448 BOTANY OF CROP PLANTS 



alfalfa resembles Turkestan. It is less hardy, however, 

 and is a poorer yielder than the American type. The latter 

 is the most common western alfalfa. Arabian alfalfas are 

 not resistant to cold, hence they are restricted to the warmer 

 States, particularly Arizona, New Mexico, Texas, and 

 California. Peruvian alfalfa is a productive sort adapted 

 to growth under irrigation in the southwest, where the winters 

 are mild. Brand proposes to place Peruvian alfalfa as a 

 distinct variety {Medicago sativa var. polio). It is taller, 

 less branched, and more rapid in its growth and recovery 

 after planting than common cultivated alfalfas. Further- 

 more the flowers are sHghtly longer, and the floral bract is 

 "longer than either calyx teeth or calyx tube. 



Environmental Relations. — Alfalfa is able to withstand 

 high temperatures if the air is dry, but high temperatures 

 accompanied by a humid air are decidedly injurious. For 

 this reason, it is particulary well adapted to the semi-arid 

 sections of the United States, where it is grown both on irri- 

 gated and non-irrigated land. Its resistance to low temper- 

 atures is a varietal characteristic, and also somewhat 

 dependent upon cultural operations. Grimm and Baltic 

 types are less Hable to suffer from winter killing than the 

 so-called common alfalfas. 



The following data shows the water requirement of alfalfas, 

 in comparison with other crops (from Briggs and Shantz). 



„ Water 



Crop ' Requirement 



Millets ' 310 



Sorghums 322 



Corns 368 



Wheats 513 



Oats 597 



Potatoes 636 



Alfalfa, Peruvian S. P. I., (30,203) 651 



Alfalfa, Grimm S. P. I. (25,695) 963 



