42 



PRINCIPLES OF SOIL MICROBIOLOGY 



comparison with the other organisms developing on the plate. Among 

 the other most important factors influencing the total and relative 

 abundance of actinomyces in the soil is the soil reaction; the less acid 

 the soil, the higher is the relative number of actinomyces. The in- 

 fluence of soil treatment upon the development of these organisms in 

 the soil is shown in table 7. 



TABLE 7 

 Influence of soil treatment on the number of actinomyces in the soil 



* 320 pounds of KC1 and 640 pounds acid phosphate per acre every year. 



TABLE 8 

 Influence of liming and fertilization upon the numbers of fungi in the soil 



SOIL TREATMENT 



Unfertilized 



Lime alone 



Minerals 



Minerals + lime 



Manure and minerals 



Manure, minerals and lime . . 



NaN0 3 and minerals 



(NH 4 ) 2 S0 4 and minerals 



Manure, NaN0 3 and minerals 



Numbers of fungi in the soil. Fungi also exist in the soil both in the 

 form of vegetative mycelium and reproductive spores. Methods for 

 demonstrating the existence of specific forms in the soil are described 

 elsewhere (p. 239). There is no method yet devised for finding out how 

 much of the fungus material exists in the soil as mycelium or as spores ; 

 we neither have means of determining how many of the colonies develop- 



