Abstract: In order to determine the best sowing time for alfalfa to survive winter safely in Horqin sandy land,in the experiment,alfalfa was seeded on July 1,July 15,August 1 and August 15,2017,respectively,without mowing at the end of autumn. From November 2017 to February 2018,the soil layer temperature of 10 cm and 20 cm of sample plot was measured,and the samples were taken for low temperature treatment at the end of autumn,the relative conductivity and root neck activity were measured,and the half lethal temperature of alfalfa was calculated with logistic regression equation,and the overwintering rate was calculated in the second year. The results showed that the average minimum temperature of 10 cm and 20 cm soil layers of alfalfa plots decreased gradually,and the average temperature difference between day and night increased with the delay of sowing time. There was a significant negative correlation between the rate of overwintering and the half lethal temperature of alfalfa (P<0.01). The half lethal temperature was negatively correlated with the minimum temperature of 10 cm and 20 cm soil layer(P<0.05),and it had a very significant positive correlation(P<0.01) with the diurnal temperature difference of 10 cm soil layer and a significant positive correlation (P<0.05) with the diurnal temperature difference of 20 cm soil layer. The half lethal temperature of alfalfa sown on July 1 was lower,and the overwintering rate of alfalfa was higher. It is considered that the best sowing time for alfalfa to survive winter safely in Horqin sandy land is at the beginning of July with no mowing at the end of autumn.

Key words: Sowing date, Alfalfa, Cold resistance, Low temperature stress

摘要： 为确定科尔沁沙地苜蓿（Medicago sativa L.）安全越冬的最佳播种时期，本试验于2017年7月1日、7月15日、8月1日、8月15日4个时期对苜蓿进行播种，秋末不刈割，2017年11月至2018年2月检测苜蓿样地10 cm，20 cm土层温度，秋末取样进行低温处理，测定相对电导率、根颈活力，协同Logistic回归方程计算苜蓿半致死温度，翌年统计越冬率。研究表明，随着播种时期的推迟苜蓿样地10 cm，20 cm土层平均最低温度逐渐减小，平均昼夜温差逐渐增大；苜蓿越冬率与半数致死温度呈极显著（P<0.01）的负相关关系，半致死温度与苜蓿样地10 cm，20 cm土层最低温度呈显著（P<0.05）的负相关关系，与10 cm，20 cm土层昼夜温差分别呈极显著（P<0.01）和显著（P<0.05）的正相关关系；7月1日播种的苜蓿半致死温度较低，且苜蓿越冬率高。本研究认为，科尔沁沙地苜蓿安全越冬的最佳播种时间为7月初，且秋末不刈割。

关键词: 播期, 苜蓿, 抗寒性, 低温胁迫