THE INFLUENCE OF ENVIRONMENTAL FACTORS ON NUMBERS OF SOIL MICROORGANISMS

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Abstract
A study was made of the changes in the numbers of bacteria, actinomycetes, and bacteria in pasture soil, as influenced by moisture content, temp. and reaction. There was a clear-cut relationship between bacterial numbers and moisture content and a similar but less definite relationship between numbers of actinomycetes and moisture. No clear correlation was noted between the abundance of fungi and soil moisture. No specific effects of temp. or reaction (range from pH 6.1-65) on abundance of organisms were established. There was some positive correlation between the numbers of bacteria and actinomycetes and negative correlation between bacteria and fungi. The seasonal changes in temp. and moisture do not seem to be the direct causes of the seasonal changes in numbers of bacteria. Through their influence on growth of vegetation, the climatic factors control the amt. of food material reaching bacteria as root excretions and root residues.