46 



Microbiological Population of the Soil 



microbiological populations. Correlations between microbial activi- 

 ties and crop yields have been derived only for certain soils. Definite 

 relations have been observed between optimum conditions for the 



Fig. 21. Colonies of bacteria, actinomycetes {lower plnfe), and fungi (upper 



plate), developing on jilates used in counting these organisms in soils (from 



Waksman and Starkey). 



growth of higher plants and for microorganisms. The possibility of 

 correlating the numbers and activities of certain groups of micro- 

 organisms and soil conditions, notably moisture and temperature, 

 has also been indicated. 



