DEVELOPMENT OF ACTINOMYCES IN SOIL 



65 



are followed by changes in the abundance and activities of the 

 microscopic population of the soil. 



Development of Actinomyces in Soil. — QuaHtatively, the 

 actinomyces react to changes in the soil environment in much the 

 same way as most of the soil bacteria do. They respond markedly 

 to the addition of organic materials, such as root residues or other 

 plant and animal remains, and may be concerned with the slow 

 decomposition of some of the most resistant organic substances 



20 -. 



60 120 



50 100 



40 



30 



80 - 



60 



20 «> 40 -► 



20 - 



13 



--20' 



'"lO 



Fig. 44. — Microorganisms in soils during the winter and spring months 

 (after Lochhead). 



in the soil. Thej^ are favored by much the same moisture content 

 as the bacteria, but may develop better than the bacteria when 

 the soil is relatively low in moisture. They are more sensitive 

 than bacteria to soil acidity, and develop best at neutral or slightly 

 alkaline reactions. These organisms appear to be more constant 

 in abundance than either the bacteria or fungi and show less 

 marked fluctuations due to environmental changes. Although 

 they decrease in abundance from the surface to the deeper layers of 



