Soil, Changes Produced By Micro-organisms. 13 
ide and water through the oxidation of carbonaceous material; 
and to the soil, carbonic acid, organic acids, organic matter and 
mineral substances. 
As yet, nothing has been said about the destruction of fats, 
gums and waxes. Whether fats or waxes, bacteria, yeasts and 
molds, through the immediate action of enzymes, convert these 
fatty substances into glycerine and fatty acids, both of which may 
be oxidized finally into carbon dioxide and water. 
Thus it is, that the carbonaceous materials contained in plant 
and animal tissues undergo decomposition at the hands of soil 
micro-organisms. The carbon of the complex compounds is trans¬ 
formed into carbon dioxide, which either passes into 1 the air to re¬ 
plenish the atmospheric supply, or unites with water to form car¬ 
bonic acid and ultimately soil carbonates. 
TRANSFORMATION OF NITROGEN. 
We come next to a consideration of soil nitrogen which, from 
the standpoint of conservation of plant food, is unquestionably the 
most important of all the elements. It is not that the supply of 
nitrogen is so limited, for approximately 79 per cent of the air con¬ 
sists of this gas, but rather, that it does not exist in any quantity in 
a form that plants can utilize. To be of value to vegetation, it must 
be present in the soil, either in the form of nitrates, or possibly as 
ammonium salts, but the stock of both of these is far from abundant. 
The world’s supply of commercial nitrate is derived almost 
exclusively from two sources—guano and Chile saltpeter; some ni¬ 
trate of potash comes from the plains of the Ganges River in India. 
All of these are becoming exhausted rapidly, and already guano 
has ceased to be of any importance. While it is difficult to obtain 
any precise estimate of the amount of available saltpeter in the beds 
of Chile and Peru, South America, it is quite certain that if the 
present rate of consumption continues,—2,597,754 tons for the year 
1910—it cannot last for any great length of time, some placing the 
limit at less than forty-five years. At $50 or $60 per ton, an appli¬ 
cation of two hundred to three hundred pounds of nitrate of soda 
per acre soon runs into money, and the commercial article, while 
rich in nitrate, is at the same time so expensive that the cost makes 
it almost prohibitive for the average farmer. 
Dr. Headden informs me that our ordinary Colorado soils con¬ 
tain from .0037 to .0121 per cent (150-450 pounds per acre foot) 
of nitrates expressed as nitrate of soda, an amount far too small to 
permit of any wasteful methods in farming. From this is is quite 
clear that unless more attention is given by our agriculturists to 
