t in all cases
state what materials were used to furnish the different kinds of plant
food, and it is not always possible to find this out by analysis.

_Low grade materials._

For instance in mixing a fertilizer one manufacturer may use dried
blood to furnish nitrogen and another may use leather waste or horn
shavings. The latter contains more nitrogen than the dried blood, but
they are so tough and decay so slowly that they are of little benefit
to a quick growing plant.

_Inflating the guarantee._

Although the dealer states correctly the per cents of plant food in
the fertilizer, he is quite frequently inclined to repeat this in a
different form, and thus give the impression that the mixture contains
more than it really does.

The dealers also give the nitrogen as ammonia because it makes a
larger showing.

Phosphoric acid is often stated as "bone phosphate" because in this
the amount appears to be greater.

For example, an analysis taken from a fertilizer catalogue reads as
follows:

Ammonia 2 to 3 per cent.
Available Phosphoric Acid 8 to 10 "
Total Phosphoric Acid 11 to 14 "
Total Bone Phosphate 23 to 25 "
Actual Potash 10 to 12 "
Sulphate of Potash 18 to 20 "

A better statement would be as follows:

Nitrogen 1.65 per cent.
Available Phosphoric Acid 8 "
Total Phosphoric Acid (furnished in Bone Phosphate) 11 "
Potash (furnished in Sulphate of Potash) 10 "

Ammonia is reduced to terms of nitrogen by multiplying by .824. All
bone phosphate is forty-six per cent. phosphoric acid. When bone
phosphate is given instead of phosphoric acid it simply makes the
mixture appear to have more in it, and when both phosphoric acid and
bone phosphate are stated one is merely a repetition of the other. The
same is true of the statements, potash and sulphate of potash, one is
a repetition of the other only a different form.

VALUATION

The experiment stations not only publish comparative analyses of the
registered fertilizers but they also compute the market values of the
plant food contained in them and compare these valuations with the
selling price of the fertilizers.

They also furnish a list of trade values of the plant foods in raw
materials for the convenience of fertilizer