Abstract: The appropriate cutting time of alfalfa was studied in the north of Keerqin sandy land alfalfa growing area. Alfalfa cutting on different growing degree-days (GDD) was used to study the effects on yield,quality and winter survival rate of alfalfa at the first cutting time and the third cutting time,and the relationship between the soluble sugar,soluble protein and the cold resistance of alfalfa was discussed. The results showed that if the first cutting time was at more than 650 GDD,it significantly decreased hay yield of the second cutting. The GDD of the first cutting was extremely significant negative correlation with crude protein and relative feed value,but positive correlation with acid detergent fiber and neutral detergent fiber. It hadn't significant correlation with interval GDD of the second cutting. In conclusion,it was suitable for the first cutting at 610~650 GDD in Keerqin sandy land,and the last harvest time before September.

Key words: Growing degree-days, Alfalfa, Cutting, Hay yield, Quality, Winter survival rate, Soluble sugar, Soluble protein, Keerqin sandy land

摘要： 为探讨科尔沁沙地北部苜蓿种植区紫花苜蓿（Medicago sativa）的适宜刈割时间，本研究采用在不同生长度日（growing degree-days，GDD）刈割紫花苜蓿的方法，研究了第1次和第3次刈割时间对科尔沁沙地紫花苜蓿产量、品质、越冬的影响，同时对可溶性糖、可溶性蛋白与苜蓿抗寒性关系进行了探讨。结果表明：在大于650 GDD以后进行第1次刈割，会显著降低第2次刈割的干草产量；第1次刈割GDD与粗蛋白含量、相对饲喂价值之间存在极显著负相关关系，与酸性洗涤纤维、中性洗涤纤维含量之间存在极显著正相关关系，与第2次刈割后GDD相关性不显著。综上所述，在科尔沁沙地，适宜在610~650 GDD进行第1次刈割，9月初前完成末次刈割。

关键词: 生长度日, 紫花苜蓿, 刈割, 产草量, 品质, 越冬率, 可溶性糖, 可溶性蛋白, 科尔沁沙地