32 PRINCIPLES OF SOIL MICROBIOLOGY
numbers, due to the fact that a continued dry period brings about a
phenomenon similar to partial sterilization of the soil and with the first
increase in moisture there is an increase of available organic and in-
organic materials, leading to a rapid increase in bacterial numbers.
Several investigators found larger bacterial numbers in the soil in sum-
mer than in winter, the maximum being reached in July and August.
In the spring of the year, with the increase in soil temperature, there is a
corresponding increase in bacterial numbers. 62 It was suggested, 38
however, that
the water content of the soil is the most important factor
bearing upon bacterial numbers: cultivation increases the number by
increasing the water content. Engberding 38 was unable to demonstrate
any influence of temperature upon the numbers of bacteria in mineral
soils. This difference in results may be due to the difference in the
composition of the soil. The numbers of bacteria (and protozoa) were
even found to fluctuate from day to day. 63 Well-marked seasonal
changes in the soil population are superimposed on the daily varia-
tions in numbers. These changes are not directly influenced by tem-
perature or rainfall, but show a similarity to the seasonal fluctuations
recorded for many aquatic organisms.
SELMAN A. WAKSMAN
Associate Professor of Soil Microbiology,
Rutgers University, and Microbiologist of the
New Jersey Agricultural Experiment Stations
http://archive.org/stream/principlesofsoilx00waks/principlesofsoilx00waks_djvu.txt
Canns' response in 5,4,3,2 ......... I'm looking forward to this one brotha. jj