HINTS ON SOILS AND FERTILIZERS 69 
bacteria “culture,” that contains countless bil¬ 
lions of these living bacteria. By sprinkling 
this liquid culture on the alfalfa seed just be¬ 
fore sowing it, he can very easily inoculate 
his soil; he can buy enough from this source 
for twenty-five cents to supply one acre of soil. 
There is still another form of these helpful bac¬ 
teria that we have not as yet discussed, and 
that is the nitrifying bacteria, so called. These 
bacteria are unlike the bacteria just discussed, 
in that they do not add any nitrogen to the soil 
by taking it from the air, but simply change in¬ 
soluble forms of nitrogen already present in the 
soil, to soluble forms of nitrogen which the 
plant can use. Most of this insoluble nitrogen 
is found in the organic matter that we have 
learned about. Hence, if there is not a suffi¬ 
cient supply of organic matter in the soil, there 
will be a shortage of this all important ele¬ 
ment, nitrogen. 
There are many different kinds of bacteria 
found in soil, and most of these are beneficial 
to the crops. There are a few kinds, however, 
which are really harmful to crop production, in 
that they tend to waste some of the elements 
In the soil that should go to nourish the crops. 
These bacteria, however, thrive best when ther* 
is only a limited amount of air in the soil. The 
farmer can largely eliminate these harmful bac¬ 
teria from his soil by aerating his soil and by 
various methods of cultivation, so that a liberal 
supply of air is always present in the soil. When 
this condition obtains, these harmful bacteria 
will have little opportunity for their destructive 
work. 
