74 PRODUCTIVE FARMING 



arise from the use of green manures. Red and crimson 

 clover, cow peas, vetch, rye, and buckwheat are commonly- 

 used as green manures, but any other crops may be grown 

 for this purpose. Those plants which belong to the legume, 

 or clover, family are among the best for this purpose, because 

 they gather nitrogen from the air and leave it available for 

 the use of other crops. The benefits of this family of plants 

 will be discussed more fully in the chapters on Farm Crops 

 and Alfalfa. 



Benefits Enumerated. — By the careful use of green 

 manures, soils may be benefited in several ways : 



1. Food is brought from great depths by the roots and 

 when turned under is left near the surface. 



2. Such food is left in a form suitable for other plants 

 to easily make use of it, because the green manure will decay 

 quickly. 



3. The decaying matter becomes humus and has many 

 beneficial effects, already studied. 



4. Chemical action in the soil is promoted. 



5. Small organisms, bacteria helpful to the soil, are 

 multiplied more rapidly. 



Planning for Green Manures. — It requires some planning 

 ahead to be most successful in securing crops suitable as 

 green manures. Certain crops, such as rye and crimson 

 clover, may be sown in the late summer or fall after the 

 season's crop is off. These may be plowed under in the spring 

 as green manure before the next season's crop is put in. Cow 

 peas or buckwheat may be used to produce a good heavy 

 green manure crop by letting it use the last half of the 

 summer after a crop of small grain has been removed from 

 the field. 



Care in Their Use. — When too heavy crops of rye or 

 clover are plowed under at one time, there are apt to be bad 

 results. This is chiefly due to the formation of acids in the 

 soil which make it sour. Such bad effects are not noticed 



