PLANTS OF THE CLOVER FAMILY. 97 



soils, that is to say, subsoils which consist of fine 

 gravel intermixed with sand. Such soils are emi- 



o 



nently adapted for growing alfalfa when water is 

 plentifully supplied from the clouds, from irrigating 

 ditches, or from the water table in the subsoil. This 

 water table must not be too near the surface, or the 

 root growth will be hindered to the great injury of 

 the plants ; nor must it be too far from the surface, 

 or it will fail to reach the plants in sufficient quan- 

 tity. When water cannot be supplied from ditches 

 or from a subterranean source, and when the sum- 

 mer climate is dry in character, it will be found that 

 alfalfa will grow best in soils that are underlaid with 

 mild, porous clay subsoils, which the roots can easily 

 penetrate. If grown under those conditions, if the 

 subsoil were sand or gravel, the plants would not 

 obtain sufficient moisture. The best soils probably 

 in the United States for growing alfalfa when amply 

 supplied with water are the volcanic ash soils, allu- 

 vial in character, that are found in the valleys west 

 and southwest of the Missouri river. The sandy 

 soils of the states south and southeast of the Ohio 

 are not usually rich enough to produce maximum 

 crops without being fertilized. The soils of the 

 upper Mississippi basin, with exceptions somewhat 

 numerous, do not seem to have the proper food ele- 

 ments. In other localities, particularly in states 

 north and east of the Ohio, are stretches of hardpan 

 subsoil, which forbid the growth of alfalfa. And 

 in all soils where the water table comes near the sur- 

 face at any time in the year, alfalfa cannot be suc- 

 cessfully grown. 



Preparing the soil. When alfalfa is to be laid 

 down for a term of years, it is important that the 

 7 



