SOME SOIL CHANGES PRODUCED 
BY MICRO-ORGANISMS 
By Walter G. Sackett 
The prosperous farmer has learned through the school of 
experience that if he follows certain practices he can keep his land 
in a productive condition. This practical knowledge is of ines¬ 
timable value, but it does not go far enough. In order to be able 
to proceed intelligently and to meet problems out of the ordinary 
routine, when they arise, he should know more about the funda¬ 
mental principles which underlie his profession. While there are 
many factors concerned in the conservation of plant food in the 
soil, the part which micro-organisms play is among the most im¬ 
portant, and in the pages which follow, it is the purpose of the 
writer to present as clearly as possible a story of the activities of 
soil bacteria, yeasts, and molds. 
Before passing to a consideration of the work which bacteria 
perform in the soil, it may be well to learn something of the 
nature of these micro-organisms themselves. 
THE NATURE OF BACTERIA. 
In the year 1675, Anton van Leeuwenhoek, a skilled lens maker 
of Delft, Holland, observed for the first time what we know today 
as bacteria. He devoted much of his time to examining through 
the microscope such material as was especially suited to testing 
his lenses, and on the occasion mentioned, he chanced to be looking 
at some tartar scraped from the teeth and mixed with a little 
water. To his great surprise and wonder, Leeuwenhoek saw what 
he believed to be, “many tiny animals which moved about in a 
most amusing fashion.” He described the different shapes and 
supplemented his observations with drawings which resemble closely 
the present day forms. He was mistaken, however, in interpreting 
what he found as animal life, for the careful study of recent years 
has shown that bacteria or germs belong to the plant kingdom. 
To be sure, they are different from the plants with which most of 
us are familiar, but their food habits, the chemical composition of 
some of them, their simple shapes and their relation to such recog¬ 
nized plant forms as the molds and yeasts place them unquestionably 
with the lower forms of vegetable life. 
Much of our knowledge of these organisms remained locked up 
