PRESS BULLETIN 168
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
IMPROVING ACID SOILS.
By A. W. Blair.
The soils in many sections of Florida are acid (sour), which is unfavor-
able for the best development of many crops. Soils that are low and wet,
especially muck soils, are likely to be acid. It is generally safe to assume
that our pine-land soils are more, or less acid if there is no indication of
phosphate rock, limestone, or marl, at or near the surface. Hammock soils
may also be acid, though in some cases the hammocks have a layer of marl
a little below the surface.
Causes of Acidity.
1. Alkaline materials, such as potash, soda, lime, and magnesia, which
can neutralize or counteract acids, have, to a large extent, been washed
out of our soils by the action of drainage waters. (The State Geologist, in
Bulletin No. 1, of the Geological Survey, stated that dissolved material is
being carried into the sea through the Silver Springs at the rate of about
600 tons per day.) In this dissolved matter, carbonate of lime greatly pre-
2. Organic matter, such as grass, weeds, or stalks, decays in the soil
with the formation of organic acids, which on account of their slow solubil-
ity tend to accumulate in soils not well supplied with alkaline materials
3. Certain fertilizing materials, sulphate of ammonia in particular, tend
to increase the acidity of soils that are naturally deficient in alkaline ma-
terials, owing to the plants using the ammonia to a greater extent than they
do the sulphuric acid.
Alkaline materials generally, will counteract or neutralize any acid.
In improving an acid soil, the aim should be to' get an alkaline material
that is cheap and that can be easily handled. To a large extent, lime in
its different forms fulfils these requirements.
Carbonate of lime is the form that occurs naturally. It is found as
crystallized limestone or marble, as massive limestone rock, as marl, and
as shells. It also occurs in certain soils in a finely divided state as the re-
'MPay 13, 1911
suit of the decomposition of some of the above-named materials. Examples
of such soils are found in the Bluegrass regions of Kentucky, and Southwest
Virginia. Carbonate of lime, in any form, if ground fine and worked into
an acid soil in sufficient quantities, will correct the sourness. It will not
take effect as rapidly as quick-lime, nor is it as concentrated. It should,
however, be much cheaper. One hundred pounds of pure quick-lime are
equivalent to 179 pounds of pure. limestone; but, because of impurities,
it would perhaps be best to take 200 pounds of carbonate of lime, in the
form of ground limestone or ground shells, as the equivalent of 100 pounds
of pure quick-lime.
Slaked Lime (hydrated lime) is made by slaking quick-lime with just
enough water to convert it into a fine powder. One hundred and thirty-two
pounds of slaked lime prepared in this way are equivalent to 100 pounds of
pure quick lime.
Unbleached hardwood ashes contain about 25 to 30 per cent. of lime
in addition to 4 to 6 per cent. of potash, and when they can be had at a
reasonable price they may be used with profit on acid soils.
Basic, or Thomas, Slag contains about 40 per cent. of lime in addi-
tion to 17 or 18 per cent. of phosphoric acid, and if a moderate application
of lime is needed along with a heavy application of phosphoric acid, this may
be used. In our experiments with pineapples, basic slag has given good re-
If ground limestone or shells are used, and the soil is found to be highly
acid (by testing with litmus paper), two tons per acre once in two or three
years will not be excessive. If the soil is only slightly acid, one ton per
acre may suffice. Only half the amount need be applied if quick-lime is
used. Old, thoroughly air-slaked, lime may be used in about the same
amount as ground limestone.
Lime may be applied at almost any time, though it would perhaps be
better to apply it during the late winter or early spring, so that it may be
thoroughly worked into the soil before the rainy season sets in. If fertilizers
containing sulphate of ammonia are used, it would be better to apply the lime
one month before or one month after the fertilizer application.
Crops Benefited by Lime.
Most vegetable and fruit crops are benefited by the use of the lime
where there is a tendency to acidity of the soil. It has, however, been
shown that watermelons do best on an acid soil. It has also been shown
that lime makes the conditions more favorable for the development of scab
on the Irish potato.
With celery, lettuce, cabbage, citrus fruit's, ihay, and forage crops, it
may be used liberally.
State papers please copy.