reduction. Considering both economic and ecological effects of water deficit in different growth periods, T3 treatment is the most conducive to keep the balance between production yield, water conservation, and emission reduction of winter wheat crops in the Guanzhong Plain.