ALFALFA 331 



the second, October 16, when the blossoms were mostly 

 dried up ; the third was left uncut. In the spring the 

 undipped plot started off with a noticeably stronger 

 growth than the others. It produced a yield in three 

 cuttings 522 pounds greater than the plot clipped Octo- 

 ber 16, and 1376 pounds greater than that clipped Sep- 

 tember 9. The September clipped plot was apparently 

 injured by the weed growth that took place after clipping. 



At Lyngby, Denmark, the effect of cutting spring-sown 

 alfalfa the same year it was seeded was tested. It was 

 found that the first season's crop plus that of the second 

 season was not equal to that of the second year's crop 

 alone on plots that had not been cut the first year. 



396. Winter-killing. The injury or destruction of 

 alfalfa in winter is associated with various factors. Among 

 the most important are the variety ; the actual minimum 

 temperature ; the amount of snow cover ; the thickness 

 of the stand ; the amount of moisture in the soil ; the 

 condition of dormancy ; alternate freezing and thawing ; 

 and particularly the condition of the plants at the begin- 

 ning of winter. 



The most cold-resistant varieties of alfalfa are Grimm 

 and strains of Turkestan and ordinary alfalfa which have 

 been grown under severe winter conditions, as in Mon- 

 tana and the Dakotas, for many years. In all these, 

 natural selection has eliminated the non-hardy individuals. 



Injury to alfalfa by cold alone is rarely serious unless 

 the temperature falls to 20 Fahrenheit or lower. In 

 North Dakota all but the most hardy varieties, when 

 planted in rows and not protected by snow, showed a 

 loss of 80 per cent or more in a winter where the minimum 

 temperature was - 31 Fahrenheit. In broadcasted 

 stands, however, the loss was much less. A thick stand 



