82 THE SPIRIT OF THE SOIL 



to show why it was that in several instances the 

 culture gave negative results when applied to the 

 land. The difficulties met with were not insuperable, 

 but as the experiments continued it became evident 

 that however successful a leguminous culture might 

 prove, it could never yield more than a fraction of 

 the results that might fairly be expected if bacterial 

 inoculation were practised from a broader outlook. 

 It was realized that Bacillus radicicola was only 

 one of several organisms connected with the work 

 of changing into nitrogenous plant food the nitrogen 

 present in the air circulating from the atmosphere 

 to the soil, and that the full benefit of soil inoculation 

 could only be obtained by supplying to the soil a 

 mixed culture which would contain the various 

 groups of bacteria acting in different ways for 

 the common end of supplying nitrogenous food in 

 soluble form that is, in a form in which it can be 

 utilized by plants. 



Chance to some extent decided the selection of 

 peat as a medium for the purpose. As a matter of 

 fact, however, there was not a large option. Some 

 substance was required that had or could be made 

 to yield a high percentage of soluble humus, for it 

 was known that it was on this that the bacteria had 

 to rely for their food. Farmyard manure was a 

 possible medium. The supply of it, however, was 

 diminishing; it was, and must always remain, un- 

 pleasant to handle, and it was objectionable because 

 of the host of mixed organisms it was bound to 

 contain. Leaf mould was objectionable on most of 

 the same grounds, and had the further disadvantage 



