关键词: 紫花苜蓿, 品种, 秋播, 播种时期, 越冬

Abstract: In order to determine the suitable autumn sowing time and varieties of alfalfa (Medicago sativa) in the cold area of North China,four alfalfa varieties were selected to study their growth characteristics and cold resistance physiological characteristics at different temperatures (-5℃,-10℃) and different growth times after sowing (45,60 and 75 d). The results showed that the root weight and root volume of "Longmu 801" were significantly higher than those of other alfalfa varieties (P<0.05). Under low temperature,the content of free proline and soluble sugar of "Longmu 801" and "WL343" was increased significantly,which was higher than that of other alfalfa varieties. In conclusion,the main root diameter,root weight and root volume of alfalfa were positively correlated with the survival rate. When was simulated wintering at -10℃,the contents of soluble sugar and free proline increased,and the comprehensive cold resistance of "Longmu 801" was the best. Under simulated wintering conditions of-5℃ and-10℃,the survival rates of four alfalfa varieties were very low when they grew 45 days after sowing;The survival rate of "Longmu 801" is only higher than 50% at 60 days and higher than 55% at -5℃ and -10℃at 75 days. Therefore,it is the safest for autumn sowing alfalfa in Northwest China to ensure the growth time of at least 75 days before winter. For some cold resistant varieties such as "Longmu 801",the autumn sowing time can be postponed appropriately,but it should also be sown 60 days before winter.

Key words: Alfalfa, Varieties, Autumn sowing, Sowing time, Overwintering