n. r. I. -57 



METHODS OF LEGUME INOCULATION. 



INTRODUCTION. 



The value of leo:umes ^ as green manures or soil renovatoTs is due 

 to certain bacteria which develop nodules upon the roots of these 

 plants and which have the power of rendering the free nitrogen of 

 the air available for plant growth. Without these bacteria, legumes, 

 like other crops, exhaust the soil of its combined nitrogen. In many 

 regions certain types of these important bacteria are abundant in the 

 soil; in other localities they must be imported, or, in other words, 

 the leguminous crop to be grown there must be inoculated. 



The inoculation of a new field may be secured either by the soil- 

 transfer method or by the use of pure cultures of the proper bacteria. 



THE FUTILITY OF INOCULATING NONLEGUMINOUS CROPS. 



It is useless to attempt to benefit crops other than legumes by treat- 

 ment with legume cultures. The only way by which a nonlegumin- 

 ous crop, such as corn or cotton, can be benefited by the legume bac- 

 teria is either to grow an inoculated leguminous crop the previous 

 year and turn under the stubble or even the entire crop as a green 

 manure, or to grow an inoculated leguminous crop between the rows 

 of the crop whi(4i it is desired to benefit. No great increase in crop 

 can be expected from the latter method. 



THE INOCULATION OF LEGUMINOUS CROPS. 



Extensive experiments conducted by the Bureau of Plant Indus- 

 try, as well as experiments carried on by other investigators in this 

 country and in Europe, have demonstrated conclusivel}' that each 

 species of legume may be inoculated more successfully by using the 

 bacteria isolated fi-om that species than by using bacteria isolated 



" Plants belonging to the pea family, such as clovers, alfalfa, cowpeas, soy beans, 

 peanuts, field peas," vetch, etc. 



[Cir. 63] 3 



