CHAPTER XIII. 

 BACTERIOLOGICAL EXAMINATION OF SOILS. 



Comparison of the Fermentative Action of Soils. 



The determination of the numbers of bacteria in soils of 

 different fields has hitherto not given very reliable indi- 

 cations of the relative fertility of the latter. Somewhat 

 better results have been obtained, however, by a com- 

 parison of the fermentative activity of the different soils 

 when introduced in similar amounts into various nutritive 

 solutions, and no doubt it is in the improvement of this 

 kind of method of soil examination that our knowledge 

 will be increased of the relationship between the fertility 

 of the soil and the biological phenomena which occur 

 within it. 



What is required are reliable methods of determining 

 the kinds and relative proportions of bacteria in the soil, 

 and the work which each kind is capable of performing, 

 rather than means of determining their total number. 



Remy, Lohnis, Buhlert, Fickendey, and others have 

 attempted to compare ' the bacteriological character of 

 soils in respect of their power of decomposing proteins 

 by introducing similar amounts of the different soils into 

 peptone solutions, and estimating the amount of ammonia 

 produced in a given time in each case. In a similar way 

 the relative power of nitrification, denitrification, and 

 nitrogen fixation possessed by various soils have been 



compared. 



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