冬季绿肥对黄土高原旱作春玉米农田土壤温室气体排放的影响

Effect of Winter Cover Cropping on Soil Greenhouse Gas Emissions in a Dryland Spring Maize Field on the Loess Plateau of China

利用田间试验研究了冬季绿肥对旱作春玉米农田土壤温室气体排放的影响.试验设燕麦、小扁豆、燕麦与小扁豆混播和裸地休闲共4个处理,采用静态箱-气相色谱法对冬闲期和春玉米生长期间土壤温室气体(CO_②、N_②O和CH_④)排放通量进行观测.结果表明,旱作春玉米-冬季绿肥种植系统土壤是CO_②、N_②O的排放源和CH_④的吸收汇.与裸地休闲相比,燕麦和小扁豆在冬闲期对土壤CO_②累积排放量没有影响,但在春玉米生长期间导致土壤CO_②累积排放量分别增加了7.77%和25.7%(P<0.05),混播导致冬闲期和春玉米生长期间土壤CO_②累积排放量分别增加了19.1%和14.5%(P<0.05).种植燕麦后冬闲期和春玉米生长期间土壤N_②O累积排放量较裸地休闲分别降低了11.6%和14.7%(P<0.05),而小扁豆分别增加了31.9%和14.9%(P<0.05);混播导致冬闲期土壤N_②O累积排放量降低了19.2%(P<0.05),但在春玉米生长期间差异不显著.与裸地休闲相比,燕麦、小扁豆和混播冬闲期土壤CH_④累积吸收量分别降低了37.9%、23.6%和29.6%(P<0.05),春玉米生长期间分别降低了19.4%、33.5%和31.5%(P<0.05),其中小扁豆和混播在冬闲期和春玉米生长期间差异均不显著.燕麦较裸地休闲在农田综合增温潜势(GWP)、春玉米产量和温室气体排放强度(GHGI)差异均不显著.小扁豆和混播显著提高了GWP,其中小扁豆显著高于混播.而与裸地休闲相比,小扁豆和混播分别提高了春玉米产量的20.3%和15.4%(P<0.05),但对GHGI没有显著影响.综合考虑GWP、春玉米产量和GHGI,本地区冬闲期间将小扁豆和燕麦二者混播能增加春玉米产量的同时有效降低土壤温室气体排放强度.

A field experiment was carried out to study the effects of winter cover cropping on soil greenhouse gas emissions in dryland maize.Four cover crop treatments,namely oat,lentil,a mixture of oat and lentil,and no cover crops(CK),were included during the winter fallow period.Greenhouse gas emission fluxes from soil were measured using the static chamber-gas chromatograph technique.The results showed that:both soil CO_②and N_②O were emitted,but the soil acted as a sink for CH_④.Compared with the that in CK,oat and lentil had no effect on the cumulative amount of soil CO_②emissions during the winter fallow period and increased the cumulative amount of soil CO_②emissions by 7.77%and 25.7%(P<0.05)in the spring maize growing period,respectively;the mixture increased the cumulative amount of soil CO_②emissions by 19.1%and 14.5%(P<0.05)during the winter fallow and spring maize growing periods.In the winter fallow and spring maize periods,compared with that in CK,oat declined the cumulative amount of soil N_②O emissions by 11.6%and 14.7%(P<0.05),and lentil increased the cumulative amount of soil N_②O emissions by 31.9%and 14.9%(P<0.05),respectively.Compared to that in the CK,the mixture declined the cumulative amount of soil N_②O emissions by 19.2%(P<0.05)in the winter fallow period but had no effect in the spring maize period.Compared with the CK,oat,lentil,and their mixture resulted in a declined cumulative amount of soil CH_④uptake by 37.9%,23.6%,and 29.6%(P<0.05)in the winter fallow period and by 19.4%,33.5%,and 31.5%(P<0.05)in the spring maize growing period,respectively.Compared with the CK,oat had no effect on global warming potential(GWP),maize yield,and greenhouse gas intensity(GHGI).Lentil and the mixture increased GWP,and lentil showed a greater increase in GWP than that of the mixture.Compared with the CK,lentil and the mixture increased maize yield by 20.3%and 15.4%(P<0.05),respectively,and had no effect on GHGI.The findings from this study show that the lentil and oat mixture can significantly increase maize yield and decrease GHGI.