10 HINTS ON SOILS AND FERTILIZERS 
tains a certain amount of the other sized soil 
grains, also. For instance, to use a specific 
example, we might classify a clay loam as a 
soil having 35 per cent of sand, 30 per cent silt, 
and 35 per cent of clay particles. In fact, it 
would be hard indeed to find a soil that had 
one hundred per cent of the same sized par¬ 
ticles in it. 
We must not leave this topic without under¬ 
standing that there are various other things 
that go to compose the soil besides the humus 
and mineral elements already mentioned. 
There are countless soil organisms existing in 
the soil, which, in most cases, work for the good 
of the soil. Such organisms are known as 
worms, bacteria, and fungi. Worms usually 
aid in making the soil porous, so that air can 
penetrate the soil. The bacteria that are pres¬ 
ent in the soil are a great help in breaking 
down the organic matter, or humus, and de¬ 
composing it so that the plant food contained 
therein may be restored to the soil. Most bac¬ 
teria aid in the manner just described, but there 
are some kinds of bacteria which are harmful 
to ideal soil conditions. Fortunately, these bac¬ 
teria are comparatively few, and cease to be a 
detriment when the soil is properly cared for. 
Air is another factor that must be counted on 
in a good soil. Strange to say, the roots of 
plants need air, to a certain extent, just as we 
need air to live. If there were no air between 
the soil grains that we have just been dis¬ 
cussing, the roots of the plants could not sur¬ 
vive. Therefore, we must make allowance for 
a certain amount of air in the soil, and this Is 
