The Function of Manures and FertUizere 35

The fact that fertilizers may now be easily secured,
and the ease of application, have encouraged a careless
use, rather than a thoughtful expenditure, of an equivalent
amount of money or energy in the proper preparation of
the soil. Of course, it does not follow that no returns
are secured from plant-food applied under unfavorable
conditions, though full retiuns cannot be secured under
such circumstances. Good plant-food is wasted, and the
profit possible to be derived fa largely reduced.
Again, because farming, in its strict sense, fa the
conversion of three essential elements into salable prod-
ucts, the time to apply plant-food must be governed
largely by its cost and the kind of crop upon which it
fa applied.
CHAPTER m

NITROGENOUS FERTILIZERS

Nitrogen is the most expensive constituent of fertilizers,
and, all things considered, it is one of the most useful.
Nitrogen exists in nature as a component of the air, and
though quite as necessary to vegetation as carbon or
oxygen, — which also exist in the atmosphere, and which
are readily acquired by all plants, — all plants do not
have the power of acquiring nitrogen from this source.
This power seems to be limited to a class of plants called
Legmninosce, to which belong the various clovers, peas,
beans, vetches and a number of others. The important
farm crops belonging to the other botanical groups of plants
obtain their nitrogen largely, if not altogether, from the soil.
