Effects of solar light and temperature on fall dormancy of alfalfa in Beijing area

The regrowth height of 11 alfalfa varieties with different fall dormancy rates were measured in order to find out the relationships of regrowth height with sunshine time and average temperature. The results showed that the fall dormancy of alfalfa appeared in October in Beijing. Photoperiod and average temperature showed impacts on the fall dormancy of alfalfa. The critical threshold conditions of different fall dormancy types were that the sunshine time was less than 11h and the average temperature was less than 7.8 ℃. The critical threshold conditions of different fall dormancy rates were that the sunshine time was less than 10.4 h and the average temperature was less than 7.8 ℃.