6 HINTS ON SOILS AND FERTILIZERS 
practices used in different parts of the coun¬ 
try, and try to present in these pages an ex¬ 
planation of different soil phenomena that oc¬ 
cur under varying condiiions, in a manner that 
will be clear to anyone capable of reading. 
Before proceeding further, we may well ask, 
“what is soil”? Ordinarily, we think of soil 
being the upper six or eight inches of the 
earth’s crust that is used for growing crops. 
Now that we have our soil located, might we 
not inquire further as to what we really mean 
when we refer to the soil. Of what is soil 
composed? True, soil is not composed of ex¬ 
actly the same ingredients and exactly the same 
amounts in all cases, but we will first consider 
its general composition. 
The real soil is made up of two chief in¬ 
gredients, namely, humus and mineral matter. 
By humus, we mean decayed, or rather, par¬ 
tially decayed organic matter, such as barn¬ 
yard manure, or a crop plowed, or turned un¬ 
der, such as rye, for instance. This matter 
of humus will be discussed more in detail in 
a later chapter, so we will not dwell further 
on this subject here. The other part of the 
soil is termed mineral matter, or mineral ele¬ 
ments. These elements concern the richness 
of the soil, or its ability to yield a crop. 
Possibly the next question that arises is con¬ 
cerning the origin of the soil, especially the 
mineral elements. There are various agencies 
that aid in soil formation, but all of these 
agencies work on one substance—rock. A rock 
may be defined as an aggregate of mineral 
elements. When certain natural forces work 
