The Process Of Cover Crop Decomposition And Its Effect On Agricultural Soil Carbon Budget In Weibei Highland

Nylon mesh bag method was used in the Weibei Highlands to study different cover crops(Changwu soybean(S),ryegrass(R)and both 1:1(M))double pressure and nitrogen levels0,60,120 kg/hm~2 under two-factor treatment,fill the process of cover crops decomposition,and the subsequent release of greenhouse gases dynamics,winter wheat yield and the influence of soil carbon budget.The main conclusions are as follows:(1)The decomposition and carbon and nitrogen release characteristics of each cover crop after turning over pressure are shown as"fast in the early stage,slow in the middle stage and faster in the late stage",and the decomposition of cover crop conforms to Olsen model,and the cumulative decay rate of each treatment on 276d is over 70%.On 0-35d,under the same nitrogen treatment,the cumulative decay rate were expressed as S>M>R(P<0.05).The cumulative decomposition rate of dry matter under the treatments of 35dS,M and R reached 61.9%,55.5%,and 47.5%,respectively.At 0-35d,nitrogen application had no significant effect on the decomposition of S and M,but significant effect on R.After 35d,the effect of nitrogen fertilizer gradually decreased.The decomposition of cover crops was accompanied by the rapid release of carbon and nitrogen,and the carbon and nitrogen residual rates in 21dS,M and R reached about 40%,50%,and 60%,respectively.On average,the carbon and nitrogen release rate of S is significantly higher than that of R,and there is no significant difference between S and M.(2)Soil CO2 and N2O emissions in the cover crop system of winter wheat increased with the application of nitrogen and the decomposition of cover crop.There was no significant effect on CH4 emission and no interaction between the two mentioned earlier.There was a significant correlation between temperature and water with CO2 and N2O,but no correlation between CH4 and soil water temperature.(3)The organic carbon and total nitrogen in the soil increased in the middle stage of decomposition,but all of them basically recovered to the initial level in the later stage,indicating that the decomposition of cover crops increased the soil carbon and nitrogen content in a short time.Compared with the control group in bare land,the fallow crop under tilting pressure could significantly increase the subsequent winter wheat yield,and its grain yield increased by 10%-35%(P<0.05),among which the low-nitrogen treatment and mixed low-nitrogen treatment with tilting pressure on Changwu soybean has the best effect.(4)The GWP of the system was improved by the cover crop turning pressure and nitrogen application.The difference in GHGI between different cover-idling pressure treatments was extremely significant(P<0.001),which was manifested as S>M>R>CK.Compared with CK,GHGI under R treatment alone,M treatment combined with M treatment and S treatment increased,and GHGI under N1 and N2 treatment were also higher than that under N0 treatment.(5)There were differences in carbon balance between nitrogen application and slack treatment.While the final carbon balance size order was R>M>CK>S;N2>N1>N0.The results showed that under this system,N0 and S treatment without nitrogen application reduced the carbon fixation,while R and M and n treatment(N1 and N2)increased the carbon fixation of the final system.In a comprehensive consideration,monocultural cultivation of Changwu soybean,mixed planting of ryegrass and Changwu soybean,as well as turning pressure before wheat sowing,are more conducive to improve soil nutrients and increase the yield of subsequent crops.This management can give consideration to both economic and ecological benefits in the Weibei Highlands.