272 SOILS AND PLANT LIFE 



drilled in, less seed is sufficient. They should not be put 

 into the ground until danger of frost is past. Inoculation 

 is often necessary in soils in which these crops have not 

 previously grown. 



Field peas, or Canadian field peas, are grown in the 

 cooler parts of the Corn Belt and northward, often with 

 oats as a pasture for hogs or for hay. They are more 

 hardy with respect to cold than are cowpeas or soy beans. 

 However, the cultural methods of the three crops are 

 similar. 



The Vetches. — Two kinds of vetch, the common, and 

 the hairy, or winter vetch, are rather extensively grown 

 especially in sandy soils. 



They may be sown broadcast in com or cotton at the 

 last cultivation. The winter vetch may be planted in 

 late summer or early autumn. 



Inoculation is usually necessary the first time the crop 

 is grown. The soil in which garden peas are growing may 

 be used for this purpose. 



Vetch may be used for hay, but it is preeminently a 

 green manure crop; that is, it is plowed under to add 

 humus to the soil. . 



204. Securing the Maximum Benefits from Legumes. — 

 If the soil is to acquire all the nitrogen which any given 

 legimainous crop takes from the air, it is, of course, necessary 

 that the latter be plowed under. This, however, is or- 

 dinarily not done. Rather the hay is fed to animals and 

 the manure returned to the land. A considerable loss of 

 nitrogen results from this in most cases ; but the profit 

 derived from the feeding of the hay more than offsets 

 this. 



On the other hand, it is not advisable in any case, if we 

 consider the effect upon the fertility of the soil, to remove 



