Effects Of Water And Nitrogen Addition On Alfalfa And Bromus Inermis In Artificial Grassland Of Meadow Steppe

China is a large grassland country,with nearly 400 million hectares of natural grassland,accounting for more than 40%of the land area,2.5 times of the forest area and 3.2 times of the cultivated land area.With the increasing demand of people for livestock products,only relying on the supply of natural grassland can not meet the demand of cattle and sheep for forage.In this study,the abandoned land and abandoned land in northern pastoral areas of China were taken as the research objects,and the forage combination,production performance,nutritional quality and their effects on Soil Nutrients of artificial grassland were carried out.The research results were expected to provide important theoretical basis and technical support for the good development of grassland animal husbandry and the optimal allocation of forage resources in northern pastoral areas.In this study,forage varieties（Ammonia P1,Alfalfa P2,Alfalfa and Ammonia P3）,nitrogen application(150kg N ha^-1a^-1 N1,low nitrogen 75kg N ha^-2 a^-1 N2,no nitrogen 0kg N ha^-2a^-1N3)and water supplementation（no water supplementation W1,15%water supplement in the dry season W2）,the observed indexes mainly included yield,soil nutrients and soil microbial biomass characteristics.Through comprehensive evaluation,the effects of both nitrogen application and water supplementation have significant effects on the establishment of leguminous and gramineae grass were summarized.The main research results are as follows:（1）The hay yield of alfalfa and Bromus inermis mixed sowing was significantly higher than that of Alfalfa single sowing and Bromus inermis single sowing.In different forage combinations,the yield of high nitrogen(N1:150 kg N ha^-1a^-1)and water（W2:15%water supplement in dry season）were significant（P<0.05）.The yield of artificial grassland with alfalfa Bromus inermis（P3）and 150kg N ha^-1a^-1（N1）and 15%water supplement in dry season reached the highest value,the highest value reached8035 kg/hm².（2）Through the measurement of soil nutrient in each soil layer,it was confirmed that the application of nitrogen fertilizer had a significant effect on all soil nutrient indexes,especially the positive correlation of soil total nitrogen and organic carbon.The soil nutrients decreased with the increase of soil layer,but the difference was not significant.In general,the artificial grassland planted with alfalfa and brome amnus mixed（P3）,the application of150 kg N ha^-1a^-1（N1）and the watering of 15%（W2）in dry season had significant effects on the soil nutrient content.（3）Soil microbial carbon and nitrogen contents showed significant differences on nitrogen addition,but there were no significant differences between planting methods and water addition factors and their interaction;Water addition and forage combination had effects on microbial carbon,nitrogen and phosphorus,but the difference was not significant.In conclusion,both nitrogen application and water supplementation have significant effects on the establishment of leguminous and gramineae grass,and it is feasible to regulate the artificial grassland through water and nitrogen factors and their coupling effects.