212 



THE ESSENTIALS OF AGRICULTURE 



make available the supply of nitrogen in the air, an abundance 

 of available plant food must be at hand. On most soils the use 

 of manure is the most important factor in securing satisfactory 

 results. While good stands and yields of alfalfa have been 

 secured on fertile soils without manure, the use of manure has 

 in almost every case lessened the risk of failure to get a stand 

 and has greatly increased the yield. Alfalfa also requires a large 

 amount of lime for a permanent stand and for its best development. 



* - 



**r^T 



3&h 



FIG. 100. Good and poor alfalfa seed 



At the right are samples of good seed pure, plump, smooth, and bright ; at the left 



are samples of poor seed irregular, shrunken, and discolored. (Photograph from 



Iowa Experiment Station) 



275. Varieties of alfalfa. There are several varieties of alfalfa, 

 such as the Turkestan, Grimm, Arabian, Peruvian, and Ameri- 

 can. At least 85 per cent of the alfalfa grown in the United 

 States is of the common American type. The Turkestan is some- 

 what more resistant to cold and drought, and is used somewhat 

 extensively in the Northwest. The Arabian and Peruvian types 

 are common in the Southern states ; and while they yield con- 

 siderably more than the American type, they lack hardiness and 

 are adapted only to the South. The Grimm is a very hardy type, 

 but its seed is expensive, and it is not yet very generally grown. 



