# Ingredients In The Mixture

The matters of interest to the farmer are

the determination of the amounts of nitrogen, phosphoric acid, and

potash that he should apply to a particular field, their availability,

and their cost. Let us assume that he has found 300 pounds of a

fertilizer containing 3 per cent nitrogen, 10 per cent phosphoric acid,

and 6 per cent potash to be an excellent application for wheat on a

thin soil that is to be seeded to clover and timothy. This fertilizer

contains 3 pounds of nitrogen to each 100 pounds. He applies 300 pounds

of the fertilizer per acre, or 9 pounds of nitrogen. The fertilizer

contains 10 pounds of phosphoric acid to the 100 pounds. He thus

applies 30 pounds of phosphoric acid per acre. The fertilizer contains

6 pounds of potash per 100 pounds, and he therefore applies 18 pounds

per acre. What he has really learned, then, is that an acre of this

land, when seeded to wheat, needs 9 pounds of nitrogen, 30 pounds of

phosphoric acid, and 18 pounds of potash. It is in these terms he

should do his thinking, and the matter of fertilization becomes simple.

In the general farming of the Pennsylvania experiment station, it is

the practice to depend upon nitrate of soda as the source of a

fertilizer for wheat. Manufacturers claim that sulphate of ammonia and

tankage would be better. The farmer soon will learn what he prefers for

his soil, provided he practices home-mixing.

Let us assume that he uses nitrate of soda, which never varies much

from 15 per cent in its content of nitrogen. If 100 pounds of nitrate

contain 15 pounds of nitrogen, the 9 pounds wanted for an acre will be

found in 9/15 of 100 pounds or 60 pounds.

Thirty pounds of phosphoric acid are wanted for an acre. If the acid

phosphate contains 14 per cent of phosphoric acid, or 14 pounds to the

100, the required amount will be 30/14 of 100, or 214 pounds.

Eighteen pounds of potash are wanted for an acre. The muriate of potash

on our markets never varies much from 50 per cent in its content of

potash. If 100 pounds of muriate contain 50 pounds of potash to the

100, the required amount wanted will be 18/50 of 100, or 36 pounds.

Adding the 60, 214, and 36 pounds, we have 310 pounds for the acre of

land. If the field contains 20 acres, the order will call for 20 times

the 60 pounds of nitrate of soda, 20 times the 214 pounds of acid

phosphate, and 20 times the 36 pounds of potash.

If the farmer prefers to use sulphate of ammonia, which varies little

from 20 per cent of nitrogen, or 20 pounds in the 100, he will get his

9 pounds of nitrogen for an acre by buying 9/20 of 100 pounds, or 45

pounds, and the substitution of the 45 pounds of sulphate of ammonia

for the 60 pounds of nitrate of soda will reduce the total application

of fertilizer per acre from 310 pounds to 295 pounds. The important

fact is that in either case there is the required amount of nitrogen.

Let us assume that the field contains enough nitrogen, but other needs

remain the same. In such case, the nitrogen is dropped out, and the

application becomes 250 pounds per acre.

The home-mixer may substitute tankage of guaranteed analysis for part

of the nitrogen and phosphoric acid. Let us assume that the tankage

runs 9 per cent nitrogen and 20 per cent phosphoric acid. If half the

required nitrogen per acre, or 4-1/2 pounds, is wanted in tankage, 50

pounds of the tankage will supply it. At the same time the 50 pounds of

tankage supplies 10 pounds of phosphoric acid, replacing one third of

the 214 pounds of acid phosphate. We thus have for the acre 30 pounds

of nitrate of soda, 50 pounds of tankage, 143 pounds of acid phosphate,

and 36 pounds of potash, or 259 pounds. The content of plant-food

remains the same, but one half of the nitrogen is only slowly

available. The farmer who buys unmixed materials will incline to use

only a few kinds, and at first he will confine himself chiefly to

materials whose composition varies little. In this way he quickly sees

in a ton of the material, not the whole bulk, but the definite number

of pounds of nitrogen and other constituents of plant-food contained in

it, and the calculations in home-mixing become simple.

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Materials That Should Not Be Combined
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