SIXTH ANNUAL YEAR BOOK — PART VIII 



785 



CONDITIONS REQUIRED BY ALFALFA. 



CLIMATE. 



In mountain regions alfalfa growing is limited at high altitudes by 

 the low winter temperature and also by the low mean summer tern- 



perature, the limit vary- 

 ing from 5,000 feet m 

 the north to about 8,00\; 

 feet in the south. Alonr? 

 the northern border alf- 

 alfa culture is limited by 

 the low winter tempera- 

 ture. , I 



Northern grown seed 

 is more hardy than south- 

 ern-grown seed, and by 

 gradual acclimatization 

 the limit of the alfalfa belt 

 will be gradually pushed 

 northward. These results 

 may be aided by the 

 introduction from the Old 

 World of strains already 

 accustomed to a cold cli- 

 mate, as has been illus- 

 trated by the importation 

 some years ago by this 

 Department of a variety 

 from northern Turkestan 

 known as Turkestan alf- 

 alfa, which showet! itself 

 better adopted to dry reg- 

 ions than the strains 

 already grown in this 

 country. But other con- 

 ditions modify the effect 

 of the winter season. 

 Alternate freezing and 

 Fig. 4. thawing tend to loosen 



the growing plants and heave them out. This action is not so likely to 

 take place in an old field where the plants are well rooted. Where the soil 

 is cold and wet in the spring, as is usually the case in New England,the 

 growth of alfalfa is greatly hindered, and this given as one of the chief 

 causes of failure by experimenters in that region. Good drainage and 

 improvement of the texture of the soil v.'ill aid in preventing such failure. 

 Although a well-set alfalfa field will withstand considerable drought 

 yet the growing of alfalfa is limited by insufficient rainfall unless water 

 can be supplied by irrigation. In general, alfalfa requires about 20 incties 

 50 



