376 ANNUAL REPORT OF THE Off. Doc. 



Instead of soils, use has recently been made of cultures of the 

 bacteria found in the root tubercles. Such cultures have already 

 become a commercial product under the name of Nitragin. 



The organisms are grown upon a specially prepared gelatin me- 

 dium. Cultures from different legumes are made and sold, so that 

 the proper organisms can be supplied for any given leguminous 

 plant. 



In using the cultures, the tubes containing them are placed in 

 luke-warm water having a temperature of about 90 degrees F., to 

 melt the gelatin and disseminate the germs throughout the medium. 

 This is then mixed with a small quantity of water, and in this the 

 seed is immersed previous to sowing, or the diluted cultures can be 

 mixed thoroughly with earth and the latter sown broadcast over the 

 land, immediately after the seed is sown. In immersing the seed in 

 the solution the germs are brought into immediate contact with the 

 developing plant, when root infection is more apt to follow. 



The experiments on the use of nitragin have been so extensive 

 and varied that it will be unprofitable to detail them here. Fur- 

 thermore, the results have been so contradictory that confusion is 

 likely to overwhelm the reader were we to review them. 



In many cases increased yields have followed the use of nitragin, 

 in others no benefit has resulted. Perhaps the failure in many 

 cases has been due to the use of inactive nitragin, but, in most in- 

 stances, it was likely owing to the fact that the necessary organisms 

 were already abundantly present in the soil. 



The question of the inoculation of soils, either with soils or with 

 nitragin, therefore, resolves itself into one of whether the necessary 

 organisms are already present. 



In the cases where beneficial results have been attained, the soils 

 on which it was used was either barren or otherwise below the 

 standard of what might be classed as fertile soils. In the case of 

 poor, sandy or worn-out lands, nitragin will doubtless be useful in 

 initiating a good growth of any particular legume, until by a first 

 crop the soil shall become well supplied with the necessary bac- 

 teria; after that there would be no advantage in its further use. 

 In ordinary arable land some form of the tubercle organism is prob- 

 ably present in proper numbers to infect the roots to a degree suffi- 

 cient at least to stock the soil with organisms of the proper viru- 

 lence for another season. 



Cases where nitragin is advisable are, therefore, the exceptions 

 rather than the rule, and on this point no hard and fast lines can 

 be drawn. The indiscriminate use of nitragin has led to many 

 failures and disappointments. Like all good things when wisely 

 used it is useful, but when used without judgment it is liable to 

 meet with unjust condemnation. 



