It may be said that the potash in the fertilizer is in form of
sulphate. Usually that profits the user nothing, and often the claim is
baseless, but if it is a sulphate, the cost of the potash should have
only 20 per cent added to the valuation of the potash, which usually
will not add one dollar to the total cost of the ton of mixed
fertilizer. Basing the valuations of the pounds of plant-food in the
mixed fertilizer on the value per pound in unmixed materials delivered
to one's own locality, there must be taken into account the added
expense of mixing.

High-grade Fertilizers.--A high-grade fertilizer is not necessarily a
high-priced one. What we want in a fertilizer is a high content of the
plant-food needed, together with desirable availability. If only
phosphoric acid is wanted, a 14 per cent, or 16 per cent, acid
phosphate is high-grade because it contains as many pounds of available
phosphoric acid in a ton as the public can buy in a large way. A 10 per
cent acid phosphate is low-grade. The effort is to escape paying
freight, and other cost of handling, on waste material as far as
possible. Generally speaking, the higher the percentages of plant-food
in a fertilizer, the cheaper per pound is the plant-food. A low-grade
fertilizer rarely fails to be an expensive one because the expense of
handling adds unduly to the price per pound of the small content of
plant-food.

CHAPTER XIX

HOME-MIXING OF FERTILIZERS

The Practice of Home-mixing.--The business of compounding fertilizers
has been involved in a great deal of unnecessary mystery. Many of our
best station scientists have labored to show that the home-mixing of
fertilizers is a simple and profitable piece of work, and the heaviest
users of fertilizers in the east now buy unmixed materials, but a
majority of farmers use the factory-mixed. Manufacturers are right in
their contention that many people do not know what materials are best
for their own fields, or what proportions are best, but the purchase of
mixed materials does not solve their problem and it does not help them
to a solution as quickly as home-mixing. The source of the plant-food
in the factory-mixed goods is not known, while it is known in the
home-mixed.

Effectiveness of Home-mixing.--Van Slyke says ("Fertilizers and Crops,"
p. 477): "Manufacturers of fertilizers and their agents have
persistently sought to discourage the practice of home-mixing, but
their statements cannot be accep