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Acid Phosphate
Acquaintance With Terms
Animal Bone
Basic Slag
Dried Blood
Muriate Of Potash
Nitrate Of Soda
Other Fertilizers
Raw Bone


Crops And Methods For Soil Improvement

A Bit Of Arithmetic
A Clean Seed-bed
A Few Combinations Are Safest
A Practical Test
A Southern Legume
A Three Years' Rotation
Adaptation To Eastern Needs
Affecting Physical Condition
All The Nitrogen From Clover
Alsike Clover
Amount Of Application
Amount Of Manure
Amount Per Acre
An Excess Of Nitrogen

Acid Phosphate

When animal bone is treated with sulphuric acid, the
result is an acid phosphate, but treated animal bone is so rare on the
market that it may be ignored. The acid phosphate on the market is
rock-phosphate treated with sulphuric acid to render its plant-food
available. The content of phosphoric acid varies because the original
rock-phosphate varies, but the most common grade on the market is
guaranteed to contain 14 per cent available phosphoric acid, and 1 to 2
per cent insoluble. Some acid phosphate is guaranteed to contain 16 per
cent available phosphoric acid, and some runs down to 10 per cent

An acid phosphate contains quickly available plant-food. A prejudice
exists against it on account of its source, and it has been a common
practice to label the bags "bone-phosphate," or "dissolved bone," or
such other designation as would imply an organic source, but the acid
phosphate is made out of rock-phosphate, regardless of the name given.
The prejudice against the rock as a source of plant-food is giving way.
It is our chief and cheapest source of supply. The combination of
sulphuric acid with rock-phosphate in the production of acid phosphate
produces sulphate of lime, known as gypsum or land-plaster. The amount
of gypsum in a ton of acid phosphate varies, but may be roughly
estimated by the buyer as two thirds of the total weight of the acid

The tendency of gypsum is, in the long run, to make a soil acid, and
its use necessarily hastens rather than retards the day when a lime
deficiency will occur. The influence in this direction is not great
enough to be a very material factor in deciding upon a carrier of
phosphoric acid. If a soil has little lime in it, a state of acidity
soon will come anyway, and the increase in amount of required lime will
be small. The cheapness of acid phosphate, as compared with animal
bone, is the decisive factor.

The ill-effects usually attributed to acid phosphate are not due in any
great degree directly to the sulphuric acid used in its making, but to
the bad farming methods that so often attend its use. When the need of
commercial fertilizers is first recognized, acid phosphate seems to
meet the need. The soil's store of available phosphoric acid gives out
first, and this fertilizer brings a new supply. If the available potash
is in scant amount, the acid phosphate helps in this direction by
freeing some potash. The phosphoric acid has peculiar ability in giving
impetus to the growth of a young plant, and that enables it to send its
roots out and obtain more nitrogen than it otherwise would do. The
farmer thus may come to regard it as a means of securing a crop, and
there is neglect of manure and clover. If a field is thin and fails to
make a sod, there is no immediate compulsion to use manure or to grow a
catch crop to get organic matter, but the field is cropped again with
grain. Soon the supply of humus is exhausted, the soil lies lifeless,
and the stores of available nitrogen and potash are in a worse depleted
state than formerly.

The fault lies with the method. The phosphoric acid in the acid
phosphate was needed. Profit from its use was legitimate, but the
necessity of supplying organic matter became even greater than it would
have been otherwise. Tens of thousands of our most successful farmers
use heavy applications of acid phosphate, but they keep their soils in
good physical condition by the use of manure or clover, and they apply
potash and nitrogen when needed. The clover is assured by using lime
wherever it is in too limited supply, and that is the case in most
instances, regardless of the use of any kind of commercial fertilizer.

Next: Basic Slag

Previous: Rock-phosphate

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