Microorganisms in Manure and in Composts 53 



Table 8. Infliexce of TEMrEnvTiRE ipov the ^IicROBiouKiUAL Population of 

 Manure Composts (from Waksmaii, Cordon, and Ilulpoi) 



Nnmhcrs per fjrani of moist compost. 



'lVm])iTaliiro 



of Period of Bacteria and 



Decomposition Decomposition Actinomycetes 



"C days 



28 



8 

 21 

 39 



50 



2 



8 



39 



65 



39 



75 



8 



21 



It was at first believed that the increase in bacterial numbers fol- 

 lowing the addition of manure was due to the introduction of organ- 

 isms present in the manure. The \'alue of addition of manure to 

 the soil was even ascribed, at least partly, to its bacterial content. 

 It was later demonstrated, howexer, that when manure is sterilized 

 before its addition to the soil the effect upon the bacterial popula- 

 tion is similar. It is the organic materials in the manure which serve, 

 therefore, as nutrients for the bacteria and other microorganisms and 

 which are responsible for their multiplication. Certain bacteria, 

 however, such as the thermophilic forms, may be introduced into 

 the soil by the manure. 



The influence of organic materials in controlling the development 

 of disease-producing bacteria and fungi in the soil is due to the fact 

 that the antagonistic organisms favored by the manure play an im- 

 portant role in suppressing the growth of plant parasites, as will be 

 shown later. 



