AS NITROGEN GATHERERS 27 



nutshell is the history of our experience and the 

 farmers of America can take it for what it is worth." 

 How and when to use cultures. Karl Kellerman* 

 has some interesting general deductions on manner 

 and time of using cultures. He admits that the 

 method of distributing practically pure cultures of 

 nitrogen fixing bacteria, dried on cotton, has not 

 proved entirely satisfactory, this owing to varying 

 conditions of air during transit in the mails, and to 

 certain matter connected with laboratory technique. 

 It is argued that inoculation may prove advanta- 

 geous: First, if the soil produces a sickly growth of 

 legumes even though their roots show some nod- 

 ules; second, if a leguminous crop has made a stand 

 but gives evidence of failure, due to the absence of 

 root nodules. Under such conditions it is advis- 

 able to apply the culture liquid by spraying, or 

 better, by top-dressing the land with soil moistened 

 with the culture liquid as explained in the directions 

 sent with all packages. It is said inoculation is 

 useless. First, if the legumes usually grown are pro- 

 ducing average yields or the roots show nodules in 

 abundance; second, if the soil is rich in nitrogen. 

 It is neither necessary nor profitable to inoculate a 

 soil rich in nitrogen since few nodules are formed 

 under these conditions. Cultures of nitrogen-fixing 

 bacteria are not to be regarded in the light of nitrog- 

 enous fertilizers, increasing yields under all condi- 

 tions. The bacteria do not contain great supplies 

 of nitrogen. If conditions are favorable, however, 

 they render nitrogen obtained from the air available 

 for the legume 



*U S dept agrl, Farmers' Bui 240. 



