ALFALFA 309 



of 1908-1909. The mortality in these plots was very 

 much less, in most cases not enough to injure the stand 

 seriously. It is not clear to what extent this lessened 

 mortality was due to the alfalfa being broadcasted and 

 the plants therefore close together, and how far the greater 

 age of the plants, and perhaps other factors, had a bear- 

 ing on the results. The fact that the surviving stand 

 varied considerably in different parts of the broadcasted 

 plots indicates that other factors than low temperature 

 were concerned. 



The data clearly show, however, that a temperature 

 of - 31 Fahrenheit in a region of comparatively low 

 humidity is decidedly injurious to most varieties of al- 

 falfa when growing in hills or rows and unprotected by 

 snow. Even the most hardy cultivated sorts suffer a slight 

 loss under such conditions. 



Undoubtedly the highest degree of cold resistance is 

 found in Siberian strains of sickle alfalfa. According to 

 Hansen this occurs even farther northward than Yakutsk, 

 latitude 62, where a minimum temperature of 83 

 Fahrenheit is recorded. 



Extensive trials of alfalfa varieties were conducted at 

 the Minnesota Experiment Station during six years, and 

 data were kept on the loss due to winterkilling. The loss 

 varied greatly in different winters and between different 

 varieties in the same winter. In most cases Grimm alfalfa 

 suffered the least loss. Turkestan proved very variable, 

 a fact doubtless connected with the wide origin of the 

 commercial seed. In one winter with a minimum tem- 

 perature of 17 Fahrenheit three strains of Turkestan 

 alfalfa suffered no loss, while 14 strains of Grimm alfalfa 

 lost from 15 to 23 per cent, a much higher loss than oc- 

 curred in other winters with more severe cold. 



