Volume 25 Number 3 -r- 2
JULY 1, 1915
COMMISSIONER OF AGRICULTURE
USES AND PURPOSES OF GROUND
Entered January 31, 1903, at Tallahassee, Florida, as second-class
matter under Act of Congress of June, 1900.
TItSt BULLETINS ARE ISSUED RU TO0 THOSE REQUESTING THrM
T. J. APPLIBTARD, State Printer,
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COUNTY MAP OF STATE OF FLORIDA.
USES AND PURPOSES OF GROUND
IMPROVING ACID SOILS.
BY A. W. BLAIR.
Chemist Agricultural Experiment Station.
The soil in many sections of Florida are acid (sour),
which is unfavorable 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 solubility, tend to accu-
emulate 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 materials, owing to
the plants using the ammonia to a greater extent than
they do the sulphuric acid.
Alkaline materials generally will counteract or neu-
tralize 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 fulfills 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 if
certain soils in a newly divided state as the result 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 con-
centrated. It should, however, be much cheaper. One
hundred pounds of pure quick-lime are equivalent to 170
pounds of pure limestone; but, because of impurities, it
should 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 addition 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 results.
If ground limestone or shells are used, and the soil is
found to be highly acid (by testing with litmus paper),
two tons per scre in two or three years will not be ex
cessive. 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 lime-
Lime may be applied at almost any time, though it
would perhaps be better to apply it during the late win-
ter 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 fruits, hay, and
forage crops, it may be used liberally.
MATERIALS FOR CORRECTING SOIL ACIDITY.
BY P. H. ROLFS.
The entire State of Florida is underlaid with lime-
stone of such quality as to make, when ground, excellent
material for correcting the acidity of the soil. Various
limestone beds have been extensively studied by our
State Geologist (Dr. E. H. Sellards, Tallahassee), whose
reports may be had for the asking. In addition to lime-
stone, we also have in Florida extensive beds of marl,
many of them sufficiently pure to make good material
for correcting soil acidity. Finally, along the sea-coast,
around the larger lakes, and along most of our water-
ways, we find extensive shell mounds. The shells of these
mounds might well be ground and utilized for correcting
Aside from these natural materials, several commer-
cial substances are available to us for neutralizing soil
acidity. In most cases, however, the results obtained
could be more cheaply accomplished by using the natural
LIMESTONE AND LIME.
Ground Limestone is the safest and most satisfactory
material to use. It is a natural product, and may be
added to the soil in any quantity without serious danger
of doing harm. It should not be forgotten, however, that
there are special cases in which it would be inadvisable
to apply ground limestone. From one to three tons should
be used on soils showing slight acidity, and a larger
amount on soils that are decidedly acid; while on some
soils that are very acid the use of as much as eight to
twelve tons will be found profitable.
Hyd~'ated Lime is made by slaking quick-lime with just
enough water to convert it into fine powder. Samples
analyzed at the Experiment Station show that commer-
cial hydrated lime is made up of oxide of lime, hydrate
of lime, and carbonate of lime. When most carefully pre-
pared, 74 pounds of hydrated lime are about equal to 100
pounds of limestone; so if we use about two-thirds the
quantity of hydrated lime in the place of ground lime-
stone we shall be nearly right.
Quick-Lime or Burnt Lime is made from limestone by
driving off the carbon dioxide gas. One hundred pounds
of pure limestone will make 56 pounds of quick-lime. If,
therefore, we wish to use quick-lime, we may apply ap-
proximately half as much as we would if we were using
Hardwood Ashes have long been employed as a source
of potash, and more recently have been used to a consid-
erable extent for correcting soil acidity. There is much
variation in the amounts of potash and lime contained
in hardwood ashes. They contain generally about 3 to 6
per cent of potash, and may be used at the same rate as
we would ordinarily apply fertilizer to the soil.
Basic Slag, or Thomas Slag, as it is sometimes called,
has been employed to a considerable extent as a fertilizer
in Florida in recent years. This material is made from
the refuse from iron or steel mills. It contains about 40
per cent. of lime in addition to about 20 per cent. of
phosphoric acid. The lime in the mixture is a strong cor-
rector of acidity, being less effective in this direction
than the same amount of quick-lime or hydrated lime,
but having the advantage of also carrying phosphoric
acid. It was found a useful source of phosphorus in our
fertilizer experiments with pineapples.
Nitrate of Soda, when used in our fertilizer tests in
the citrus groves, was shown by Prof. Collison to correct
the acidity of the soil. The soda left in the soil after the
nitrate had been used by the plants acted as an alkali.
USING GROUND LIMESTONE.
BY P. H. ROLFS.
The amount of ground limestone to be used will vary
greatly, according to the acidity of the particular piece
of land, even different parts of the same acre showing
different degrees of acidity. A soil that is only slightly
acid will need from one to two tons of ground lime-
stone; soils that are decidedly acid will require about
twice as much; and some of our most acid soils will be
benefited by as much as 8 to 12 tons per acre. Many
farm crops are benefited by an application of ground
limestone, even when the soil does not show acidity.
Plants of the legume family are especially benefited by
such an application. Celery, lettuce, cabbage, citrus
fruits, hay and forage crops, generally prefer a large
quantity of lime in the soil. Watermelons, on the other
hand, do well on an acid soil.
WHEN TO APPLY GROUND LIMESTONE.
It is best to apply ground limestone to the soil a con-
siderable time before the crop is to be planted. The ap-
plication should be made before plowing, as this will
plication should be made before plowing, as this will
give an opportunity to incorporate the material more
evenly with the soil, and will give the beneficial soil
organisms an opportunity to increase to large numbers.
If it has not been possible to apply ground limestone
before the soil is broken up, it may be applied before
planting time. It is advisable, however, to apply it a
considerable time before one wishes to use fertilizer,
since the acid phosphate of the fertilizer on coming in
contact with the ground limestone is likely to be re-
verted more quickly than desirable.
Formerly it was considered necessary to have the lime-
stone ground into a very fine powder; later experimenta-
tion has shown that a rather more closely ground lime-
stone is quite as beneficial and more lasting. Dr. Hop-
kins, of the Illinois Experiment Station, considers that
the limestone is ground fine enough if it can pass through
a sieve with 10 meshes to the inch. Since there are in-
cluded in this material all the finer particles that are
produced in grinding, a sufficient amount of lime will
be available at once for the needs of the plants.
MOST FLORIDA SOILS ARE ACID.
The soils of Florida are for the most part made up of
silicious particles, and have no available alkali or base
to neutralize any acidity. In a few cases where an
abundance of limestone occurs in our surface soil it is
a corrector of acidity, but by far the larger percentage
of our sandy soils are acid.
Our muck soils are nearly all acid, there being very
few exceptions. These are not only acid, but very strongly
so, and frequently require a very large amount of ground
limestone to correct the acidity.
In addition to the fact that most of our soils are nat-
urally acid, this condition is intensified by some of our
fertilizers, especially where large amounts of sulphate
of ammonia are used. When such materials are broken
up, as they are in the process of being made available
to plants, the acid radical is left in the soil. This fact
was brought out in our experimental citrus grove and
noted in our Annual Report.
HOW TO TEST FOR SOIL ACIDITY.
Soil may be tested readily for acidity. This can best
be done in the field. Procure strips of litmus paper from
the drug-store, of both k=:cs, pink and blue. In using
this litmus paper, care should be taken that the fingers
do not touch it, since the perspiration from the hands
is usually acid enough to turn the blue to pink, and in
testing soil after the paper has been handled a false
reaction might occur. The soil to be tested must not be
too dry. A small amount of soil may be taken up, and
if it can be pressed into a good ball it usually contains
enough moisture to show the reaction. Break the ball of
soil open and place two strips of paper (blue and pink)
in the break, then. press tightly together again. In the
course of ten minutes examine, and if the paper has been
thoroughly wetted the condition of the soil may be noted.
If the blue litmus paper has turned pink the soil is acid.
If the pink paper has turned blue the soil is alkaline. If
no change in color occurs the soil is neutral. The degree
of acidity can be told in a general way by the degree of
pinkness if the paper was formerly blue. The subsoil as
well as the soil should be tested.
GROUND LIMESTONE FOR SOUTHERN SOILS.
BY PROFESSOR CYRIL G. HOPKINS.
"A limestone country is a rich country." This is a
proverb and a trueism much older than American agri-
culture. But every soil can be made a limestone soil,
simply by liberal applications of pulverized limestone.
The initial application of four tons per acre of ground
limestone, with subsequent applications of two tons per
acre every four years, will make and maintain a lime-
stone soil on every Southern farm; and this is the first
great economic step to be taken in that positive soil en-
richment which is needed to treble the average acre-yield
of the land now under cultivation and to restore to profit-
able agricultural use the vast areas of tillable land now
lying neglected or agriculturally abandoned in most
In the northern part of the Southland, especially in
the Piedmont and intermountain regions, some soils are
found for whose permanent improvement ground lime-
stone is all the farmer needs to buy, although as a gen-
eral rule phosphates must also be applied; and in many
cases, especially on the more sandy soils of the Coastal
Plain, potash salts must likewise be added. In a few
places soils have been found which, though deficient in
potassium (the important plant-food element contained
in potash salts), are naturally rich in phosphates (com-
pounds containing the element phosphorus), and thus
require the purchase of only limestone and potash salts.
Southern farm soils are almost invariably sour, or acid.
In other words, they contain essentially less than no
limestone, for moderate applications of limestone will be
destroyed by the soil acidity. Thus one may apply one
ton of ground limestone per acre to certain land and still
have no limestone in the soil, or a four-ton application
may leave only three tons for future benefit, after the
acidity existing in the plowed soil has been neutralized.
LIMESTONE AND LEGUMES.
With liberal applications of limestone (and phosphorus
'or potassium added, if needed) most Southern soils can
be made to produce abundant crops of such valuable bi-
ennial or perennial legumes as red clover, alsike clover,
sweet clover (mellilotus) and alfalfa; and these when in-
fected with the proper bacteria have direct access, almost
twelve months in the year, to the inexhaustible supply of
nitrogen in the air. The biennial and perennial legumes
store up very much more nitrogen and organic matter in
their roots than do the annual plants, such as cowpeas,
and one seeding (sometimes with a nurse crop and with
no extra preparation of the seed bed) may .provide a
legume crop to occupy the land for from two years to
five years or more.
These deep-rooting legumes are the "best subsoilers,"
and in many ways they are the best soil-improving crops.
Furthermore, they are splendid pasture crops, and if not
cropped too closely (a bad practice for any pasture) they
will furnish grazing from early spring till early winter.
These are am6ng the most valuable crops in profitable
live-stock farming; and nothing is needed more for the
development of live stock in the South. Moreover, clover
and alfalfa are the best crops to precede corn, as is well
known by every corn-belt farmer.
Limestone and legumes must constitute the foundation
for corn and cattle in the South.
KINDS OF LIME.
Ordinary limestone is calcium carbonate (CaCO,),
composed of the three primary elements, calcium, carbon,
and oxygen, as anyone might know from the name if he
will only remember that the ending "ate," on the more
common chemical names, signifies oxygen.
When 100 pounds of pure limestone are burned, 44
pounds of the gas carbon dioxide (CO2) are driven off,
and 56 pounds of quicklime, or calcium oxide (CaO).
remain. Quicklime is ordinary fresh-burned caustic lime.
When moistened, the 56 pounds of quicklime taks up 18
pounds of water (H2O) and make 74 pounds of water-'
slaked, or hydrated, caustic lime (CaO2H,). If this is
exposed to the air it gradually absorbs carbon dioxide.
gives off water; and finally returns to the original com-
pound, calcium carbonate; so that 100 pounds of thor-
oughly air-slaked lime has exactly the same composition
as 100 pounds of ground limestone. The hydrated limes
on the market usually contain some moisture in excess of
that required for hydrating or slaking; also some ab-
sorbed carbon dioxide, and often the most impure lime
from the kiln is used for making this product, so that 80
or 90 pounds of hydrated lime may correspond to 100
pounds of limestone.
A somewhat less common but yet very abundant form of
limestone is dolomite, or dolomitic limestone. This when
pure is a double compound of calcium carbonate (CaCo,)
and magnesium carbonate (MgCOs), or calcium magnes-
ium carbonate, CaMg (CO,),, containing with 100 parts
of calcium carbonate 84 parts of magnesium carbonate.
USES OF LIME.
Ordinary limestone serves two very important purposes
in soil improvement: One is to correct the acidity 9f sour
soils, and the other is to supply the element calcium as
plant food; and in most soils calcium is much more defi-
cient than potassium, and even more deficient than phos-
phorus in many soils. Dolomite not only corrects soil
acidity and supplies calcium, but it also supplies mag-
nesium, another essential element of plant food, the sup-
ply of which is very limited in some soils. Dolomite has
even greater power than the more common limestone in
correcting acidity, 184 pounds of dolomite being equiva-
lent to 200 of calcium carbonate.
In pure form 56 pounds of quick lime or 74 pounds of
hydrated lime would have the same power to correct soil
acidity as 92 pounds of dolomite or 100 pounds of ordi-
nary limestone. In other words, with ground limestone
at $1.00 a ton or ground dolomite at $1.09, the hydrated
lime would be worth $1.35, and the quick lime $1.79 per
ton, except for one other very important fact: and this
fact is that caustic lime is caustic.
THE KIND OF LIME TO USE.
According to the dictionaries, the word caustic means
"capable of destroying the texture of anything by eating
away its substance by chemical action." This definition
well describes the destructive action of caustic lime on
the humus or vegetable matter of the soil: and when the
vegetable matter is destroyed the nitrogen which it con-
tains is liberated and in part dissipated, so that the use
of caustic lime, whether fresh-burned or hydrated, aug-
ments the difficulty of increasing or maintaining the
humus or nitrogenous vegetable matter of the soil. This
problem is already serious enough in Southern agricul-
ture, and if possible we should avoid burning the humus
out of the soil with caustic lime.
In agriculture, as well as in religion, it is well to re-
member the injunction to "be ready always to give an
answer to every man that asketh you a reason of the hope
that is in you;" and attention is called to the following
reasons for the hope of Southern agriculture in ground
FINENESS OF GRINDING FOR LIMESTONE.
Ground limestone is readily available; and if very
finely ground it is likely to be too available, too easily
soluble; because, as a rule, the loss by leaching far ex-
ceeds that by cropping. As an average of forty years at
Rothamsted, the annual loss amounted to about 800
pounds of lime carbonate per acre. In Illinois an inves-
tigation covering ten years showed the average annual
loss to be 780 pounds per acre. With the more porous
soils and heavier rainfall of the South the danger of loss
is still greater.
Preliminary investigations by the Illinois Experiment
Station indicate the dolomite is more durable than the
ordinary limestone. The information bearing on the
fineness of grinding is sufficient to justify the conclusion
that the screen or sieve used need not be finer than 10
meshes to the inch (100 per square inch), and that it
should not be coarser than 4 meshes to the inch, with all
of the finer material produced in the process included
in the product.
The advice sometimes given that limestone should be
ground so that it will all pass through a screen with 50
or 100 meshes to the linear inch has no justification.
Such grinding increases unnecessarily the cost of ma-
terial, increases the cost of application (by requiring
annual or frequent application) and increases the loss by
leaching. Where used liberally at less frequent intervals
in rational, profitable, permanent systems, an 8-mesh or
10-mesh screen is amply fine for the most economic
product, especially for the ordinary limestone consisting
chiefly of calcium carbonate.
AMOUNT OF LIMESTONE TO USE.
While heavier initial applications of ground. limestone
may produce even greater benefit, and would certainly
do no harm, four tons per acre are sufficient to give very
satisfactory results, and subsequent applications of two
tons per acre every four years will maintain limestone in
the soil. Heavy applications reduce expenses in perma-
nent system of soil improvement, by saving in labor of
frequent applications and by making use of less finely
In all systems of permanent profitable agriculture
durability is of greater importance than immediate avail-
ability. If all of an application is "immediately avail-
able," it may be almost immediately lost by leaching with
heavy rains. For high-priced truck crops which must be
hastened for the early market, the grower may need to
take this risk, but in general farming it is far better to
use durable materials, which gradually becomes available
during the growing season, and for several seasons. From
the standpoint of permanent farm profits, there rhs been
vastly too much emphasis placed upon "availability" and
far too little upon durability in soil improvement.
An English record of 1795 mentions the "prevailing
practice of sinking pits for the purpose of chalking the
surrounding land therefrom," and states that "the chalk-
ing of land so circumstancced is the best mode of culture
they are capable of receiving." Director Hall of Rotham-
sted (the oldest Agricultural Experiment Station in the
world), in referring to this use of natural lime carbon-
ate, states that many of the farmers in that part of Eng-
land are still reaping profitable crops from lands en-
riched by heavy applications of chalk.
As much as 20 tons per acre of ground dolomite lime-
stone has been used in this country with only beneficial
results; and there are fields in England which have re-
ceived more than 100 tons per acre of lime carbonate,
resulting only in favorable effects extending over more
than a century. Of course such enormous applications
are altogether unnecessary, but they are likewise alto-
gether harmless and the material is not lost, but it ap-
proaches a permanent investment, somewhat like the
purchase of the $200 corn-belt land with its immense
store or stock of fertility.
THE TIME TO APPLY LIMESTONE.
As to time of application, due consideration should
be given to other necessary farm work, conditions of
weather, land and roads in relation to the hauling and
spreading of limestone. It is not applied for the sole
benefit of one crop, but for all the crops in rotation, al-
though its greatest benefit is upon the legume crops; and
one good plan is to apply the limestone after plowing the
ground (or, with heavy applications, part before and part
after plowing), and before preparing the seed-bed where
some of the clovers or alfalfa are later to be seeded, but
whether a day or six months later is a matter of sec-
ondary importance. The primary essential is to get the
limestone on the land, and convenience or economy in
getting the work done is usually the factor which should
govern the time of application.
No single method need be followed in applying lime-
S stone to the land. It may be applied by hand with a
light shovel, either from the wagon or from small equal
sized piles placed at regular intervals. Thus a pile of
100 pounds every 24 feet each way makes about four tons
to the acre.
HOW TO MAKE A SPREADER FOR LIMESTONE.
A spreader made for the purpose of applying ground
limestone is very useful. Several spreaders are manu-
factured that serve well for applying small quantities of
lighter material, but most of them are not suited .for
handling heavy applications of such material as ground
stone or rock. A "home-made" spreader, which any
farmer can have made with the help of a local black-
smith is more satisfactory for spreading these heavy
materials than most of the machines on the market.
Make a hopper similar to that of an ordinary grain
drill, but measuring 81 feet long with side at least 20
inches wide and 20 inches apart at the top. The sides
may be trussed with 3-8 inch iron rods running from the
bottom at the middle to the top at the ends of the hopper.
Let the bottom be 5 inches wide in the clear with 2-inch
holes 5 inches between centers. Make a second bottom to
slide under the first on straps of iron 10 inches apart,
which should be carried from one side to the other under
the hopper to strengthen it, also with holes to register.
Both bottoms may be of sheet steel or the lower one may
be of hard wood, reinforced with strap iron if necessary.
To the lower and movable bottom attach a V-shaped
arm projecting an inch from under the hopper, with a
half-inch hole in the point of the V, in which drop the
end of a strong lever, bolting the lever loosely but secure-
ly to the hopper with a single bolt, and fasten to the top
of the hopper a guide of strap iron in which the lever may
move to regulate the size of the opening by sliding the
lower bottom. Make a strong frame for the hopper, with
a strong, well-braced tongue.
Take a pair of old mowing machine wheels of good size
and with strong ratchets in the hubs, and fit these to an
axle of suitable length (about 10 feet) and 1 3-8 or 1
inches in diameter. The axle should be fitted with jour-
nals bolted to the under side of the frame. Make a reel
to work inside the hopper by securing to the axle, 10
inches apart, short arms of 3-8 inch by 1-inch iron and
fastening to the arms four slats or beaters of 5-8 by 3-4
inch iron about an inch shorter than the inside of the
hopper, the reel being so adjusted that the beaters will
almost scrape the bottom but will revolve freely between
the sides. The diameter of the completed wheel is about
5 inches and it serves as a force feed.
Hundreds of these "home-made" machines are in use.
and they are usually more satisfactory and more durable
than anything on the market. The cash expense for such
a machine has varied from less than $10 to more than
$30, depending on how much of the materials and labor
must be paid for. Farmers with some mechanical skill
may hire only the necessary blacksmithing.
SUGGESTIONS REGARDING APPLICATION.
In hauling and spreading limestone it is of first im-
portance to save time and labor. As a rule it is far more
economical to purchase in bulk and have it shipped in
box-cars, although wetting will do no harm except to give
trouble in spreading. Bags are expensive and easily
damaged, and with tight wagon boxes they are wholly
unnecessary. If bags must be used in handling the lime-
stone the purchaser should bag it when hauling from the
car. As a rule, the plan should be to haul the limestone
directly from the car to the field, transfer from the
wagon to the spreader and spread at once upon the land.
With a haul of two miles or less, and with two men.
one boy and two teams, with three wagons and one
spreader, 40 tons of ground limestone can be taken from
the car and spread over 19 or 20 acres of land in three
days, providing the roads and other conditions are favor-
able, or 30 tons can be removed from the car in two days,
the last two or three loads being kept on the wagon and
spread the third day if necessary. When the haul is
longer, one or more additional teams are needed on the