ach. To furnish the phosphoric acid he can
buy 1,786 pounds acid phosphate. Seven hundred pounds of either
sulphate or muriate of potash will furnish the potash. These materials
can be easily mixed by spreading in alternate layers on a smooth floor
and then shovelling over the entire mass several times. The mixture
can be further improved by passing it through a sand or coal screen or
sieve.

By following this method of buying the raw materials and mixing them
on the farm, the farmer can reduce his fertilizer bill by quite a
considerable amount and at the same time can obtain just the kinds and
proper amounts of plant foods needed by his crops.

KIND AND AMOUNT TO BUY

The farmer should make the best use of farm manures and through
tillage to render plant food available for his crops before turning to
commercial fertilizer for additional plant food.

If he grows leguminous crops for green manuring, for feeding stock or
for cover crops, he can in many cases secure, chiefly through them,
sufficient high priced nitrogen for the needs of his crops, and it is
necessary only occasionally to purchase moderate amounts of phosphoric
acid, potash and lime.

For special farming and special crops it may be necessary to use the
commercial fertilizer more freely.

It is impossible to say here just what amounts or what kinds of
fertilizer should be purchased, because no two farms are exactly alike
as to soil, methods of cropping or methods of tillage.

There are certain factors, however, which will serve as a general
guide and which should be considered in determining the kind and
amount of fertilizer to buy.

These factors are:

The crop.
The soil.
The system of farming.

THE CROP

Crop roots differ in their powers of feeding, or their powers of
securing plant foods. Some roots can use very tough plant foods, while
others require it in the most available form. Some roots secure
nitrogen from the air. The cowpea roots, for example, can take
nitrogen from the air and they can use such tough phosphoric acid and
potash that it seldom pays to feed them directly with fertilizers.

A bale per acre crop of cotton requires for the building of roots,
stems, leaves, bolls, lint and seed:

103 pounds of Nitrogen.
41 " " Phosphoric Acid.
65 " " Potash.

and yet experiment and experience have proved that the best fertilizer
for such a crop contains the following amounts of plant food:

Nitrog