Study On The Adaptability Of Eleven Fall Dormancy Standard Check Alfalfa (Medicago Sativa) Varieties

Alfalfa is a perennial legume with the main root is long and secondary root distributes widely. It has natural advantage in improving the soil environment and protecting slope,and merits such as high yield, good quality, good resistance to cut, wide distribution, etc, which make it become the largest cultivation area. In recent years,with the study of alfalfa goes deaply, it has been successfully cultivated in many tropical climate conditions of new varieties of high fall dormancy. while with the need of quality and quantity of forage in the southern region,alfalfa as a member of the forage, has been cultivated from the north to the south.gradually. In this paper,11 alfalfa varieties which of standard of the United States fall dormancy rate are planted in Guizhou, Beijing area to study the growth performance, the impacts of light and temperature andsemi-lethal temperature on it, and growth adaptability of different fall dormancy rate alfalfa cultivars. The Results shows that:The semi-lethal temperature of different fall dormancy rate alfalfa varieties is determined by cell damage rate with simulating logistic equation in different temperature.The Regression equation of semi-lethal temperature and temperature is y=0.348x+50.381 with a correlation coefficient of 0.6868.The fall dormancy of alfalfa show in October in Beijing,Photoperiodic and average temperature have great impacts on the fall dormancy of alfalfa, the critical threshold conditions of different fall dormancy type alfalfa are:the sunshine time is less than llh and the average temperature is less than7.8℃; the critical threshold conditions of different fall dormancy rate alfalfa are the sunshine time is less than 10.4h and the average temperature is less than7.8℃.Non-dormancy and extremely non-dormancy alfalfa varieties have advantage in the fresh yield than fall dormancy and Semi-dormancy alfalfa varieties in the Guizhou area,Meanwhile,the Non-dormancy and extremely non-dormancy alfalfa varieties have a higher summer survival rate,it selected suitable fall dormancy rate of them for Guizhou area is 7-10 preliminarily which have more economic benefits and ecological benefits. The biomass of semi-dormancy alfalfa varieties is the highest in Beijing area, it selected fall dormancy rate in Beijing area is 4-6 which have more economic benefits.