Effects Of Cover Crop-Winter Wheat System On Soil Water,Greenhouse Gas Emission And Carbon And Nitrogen Budget

Field experiment was conducted to study the effects of cover cropping and nitrogen application on soil moisture and crop yield in a winter wheat farmland.The experiment adopted a randomized block treatment of two factors:cover crops(ryegrass(R),changwu soybean(S),mixed of ryegrass and changwu soybean(MIX),fallow control(NC)and nitrogen levels(0,60,120 kg·N·hm-2)design.In the research,we study cover cropping how to affect the precipitation storage efficiency,winter wheat yield,the greenhouse gas emissions and GWP in the Loess Plateau winter wheat field during the leisure period.The main results are as follows:(1)Cover cropping made precipitation storage efficiency and soil water at wheat,among them planting signifcantly with Changwu soybean and mixed.Compared that with fallow,the soil water content of wheat before sowing of S,R,and MIX treatments decrease were the 2.1%-4.9%(P<0.05)?0.7%-1.3%and 2.6%-4.1%(P<0.05).On the growth period of cover crop,the precipitation storage efficiency of S,R,and MIX treatments were respective layer decrease the control by 7.3%-33.5%(P<0.05)?0.7%-9.2%?15.7%-29.1%(P<0.05).The effect on soil moisture of shallow layer(20-120cm)was the great in the precipitation average summer vacation,but if long-term no rainfall in summer,the effect on soil moisture of deep layer(120-200cm)will the great.Nitrogen application reduced the soil moisture content of wheat before sowing compared with no nitrogen application(P<0.05),but had no effect on precipitation storage efficiency.(2)Cover cropping increased the CO2 flux and reduced the N2 flux and had no effect on soil CH4 flux and increased the GWP.Compared NC,CO2 flux of S,R,and MIX treatments increased 24.5%(P<0.05).12.8%and 19.3%respectively,Changwu soybean soil CO2 flux reached 4.58kgC·hm-2 d-1.the soil N2O flux of S,R,and MIX treatments decrease were the 22.6%(P<0.05)?1.3%and 46.1%(P<0.05)respectively,Changwu soybean and mix soil N2O flux reached 0.58gN·hm-2·d-1 and 0.42gN·hm-2·d-1.GWP of S,R,and MIX treatments decreased 24.7%(P<0.05)?13.4%?19.9%respectively.Compared with no nitrogen treatment,N2 treatment soil N2O flux increased 1.33 times(P<0.05).(3)As for soil carbon expenditure,S(225.81kgC·hm-2)>NC(217.83 kgC·hm-2)>R(211.91 kgC·hm-2)>MIX(208.75 kgC hm-2)S and MIX treatments shoot biomass carbon content contained was higher than R 52.65%and 72%respectively,and there was no difference in.root biomass carbon content.Compared with NC,cover cropping reduced soil nitrate nitrogen content of 0-40cm and reduce total N2O flux.S?R and MIX treatment nitrate nitrogen content reduced 15.7%(P<0.05)?16.8%(P<0.05)and 24.5%(P<0.05).S and MIX treatment total soil N2O flux decreased 21%and 42%.(4)Cover cropping reduced winter wheat yield.Compared with NC,the winter wheat biomass of S and MIX treatment reduced 18.6%(P<0.05)and 17.4%(P<0.05),the winter wheat yield reduced 18%(P<0.05)and 18.3%(P<0.05),wheras cover cropping did not affect ryegrass.Cover cropping had no effect on the harvest index and 1000-grain of winter wheat.winter wheat yield.Compared with no nitrogen application,nitrogen application wheat yield increased 31%-48%(P<0.05).