Effects Of Forage Combination And Nitrogen Addition On Artificial Grassland Yield And Soil Carbon Composition

Grassland degradation caused by overgrazing and human factors is most intuitively manifested by the reduction of grassland productivity,which has a great impact on the feed supply of herbivorous livestock.The restoration of natural degraded grasslands is a long-term process,how to reduce the grazing pressure of natural grasslands,improve productivity,but also to solve the demand for livestock forage,artificial grasslands play an important role in which the high yield and quality characteristics of artificial grasslands play an increasingly important role in the supply of forage.Nitrogen is an important factor governing ecosystem productivity and carbon sink function,resulting in a significant increase in N input,which in turn has an impact on the carbon cycle.Different forage combinations can be used as plant carbon input and can slow down the loss of soil carbon.Therefore,this experiment was conducted in Hulunbeier artificial grassland with forage species treatments（Medicago sativa,Bromus inermis,Medicago sativa and Bromus inermis mixed）and N application treatments（no N application 0 kg/hm²a,low N 75 kg/hm²a,high N 150 kg/hm²a）.Through different forage combinations and treatments with different concentrations of N addition,the changes in soil organic carbon and its different active components were studied to provide a theoretical basis for the study of suitable forage combinations to be promoted in the northern cold and arid regions and the mechanism of influence on soil organic carbon,and to provide the best cultivated grass management plan for functional departments and enterprises.The main research results are as follows.（1）The study of forage yield at different levels of N addition under three forage combinations of planting methods found that the grass planting pattern of awnless sparrow+alfalfa with high N treatment was beneficial to improve the productivity of artificial grass and increase the forage yield.It is suitable for the establishment of artificial grasses in the north.（2）The content of soil organic carbon and its components decreased with increasing soil depth.The content of different soil organic carbon fractions was higher in the high N treatment than in the no N treatment.Nitrogen addition was able to enhance the accumulation of each soil organic carbon fraction also enhanced the proportion of LFOC allocated to organic carbon and reduced the proportion of WSOC,MBC and ROC allocated,which helped to increase the activity of soil organic carbon and increase soil fertility.（3）The different N addition levels had significant effects on N₂O fluxes and not on CH₄and CO₂ emission fluxes under the three forage combinations of cropping practices.High N application increased GHG emissions and there was a potential for global warming.Compared with the N0 and N150 treatments,the N75 treatment reduced total GHG emissions and also reduced the global warming trend.