F. C. (Frederick Charles) Bauer.

Response of Illinois soils to limestone online

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stone on these fields provided for its rather liberal use, as described
on page 305, in order to make sure that enough would be applied to
replace the losses that occur as a natural consequence of cropping
and leaching.

With the passing years questions began to arise about whether
so much limestone was necessary. If limestone was not lost so rapidly
from the soil as had been supposed, then smaller applications or a
less frequent use of it would be even more profitable than the larger
amounts called for in the early experiments. The advisability of ap-
plying limestone at uniform and regular rates on all kinds of soils
also began to be questioned. Limestone was not producing profitable
increases on some of the experiment fields, probably because it was not
needed. Then there arose the question whether excessive quantities
of limestone might not have a retarding influence on various soil
processes related to crop production. These questions can be con-
sidered in the light of existing experiment-field results. Still others
can be answered only by further investigation in the field and in the
laboratory. A brief discussion of some of these problems is of interest
at this point.

Soil Acidity

One of the important functions of limestone is to correct certain
conditions that hinder the growth of some legume crops. The most
important of these conditions is known as soil acidity.

It is well known that soil acidity varies greatly among soil types
and to some extent within the same soil type (see Table 2). Because
of this fact it is likely to vary more or less among fields on the same
farm and even in different parts of the same field. Thus such legumes
as sweet clover, alfalfa, red clover, etc., may grow well on some soil
types, or on some fields, or in some parts of a particular field, and
grow indifferently or not at all in other places, according to the
acidity of the soil.

Since in residues systems of farming the proper utilization of the
legume crop has marked effect upon the general crop-producing power
of the soil, the farmer's chief interest should be to so maintain the
fertility of his soil that legumes will grow abundantly. And since the
ability of soils to grow the various legumes successfully is more or
less directly related to the degree, or intensity, of soil acidity, the
best plan is to use limestone in direct proportion to the intensity of
the acidity of the soil. In other words, limestone should be applied
only when it is needed to encourage the growth of leguminous crops.
Such a practice would often do away with regular applications.

354 BULLETIN No. 405 [June,

On many of the experiment fields the initial application of lime-
stone is proving effective for longer periods than was anticipated
when the fields were established. The results from the West Salem
field, described on page 343, for example, are especially significant.

Phosphorus Availability

The opinion is now widely held that a too liberal use of limestone
may interfere with the availability of phosphates and especially of
applied rock phosphate.

Theoretical reasoning provides justification for the above opinion.
There are several forms of calcium phosphates which vary consider-
ably in solubility and hence in availability. Rock phosphate has most
of its phosphorus in the form of tricalcium phosphate, which is rela-
tively insoluble in water. When acted upon by acids it loses some
of its calcium, which is converted into the calcium salts of those acids.
When one-third of the calcium is removed, the phosphate becomes
dicalcium phosphate, and when two-thirds are removed it becomes
monocalcium phosphate. The more calcium the phosphate loses, the
more soluble it becomes and the more available for plant use. How-
ever, unless conditions exist that will dispose of the calcium that is lost
from the phosphate, it may reunite with the phosphate and again
render the phosphate less available.

The growing of such crops as alfalfa, red clover, sweet clover, and
others that have high calcium requirements provides one way in which
to utilize this calcium. Good drainage may also be helpful in re-
moving it. Soil acids, by uniting with the calcium, are another means
of preventing calcium from reuniting with the phosphate. Some soil
acidity is likely, therefore, to be of value in rendering phosphates
available, especially the phosphates of rock phosphate. If, on the other
hand, limestone, which is also a calcium compound, is applied too
liberally it may tend to satisfy the calcium requirements of both the
high-calcium crops grown and the acids in the soil and in this way
prevent the removal of calcium from the phosphate and reduce the
effectiveness of the phosphate.

The above reasoning is supported by experiments in the green-
house and in the laboratory. It is supported also by field investigations
in many states, including experiments started on the Aledo field in
Mercer county, Illinois, in 1916.

Four carriers of phosphorus have been applied to plots on the
Aledo field with and without limestone. Where used, the limestone was
applied at the rate of 6 tons an acre. The values of the crop increases




for the phosphates during the last rotation period (1929-1932) are
recorded in Table 12. Without exception the phosphates were less
effective when applied with limestone than when used alone. This
would seem to indicate that limestone reduces the effectiveness of
phosphates and that in practice limestone should not be applied with
phosphates or at least should be applied only sparingly.



(Aledo field, 1929-1932)

Phosphorus carrier



Decrease for

Bone phosphate








Rock phosphate




Slag phosphate




Whether such a conclusion is entirely sound depends upon other
considerations. Since both the limestone and the phosphates carried
calcium, it is possible that at least part or even all of the effects of the
phosphates were in reality due to the calcium, which has a high value
on acid soils. It is of interest, therefore, to compare the total com-
bined increases resulting from the limestone and the phosphates when
used separately with the increases from these two fertilizing materi-
als when applied together. If the increases from the associated ap-
plications were equal to the total combined increases from the sepa-
rate applications, then it would be clear that limestone and phosphates
were exerting independent action on crop yields. If the increases
from the associated applications were smaller than the total com-
bined increases from the two separate treatments, then it would ap-
pear that these two materials do have some overlapping effects and
that one may be substituted for the other to the extent of such over-

As a matter of fact, the increases from limestone and phosphate
applied together were considerably smaller than the total combined
increases from the separate applications (Table 13), indicating that
under these soil conditions these two materials do have, in part, a
common function. The extent to which overlapping occurred sug-
gests that phosphorus is a relatively unimportant fertilizer on this
field, for when the overlapping values are subtracted from the values
obtained with phosphate used alone, the increases are hardly sufficient
to cover the cost of the phosphate. If calcium is the material most
needed, it would appear that limestone alone would be the more




profitable investment. There is of course the possibility that smaller
applications of limestone might have permitted larger responses from
the phosphate, but the important question is whether such combi-
nations would be as profitable.

While the above conclusions seem applicable to the Aledo field and
probably to other kinds of soils also, this does not mean that all soils
would give similar results. Some soils may be so deficient in phos-
phorus as to respond satisfactorily to phosphate fertilizers even when



(Aledo field, 1929-1932)


Carrier of

Increases from limestone and
phosphate used separately

from associ-
ated applica-

effects 1










Slag phosphate ....

'Calculated as the difference between the combined effects when used separately (Column 3) and
the increases from associated applications (Column 4).

applied with limestone. The Bloomington field, located in McLean
county on a semimature, dark-colored soil that has a heavy, noncalcare-
ous subsoil, has exhibited such a response. On this field rock phos-
phate used in addition to limestone has given increases in crop yields
worth $10.15 an acre annually as an average during the last five years.
Superphosphate and bone phosphate applied with limestone have given
values of $7.54 and $11.94 respectively. Somewhat similar results
have been obtained on other fields. On very acid soils lime applica-
tions have long been recognized as essential for best results from
phosphates. In these soils the iron and aluminum compounds tend to
convert the phosphorus into rather insoluble forms, while limestone
tends to keep it in forms more readily available for crop use.

Thus it would appear that type of soil is an important factor in
the interaction between limestone and phosphate ; and that while some
soil acidity may increase the effectiveness of rock phosphate, too in-
tensive acidity may have' the opposite effect. So far as phosphorus
availability is concerned, therefore, care should be taken to avoid
both overliming and underliming. Until these matters are better
understood, limestone applications should be made as indicated by a


systematic soil-testing program such as is outlined in Circular 346 of
this Station, "Test Your Soil for Acidity."

The interaction between limestone and phosphate in the soil, just
discussed, raises another question. If strongly acid soils tend to change
phosphorus to the more insoluble iron and aluminum forms, and thus
perhaps cause a deficiency of phosphorus for crop production, would
the application of limestone without accompanying phosphate appli-
cations tend to reduce the phosphorus deficiency? If so, would such
reduction remove the necessity for applying phosphates, or at least
delay the need for them?

Some preliminary studies, especially those with deep-rooting le-
gumes, indicate that the availability of phosphorus has been greatly
increased in some soils so treated and unaffected in others. The prob-
lem presents complications that need thoro study before final con-
clusions can be drawn. It is quite possible, however, that the effect-
iveness of limestone in making available the supplies of phosphorus
naturally in the soil may be a better explanation for the poor crop
response to applied phosphate on some soils than an explanation based
on the overliming idea.

Potash Availability

Potassium is another plant- food element whose availability may
be interfered with by the use of limestone. This is suggested by the
results from certain experiments with potash fertilizers and limestone
on silt loam soils, practically all of which contain naturally rather
large amounts of potassium. Corn yields on the Ewing field, for
example, a silt loam, have shown little variation on unlimed land (R)
over a period of twenty-three years (Fig. 27). Yields on limed land
(RL and RLP) have declined at the rate of three-quarters of a
bushel to nearly a bushel annually. Yields on plots given the same
treatments as those just mentioned, except for the addition of potas-
sium (RLPK), have increased by more than half a bushel of corn
an acre a year, changing from 37.6 bushels in 1910 to 49.3 bushels
in 1932.

Experience with alkali soils further strengthens the suggestion
that limestone may be involved in the development of a potash de-
ficiency from the standpoint of crop production. It has long been
known that alkali soils, which are characterized by high carbonate
content, respond markedly to potassium fertilizers even tho the natural
content of the soil may be fairly high. The alkali appears to reduce
the solubility and availability of the soil potassium. Since the amount
of limestone applied in the Ewing experiments and others was some-




what liberal, the effects may be somewhat similar to those in soils
where natural alkali conditions exist.

Experiments in Tennessee and elsewhere, showing that the amount
of potassium leached from soils can be reduced by applying various
kinds of limestone, add further weight to the suggestion that the
application of limestone to the Ewing field may have reduced the
availability of the soil potassium.



ffl 30









On some of the more mature soils the use of limestone appears to lead to
a potash deficiency. On the unlimed soil of the Ewing field the corn yields
showed a moderate downward trend over a twenty-two year period, but where
limestone was applied in addition to crop residues, a much more marked decline
occurred. The use of potash fertilizers has resulted in steadily improving yields.
(Trends calculated from annual yields by using formula y = n + mx.)

Another explanation for the increasing deficiency of available
potassium that has accompanied applications of limestone is that lime-
stone, by encouraging larger crops thru the growth of legumes, has
caused a greater draft on the natural supplies of available potassium.
When these fields were first established, the limestone applied helped
materially in growing larger crops. The larger crops naturally took
larger amounts of potassium from the soil. As time went on, the
amounts of available potassium were depleted faster than the unavail-
able forms could be converted into forms for crop use, and the plants
encountered more and more difficulty in getting the potassium they
needed for normal growth. Under such circumstances the applica-


tion of potassium in available form would be expected to have grad-
ually increasing effects on crop yields.

In the Illinois experiments sweet clover, which was always grown
on the plots receiving limestone, was usually plowed under the fol-
lowing spring as a green manure for corn. The benefits from applied
potash have seemed to increase when the sweet clover was handled
in this way, even tho sweet clover itself contains a good percentage
of potassium. Some investigators have suggested, in explanation of
these results, that a biological factor involving the excessive produc-
tion of nitrate nitrogen might be responsible for the declining crop
yields on limestone-sweet-clover plots to which no potash was applied.
Their explanation is that the limestone-sweet-clover combination pro-
vides especially favorable conditions for the excessive production of
nitrate nitrogen, and that in the absence of sufficient available potas-
sium, large accumulations of nitrate nitrogen may have a detrimental
effect on crop growth, especially on a crop like corn. Under such con-
ditions the application of potash fertilizers would have marked bene-
ficial effects.

Whatever the cause may be for the available potassium deficiency
under the limestone-sweet-clover system of soil management, it seems
safe to conclude that the system has unquestioned merit for large
areas of Illinois soils even tho on some soils applications of potash
are needed for the best results.


The important place that limestone occupies in the management
of Illinois soils is clearly demonstrated by the analyses presented in
the foregoing pages. The dissemination of facts concerning liming
experiments as they have become available, and later the encourage-
ment given soil-testing and mapping by extension agencies, have
brought about a widespread use of limestone by Illinois farmers. The
first authentic record of the amount of limestone applied to Illinois
soils covers the year 1906 and shows a total of 2,000 tons. Continuous
and rapid increases took place each year until a peak of 925,000 tons
was reached in 1929. This amount, according to statistics published
by the National Lime Association, was about one- fourth the total
amount of lime materials used for agricultural purposes in the United
States that year.

Even tho large tonnages of agricultural limestone have been used

360 BULLETIN No. 405 [June,

in Illinois, there are still many lime-deficient fields that have never
had limestone applied to them. Some of these fields are located on
marginal land to which the application of limestone would probably
not be economically justified even under more normal times. There
are many other fields, however, on which limestone will prove profit-
able when economic conditions are more normal. There are other
soils in the state possessing high levels of productivity that are be-
ginning to show lime deficiencies which will be intensified under con-
tinued cultivation unless limestone is applied.

Lime renewals will always need the attention of Illinois farmers,
and limestone must remain the key to any successful soil-building
program on the lime-deficient soils of the state. 1


Limestone has long been recognized as of fundamental importance
in Illinois agriculture. For the past twenty-five years its use steadily
increased until the present depression period. This bulletin analyzes
the response of various soils and crops to limestone on forty experi-
ment fields located thruout the state on various kinds of soil, some of
the fields having been in operation for thirty years. The principal facts
brought out by the study are the following:

1. The degree of response made by Illinois soils to limestone, as
measured by crop increases, is closely related to the natural produc-
tivity of the soil. Soils of high natural productivity respond least and
those of low natural productivity most. The range in response for
the different kinds of soils, as measured by yields of all crops grown,
varied from nothing to more than 150 percent.

2. The degree of response to limestone bears a close relationship
to certain chemical characters of the soil, one of which is the degree
of saturation with replaceable calcium and magnesium as compared
with the total base-exchange capacity of the soil. Soils with a low
percentage saturation respond best to limestone. Soils exhibiting about
80 percent saturation give little or no response. Comparison of the
various chemical characters of a soil with its response to limestone
indicates the value of proper chemical tests for quickly determining
the lime requirements.

3. Different crops respond differently to limestone applications.
On the dark-colored soils the response of the corn, oats, wheat, and

'See Circular 375 of this Station, "Limestone the Key to Soil Building and
Higher Crop Yields," for further discussion of this subject.


hay crops \vas somewhat similar, tho oats tended to be the least re-
sponsive. On the light-colored soils wheat made a much better re-
sponse than corn, tho all crops, especially hay, made large responses.
On sandy soil the differences between the corn and wheat responses
were not great ; and both crops showed better responses on this soil
than on the dark-colored soils. On the sandy soil the application of
limestone made the difference between good hay yields and no yields
at all.

4. The use of limestone on the light-colored soils has tended to
raise the productive levels of such soils to about 50 percent of the
levels of the better untreated dark-colored soils. The combined in-
fluence of organic manures and limestone has raised the light-colored
soils to levels approximately 60 percent as high as the better untreated
dark-colored soils.

5. Soils that have shown a high response to limestone applications
have tended to show that response quickly. Soils that have shown
only a moderate response have tended to be somewhat slow in evi-
dencing that response, tho they usually have shown considerable ac-
celeration in response after the first or second rotation. Some highly
productive soils have shown no response until recent years, indicating
that there has been a slow development of lime deficiency. Some soils,
after exhibiting considerable acceleration in their response for a num-
ber of years, have then shown a leveling out of response and then
a falling off. Such behavior is probably due to increasing deficiencies
in the supplies of other plant nutrients. On many soils increases
from limestone have continued for some years after applications have
been discontinued, showing the cumulative effect of proper applica-
tions of limestone.

6. Increasingly larger crop yields for eight years were obtained
from a single 4-ton application of limestone on a lime-deficient light-
colored soil. After eight years there was a leveling out of the re-
sponse and then a decline. After twenty years, however, the single
application still showed some effect on crop yields. Repeated applica-
tions during this twenty-year period proved no more effective than the
single application until after the eighth year, when greater crop in-
creases were shown for them than for the single application.

7. Limestone should be applied in amounts meeting rather closely
the actual crop requirements. Smaller amounts may be altogether
without effect. Larger amounts will be not only uneconomical but they
may tend to reduce the availability of other plant nutrients, such as
phosphorus and potassium. These facts indicate the value of definite

362 BULLETIN No. 405 [June,

tests by which the lime deficiency of given fields or parts of fields may
be quickly and accurately judged.

8. The thirty years of experimental evidence summarized here in-
dicates that lime materials are

a. Indispensable for successful crop production on many soils.

b. Highly desirable for efficient production on other soils.

c . Without much actual or economic effect on other soils.

There is also evidence showing that nonresponsive soils may, with
continued cultivation, become sufficiently lime-deficient to respond to
limestone applications ; and that the chemical, physical, and biological
changes produced by the application of lime materials may in time
create new soil conditions that have to be recognized in management


For the practical application of the facts dis-
cussed in this bulletin, see

Circular 346, "Test Your Soil for Acidity"

Circular 375, "Limestone the Key to Soil

Building and Higher Crop Yields"


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Online LibraryF. C. (Frederick Charles) BauerResponse of Illinois soils to limestone → online text (page 5 of 5)