I3O THE FORAGE AND FIBER CROPS IN AMERICA 



a given legume is extensively grown there is probably a wholesale inoculation 

 of surrounding soils by means of the wind, which carries the germ-laden 

 dust. This seems to be the explanation of the fact that on no soil has the 

 writer been able to find cowpeas free from tubercles, and many observations 

 have been made, all in localities where the culture of this plant is general. 

 The seed of certain legumes may also be the means of conveying the nec- 

 essary germs to a soil lacking the appropriate form of germ life. This seems 

 to be the true explanation of the fact that lespedeza (and bur clover from 

 unhulled seed) have developed tubercles in all soils where we have thus far 

 tested them. Seeds of both these plants are borne in close contact with the 

 ground where particles of the germ-laden soil easily lodge upon the burs or 

 seed coats. 



"Even though few or no tubercles may be produced the first year where 

 a rare legume is grown for the first time, there is an increase in the number 

 of tubercles from year to year if the same legume continues to occupy the 

 land. Hence we should not look upon inoculation as needing to be repeated, 

 but as a procedure useful only or chiefly in the first year's growth of a 

 rare legume." 1 



Poor, thin soils deficient in humus and lime may make it 

 worth while to use inoculation materials even for legumes that 

 are not rare. 



138. Need of Inoculation. In the case of certain legumes, 

 notably alfalfa and soy beans, it has been abundantly demon- 

 strated that by placing 100 pounds or more of soil from a field 

 which had the previous year grown tubercle-bearing plants of 

 the same species upon each acre to be sown with the legume 

 in question, the frequency of tubercles upon plants is in- 

 creased thereby and the vigor of the plant is enhanced. (209) 



When leguminous plants are grown in sterilized soil to which 

 no organisms are allowed entrance the plants do not develop 

 tubercles; but if a pure culture of the proper organism is added, 

 tubercles will develop abundantly, assuming other conditions to 

 be suitable. Further, if certain legumes, notably alfalfa and 

 soy beans, are grown in soil which has not previously grown 

 them, although the soil may have grown distantly related 

 legumes, in many instances the plants will either not develop 

 tubercles or will develop them sparingly; while if the propef 



i Alabama Sta. Bui. No. 87 (1897), pp. 482, 483. 



