CHEMICAL FERTILIZERS

I am half tempted to omit entirely any discussion of chemical
fertilizers: to give a list of them, tell how to apply them, and let
the why and wherefore go. It is, however, such an important subject,
and the home gardener will so frequently have to rely almost entirely
upon their use, that probably it will be best to explain the subject as
thoroughly as I can do it in very limited space. I shall try to give
the theory of scientific chemical manuring in one paragraph.

We have already seen that the soil contains within itself some
available plant food. We can determine by chemical analysis the exact
amounts of the various plant foods--nitrogen, phosphoric acid, potash,
etc.--which a crop of any vegetable will remove from the soil. The idea
in scientific chemical manuring is to add to the available plant foods
already in the soil just enough more to make the resulting amounts
equal to the quantities of the various elements used by the crop grown.
In other words:

)
Available plant food elements in (
the soil, plus > == Amounts of food elements
Available chemical food elements ( in matured crop
supplied in fertilizers )

That was the theory--a very pretty and profound one! The discoverers of
it imagined that all agriculture would be revolutionized; all farm and
garden practice reduced to an exact science; all older theories of
husbandry and tillage thrown by the heels together upon the scrap heap