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  Right Use of Lime In Soil Improvement

  _By_ ALVA AGEE


  [Illustration: Applying Lime]


  Secretary New Jersey State Department of Agriculture

  Formerly director of agricultural extension in the Pennsylvania State
  College and New Jersey State College of Agriculture.

  _Illustrated_

  NEW YORK
  ORANGE JUDD COMPANY

  LONDON
  KEGAN PAUL, TRENCH, TRUBNER & CO., LIMITED

  1919

  Copyright 1919, by
  ORANGE JUDD COMPANY

  _All Rights Reserved_

  Printed in U. S. A.


       *       *       *       *       *


   CONTENTS

   CHAPTER                                                          PAGE

   1. INTRODUCTION                                                     1

   2. THE LIME IN SOILS                                                4

   3. SOUR SOILS                                                      10

   4. EVIDENCES OF ACIDITY                                            15

   5. TESTS FOR ACIDITY                                               20

   6. SOURCES OF LIME                                                 24

   7. DEFINITIONS                                                     28

   8. GROUND LIMESTONE                                                33

   9. STORING LIME IN THE SOIL                                        38

   10. FRESH BURNED LIME                                              44

   11. BURNING LIME                                                   49

   12. LIME HYDRATE                                                   53

   13. OTHER FORMS OF LIME                                            57

   14. MAGNESIAN LIME                                                 64

   15. WHAT SHALL ONE BUY?                                            68

   16. METHODS OF APPLICATION                                         78

   17. AMOUNT OF LIME PER ACRE                                        82

   18. SPECIAL CROP DEMANDS                                           86




   ILLUSTRATIONS

   Applying Lime      Frontispiece

   FACING PAGE

   I. Clover and Timothy Unfertilized at the Pennsylvania
   Experiment Station Yielded 2,460
   pounds per acre                                                    10

   II. Clover and Timothy with Fertilizer alone at
   the Pennsylvania Experiment Station Yielded
   3,900 pounds per acre                                              11

   III. Clover and Timothy with Lime alone at the
   Pennsylvania Experiment Station Yielded
   4,900 pounds per acre                                              14

   IV. Clover and Timothy with Fertilizer and Lime
   at the Pennsylvania Experiment Station
   yielded 6,290 pounds per acre                                      15

   V. Limed and Unlimed Ends of a Plot at the
   Ohio Experiment Station                                            16

   VI. Effect of Finely Pulverized Limestone on Clover
   in a Soil having a Lime Requirement of
   5,200 Pounds of Limestone per Acre, at the
   Pennsylvania Experiment Station                                    17

   VII. Lime Favors Clover at the Ohio Experiment
   Station                                                            24

   VIII. Lime Affects Growth of Corn at the Ohio Experiment
   Station                                                            25

   IX. An Indiana Limestone Quarry                                    32

   X. A Limestone Plant                                               33
   (Courtesy of the Michigan Limestone Company.)

   XI. A Limestone Pulverizer for Farm Use                            38
   (Courtesy of the Jeffrey Manufacturing Company,
   Columbus, Ohio.)

   XII. A Lime Pulver in Operation                                    39
   (Courtesy of the Jeffrey Manufacturing Company.)

   XIII. Laying Foundation for a Lime Stack at the
   Pennsylvania Experiment Station                                    48

   XIV. A Stack nearly Completed at the Pennsylvania
   Experiment Station                                                 49

   XV. Effect of Excessive Use of Burned Lime without
   Manure at the Pennsylvania Experiment
   Station                                                            52

   XVI. A Hydrated Lime Plant                                         53
   (Courtesy of the Palmer Lime and Cement Company,
   York, Pa.)

   XVII. Filling the Lime Spreader at the Ohio Experiment
   Station                                                            78

   XVIII. Lime Distributors                                           79

   XIX. Remarkable Effect of Lime on Sweet Clover at
   the Ohio Experiment Station                                        86

   XX. Sweet Clover Thrives When Lime and Manure
   are Supplied, Ohio Experiment Station                              87


       *       *       *       *       *


CHAPTER 1

INTRODUCTION


There is much in the action of lime in the soil that is not known, but
all that we really need to know is simple and easily comprehended. The
purpose of this little book is to set down the things that we need to
know in order that we may make and keep our land friendly to plant life
so far as lime is necessarily concerned with such an undertaking.
Intelligent men like to reason matters out for themselves so far as
practicable, taking the facts and testing them in their own thinking by
some truth they have gained in their own experience and observation, and
then their convictions stay by them and are acted upon. The whole story
of the right use of lime on land is so simple and reasonable, when we
stick only to the practical side, that we should easily escape the
confusion of thought that seems to stand in the way of action. The
experiment stations have been testing the value of lime applications to
acid soils, and the government has been finding that the greater part
of our farming lands is deficient in lime. Tens of thousands of farmers
have confirmed the results of the stations that the application of lime
is essential to profitable crop production on their farms. The confusion
is due to some results of the misuse of lime before the needs of soils
were understood, and to the variety of forms in which lime comes to us
and the rather conflicting claims made for these various forms. It is
unfortunate and unnecessary.

The soil is a great chemical laboratory, but exact knowledge of all its
processes doubtless would enrich the farmer's vocabulary more than his
pocketbook. We are concerned in knowing that lime's field of usefulness
is broad in that it is an essential plant food and provides the active
means of keeping the feeding ground of plants in sanitary condition. We
want to know how it comes about that our soils are deficient in lime,
and how we may determine the fact that they are deficient. We wish to
know the relative values of the various forms of lime and how we may
choose in the interest of our soil and our pocketbook. The time and
method of application are important considerations to us. There are
many details of knowledge, it is true, and yet all fit into a rational
scheme that shows itself to be simple enough when the facts arrange
themselves in an orderly way in our minds.

Lime cannot take the place of nitrogen, nor phosphorus, nor any other of
the essential plant foods. It is not a substitute for any other
essential factor in plant growth. It would be folly to try to depend
upon lime as a sole source of soil fertility. On the other hand, we have
learned very definitely within the last quarter of a century that it is
foolish to depend upon commercial fertilizers and tillage and good seeds
for full production of most crops from great areas of our farming
country that have a marked lime deficiency. The obvious need of our
soils is the rich organic matter that clover and grass sods could
furnish, and their fundamental need is lime. Most farms cannot possibly
make full returns to their owners until the land's hunger for lime has
been met. The only question is that regarding the best way of meeting
it.




CHAPTER II

THE LIME IN SOILS


_Limestone Land._ Soil analyses are serviceable only within certain
limits, and in the case of the normal soils that comprise the very great
part of the entire humid region of the United States the practical man
gives little heed to what special analyses might show him when deciding
upon the purchase of a farm. He does know, however, that a limestone
soil has great natural strength, and recovers from mistreatment more
readily than land low in lime. It has staying powers, and is dependable,
unless through natural processes the lime leaches out or loses
availability. All limestone areas have gained reputation for themselves
as producers of grain and grass.

_Other Calcareous Soils._ It is not only the limestone areas that stand
high in esteem. There are types of soil with every varying percentage of
lime down to clear sand or to peat, and some of the types are finely
calcareous, containing such a high percentage of lime that nothing more
could be desired.

The actual percentage is not the determining factor, a clay soil needing
greater richness in this material than a loam, and a sandy soil giving a
good account of itself with an even less total content of lime, but in
its way the particular soil type must be well supplied by nature with
lime if its trees and other vegetation bear evidences of its strength
and good agricultural value.

_Natural Deficiency._ It is interesting to note the differences in
evidences of prosperity that are associated with lime percentages. The
areas that are able to produce the vegetation characteristic of
calcareous soils are obviously the most prosperous. The decidedly
lime-deficient sections, advertising their state by the kind of original
timber, and later by unfriendliness to the clovers, do not attract
buyers except through relatively low prices for farms. Such areas are
extensive and have well marked boundaries in places.

It does not follow that every farm in such limestone valleys as the
Shenandoah, Cumberland, and Lebanon, or in the great corn belt having a
naturally calcareous soil, is prosperous, or that a multitude of owners
of such lime-deficient areas as the belt in a portion of southern New
York and northern Pennsylvania, or the sandstone and shale regions of
many states, have not overmatched natural conditions with fine skill. We
treat only of averages when saying that a "lime country" shows a
prosperity in its farm buildings and general appearance that does not
come naturally and easily to any lime-deficient territory. In the latter
a man rows against the current, and if livestock farming is not employed
to furnish manure, and if the manure is not supplemented by tillage and
drainage to secure aeration, or if lime is not applied, the land reaches
such a degree of acidity that it loses the power to yield any profit.

_Nature's Short Supply._ The total area of lime-deficient soil is large,
comprising certainly much more than half of all the land east of the
semi-arid belt of the United States. No small part of this area was not
deficient at one time, as the nature of the original timber indicates,
and it is well within the knowledge of practical men that land which
once produced the walnut and ash and shellbark hickory can be brought
back to productivity with reasonable ease after very hard usage. It has
a good inheritance. It is a disconcerting fact in our American
agriculture that, fertile as our country is as a whole, very great areas
were so deficient in lime before they came under man's control that the
chestnut, pine, and the oaks of mean growth were fully at home. The
gradation from low lime content to high, and its relation to soil type,
give us all sorts of mixtures of lime-loving and acid-resistant
varieties of trees in original forests, but our agriculture is hampered
by the high percentage of land for which nature made no great provision
of lime, and on this land farming lags.

_Effect of Irrational Farming._ Interest in liming might well have been
due to the amendment of all this soil, but the rational use of lime that
has been the subject of much study in the last quarter of a century
concerns chiefly great areas that probably could have been kept in
alkaline condition and friendly to the clovers for a long time despite a
short natural supply as compared with the content of our limestone
lands. The success of individual farmers in areas now admittedly acid as
a whole is convincing on this point. Nature tries constantly to cure
the ills of her soil through the addition of vegetable matter. An excess
of water or a deficiency is atoned for in a degree by the leaves and
rotted wood of her forests. Aeration is kept possible. The lime in the
product of the soil goes back to it. A system of farming that involves
the application of manure, thorough tillage, drainage where needed, and
the free use of sods in some way, has kept portions of these
non-calcareous soils out of the distinctly acid class. Clover grows
satisfactorily, grass sods are heavy, and there is no acute lime
problem. Such farms are relatively few in the great stretches of land
now classed as acid soil, and probably the most of the lime that is
being applied goes only on ground that once was sufficiently alkaline to
grow the clovers. The loss of organic matter through failure to use the
best methods of farming is responsible for no small part of the
widespread need of lime today. This subtracts nothing from the urgency
of its use to restore a condition favoring clover and grass sods, but it
does teach a lesson of the highest value. The day of destructive soil
acidity can be retarded by good farming, but in the long run the
inevitable losses of lime from most soils must be met by applications.

_Limestone Soils._ The old-time practice of making heavy applications of
fresh burned lime to stiff limestone soils to make them friable, and to
make their plant food available, led to disuse of all lime in some
sections on account of the exhaustion that followed dependence upon
these large amounts as a manure. Queerly enough, these original
limestone soils have latterly been going into the acid class through
loss of their distinctive elements, and they, too, have become dependent
upon means for the correction of acidity.




CHAPTER III

SOUR SOILS


_Loss of Lime._ Nature made the value of land as a producer of food
utterly dependent upon the activity of lime, and at the same time gave
it some power to shirk its work. In a normal soil is a percentage of
lime that came from the disintegration of rock of the region or was
transported by action of water on a huge scale. Possibly rarely would it
be in insufficient amount to keep a soil in a condition friendly to
plant life, and to feed the plant, if it stayed where nature placed it
and kept in form available for the needs it was intended to meet. There
is land that always was notably deficient in this material, and there is
land that was known in the early history of the world's agriculture to
be "sour," but the troubles of our present day in the case of the
farming country in the humid region of the United States is less due to
any natural absolute shortage than to combination that destroys value
and to escape by action of water.

[Illustration: Clover and Timothy Unfertilized at the Pennsylvania
Experiment Station Yielded 2460 Pounds per Acre]

[Illustration: Clover and Timothy with Fertilizer alone at the
Pennsylvania Experiment Station Yielded 3900 Pounds per Acre]

_Prevalence of Acidity._ The results of experiment station and farm
tests are conclusive that the soils of the greater part of all the humid
region of the United States show lime deficiency. Formerly, acidity was
associated in our minds with wet, low-lying land, but within the last
twenty years we have learned that it prevails in light seashore sands
along the Atlantic shore, in clays, loams and shales stretching to the
Appalachian system of mountains, on top of mountain ranges and across
foothills to our central states, and through them in stretches to the
semi-arid lands of the west. While not all this land has fallen into the
lime-deficient class, and the great part of some states remains
alkaline, the tendency toward acidity is continuous.

Crop production in great portions of the Mississippi valley is
restricted by lack of lime in the soil, and some states to the eastward
have one-half to nine-tenths of their acreage too low in lime for the
best results. Calcareous soils have been losing their distinctive
feature, and the immense areas of land naturally low in lime have
remained hampered in ability to make full returns for labor, fertilizer
and seed. It is this situation that brings the right use of lime on
land to the front as a matter of fundamental importance to the farmer.

_Causes of Soil Acidity._ If any discussion of the causes of soil
acidity would delay a decision to apply lime where needed, the time
given to such discussion would be worse than wasted. It is much more
important to be able to detect the presence of harmful acids and to
neutralize them than it is to know why the soil should be in such plight
that it could not supply the required lime and had become dependent upon
its owner for assistance. On the other hand, some of us find it
difficult to accept a fact without seeing a reason for it, and we may do
well to consider several causes that may be at work to put a soil out of
the alkaline class.

_Leaching._ One cause that appears obvious and easy of acceptance is
leaching. In the case of one Pennsylvania farm, lying in a limestone
valley, the lime had been washed out by action of water so freely that
caverns formed under the surface, and a test showed a marked deficiency
in the top soil. This land ceased to grow clover, and plantain and
sorrel abounded. This case, which is not an isolated one, showed an
unusually rapid loss, but we always expect to find the water from wells
and springs in a limestone country strongly impregnated with lime.
Drainage waters contain it. The draft by action of water is continuous,
and in some types could easily account for sufficient loss to change the
nature of the soil. We may place undue emphasis upon this factor, as
other causes are at work, but leaching is a leading source of loss.

_Chemical Compounds._ A serious cause of lime exhaustion that is being
studied by soil chemists is the presence of compounds in the soil that
combine with the lime and rob it of ability to serve the soil when new
acids form. The practical farmer accepts the statements of the chemists
on this point, and probably would not have his interests served by any
exact knowledge of the nature of these agents.

_Decaying Vegetation._ A cause of acid conditions that is widely known
and accepted, and that may therefore stand out in our thinking with
undue prominence, is connected with the decay of green vegetable matter
in the soil. Many of us have seen fields rendered temporarily
unproductive by the plowing down of a mass of immature plants in
midsummer. All organic matter, indeed, in its decay makes a draft upon
the lime content of the soil in which it may be buried.

_Removal in Crops._ Lime is taken out of land by plants, and the loss is
a considerable item, but our interest is in the form of lime that can
correct soil acidity, and we know that compounds of lime that are
worthless for this purpose may be the chief source of the lime in our
crops. A determination of the lime in the ash of a crop does not give
data of much practical value.

[Illustration: Clover and Timothy with Lime Alone at the Pennsylvania
Experiment Station Yielded 4900 Pounds per Acre]

[Illustration: Clover and Timothy with Fertilizer and Lime at the
Pennsylvania Experiment Station Yielded 6290 Pounds per Acre]




CHAPTER IV

EVIDENCES OF ACIDITY


_Character of Vegetation._ The character of the original forests is
determined much by the lime-content, and the practical man, when buying
a farm, rates its productive power by the kinds of timber it has
produced. The black walnut, ash, shellbark hickory, black and white oak,
sturdily grown, evidence a soil rich in lime, while the pines, small
blackjack and post oaks, and the chestnut are at home in non-calcareous
soils. The latter class of lands gains nothing in lime as time passes,
and the timber continues to be a sure index, but in the former class the
surface soil may have lost enough lime to limit crop production
materially while the trees continue to find in the subsoil all that they
need. It does not follow that the land has gone down in value to the
naturally lime-deficient class, but its power to produce is impaired,
and will remain so until there has been restoration of its original
alkaline state.

_Sorrel and Plantain._ We determine quite surely the state of the soil
by observance of the vegetation that roots in the surface soil and the
immediate subsoil. Sorrel is a plant popularly associated with soil
acidity, but this is not through any dislike for lime. It has been
observed growing in the edge of a heap. Its presence suggests acidity
because it can thrive in a sour soil that will not produce plants of
value which on even terms could crowd the sorrel out. There is constant
competition among plants for food and water and space, and some of our
worst weeds are not strong competitors of clover and grass where soil
conditions are not unfavorable to the latter.

Blue grass, the clovers and timothy give a good account of themselves in
a contest with sorrel and plantain where lime is abundant. This does not
mean that the seeds of these weeds may not be so numerous that an
application of lime cannot cause the clover and grasses immediately to
take the ground to the exclusion of other plants, but it is true that
the crowding process will continue until the time comes in the crop
rotation that these weeds cease to be feared, and clean sods can be
made. It is the absence of lime that permits such weeds to maintain
their reputation for good fighting qualities.


[Illustration: Limed and Unlimed Ends of a Plot at the Ohio Experiment
Station]

[Illustration: Effect of Finely Pulverised Limestone on Clover in a Soil
Having a Lime Requirement of 5200 Pounds of Limestone per Acre at the
Pennsylvania Experiment Station]

_The Clovers._ Red clover can make growth in some soils that have a lime
deficiency. If all other conditions are favorable, the lime requirement
may exceed one-half a ton per acre of fresh burned lime and not affect
the clover adversely, but farm experience throughout the country has
demonstrated that when soil acidity is only slight and clover grows with
difficulty, an application rarely fails to favor the clover in a marked
degree. Experience has taught the land owners to fear soil acidity when
red clover does not thrive where formerly it made good growth.

The prevalence of alsike clover in a farming region is indicative of
lack of lime. This clover thrives in a calcareous soil, but is more
indifferent to a small lime supply than is the red clover. As red clover
seedings begin to fail, the alsike gains in popularity, and where a soil
is decidedly sour the alsike is most in evidence. The latter has less
value to the farmer, rooting nearer the surface of the soil, and making
less growth of top, but it has gained in favor with farmers as soil
acidity has increased.

_The Grasses._ Timothy is more resistant to acidity than red clover,
but often fails to make a heavy sod where the deficiency in lime is
marked. Rhode Island Bent, known as redtop, is less exacting, and where
it thrives to the exclusion of timothy, or is in evidence in grass
lands, the inference is fairly safe that a test would show that the soil
is sour.

_When Production Decreases._ It is not a matter of any moment to the
owner of a productive soil whether or not his soil would give an acid or
an alkaline reaction under test. Returns from his labor are
satisfactory. Some land in this class is not strictly alkaline. The man
most interested in the effects of lime applications is the one who is
not satisfied with yields. The tests for acidity have been so many
throughout our eastern and central states that the owner of land which
is not productive has reason for the presumption that its percentage of
lime is too low. There is danger of error, and a scientific test is
surer, but in most cases the land which has been reduced from a fertile
to an unproductive state has lost its alkaline nature.

_Naturally Thin Soils._ Nature may be prodigal in supplies of nearly all
the elements of plant food to land and yet skimp its supply of lime,
but naturally poor soils are quite surely in the acid class. The
exceptions in our humid region are not extensive. When improvement is
planned for, involving additions of organic matter and plant food, the
application of lime to correct acidity is the first requirement. If such
land could be given the characteristics of a limestone soil so far only
as the lime factor is concerned, the building up of fertility would be
relatively easy. Liming must form the foundation of a new order of
things. The ability to grow the clovers and to furnish rich vegetable
matter to the soil, which naturally is poor in humus, rests upon lime
application first, and then upon any supply of plant food that may
continue to be lacking.




CHAPTER V

TESTS FOR ACIDITY


_The Litmus Paper Test._ A method of testing soils for acidity, which
has been in use for many years, is the simple litmus paper method.
Because of its simplicity and fair degree of accuracy, the litmus paper
test is still used to a considerable extent in estimating the degree of
acidity of certain soils. The best manner of using litmus is to place a
strip of the blue paper in the bottom of a glass saucer, covering it
with filter paper or other paper which is neutral--that is, paper which
is neither acid nor alkaline.

A small quantity of the soil to be tested is moistened with rain or
distilled water and placed on this paper. If the acid is present the
blue paper will be changed to a reddish color, varying in intensity
according to the degree of acidity in the soil. Two objections to the
use of litmus paper are to be noted: One of these is that the red color
may be produced by carbonic acid gas without a trace of more powerful
acids being present, and this may give a wrong impression to the
operator. Another objection to the use of litmus is that the degree of
acidity is not accurately indicated, and therefore the farmer is
sometimes at a loss to know just how much lime should be applied to make
soil conditions favorable for growing crops.

_A More Accurate Method._ Within the last few years improved methods for
determining the presence of acidity in soil have been developed. Some of
these are suitable only for the chemist with his complete laboratory
equipment, while others are more simple and can be used by anyone
willing to exercise reasonable care.

One of the simplest and most accurate tests to date is that devised by
Professor E. Truog of the agricultural experiment station of the
University of Wisconsin. This test not only detects positively the
presence of soil acidity, but also gives definite information as to the
degree of acidity. The test is based upon the principle that when zinc
sulfid comes in contact with the acid, hydrogen sulfid gas is formed,
and when this gas comes in contact with lead acetate, lead sulfid, a
black chemical, is formed.

The method of making this test is simple, and consists in placing a
measured quantity of soil in a flask, to which is added a solution
composed of 20% calcium chlorid and 2% zinc sulfid. The mixture of soil
and chemical solution is heated to the boiling point by means of an
alcohol lamp, and the boiling continued for a minute for the purpose of
driving off the carbonic acid gas, which is liberated first. The boiling
is continued and a piece of moistened paper, previously impregnated with
lead acetate, is placed over the mouth of the flask. If the soil
contains acid, a chemical reaction occurs between it and zinc sulfid,
and hydrogen sulfid gas is liberated. The quantity of acidity in the
soil determines the quantity of gas which comes in contact with the lead
acetate paper, and this determines the depth of color produced on the
paper. A slight brownish color indicates the presence of very little
acidity, while an intense black signifies the presence of injurious
amounts of acidity. There are various degrees of coloration between
these two extremes, and each gives an accurate indication as to the
quantity of lime required to correct the acidity.

This test is simple and inexpensive, and at the present time most county
agent offices are equipped with this apparatus or a similar one for
testing soils for farmers. Some newer methods are being devised, and
doubtless this method will be improved upon as time passes, but the
Truog test has qualities of accuracy and simplicity which will always
make it valuable.




CHAPTER VI

SOURCES OF LIME


_Nature's Provision._ Soils are composed of pulverized stone and organic
matter. Much of the original stone contained little lime, and the human
race would become nearly helpless if there were no stores of supply in
the form of limestone, chalk, marl, etc. The day would come when the
surface soil could not produce our staple crops if its loss of lime
continued, and a means of replenishing the stock were not at hand. The
huge deposits of limestone that have not been disintegrated by processes
of weathering are assurance that the soil's need can be met forever. The
calcium and magnesium in the stone are in chemical combination with
carbonic acid forming carbonates, and there is an additional mixture of
other earthy material that was deposited by the water when the stone was
being formed, but much limestone possesses an excellent degree of
purity.

[Illustration: Lime Favors Clover at the Ohio Experiment Station]

[Illustration: Lime Affects Growth of Corn at the Ohio Experiment
Station]

_Confusion Respecting Forms._ In the public mind there is much confusion
respecting the sources and forms of lime most to be desired. Wood
ashes appealed to people, especially in an early day in our agriculture,
partly because the ashes were so universally present that tests had been
made voluntarily and otherwise in millions of instances. The value of
such tests had been obscured by the fact that the ashes contained
potash, and much of the credit of any good effect was attributed to that
fact. It has been generally known, however, that lime in peculiarly
effective form is in wood ashes, and the favor in which ashes have been
held rested not a little upon the curious preference for an organic
source of all soil amendments. This is seen in the case of direct
fertilizers.

_Dealers' Interests._ The doubts regarding the wisdom of selecting any
one form of lime for the betterment of soil conditions have been
promoted very naturally by the conflicting interests of men who would
furnish the supply. Some dealers in fresh burned lime have asserted that
it was folly to expect any appreciable result from the use of unburned
limestone. The manufacturer of ground limestone has pointed out the
possibility of injuring a soil by the use of caustic lime, and
oftentimes has so emphasized his point that farmers have become
unwilling to apply fresh or water-slaked lime to their land.
Manufacturers of hydrated lime in some instances have made a confused
situation worse by insisting upon the claim that there was a fertilizing
quality in their goods. Some dealers in lime marls have been unwilling
to have the value of their goods rated according to the content of
carbonate of lime, and have emphasized the value of fine division of the
particles and the absence of any caustic properties. The presence of
shells, evidencing an organic source of the material, has helped in the
appeal to buyers.

The rightful place of magnesia, and the possible danger of injury from
its use, have been a fruitful cause of perplexity, making price per ton
only a secondary consideration to the man wanting to supply his soil's
needs.

_Scientists' Failure to Agree._ It is only fair to say that much of the
doubt and indecision on the part of the public is directly attributable
to the conflicting statements of our scientists. It should be borne in
mind that careful investigation in respect to the relative values of
the various forms and sources of lime has been confined largely to the
short period of time that has elapsed since recognition of the lime
deficiency of our country's soils. Our agricultural literature contained
little about soil acidity 20 years ago, and our experiment station tests
afford only relatively recent results. Some knowledge of sour soils and
the efficacy of lime in their amendment is nearly as old as the history
of agriculture, it is true, but answers to the questions uppermost in
the minds of men wanting to apply lime to land have been sought only
within recent years. The variation in soil types, and in sources of
lime, and in preconceived ideas of men drawing conclusions from
incomplete data may easily account for failure of our soil scientists to
be in the close agreement in statement that would remove all confusion
in the public mind. However, the agreement respecting the facts is
becoming better assured with every added year of investigation, as a
study of station bulletins shows.




CHAPTER VII

DEFINITIONS


_Technical Terms._ The practical man uses a great number of technical
terms in his own field of labor, and often fails to recognize the fact
that they are technical, and may be puzzling to many other people. He
uses such terms for the sake of accuracy, desiring to express to his
fellow-workmen exactly what he means. The farmer, stockman, carpenter,
banker--all have command of such terms, and need them, but the chemist
who, in a way, must come even nearer to accuracy in expression, finds
that many people who want his assistance do not care to master and use
any of his terms. Failure to do so compels misunderstanding. Anyone who
is interested in the right use of lime should be willing to add a few of
the chemists' technical terms to the scores in his own line of work that
he uses constantly, and thus let the whole matter of liming land come to
appear more simple to him. Acquaintance with a few terms is necessary
to any understanding of statements of analyses upon which purchase
should be made.

_An Element_ is a substance that cannot be divided into simpler
substances. The number of elements necessary to the growth of plants is
small, and of this number calcium is one and magnesium is another.

_Compounds._ We do not find these elements merely mixed with other
elements to form a soil. They unite in definite proportions by weight to
form chemical compounds. As conditions change, many of these compounds
undergo change, giving up one element, or group of elements, and uniting
with another element or group from a different compound. Heat, moisture
and the action of bacteria are factors in promoting the changes. There
is no more restless activity than may be found among the elements
composing a productive soil.

_Calcium_ is an element which will unite with oxygen and carbon dioxide
to form a compound known as calcium carbonate. The chemist's symbol for
calcium is Ca.

_Calcium Oxide_ is a compound left after the burning of limestone, and
is known as fresh burned lime, or quick lime. Its formula is CaO. It
contains, when pure, 40 parts of calcium and 16 parts oxygen by weight.

_Carbon Dioxide_ is a compound whose formula is CO2.

_Calcium Carbonate_, known also as carbonate of lime, has a definite
composition, containing, when pure, 56 parts CaO and 44 parts CO2. It
is known to the chemist as CaCO3, and forms practically all of very
pure limestones. Impure limestones contain some earthy materials that
became mixed with the lime carbonate when the rock was being formed.

_Calcium Hydroxide_ is a compound made by permitting calcium oxide to
combine with water, and is known as lime hydrate. It contains 56 parts
by weight CaO and 18 parts water, and has the formula Ca(OH)2.

_Magnesium_ is an element, and is found in magnesium carbonate, a
compound that is effective in correcting soil acidity.

_Magnesian Limestone._ Magnesium carbonate is usually found in
combination with calcium carbonate, and when about 47 per cent of the
total carbonates is magnesium carbonate, the limestone is known as
dolomite.

_Ground Limestone_ is the stone pulverized so that it can be
distributed. It is carbonate of lime (CaCO3), or a combination of
calcium and magnesium carbonate, and in a way has a right to be
designated as "lime," but such use leads to confusion.

_Fresh Burned Lime_. Calcium oxide (CaO) formerly was accurately
designated as "lime," but the words "fresh burned" are often prefixed to
prevent confusion with lime carbonate or the hydrate. It is known as
"lump lime," "caustic lime" and "stone lime."

_Ground or Pulverized Lime_. Fresh burned lime may be ground fine, so
that it can be spread on land without slaking. This product should not
be confused with ground limestone or hydrated lime. Fresh ground lime is
worth nearly twice as much per ton as ground limestone, but some of the
product on the market is far from pure. There is opportunity to grind up
unburned and waste material with the caustic lime, and this form of lime
usually contains some hydrated material.

_Hydrated Lime_ is the compound formed by the action of water or steam
on fresh burned lime.

_Air-Slaked Lime_ is a compound formed by the action of carbon dioxide
from the air on hydrated lime, and its formula is CaCO3, which is
that of pure limestone.

[Illustration: An Indiana Limestone Quarry]

[Illustration: A Limestone Plant (Courtesy of the Michigan Limestone
Company)]




CHAPTER VIII

GROUND LIMESTONE


_Variation in Quality._ Limestones vary widely in purity. They were
formed under water, and clay and sand were laid down with the lime in
such quantity in some cases that the resulting stone is not worth
handling for soil improvement. A stone that is practically all carbonate
of calcium, or a combination of calcium and magnesium, is wanted because
it is these two elements that give value to the material. If a poor
stone is used, too much waste matter must be handled. Twenty-five per
cent more ground limestone of 80% purity must be applied than would be
required in the case of an absolutely pure limestone. Any stone above
90% pure in carbonate of lime and magnesia is rated as good, but the
best stone runs from 96% to 99%.

Limestones vary greatly in ability to resist disintegration, and this
variation is a big factor in determining the agricultural value of
ground limestone that has not been reduced to a fine powder. Particles
of a hard limestone may lie inert in the soil for many years. Hardness
also affects the cost of grinding.

_A Matter of Distribution._ Nature has used various agencies in reducing
limestone for the making of soils. The stone contained its lime in
carbonate form, and when reduced to good physical condition for
distribution it helped to make highly productive land. We know that lime
carbonate does the needed work in the soil so far as correction of
acidity is concerned, but in the form of blocks of limestone it has no
particular value to the land. Burning and slaking afforded to man a
natural means of putting it into form for distribution, and it is only
within recent years that the pulverization of limestone for land has
become a business of considerable magnitude. The ground limestone used
on land continues to be in part a by-product of the preparation of
limestone for the manufacture of steel, glass, etc., and the making of
roads, the fine dust being screened out for agricultural purposes. These
sources of supply are very inadequate, and too remote from much land
that requires treatment. Large plants have been established in various
parts of the country for the purpose of crushing limestone for use on
land, and quite recently low-priced pulverizers for farm use have come
upon the market and are meeting a wide need.

_Low-Priced Pulverizers._ A serious drawback to the liming of land is
the transportation charge that must be paid where no available stone can
be found in the region. Great areas do have some beds that should be
used, and a low-priced machine for pulverizing it is the solution of the
problem. Such a machine must be durable, have ability to crush the stone
to the desired fineness and be offered at a price that does not seem
prohibitive to a farmer who would meet the demands of a small farming
community. In this way freight charges are escaped, and a long and
costly haul from a railway point is made unnecessary. The limestone of
the locality will be made available more and more by means of this type
of machine, and the inducement to correct the acidity of soils will be
given to tens of thousands of land-owners who would not find it feasible
to pay freight and cartage on supplies coming a long distance. There
should be a market many times greater than now exists for the product
of all large plants, while the number of small pulverizers multiplies
rapidly. The very large areas that have no limestone at hand must
continue to buy from manufacturers equipped to supply them, and farmers
within a zone of small freight charges should be able to buy from such
manufacturers more cheaply than they could pulverize stone on their own
farms.

An individual, or a group of farmers, will buy a machine for pulverizing
limestone at a cost of a few hundred dollars when costly equipment would
be out of the question. If he has a bed of limestone of fair quality,
and the soil of the region is lacking in lime, an efficient grinder or
pulverizer solves the problem and makes prosperity possible to the
region. Within the last few years much headway has been made in
perfecting such machines, and their manufacturers have them on the
market. Any type should be bought only after a test that shows capacity
per hour and degree of fineness of the product. As a high degree of
fineness is at the expense of power or time, and as the transportation
charge on the product to the farm is small, there is no requirement for
the fineness wanted in a high-priced article that must be used
sparingly.

The aim should be to store in the soil for a term of years, and the
coarse portion is preferable to the fine for this purpose because it
will not leach out. The heavy application will furnish enough fine stuff
to take care of present acidity. If nearly all the product of such a
pulverizer will pass through a 10-mesh screen, and the amount applied is
double that of very fine limestone, it should give immediate results and
continue effective nearly twice as long as the half amount of finer
material. There could hardly be a practical solution of the liming
problem for many regions without the development of such devices for
preparing limestone for distribution, and it is a matter of
congratulation that some manufacturers have awakened to the market
possibilities our country affords.




CHAPTER IX

STORING LIME IN THE SOIL


_Liberal Use of Limestone._ Land never does its best when skimped in any
way. As we raise the percentage of carbonate of lime in land that
naturally is deficient, we give increasing ability to such land to take
on some of the desirable characteristics of a limestone soil. It is poor
business to be making a hand-to-mouth fight against a state of actual
acidity unless the cost of more liberal treatment is prohibitive. The
most satisfactory liming is done where the expense is light enough to
justify the free use of material. When this is the case, extreme
fineness of all the stone is undesirable. There is the added cost due to
such fineness and no gain if the finer portion is sufficient to correct
the acidity, and the coarser particles disintegrate as rapidly as needed
in later years.

_Loss by Leaching._ Another valid argument against extreme fineness of
the stone used in liberal applications is the danger of loss by
leaching. Soils are so variable in their ability to hold what may be
given them that it is idle to offer any estimate on this point. The
amount of lime found in the drainage waters of limestone land teaches no
lesson of value for other land, the excessive loss in the former case
being due oftentimes to erosion that creates channels through the
subsoil, through which soil and lime pass.

[Illustration: A Limestone Pulverizer for Farm Use (Courtesy of the
Jeffrey Manufacturing Company, Columbus, Ohio)]

[Illustration: A Lime Pulver in Operation (Courtesy of the Jeffrey
Manufacturing Company)]

But we do know the tendency of lime to get away, and the use of several
tons of fine stone per acre may easily be followed by loss in many types
of soil. It is wholly reasonable to believe that some portion of such an
application should be coarse enough to stay where put until needed by
exhaustion of the finer portion. It is upon this theory that coarser
material often is preferred to the very finest.

_What Degree of Fineness?_ Assuming that the farmer is in a position to
store some carbonate of lime in his land for future use, giving the soil
an alkaline character for five or 10 years, the degree of fineness of
the stone is important, partly because there will be distinct loss by
leaching from many types of soils if all the material is fine as dust,
and specially because less finely pulverized material can be supplied
him at a lower price per ton. Much by-product in the manufacture of
coarse limestone for other purposes contains a considerable percentage
of material that would not pass through a 60-, or 40-, or 10-mesh
screen, but it does contain a big percentage of immediately available
lime, and a more complete pulverization of this by-product would add
greatly to its cost.

It is quite possible that a ton of such stone may be bought at a price
that would cover the value only of the fine portion, estimated on the
basis of the prevailing price of finely ground material, the coarse
material being obtained without any cost at all. It is this situation,
or an approach to it, that leads some authorities to become strenuous
advocates of the use of coarsely pulverized stone. The advice is right
for those who are in a position to accept it. If the money available for
liming an acre of land can buy all the fine stone needed for the present
and some coarser stone mixed with it for later use by the soil, the
purchase is much more rational than the investment of the same amount of
money in very fine stone that has no admixture of coarser material. If
the investment in the former case is larger than in the latter, it
continues to be good business up to a certain point, and the room for
some uncertainty is wide enough to provide for much difference in
judgment.

_Quality of the Stone._ Another factor of uncertainty is the hardness of
the stone. A limestone may have such flinty characteristics that a piece
barely able to pass through a 10-mesh screen will not disintegrate in
the soil for years, and there are other types of limestone that go into
pieces rapidly. The variation in quality of stone accounts for no little
difference in opinion that is based upon limited observation.

_Using One's Judgment._ It is evident that no hard and fast rule
respecting fineness may be laid down, and yet a rather definite basis
for judgment is needed. There is much good experience to justify the
requirement that when all ground lime is high-priced in any section for
any reason, and the amount applied per acre is thereby restricted, the
material should be able to pass through a screen having 60 wires to the
linear inch, and that the greater part should be much finer. Usually
some part of such stone will pass through a 200-mesh screen. When a
limestone on the market will not meet this test, some concession in
price should be expected. If the stone is not very flinty, a 40-mesh
screen may be regarded as affording a reasonably satisfactory test.

An increasing percentage of coarser material makes necessary an increase
in amount to meet the lime deficiency, and a distinct concession in
price is to be expected when a 10-mesh screen is used in testing. At the
same time a careful buyer will use a 60-mesh screen to determine the
percentage that probably has availability for the immediate future. A
coarsely ground article, containing any considerable percentage that
will not pass through a 10-mesh screen, must sell at a price justifying
an application sufficient to meet the need of the soil for a long term
of years, as the greater part has no immediate availability, and only a
heavy application can provide a good supply for immediate need.

_New York State Experience._ A bulletin of the New York agricultural
experiment station, published early in 1917, calls attention to the
rapid increase in demand for ground limestone in New York. Within the
last five years the number of grinding plants within the state had
increased from one to 56, and more than a dozen outside plants are
shipping extensively into the state. The bulletin says: "Farmers who
have had experience with the use of ground limestone are as a rule
satisfied with only a reasonable degree of fineness, and are able to
judge the material by inspection. When limestone is ground so the entire
product will pass a 10-mesh (or 2 mm.) sieve, the greater part of it
will be finer than a 40-mesh (or 1/2 mm.) sieve.... There are now in
operation in this State more than a dozen small portable community
grinders; they are doing much to help solve the ground limestone problem
and their use is rapidly increasing. In the practical operation of these
machines they grind only to medium fineness (2 mm.). To insist upon
extreme fineness is to discourage their use."

This State experiment station is only one of many scientific authorities
approving the use of limestone reduced only to such fineness that it
will pass through a 10-mesh screen, the cost of the grinding being
sufficiently small to permit heavy applications.




CHAPTER X

FRESH BURNED LIME


_An Old Practice._ The beneficial effect of caustic lime on land is
mentioned in some ancient writings. Burning and slaking afforded the
only known method of reducing stone for use in sour soils. Lime in this
form not only is an effective agent for correcting soil acidity, but it
improves the physical condition of tough and intractable clays,
rendering them more friable and easy of tillage. Caustic lime also
renders the organic matter in the soil more quickly available, an
increase in yield quickly following an application. These three effects
of burned lime brought it into favor, and a rational use would have
continued it in favor.

_Irrational Use._ The ability of caustic lime to improve the physical
condition of land and to make inert plant food available has led many
farmers to treat it as a substitute for manure, sods and commercial
fertilizers. Immoderate use gave increased crop yields for a time, and
the inference was easy that lime could displace the old sources of
plant food supplies. It became the custom in some regions to apply 200
to 300 bushels per acre to stiff limestone soils that had no lime
deficiency, as a test for acidity would have shown. The lime not only
made some mineral plant available, but it attacked the organic matter of
the soil, making it ready for immediate use and leaving the land
deficient in humus. Wherever stable manure and clover sods were not
freely used, the heavy application of caustic lime was followed
ultimately by decline in productive power. Such practice has come under
the condemnation of people who have not seen that the ill results have
no relation to the rational use of lime.

_What Lime Is._ There is abundant evidence that pulverized limestone, or
lime marl, or oystershell, or any other form of carbonate of lime,
corrects soil acidity and helps to make a soil productive. It is good,
no matter whether nature mixed the lime carbonate with clay, etc., to
make a choice limestone soil, or man applied it. Fresh burned lime is
only the stone after some worthless matter has been driven off by use of
heat. The limestone, carbonate of lime, is represented by the formula
CaCO_3. When heat is applied under right conditions the carbon dioxide,
CO_2, is driven off, and there remains CaO, which is calcium oxide,
called fresh burned lime.

If there were 100 pounds of the stone, and it was absolutely pure, 44
pounds would escape in form of the carbon dioxide, which had no value,
and 56 pounds would remain. The 56 pounds calcium oxide, or fresh burned
lime, have the same power to correct acidity as this same material had
when it was bound up in the 100 pounds of limestone. The 44 pounds were
driven off by heat, while if the limestone had not been burned the 44
would have separated from the 56 pounds in an acid soil, leaving the
actual lime to do the needed work of correcting acidity.

_Affecting Physical Condition._ While burning the stone does not affect
the ability to correct acidity, it does increase the power to make a
stiff soil friable and to bind a sandy soil. No one may say how much
this power to influence soil texture is increased, but it is marked, and
when improved physical condition is the chief reason for applying lime,
there is no question that fresh burned material is to be preferred to
pulverized stone or marl, or any other carbonate form. A light
application is not markedly effective in this respect, and the chief use
for this purpose has been in limestone areas that may not have had any
lime deficiency, but did have a stiff soil. The presence of the stone in
great quantity for burning on the farm made heavy applications possible.

_Using Up Organic Matter._ The presence of carbonate of lime in the form
of pulverized limestone or marl favors the disintegration of any organic
matter, but the action is so slow that it may not be observed. While the
use of limestone in manure piles is inadvisable for this reason, the
loss is not comparable to that resulting from mixing caustic lime with
manure. The caustic lime in a soil hastens decay of vegetable matter in
a degree impossible to the limestone or marl. Irrational use of the
former has produced such destructive action in many instances that the
failure to add manure or heavy sods for a long term of years has led to
heavy decline in producing power.

We are naturally so lacking in judicial temper that opinion has swung
violently from favor to disfavor. As most soils need organic matter, we
seize upon the thought that anything evidently inclined to use it up is
an evil. The purpose of tillage is in no small degree to bring about
disintegration and resulting exhaustion of vegetable matter. The latter
is a storehouse of plant food, and some of it is needed to feed the crop
desired. Tillage is no more to be commended for this purpose than a
quantity of lime equivalent in power to do the needed work. Excepting
the case of raw soils rich in the remains of plants, most land hardly
needs lime for this purpose, it may be, the tillage required for making
a seed bed retentive of moisture and for control of weeds being
effective, but the point is emphasized that the disintegration of
organic matter into available plant food is one of the chief aims of a
good farmer. It is only the excessive use of caustic lime that causes
loss.

The use of caustic lime in sufficient amount to correct all acidity, and
the use of such material to free plant food in humus sufficiently to
produce heavy sods, are just as good farm practices as drainage and the
application of manure.

[Illustration: Laying Foundation for a Lime Stack at the Pennsylvania
Experiment Station]

[Illustration: A Stack Nearly Completed at the Pennsylvania Experiment
Station]




CHAPTER XI

BURNING LIME


_Methods of Burning._ Limestone contains the calcium and magnesium that
must be the chief source of supply of American soils, though marls,
ashes, etc., have their place. The burning of the stone has been the
leading means of bringing it to a condition of availability to the soil,
excepting, of course, the vast work of disintegration carried on through
all the ages by nature. Pulverization of the rock by machinery for use
on land is recent.

The devices for burning are various, a modern lime plant containing
immense kilns, cylindrical in form, the stone being fed into them at the
top continuously, and the lime removed at the bottom. A large part of
the lime that is sold for use on land is made in plants of this kind.
Some is burned in kilns of cheap construction, but a traveler through a
limestone country finds few such kilns now in use.

_The Farm Lime Heap._ A common method of producing lime for farm use
has been, and continues to be, a simple and inexpensive one, involving
the use only of wood, coal and limestone, with earth as a covering. Dr.
Wm. Frear, chemist of the Pennsylvania station, in Bulletin 261 of the
Pennsylvania department of agriculture, describes a method of burning
lime on the farm as follows: "A convenient oblong piece of ground is
cleared, and leveled if need be, to secure a fit platform. Upon this
level is placed a layer or two of good cord wood, better well seasoned,
arranged in such manner as to afford horizontal draught passages into
the interior of the heap. Between the chinks in the cord wood, shavings,
straw or other light kindling is placed. The stone having been reduced
to the size of a double fist, sometimes not so small, is laid upon the
cord wood, care being taken to leave chinks between the stones just as
between the bricks in a brick kiln. It is preferred that this layer of
stone should not exceed six to ten inches in thickness.

"In some cases, temporary wooden flues, filled with straw, are erected,
either one at the center or, if the heap is elliptical, one near each
end, and the stone and coal are built up around them; thus, when they
are burned out, a chimney or two is secured, which may be damped by
pieces of stone or sod. Upon this first layer of stone is spread a layer
of coal, and upon that a thicker layer of stone (12 inches), and so on,
coal and stone alternating until the heap is topped with smaller stone.
The largest stones should be placed near the top of the heap, but not
near the outside, so that they may be exposed to the highest heat. The
proportion of coal is diminished in the upper layers, the effort being
to distribute one-half of the total coal employed in the two lower
layers, so as to secure the highest economy possible in the use of the
fuel.

"Fire is then kindled in the straw or shavings; when the flames have
communicated themselves to the cord wood and lowermost layer of coal,
and tongues of flame shoot out from the crevices in the sides of the
heap, earth, previously loosened by a few turns of the plow about the
heap, is rapidly spread over the entire heap, thus damping the drafts
and retarding the combustion. Steam and smoke slowly escape during the
first hours, but later the entire heap, including the outer covering of
earth, is heated to a dull red glow. The burning goes on slowly for
several days, the interior often being hot for several weeks. When the
lower portion of the heap has reached an advanced stage of calcination,
a portion of the outer layer of lime sometimes slips down; if so, a
fresh covering of earth must promptly be applied at the exposed point;
otherwise it will serve as a vent for the heat, and the top and other
sides will fail of proper calcination."

[Illustration: Effect of Excessive Use of Burned Lime Without Manure at
the Pennsylvania Experiment Station]

[Illustration: A Hydrated Lime Plant

(Courtesy of the Palmer Lime and Cement Company, York, Pa.)]




CHAPTER XII

LIME HYDRATE


_Slaking Lime._ The usual means of reducing fresh burned stone lime to a
condition that makes even distribution upon land possible is by slaking.
A few years ago considerable effort was made to create a market for lime
pulverized by machinery, but the difficulty in excluding the moisture of
the air so that packages would not burst has been in the way of
developing a market. Slaking, by the addition of water to the fresh
burned lime, is the common method of getting the required physical
condition. When the slaking is done on the farm, the custom has been to
distribute the lime in small piles in the field, placing the piles at
such convenient distance apart that the lime, after slaking, could be
spread easily with a shovel.

The water for slaking comes from rains, or from moisture in the air and
earth. The method is wasteful and can be justified, if ever, only where
farm-burned lime costs little per ton, and the nature of the soil is
such that a relatively heavy application can be safely made. The
distribution is necessarily uneven, and if the required amount goes upon
all the surface, a great excess is sure to go upon a portion of it. Very
often an excess of water puddles much of the lime in the pile, and lumps
may be seen lying in ineffective form in the soil for years. The
practice is responsible for much of the excessive application that
brought the use of caustic lime into disrepute.

_Slaking in Large Heaps._ A preferable method is to put the lime in flat
heaps of large size and about four feet deep, so that water may be
applied or advantage be taken of rainfall. The value of the lime is so
great that one can well afford to draw water and apply with a hose so
that the quantity can be controlled with exactness. When fresh burned
lime is perfectly slaked, each 56 pounds of pure lime becomes 74 pounds
of hydrated lime, water furnishing the added weight.

_Hydrated Lime on the Market._ A popular form of lime on the market is
the hydrate. Manufacturers first burn the stone, and in the case of a
pure limestone they drive off 44 pounds of each 100 pounds of the
weight in burning. Then, they combine enough water with the lime to
change it to hydrate form, and that adds 18 pounds weight. It is run
through a sieve to remove any coarse material, and then packed in bags
which help to exclude the air. The small packages in which it comes upon
the market make handling easy, and this helps to bring it into demand.
Its good physical condition makes even distribution possible, and thus
permits maximum effectiveness to be obtained. It is only slaked lime,
identical in composition and value with lime of the same purity slaked
on the farm, but some dealers have been able to create the impression
that it has some added quality and peculiar power. This does no credit
to the public intelligence, but the hunger of soils for lime is so great
that investment at a price wholly out of proportion to the price of
farm-slaked lime has rarely failed to yield some profit.

_Degree of Purity._ It is always a reasonable assumption that hydrated
lime has been made from stone of a good degree of purity. A local stone,
burned on the farm, may be of low grade, but no man of business judgment
would erect a costly plant for burning and hydrating lime where the
purity of the stone would not afford a good advertisement in itself.

On the other hand, we find very little hydrated lime on the market that
has not had sufficient exposure to the air to become changed in some
part to an air-slaked condition, or has had refuse mixed with it.
Air-slaked lime is not worth as much per ton as the hydrate because it
cannot correct as much soil acidity, and the percentage of the former
cannot be determined by the buyer. Its presence may not be due to any
wrong-doing of the manufacturer, and, on the other hand, the increase in
weight that attends air-slaking may be welcomed in some degree by a
dishonest manufacturer before the goods are shipped. The difficulty in
preventing hydrated lime from adding to its weight by becoming
air-slaked is a point to be taken into consideration.

The percentages of air-slaked material in hydrated limes are widely
variable, and no manufacturer can standardize his product on the market
surely for the benefit of the farmer. In some instances the product is
adulterated with refuse material in finely pulverized condition.




CHAPTER XIII

OTHER FORMS OF LIME


_Air-Slaked Lime._ A pure limestone is a carbonate, and the chemical
formula is CaCO_3. When it is burned, the carbon dioxide (CO_2) is
driven off, leaving CaO, which is calcium oxide, called fresh burned
lime. In this process 44 pounds of a stone weighing 100 pounds passes
into the air, and there remain 56 pounds of lime. When it air-slakes, it
takes back the carbon dioxide from the air, and the new product becomes
CaCO3, or carbonate of lime, and regains its original weight of 100
pounds. This is what would happen if the process were complete, and it
is nearly so when the exposure to the air is as perfect as possible.

Fifty-six pounds of valuable material are in the 100 pounds of
air-slaked lime, just as is the case with limestone, and there is no
difference in effectiveness except in so far as the air-slaked material
is absolutely fine and available, while most pulverized limestone is
less so. In making purchase for use of land the buyer cannot afford to
make any appreciable difference in price in favor of air-slaked lime,
as compared with a fine stone.

_Air-Slaking a Slow Process._ Lime changes to an air-slaked condition
slowly unless it has full exposure. Old heaps will remain in hydrate
form for many years, excepting the outside coat, which excludes the air.
Complete air-slaking would not reduce ability to correct soil acidity,
the total amount of calcium and magnesium remaining constant, but weight
would be added in the slaking, and therefore the value per ton would be
reduced. The slowness with which air-slaking proceeds gives reason to
expect that any bulk of old lime may contain a considerable percentage
of the hydrate, and therefore have greater strength than a true
carbonate like limestone. This is a consideration of value to a buyer.

_Agricultural Lime._ Some manufacturers have found in the demand for
lime by farmers an opportunity of disposing of much material that would
not be satisfactory to manufacturers and builders. In some cases this
so-called agricultural lime is sold at a price that is not beyond value,
but it varies much in its content of pure lime. If the unburned cores
of kilns are ground up, the material simply retains the value of
unburned stone. Any air-slaked material put into it has like value.
Forkings, ground up, have less value, and sometimes no value at all.
Some better material may go into this mixture that is given the name
"agricultural lime," and the product cannot be standardized or have a
valuation given it that would be true for another lot.

Some manufacturers are marketing limes of fair values under this
designation, but the values change as the material changes. There are
other manufacturers who are putting poor stuff on the market. Unless one
knows the manufacturer and his processes, he should not pay a great deal
for "agricultural lime." It is much better to buy a high-grade lime or
limestone that is more nearly constant in composition. When the word
"agricultural" is part of the brand, there is assurance that the
percentage of waste stuff in it is relatively high. Unless one knows to
the contrary, he should assume that a ton of finely pulverized limestone
is worth more per ton than "agricultural lime."

_Marl._ Marls vary in composition, as limestones do, but there are beds
of chalky marl that contain very little clay and sand and are nearly a
pure carbonate. It is only marls of high degree of purity that can be
put on the market with profit, but beds of less pure marl furnish
dressings for farms of the locality in many sections of the country.
Some of these inferior marls have had so much clay and sand mixed with
the lime carbonate that dressings must be heavy. The best lime marls
provide excellent material for the correction of soil acidity, the
actual value per ton being practically the same as that of the finest
pulverized limestone. Some dealers in marl make extravagant claims for
their goods, but any farmer may easily put these claims to the test and
learn that he should not expect more than a fairly good carbonate of
lime can do.

Marl improves the physical condition of stiff soils only when used in
large amount per acre, and this is true of any carbonate form, such as
limestone. Little effect upon physical condition should be expected from
the light application usually given when marl is purchased and
transported some distance to the farm. The chalk marl on the market is
used to correct soil acidity, and at the best it is worth only what good
lime carbonate is worth. It has no hidden virtues, and cannot take the
place of fertilizers. It is an excellent means of meeting the
lime-requirement of land when bought right, and its fine division makes
it distinctly superior to coarse stone.

There should be no confusion of a lime marl with the so-called "green
sand" marl. The latter is low in lime, and may be acid, the value of the
marl being in a considerable percentage of plant food contained.

_Oyster Shell._ Ground oyster shell is a good source of carbonate of
lime. The percentage falls below that of limestone, but in addition
there is a little nitrogen and phosphoric acid. An analysis of a good
quality of oyster shell, as found on the market, will show 90% carbonate
of lime.

Burned oyster shell has something near the same composition as lime made
from stone, but it goes back to hydrate and air-slaked forms rapidly.
There is no large amount of burned shell lime on the market, the
material known as shell lime being the ground shell, or lime carbonate.

_Wood Ashes._ A large supply of lime in excellent form was afforded by
hardwood ashes, but this product has ceased to have any important value
to our agriculture. The chief supply on the market is low in quality,
containing moisture and dirt in considerable amount, the form of lime
being changed from an oxide to the hydrate and carbonate.

_Gas Lime._ Prof. E. B. Voorhees, in "First Principles of Agriculture,"
says: "Gas lime is also frequently used as manure; in gas works,
quicklime is used for removing the impurities from the gas. Gas lime,
therefore, varies considerably in composition, and consists really of a
mixture of slaked lime, or calcium hydrate, and carbonate of lime,
together with sulfites and sulfides of lime. These last are injurious to
young plant life, and gas lime should be applied long before the crop is
planted, or at least exposed to the air some time before its
application. The action of air converts the poisonous substances in it
into non-injurious products. Gas lime contains on an average 40% of
calcium oxide, and usually a small percentage of nitrogen."

_Lime After Magnesium Removal._ A by-product in the removal of
magnesium from a magnesian limestone is an excellent material for
correction of soil acidity, on account of its physical condition. Its
exposure to the air causes much of the hydrate to change to an
air-slaked form, and its value per ton lies somewhere between that of
very finely pulverized limestone and hydrated lime.




CHAPTER XIV

MAGNESIAN LIME


_Magnesium._ As an element of plant food, magnesium is as essential as
calcium. It leaches out of the soil less readily, and there may be even
less need of its application as a plant food, though the need of calcium
applications for this purpose is assumed to be small. In the correction
of soil acidity magnesium is more effective than calcium, 84 pounds of
the carbonate being equal to 100 pounds of calcium carbonate. It is a
curious fact, however, that there is widespread fear of magnesium as a
soil amendment. This is not traceable to any considerable experience by
practical farmers that inspires caution in its use, although immense
quantities of magnesian limestone and lime have been used. Neither is it
due to any weight of evidence against it in the experience or teachings
of soil chemists and experiments. The facts of the case appear to be as
follows:

1. An investigator found in his laboratory that a plant growing in a
water solution was injured when magnesium was added, and that the
injury was checked when calcium in equal amount was added to the water.
The theory was worked out that a soil should not contain a greater total
amount of magnesium than of calcium, and as the soil's supply of calcium
tends to leach out more readily than the supply of magnesium, it was
best to use a high-calcium lime. If this discovery of the laboratory had
been carried into the field, its significance would have dwindled to
zero in the case of normal soils, and a lot of exploitation would have
been rendered impossible. As it was, the discussion went merrily along
until it occurred to some one to test the matter in the soils where
plants grow, and one would now hear little of it if commercial interests
were not at stake.

2. Very much of our limestone supply is high in magnesium, and some men
who have limestone very low in magnesium and high in calcium have done a
good stroke of business for themselves by deepening the public's
impression, due to laboratory tests with water cultures, that magnesium
in lime is injurious.

3. Many people knew "lime," but had no knowledge of magnesia, and if it
was an impurity like clay or sand, cutting down value per ton, and if it
was worse because harmful, they wanted none of it.

_The Fact's Importance._ If every farm could get its supply of pure
calcium lime as cheaply as it can have magnesian lime, the truth
respecting the value of the latter would have small agricultural
importance, but as a great bulk of farm and commercial supplies of lime
is magnesian, financial injury has been done consumers who have paid
more than should have been paid for relatively pure calcium lime and
limestone, being afraid to use goods whose content of magnesium was not
small. It is poor policy to use either kind of burned lime in great
excess, but when rationally used on all soils except sandy ones, there
is no preference to be exercised that can be based upon performance. A
magnesian lime corrects as much acidity as a high calcium lime, and a
little more, and its use is to be recommended if there is any advantage
in the matter of price, except in the case of distinctly sandy soils.

_Magnesian Limestone._ Leading scientists making tests of limestone for
normal soils, use magnesian limestone freely. They recommend its use to
farmers wherever there is advantage in point of price. The advice is
safe that the limestone of a given fineness should be chosen whose total
percentage of carbonates of calcium and magnesium is the highest. The
example of these scientists, buying pulverized limestone for
agricultural colleges and experiment farms, and for their own farms,
should loosen the curious hold that the early warnings of a laboratory
experimenter took upon public imagination. The farmer should buy
limestone on a basis of ability to correct soil acidity, and make each
dollar do the most possible toward that end.

Most limestones contain some percentage of magnesium, and in the case of
a pure dolomite over 45% carbonate is present in combination with
calcium carbonate. A stone rich in magnesium slakes less readily than
one high in calcium, and therefore is preferred by manufacturers
shipping pulverized burnt lime to reach its destination before slaking.




CHAPTER XV

WHAT SHALL ONE BUY?


_Relative Values._ The relative strengths of the various materials
containing lime may be known and yet doubt continue respecting the
choice to be made. The conflicting claims of dealers, and inaccurate
deductions from a single test made by some individual, aid the
confusion. If there were always the single purpose of correcting soil
acidity, and if there were the same ease of application in case of all
the materials, the choice would present much less difficulty.
Notwithstanding this, most land now has a lime requirement, or will have
one as leaching, crop removal and chemical change within the soil
continue, and the puzzle is no worse than a score of others that present
themselves continuously in farming.

_Destroying Acids._ The cost of liming to improve the physical condition
of land is prohibitive for most farms remote from supplies of stone that
can be burned and put upon the land at a low price per ton. Where stone
is at hand, and soils are intractable, lime burned on the farm should
be used. Some slight benefit to a stiff soil may be obtained from the
light application that is deemed practicable where all forms are costly,
but this benefit is not usually marked in case of an application of a
ton or less of burned lime. It is a safe statement that most buyers of
lime in some form or other will profit chiefly through the correction of
soil acidity and promotion of bacterial life. This renders the situation
more simple as any carbonate, hydrate or oxide of lime will accomplish
these purposes.

_Composition._ The first consideration is the actual content of calcium
and magnesium. A guaranteed analysis is the only safe basis of purchase.
The unstable nature of fresh burned and hydrated forms makes an exact
statement of percentages impossible for goods not wholly fresh, but at
least the purity of the original limestone can be judged.

_Equivalents._ One ton of fresh burned lime, made from pure stone, is
equivalent to 2640 pounds of the hydrate, and to 3570 pounds of
pulverized limestone or of air-slaked lime. It is easy to carry in mind
the proportions expressed by 1, 1-1/3 and 1-3/4. If there were no other
considerations, such as convenience in handling, evenness of
distribution, etc., to take into account, one ton of fresh burned lime,
one and a third tons hydrated and one and three-quarters tons finely
pulverized limestone would have the same value when delivered in the
field. Lime fully air-slaked, high-grade marl, and finely pulverized
limestone would have the same value, ton for ton.

_Even Distribution._ The value of even distribution is not easily
overestimated. If lime in proper amount does not go into each square
foot of an acid soil, some of the soil will remain sour unless mixing is
done by implements of tillage. Lime is diffused laterally through the
soil in a very slight degree. If a strip of sour land is protected by
canvas, so that no dust from lime applied to uncovered land can blow
upon it, a seeding to clover will show that plants a few inches from the
edge of the limed area will fail to start thriftily and may die before
their roots reach the lime. Full effectiveness of an application is
possible only through even distribution.

_Using Lump Lime._ Lump lime, slaked on the farm, is difficult to apply
satisfactorily. Spreading with a shovel from small heaps is bad
practice, and when the lime is slaked in a large heap, it cannot be
handled as well as pulverized stone or commercial hydrated lime. The
latter two are in condition for application by means of a lime
distributor, or even a fertilizer attachment of a grain drill. The
farm-slaked lime contains impurities that interfere with distribution.

_An Estimate._ It is always hazardous to attempt an estimate of cost of
labor without knowing the particular farm conditions, but the expense
and discomfort attending the slaking and use of lime bought in lump
state justify a willingness to pay as much for a ton of hydrated lime as
lump lime would cost, although the former has only three-fourths as much
strength as the latter. Some farmers pay nearly twice as much for the
hydrated, partly to escape the inconvenience and partly because they
hope that the extraordinary claims for superiority made by some dealers
may prove true. They should know that it is only fresh burned lime
slaked, but incline to credit a claim that special treatment enhances
value in some mysterious way.

Comparing lump lime with finely pulverized limestone, the factors of
expense and discomfort and final lack of perfect distribution of the
former remain important. The stone is relatively easy to handle, being
slightly granular and passing through a distributor without trouble. The
fact that it is not caustic, like the hydrated, is in its favor. When
everything is taken into account, one is justified in using limestone or
air-slaked lime at a cost per ton three-fourths as great as that of lump
lime. It is to be borne in mind that in these estimates the cost per ton
is not that at the factory or at one's own railway station, but on the
farm. The freight and cartage to the farm are based on weight of
material, and more material per acre is required when the worthless
portion has not been driven off by burning. If one must use one and
three-quarters tons of limestone to have the equivalent of one ton of
fresh burned lime, it is evident that the cost of freight and cartage of
the worthless portion might make cost prohibitive if distances were very
great. Farms lying a long distance from a railway station may easily
find that fresh burned lime is the only form of lime they can afford.
The basis for correct estimate is cost delivered in the field.

_Storage._ One advantage possessed by the limestone is ease of storage.
There is no inconvenience or loss. The stone may be ordered at any time
of the year when teams are least busy upon other work, and it can be
held till wanted. In this way the cost of cartage to the farm may be
kept relatively low, and the material is at hand when wanted, regardless
of rush of work or delays of railroads. This advantage is partial
counterbalance to the cost of freight on the worthless portion of
unburned stone.

_Valuing Limestone._ The estimates, so far as labor and convenience are
concerned, are merely suggestive, and rest upon the presumption that the
stone is satisfactorily fine. It has been urged in another chapter that
immediate effectiveness is determined by fineness, but as a working
basis we assumed that when all the stone would pass through a screen
having sixty wires to the inch it would give the desired results. The
coarsest portion would not be available at once, but when an application
is heavy enough to serve for a year or more, we have enough very fine
material in such a grade of stone to meet immediate need. When
estimating values of such a grade and coarser grades, the amount per
acre to be used is a factor. The coarse is unsatisfactory if the price
is not low enough to permit an application sufficient for a considerable
term of years, so that it will contain all the fine material needed at
once. In that case the coarser material may be expected to meet later
need, and may be even more desirable for such purpose, as it would not
be subject to leaching.

Coarse grinding costs much less than fine grinding, and it is the
resulting low price that permits the heavy application. As stone varies
in hardness and ability of the small particles to withstand
disintegrating forces in the soil, an estimate of the difference in
price between a 60-mesh limestone and a 10-mesh one could not serve as a
safe guide. The buyer should know the percentages of a limestone passing
through screens of various sizes before he makes a purchase, and should
demand part of the saving in cost of production that attends coarse
grinding.

_Oyster Shell._ Ground oyster shell should be given about the same
valuation as limestone. It is a lime carbonate, and the percentage of
worthless material in it varies somewhat It is coarsely ground, but the
large pieces disintegrate in the soil much more rapidly than limestone
would do. It contains a little nitrogen and phosphoric acid, partially
available, as an offset to coarseness and some lack of purity, as
compared with the highest grade of fine stone. It is profitable to buy
oyster shell at limestone prices if used liberally enough to furnish a
supply for a term of years. The oxide, or burned shell lime, would be
nearly the equivalent of burned stone if it did not change to hydrate
and air-slaked forms so rapidly that it rarely is on the market in the
~full~ strength of fresh burned lime.

_Hardwood Ashes._ As a source of lime, ashes have become far too
expensive. The composition of ashes on the market is widely variable,
dirt and moisture often accounting for much of the weight. The lime in
fresh burned ashes is peculiarly effective, being finely divided and in
oxide form, but the ashes on the market have much of the lime
water-slaked and air-slaked. Unless analysis is made at time of
purchase, a buyer should not estimate the content of lime in a ton at a
value greater than assigned to one-half of a ton of limestone. The
additional value of the ashes, due to the potash content, is wholly
another consideration.

_Marl._ No more should be paid for a ton of good chalk marl than an
equal weight of fine limestone would cost. Each is a good carbonate of
lime, with the same capacity for destruction of acids.

_Agricultural Lime._ This variable product should not be bought unless
actual composition is known, or the cost is as low as that of pulverized
limestone, and even then it may be a bad purchase, the methods of the
manufacturer being the determining factor. If such lime is chiefly a
dumping place for low-grade stone and forkings, it has small
agricultural value.

_Land Plaster._ The soil wants lime in carbonate form. The oxide and
hydrate change to carbonate, and therefore are good. Land plaster is a
sulphate, and its tendency is to make a soil sour. It should not be
considered as a means of correcting soil acidity.

_Basic Slag._ The amount of effective lime in basic slag, as made by
modern methods, is so small that its value is nearly negligible. Basic
slag is a good source of phosphorus, and in addition has a tendency
toward correction of soil acidity, but such tendency has little cash
value for land that requires a considerable dressing of lime to furnish
a base with which soil acids may combine.

An expression of opinion was obtained recently from some leading soil
chemists of this country, and upon such expression we base the estimate
that when pulverized limestone costs three dollars a ton, the value of
the lime in a ton of basic slag should not be placed higher than 50
cents, and some chemists believe that the lime content is entirely
negligible as an agent in soil amendment.

_Lime in Other Fertilizers._ The demand for lime is leading some men to
state a lime content for their goods that is designed to mislead. Such
lime is not in a form to combine with soil acids, and is as valueless as
the very large amount of lime in acid soils that is in compounds having
no power to affect free acids.




CHAPTER XVI

METHODS OF APPLICATION


_A Controlling Principle._ The chief purpose of liming land is to
provide a base with which acid may combine, so that the soil may be
friendly to plant life. Lime has little power to distribute itself
through a soil, and harmful acid may remain only a few inches distant
from the point where lime has been placed. In a general way, the
tendency of lime is downward, especially when the application at the
surface is heavy. Economical use demands even distribution through the
soil so that a sufficient amount is in every part. Means to that end are
good means of distribution.

_Spreading on Grass._ Where lime is burned on the farm, and little
account of labor is taken, it has been a common custom to spread the
lime on grass sods the year previous to breaking the sod for corn, using
100 to 300 bushels per acre. Rains carried some of the lime through the
soil, and the increased yields for a few years were due to the improved
physical condition of a stiff soil that a heavy application of
caustic lime produces, and to the disintegration of organic matter and
to change in compounds of mineral plant food. The practice is rightly
going into disrepute, being wasteful and harmful.

[Illustration: Filling the Lime Spreader at the Ohio Experiment Station]

[Illustration: Lime Distributors]

The smaller application of any form of lime to correct soil acidity may
be made on grass land that should not be plowed, but the full
effectiveness of an application is not secured in top-dressings. If the
land is under a crop rotation, it is better practice not to apply the
lime on grass, but to defer application until the sod has been broken,
when the lime can be intimately mixed with the soil by use of harrows.
It is the rule that it should go on plowed land, and should be mixed
with the soil before rain puddles it. In no case should it be plowed
down.

When clover or alfalfa shows a lime deficiency, it is advisable to make
an application, either in the spring or after a cutting, obtaining
whatever degree of effectiveness may be possible to this way, but the
fact remains that full return from an application is secured only after
intimate mixture with the soil particles. On the other hand, if land
needs lime, and there is not time or labor for the application when the
soil can be stirred, it is far better to apply on the surface during any
idle time than to leave the soil deficient in lime.

_Distributors._ The most satisfactory means of distribution is a machine
made for the purpose. A number of good distributors are on the market.
They are designed to handle a large quantity of material after the
fashion of a fertilizer distributor ordinarily attached to a grain
drill. A V-shaped box, with openings at the bottom, and a device to
regulate the quantity per acre, enables the workman to cover the surface
of the ground with an even coat, and the mixing with the soil is done by
harrows.

Light applications can be made with a drill having a fertilizer
attachment. Some makes of drill have much more capacity than others.
Granular lime, such as limestone, is handled more satisfactorily than a
floury slaked lime.

_Farm-Slaked Lime._ Lime slaked on the farm must continue to be a
leading source of supply to land. If there is stone on the farm, and
labor in the winter is available, it is not a costly source of supply.
The chief drawback to the use of farm-slaked lime is the difficulty in
securing even distribution. The loss from spreading with shovels from
small piles slaked in the field is heavy. The quantity per acre must be
large to insure sufficient material for every square foot of surface.
The lime slaked in a large heap can be put through distributors only
after screening to remove pieces of stone, unless they are made with a
screening device, and the caustic character and floury condition make
handling disagreeable, but no other method is as economical when lime is
high in price.

_Use of the Manure Spreader._ The next best device is the manure
spreader. The makes on the market vary in ability to do satisfactory
work with lime, and none does even work with a small quantity per acre.
An addition to the bulk to be handled by placing a layer of other
material in the spreader before filling with lime helps, but some
spreaders do fair work in spreading as little as 3000 pounds of slaked
lime per acre, and certainly far better work than usually is done with
shovels from a wagon.




CHAPTER XVII

AMOUNT OF LIME PER ACRE


_Soils Vary in Requirement._ There is always the insistent question
respecting the amount of lime that should be used on a particular field.
Usually _no_ definite reply can be safely made. The requirement of the
present, and probably of the _next_ few years, should be met by one
application. The existing degree of acidity is an unknown quantity until
a careful test has been made. There are soils so sour that several tons
of fresh burned lime per acre would only meet present requirement, and
there are soils so soundly alkaline that they need none at all. This
uncertainty regarding amount required is responsible for much failure to
do anything, even when some acidity is indicated by general appearance.

_A Working Basis._ If land has once been productive and in later years
clover has ceased to grow and grass sods are thin, there is a strong
probability that liming will pay, and the experience of farmers on
normal soils, and the tests of experiment stations, justify the
estimate that two tons of fine stone, or one and a quarter tons of fresh
burned lime per acre, can be used with profit. This amount probably will
permit fertilizers and tillage to make their full return in heavy sods
that will provide humus. It is a reasonable expectation that the
application will serve through a crop rotation of four or five years.

If the soil was not very sour, the second application at the end of four
or five years may be reduced somewhat, and even a ton of stone given
once in the crop rotation may fully meet the requirement.

In the case of the normal soil that has ceased to grow clover, and does
grow plants that are acid-resistant, it is better practice to secure a
relatively low-priced supply of coarsely pulverized stone and apply
three or four tons per acre, and thus lengthen the interval between
applications to eight or 10 years. The fine material in the heavy
application will take care of present need, and the coarser particles
will disintegrate later on.

The quantities suggested may not be the most economical for the reader,
but their use cannot be attended by loss if a soil is sour, and there
is reason to believe that it is much better to use such quantities
without question than to defer liming for a year in the hope that some
more definite knowledge of a particular field's needs may be secured.

_Small Amounts Per Acre._ There is much experience as a basis for the
claim that a few hundred pounds of burned lime per acre may have marked
results. Fields that indicated an actual lime requirement of a ton of
fresh lime per acre have had a test of 500 pounds per acre made in
strips, and the clover later on was so superior to that which was
struggling to live in the untreated portion that the light application
appeared almost to be adequate. In such land there cannot be full
bacterial activity or continuing friendliness to plants unless the need
is met fully. A larger application would have paid better. It is the
soil rich in lime that can make the best response to tillage and
fertilization.

_A Heavy Soil._ When burned lime is not high in price, an application of
two tons per acre may be more profitable than a smaller one. A heavy
soil needs to be richer in lime than a light one for best results, and
physical condition also is improved by the larger quantity. A
correspondingly heavy coat of stone will give quite satisfactory
results, but effect upon the texture of the soil is less marked.

_Sandy Soils._ It is inadvisable to apply any large quantity of caustic
lime to a light soil. Such a soil does not need as high a percentage in
it as a heavy soil requires for good results, and caustic lime can
easily injure physical condition. Limestone is safe for use, and is to
be advised for all quite sandy land. Acidity rarely runs high in a light
soil, and the opinion is hazarded here that one ton of stone per acre
meets the needs of a light soil about as surely as two tons supply a
heavy soil. In case of each type of soil there are wide exceptions, and
yet these estimates form a basis for the judgment of the individual
farmer.




CHAPTER VIII

SPECIAL CROP DEMANDS


_Lime-Loving Crops._ There are plants which are acid-resistant, giving a
good return for fertilization and care when the soil is sour. There are
a few kinds of cultivated plants that seem to prefer an acid soil, and
to resent lime applications. Most staple crops prefer an alkaline soil,
or at least one that has no large requirement, and there are plants that
thrive best only in land rich in lime. Not all such plants require more
as a component part of their structure, but do have a high percentage in
their ash.

_Liming for Alfalfa._ When all other conditions are right, alfalfa
thrives or fails according as a soil is rich in lime or is distinctly
deficient. It is entirely possible to get fair yields of this legume for
a short time from land that is not fully alkaline, but full yields and
ability to last for a term of years depend upon a liberal lime supply.
Alfalfa is at home only in a naturally calcareous soil, or one that has
been given some of the characteristics of such land by free use of
lime. In the case of neutral or slightly acid ground it is good practice
to mix four tons of limestone per acre thoroughly with the soil. Such
treatment gives greater permanence to the seeding, enabling the plants
to compete successfully with the wild grasses and other weeds that are
the chief obstacle to success in the humid climate of our Mississippi
valley and eastern states. When this amount of stone is used, the finest
grade may not be preferred to material having a considerable percentage
of slightly coarser grains.

[Illustration: Remarkable Effect of Lime on Sweet Clover at the Ohio
Experiment Station]

[Illustration: Sweet Clover Thrives When Lime and Manure Are Supplied,
Ohio Experiment Station]

_Red Clover._ When land is in excellent tilth, it may grow red clover
satisfactorily while showing a decided lime deficiency. On the other
hand, much slightly acid land fails to grow clover, and an application
of lime is followed by heavy growths. Red clover is most at home in
calcareous soils, and lack of lime is a leading cause of clover failure
in this country. Other causes may be important ones in the absence of
lime and be overcome when it is present.

_Alsike Clover._ Most legumes like lime, and alsike clover is not an
exception, but is far more acid-resistant than the red. It is less
valuable, both for soil improvement and for forage, having an inferior
root system, but has proved a boon to farmers in areas that have been
losing the power to grow red clover. The custom of mixing red and alsike
seed has become widespread, and distinctly acid soils are marked in the
clover flowering season by the profusion of the distinctive alsike bloom
to the exclusion of the red. While there is acid-resistant power, this
clover responds to liming.

_Crimson Clover._ Among lime-loving plants crimson clover has a rightful
place, but it makes fairly good growth where the lack of lime is marked.

_Bluegrass._ The heaviest bluegrass sods are found where lime is
abundant in the soil. This most valuable pasture grass may withstand the
encroachments of weeds for a long time when lime is not abundant, if
plant food is not in scant supply, but dependable sods of this grass are
made only in an alkaline soil. Heavy liming of an acid soil pays when a
seeding to permanent pasture is made, and old sods on land unfit for
tillage may be given a new life by a dressing.

_Crops Favored by Lime._ Nearly all staple farm crops respond to
applications given acid soils. Corn, oats, timothy, potatoes and many
other crops have considerable power of resistance to acids, but give
increased yields when lime is present. Liming is not recommended for
potatoes because it furnishes conditions favorable to a disease which
attacks this crop. When clover is wanted in a crop rotation with
potatoes, it is advisable to apply the lime immediately after the potato
crop has been grown, and to use limestone rather than burned lime. Most
kinds of vegetables thrive best in an alkaline soil.




INDEX


   Page

   Air-slaked lime, composition and relative value of, 31, 57

   Agricultural lime, composition and relative value of, 58, 76

   Amount of lime per acre, 82

   Basic slag, 76

   Burning lime, methods of, 49

   Calcium, 29
     carbonate, 30
     hydroxide, 30
     oxide, 29

   Carbon dioxide, 30

   Causes of soil acidity, 10, 12, 13, 14

   Caustic lime affects physical condition, 44, 46
     acts on humus, 44, 47
     frees inert plant food, 44
     compared with limestone, 45
     irrational use of, 44
     may injure a sandy soil, 66, 85
     right use of, 48

   Caustic magnesian lime on sandy land, 66

   Chemical changes produce acidity, 13

   Clover, 17, 19, 87

   Composition of limestone, 24, 30, 31, 46

   Distribution of lime, 70, 78

   Distributors, 80, 81

   Dolomite, 30, 67

   Equivalents in value, 69

   Extent of soil acidity, 6, 11

   Fineness of limestone, 39, 73

   Frear, Dr. Wm., 50

   Fresh burned lime, 44
     composition and relative value of, 29, 31, 45, 69, 71

   Gas lime, 62

   Ground limestone, composition and relative value of, 30, 33, 69, 72

   Hydrated lime, composition and relative value of 30, 31, 53, 71

   Indications of soil acidity, 5, 15, 17, 18

   Irrational use of lime, 9, 44

   Land plaster, 76

   Leaching, 12, 38

   Lime for alfalfa, 86
     alsike clover, 87
     bluegrass, 88
     crimson clover, 88
     potatoes, 89
     red clover, 87
     most staple crops, 88
     in fertilizers, 77
     is unstable, 10
     necessary content variable, 5
     on sandy soils, 85

   Limestone burned to effect distribution, 34
     land, value of, 4, 6
     varies in composition, 33

   Litmus paper test, 20

   Low-priced pulverizers, 35

   Lump lime and hydrate compared, 71
     limestone compared, 72

   Magnesian lime, 64
     limestone, 66

   Magnesium, 30, 64

   Marl, composition and relative value of, 59, 76

   New York experiment station, 42

   Old heaps of burned lime, 58

   Oyster shells, composition and relative value of, 61, 75

   Redtop, 18

   Relative values of lime, 68, 71, 72

   Removal of lime in crops, 14

   Slaking lime, 53

   Small applications may pay, 84

   Soil acidity, cause of, 10, 12, 13, 14
     extent of, 6, 11
     indications of, 5, 15, 17, 18
     tests for, 20, 21

   Soils vary in lime requirement, 82

   Sorrel and plantain, 15

   Spreading farm-burned lime, 70, 80

   Storing lime in the soil, 38

   Storing limestone, 73

   Source of lime, as:
     agricultural lime, 58, 76
     air-slaked lime, 31, 57
     fresh-burned lime, 29, 31, 44
     gas lime, 62
     ground lime, 31
     ground limestone, 30, 33
     hydrated or slaked lime, 31, 53
     magnesian limestone, 30
     marl, 59
     oyster shells, 61, 75
     wood ashes, 61, 75

   Source of lime in soils, 10, 24

   Technical terms, 28

   Tests for soil acidity, 20, 21

   Thin soils usually acid, 18

   Timber as an index, 7, 15

   Timothy, 17, 88

   Truog, Prof. E., 21

   Truog test, 21

   Value of lime after magnesium removal, 62

   Voorhees, Dr. E. B., 62

   Warding off soil acidity, 7

   When production decreases, 18

   Wood ashes, composition and relative value of, 25, 61, 75





End of Project Gutenberg's Right Use of Lime in Soil Improvement, by Alva Agee