NITROCULTURE 201 



1. When the leguminous crops that are usually grown 

 are producing up to the average, and the roots show nod- 

 ules in normal abundance. 



Cultures of nitrogen-fixing bacteria are not to be 

 regarded in the light of fertilizers, or as capable of 

 increasing the yield under average conditions. They do 

 not contain nitrogen itself, but bacteria, which make it 

 possible for the legumes to secure nitrogen from the air 

 (through the formation of root nodules). Where the 

 soil is already adequately supplied with these bacteria, it 

 will not usually pay to practice artificial inoculation. 



2. When the soil is already rich in nitrogen. 



It is neither necessary nor profitable to inoculate a soil 

 rich in nitrogen when sowing legumes. Not only does 

 the available nitrogen in the soil render the formation of 

 nodules less necessary, but the nitrogenous materials in 

 the soil largely prevent the bacteria from forming nodules. 



Any increased virility in nitrogen-fixing power pos- 

 sessed by any of the types of bacteria yet distributed, may 

 be rapidly lost in a soil containing an abundance of nitro- 

 gen, because the bacteria are in a medium in which there 

 is no demand for activity in securing atmospheric 

 nitrogen. 



When Failure is to be Expected — Inoculation will fail 

 where other conditions (aside from the need of bacteria) 

 are not taken into account, among which are the fol- 

 lowing — 



I. In soil that is acid and in need of lime. 



Liming to correct acidity is as important for the proper 

 acidity of the bacteria as for the growth of the plants. 



