32 PRINCIPLES OF FARM PRACTICE 



other field, where the same or a similar kind of legume has 

 been growing. For example, to establish alfalfa in a place 

 where it has never grown before, soil should be taken from 

 a field of vigorously growing alfalfa, and uniformly scattered 

 over the new area to be planted, at the rate of about 160 

 pounds to the acre; or inoculating material may be obtained 

 from a soil on which sweet clover is growing. Owing to the 

 destructive action of the sun's rays on bacteria it is important 

 to spread the inoculating material during a cloudy day and 

 to work it into the soil immediately. 



Another method is to treat the seed of a legume, before 

 sowing, with a solution containing nitrogen-fixing bacteria. 

 Material for this method of inoculation, together with de- 

 tailed directions for use, may be obtained from a State Ag- 

 ricultural Experiment Station, or from a commercial firm 

 recommended by the Station. 



The use of legumes for maintaining soil fertility cannot be 

 overestimated. They are also a valuable crop for feeding 

 farm animals. On every farm a rotation should be established 

 which will include a leguminous crop every few years, never 

 more than five years apart. The selection of a particular 

 legume may depend upon the use for which it is intended 

 and upon its adaptability to climate and soil. In some 

 places it may be clover; in others, alfalfa; in another, cow- 

 peas or soy beans; the important thing is to include some 

 kind of legume in a rotation. 



Commercial fertilizers as a source of nitrogen. If nitro- 

 gen cannot be maintained in the soil in the ways described, 

 as a last resort it may be purchased in the form of a fertilizer; 

 but it will be found more expensive than any other kind of 

 commercial fertilizer. Therefore it should be supplied in 

 other ways whenever possible. The use of nitrogen in the 



