PLANTS OF THE CLOVER FAMILY. 9! 



will frequently flourish in clay soils with no slight 

 degree of adhesion in them, providing the subsoil 

 conditions are suitable. The vegetable soils of the 

 western prairies are not usually well adapted to the 

 growth of alfalfa. The volcanic soils of the Rocky 

 mountain region furnish ideal conditions when suffi- 

 ciently supplied with moisture. 



In a subsoil in which alfalfa roots are to grow 

 vigorously, the most important requisite is that it 

 should be easily penetrable. Ideal conditions are 

 sometimes found for starting an alfalfa crop success- 

 fully, and yet the plants soon fail because of the 

 impenetrable character of the subsoil. The second 

 great requisite in the subsoil is, it should be deep. 

 The necessary depth will vary, but it should not be 

 less than several feet to provide ample feeding 

 ground for the roots; and a third requisite is that 

 the subsoil should be moist. But at all seasons of 

 the year it should be free from stagnant water to the 

 depth of several feet from the surface. These con- 

 ditions are best obtained in certain of the almost 

 rainless river valleys of the west. If the soils and 

 subsoils are sandy or gravelly, and underneath them 

 are sheets of water at varying depths, the plants are 

 supplied with moisture from this water through the 

 process of capillary attraction. With similar con- 

 ditions of soil and subsoil, except that the ground 

 water is absent, the alfalfa plants would perish unless 

 irrigated. This explains why alfalfa cannot be 

 grown in wide areas of the semi-arid country west 

 of the Mississippi, where the soil and subsoil requi- 

 sites are all that could be desired, but for the absence 

 of the ground waters. 



