Analysis On The Effects Of Farmland Management Measures On Soil N₂O And CO₂ Emissions In Winter Wheat Fields

Global warming caused by greenhouse gases has always been a hot topic in the field of climate and environment.To explore the effects of three kinds of farmland management measures,such as irrigation,tillage and straw retention,on soil greenhouse gas emissions and yield in wheat field in North China,a typical wheat farmland in Jinzhou City,Hebei Province was selected as the experiment spots.Field experiments were carried out with different irrigation amount,tillage method and straw retention treatment.The emission fluxes of N₂O and CO₂ on soil were collected and analyzed by Static chamber-gas chromatography method.Based on the analysis of the experimental data and the comprehensive consideration of greenhouse gas emission and winter wheat yield,the TOPSIS method was used to select the relatively optimal treatment.The main conclusions are as follows:(1)According to the local irrigation amount CK(89.96mm),T1(80.96mm),T2(71.97mm),T3(62.97mm),T4(53.98mm)and T5(44.98mm)were set.The results showed that soil N₂O cumulative emissions from T1-T5 treatment were 24.99%,10.90%,39.15%,48.99%and 56.11%lower than CK.And soil CO₂ cumulative emissions were 5.47%,4.75%,9.65%,7.52%and 12.33%lower than CK,respectively.Compared with CK,the comprehensive greenhouse effect of soil N₂O and CO₂emissions from T1 to T5 treatment was reduced by 8.20%,5.61%,13.76%,13.30%and18.43%respectively.Combined wheat yield,the irrigation amount corresponding to T3treatment is the relatively optimal irrigation amount.(2)Six kinds of fertilization levels:F_0.3,F_0.4,F_0.5,F_1.0N₀,F_1.0N_0.5,F_1.0N_1.0 and two kinds of tillage methods:X(rotary tillage),S(deep tillage)were set up for 12 treatments.Under F_0.3 fertilization,S treatment increased by 30.92%compared with X treatment,under the fertilization levels of F_0.4,F_0.5,F_1.0N₀,F_1.0N_0.5 and F_1.0N_1.0,S treatment reduced 25.22%,30.10%,35.78%,18.38%and 40.38%respectively compared with X treatment.It can be seen that the change of cultivation method from perennial rotary tillage to deep tillage can effectively reduce the emission of N₂O and CO₂ on wheat farmland soil.Based on the analysis of wheat yield,it is considered that F_1.0N₀S treatment is the relatively best tillage method.(3)Two kinds of tillage methods:X(rotary tillage),S(deep tillage)and three methods of straw returned:SR₀(no straw returning to the field),SR_0.5(half straw returning to the field),SR_1.0(full straw returning to the field)were set up for 6treatments.Under deep ploughing conditions,compared with SR₀,the comprehensive greenhouse effect of soil N₂O and CO₂ emissions increased by 16.50%and 35.96%respectively under the treatment of SR_1.0 and SR_0.5,while the wheat yield decreased by2.94%and 26.47%respectively.Under the condition of rotary tillage,the comprehensive greenhouse effect of soil N₂O and CO₂ emissions from SR_1.0 and SR_0.5increased by 17.15%and 46.56%respectively compared with SR₀.While the wheat yield of SR_1.0 increased by 17.86%,and the wheat yield of SR_0.5 decreased by 14.29%.In consideration of gas emission,wheat yield and straw utilization,it is considered that the full return of corn straw under rotary tillage and the non-return of corn straw under deep tillage is a more suitable method for local straw treatment.