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. 

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 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

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CHAPTER 1

INTRODUCTION

There is much in the action of lime in the soil that is not known, butall that we really need to know is simple and easily comprehended. Thepurpose of this little book is to set down the things that we need toknow in order that we may make and keep our land friendly to plant lifeso far as lime is necessarily concerned with such an undertaking. Intelligent men like to reason matters out for themselves so far aspracticable, taking the facts and testing them in their own thinking bysome truth they have gained in their own experience and observation, andthen their convictions stay by them and are acted upon. The whole storyof the right use of lime on land is so simple and reasonable, when westick only to the practical side, that we should easily escape theconfusion of thought that seems to stand in the way of action. Theexperiment stations have been testing the value of lime applications toacid soils, and the government has been finding that the greater partof our farming lands is deficient in lime. Tens of thousands of farmershave confirmed the results of the stations that the application of limeis essential to profitable crop production on their farms. The confusionis due to some results of the misuse of lime before the needs of soilswere understood, and to the variety of forms in which lime comes to usand the rather conflicting claims made for these various forms. It isunfortunate and unnecessary. 

The soil is a great chemical laboratory, but exact knowledge of all itsprocesses doubtless would enrich the farmer's vocabulary more than hispocketbook. We are concerned in knowing that lime's field of usefulnessis broad in that it is an essential plant food and provides the activemeans of keeping the feeding ground of plants in sanitary condition. Wewant 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 toknow the relative values of the various forms of lime and how we maychoose in the interest of our soil and our pocketbook. The time andmethod of application are important considerations to us. There aremany details of knowledge, it is true, and yet all fit into a rationalscheme that shows itself to be simple enough when the facts arrangethemselves in an orderly way in our minds. 

Lime cannot take the place of nitrogen, nor phosphorus, nor any other ofthe essential plant foods. It is not a substitute for any otheressential factor in plant growth. It would be folly to try to dependupon lime as a sole source of soil fertility. On the other hand, we havelearned very definitely within the last quarter of a century that it isfoolish to depend upon commercial fertilizers and tillage and good seedsfor full production of most crops from great areas of our farmingcountry that have a marked lime deficiency. The obvious need of oursoils is the rich organic matter that clover and grass sods couldfurnish, and their fundamental need is lime. Most farms cannot possiblymake full returns to their owners until the land's hunger for lime hasbeen met. The only question is that regarding the best way of meetingit. 

CHAPTER II

THE LIME IN SOILS

_Limestone Land. _ Soil analyses are serviceable only within certainlimits, and in the case of the normal soils that comprise the very greatpart of the entire humid region of the United States the practical mangives little heed to what special analyses might show him when decidingupon the purchase of a farm. He does know, however, that a limestonesoil has great natural strength, and recovers from mistreatment morereadily than land low in lime. It has staying powers, and is dependable, unless through natural processes the lime leaches out or losesavailability. All limestone areas have gained reputation for themselvesas producers of grain and grass. 

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

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

_Natural Deficiency. _ It is interesting to note the differences inevidences of prosperity that are associated with lime percentages. Theareas that are able to produce the vegetation characteristic ofcalcareous soils are obviously the most prosperous. The decidedlylime-deficient sections, advertising their state by the kind of originaltimber, and later by unfriendliness to the clovers, do not attractbuyers except through relatively low prices for farms. Such areas areextensive and have well marked boundaries in places. 

It does not follow that every farm in such limestone valleys as theShenandoah, Cumberland, and Lebanon, or in the great corn belt having anaturally calcareous soil, is prosperous, or that a multitude of ownersof such lime-deficient areas as the belt in a portion of southern NewYork and northern Pennsylvania, or the sandstone and shale regions ofmany states, have not overmatched natural conditions with fine skill. Wetreat only of averages when saying that a "lime country" shows aprosperity in its farm buildings and general appearance that does notcome naturally and easily to any lime-deficient territory. In the lattera man rows against the current, and if livestock farming is not employedto furnish manure, and if the manure is not supplemented by tillage anddrainage to secure aeration, or if lime is not applied, the land reachessuch 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 thesemi-arid belt of the United States. No small part of this area was notdeficient at one time, as the nature of the original timber indicates, and it is well within the knowledge of practical men that land whichonce produced the walnut and ash and shellbark hickory can be broughtback to productivity with reasonable ease after very hard usage. It hasa good inheritance. It is a disconcerting fact in our Americanagriculture that, fertile as our country is as a whole, very great areaswere so deficient in lime before they came under man's control that thechestnut, pine, and the oaks of mean growth were fully at home. Thegradation from low lime content to high, and its relation to soil type, give us all sorts of mixtures of lime-loving and acid-resistantvarieties of trees in original forests, but our agriculture is hamperedby the high percentage of land for which nature made no great provisionof lime, and on this land farming lags. 

_Effect of Irrational Farming. _ Interest in liming might well have beendue to the amendment of all this soil, but the rational use of lime thathas been the subject of much study in the last quarter of a centuryconcerns chiefly great areas that probably could have been kept inalkaline condition and friendly to the clovers for a long time despite ashort natural supply as compared with the content of our limestonelands. The success of individual farmers in areas now admittedly acid asa whole is convincing on this point. Nature tries constantly to curethe ills of her soil through the addition of vegetable matter. An excessof water or a deficiency is atoned for in a degree by the leaves androtted wood of her forests. Aeration is kept possible. The lime in theproduct of the soil goes back to it. A system of farming that involvesthe application of manure, thorough tillage, drainage where needed, andthe free use of sods in some way, has kept portions of thesenon-calcareous soils out of the distinctly acid class. Clover growssatisfactorily, grass sods are heavy, and there is no acute limeproblem. Such farms are relatively few in the great stretches of landnow classed as acid soil, and probably the most of the lime that isbeing applied goes only on ground that once was sufficiently alkaline togrow the clovers. The loss of organic matter through failure to use thebest methods of farming is responsible for no small part of thewidespread need of lime today. This subtracts nothing from the urgencyof its use to restore a condition favoring clover and grass sods, but itdoes teach a lesson of the highest value. The day of destructive soilacidity can be retarded by good farming, but in the long run theinevitable losses of lime from most soils must be met by applications. 

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

CHAPTER III

SOUR SOILS

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

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

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

_Prevalence of Acidity. _ The results of experiment station and farmtests are conclusive that the soils of the greater part of all the humidregion of the United States show lime deficiency. Formerly, acidity wasassociated in our minds with wet, low-lying land, but within the lasttwenty years we have learned that it prevails in light seashore sandsalong the Atlantic shore, in clays, loams and shales stretching to theAppalachian system of mountains, on top of mountain ranges and acrossfoothills to our central states, and through them in stretches to thesemi-arid lands of the west. While not all this land has fallen into thelime-deficient class, and the great part of some states remainsalkaline, the tendency toward acidity is continuous. 

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

_Causes of Soil Acidity. _ If any discussion of the causes of soilacidity would delay a decision to apply lime where needed, the timegiven to such discussion would be worse than wasted. It is much moreimportant to be able to detect the presence of harmful acids and toneutralize them than it is to know why the soil should be in such plightthat it could not supply the required lime and had become dependent uponits owner for assistance. On the other hand, some of us find itdifficult to accept a fact without seeing a reason for it, and we may dowell to consider several causes that may be at work to put a soil out ofthe alkaline class. 

_Leaching. _ One cause that appears obvious and easy of acceptance isleaching. In the case of one Pennsylvania farm, lying in a limestonevalley, the lime had been washed out by action of water so freely thatcaverns formed under the surface, and a test showed a marked deficiencyin the top soil. This land ceased to grow clover, and plantain andsorrel abounded. This case, which is not an isolated one, showed anunusually rapid loss, but we always expect to find the water from wellsand 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 thenature of the soil. We may place undue emphasis upon this factor, asother causes are at work, but leaching is a leading source of loss. 

_Chemical Compounds. _ A serious cause of lime exhaustion that is beingstudied by soil chemists is the presence of compounds in the soil thatcombine with the lime and rob it of ability to serve the soil when newacids form. The practical farmer accepts the statements of the chemistson this point, and probably would not have his interests served by anyexact knowledge of the nature of these agents. 

_Decaying Vegetation. _ A cause of acid conditions that is widely knownand accepted, and that may therefore stand out in our thinking withundue prominence, is connected with the decay of green vegetable matterin the soil. Many of us have seen fields rendered temporarilyunproductive by the plowing down of a mass of immature plants inmidsummer. All organic matter, indeed, in its decay makes a draft uponthe 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 isa considerable item, but our interest is in the form of lime that cancorrect soil acidity, and we know that compounds of lime that areworthless for this purpose may be the chief source of the lime in ourcrops. A determination of the lime in the ash of a crop does not givedata of much practical value. 

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

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

CHAPTER IV

EVIDENCES OF ACIDITY

_Character of Vegetation. _ The character of the original forests isdetermined much by the lime-content, and the practical man, when buyinga farm, rates its productive power by the kinds of timber it hasproduced. The black walnut, ash, shellbark hickory, black and white oak, sturdily grown, evidence a soil rich in lime, while the pines, smallblackjack and post oaks, and the chestnut are at home in non-calcareoussoils. 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 thesurface soil may have lost enough lime to limit crop productionmaterially while the trees continue to find in the subsoil all that theyneed. It does not follow that the land has gone down in value to thenaturally lime-deficient class, but its power to produce is impaired, and will remain so until there has been restoration of its originalalkaline state. 

_Sorrel and Plantain. _ We determine quite surely the state of the soilby observance of the vegetation that roots in the surface soil and theimmediate subsoil. Sorrel is a plant popularly associated with soilacidity, but this is not through any dislike for lime. It has beenobserved growing in the edge of a heap. Its presence suggests aciditybecause it can thrive in a sour soil that will not produce plants ofvalue which on even terms could crowd the sorrel out. There is constantcompetition among plants for food and water and space, and some of ourworst weeds are not strong competitors of clover and grass where soilconditions are not unfavorable to the latter. 

Blue grass, the clovers and timothy give a good account of themselves ina contest with sorrel and plantain where lime is abundant. This does notmean that the seeds of these weeds may not be so numerous that anapplication of lime cannot cause the clover and grasses immediately totake the ground to the exclusion of other plants, but it is true thatthe crowding process will continue until the time comes in the croprotation that these weeds cease to be feared, and clean sods can bemade. It is the absence of lime that permits such weeds to maintaintheir reputation for good fighting qualities. 

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

[Illustration: Effect of Finely Pulverised Limestone on Clover in a SoilHaving a Lime Requirement of 5200 Pounds of Limestone per Acre at thePennsylvania Experiment Station]

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

The prevalence of alsike clover in a farming region is indicative oflack of lime. This clover thrives in a calcareous soil, but is moreindifferent to a small lime supply than is the red clover. As red cloverseedings begin to fail, the alsike gains in popularity, and where a soilis decidedly sour the alsike is most in evidence. The latter has lessvalue to the farmer, rooting nearer the surface of the soil, and makingless growth of top, but it has gained in favor with farmers as soilacidity 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 ismarked. Rhode Island Bent, known as redtop, is less exacting, and whereit thrives to the exclusion of timothy, or is in evidence in grasslands, the inference is fairly safe that a test would show that the soilis sour. 

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

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

CHAPTER V

TESTS FOR ACIDITY

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

A small quantity of the soil to be tested is moistened with rain ordistilled water and placed on this paper. If the acid is present theblue paper will be changed to a reddish color, varying in intensityaccording to the degree of acidity in the soil. Two objections to theuse of litmus paper are to be noted: One of these is that the red colormay be produced by carbonic acid gas without a trace of more powerfulacids being present, and this may give a wrong impression to theoperator. Another objection to the use of litmus is that the degree ofacidity is not accurately indicated, and therefore the farmer issometimes at a loss to know just how much lime should be applied to makesoil conditions favorable for growing crops. 

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

One of the simplest and most accurate tests to date is that devised byProfessor E. Truog of the agricultural experiment station of theUniversity of Wisconsin. This test not only detects positively thepresence of soil acidity, but also gives definite information as to thedegree of acidity. The test is based upon the principle that when zincsulfid comes in contact with the acid, hydrogen sulfid gas is formed, and when this gas comes in contact with lead acetate, lead sulfid, ablack chemical, is formed. 

The method of making this test is simple, and consists in placing ameasured quantity of soil in a flask, to which is added a solutioncomposed of 20% calcium chlorid and 2% zinc sulfid. The mixture of soiland chemical solution is heated to the boiling point by means of analcohol lamp, and the boiling continued for a minute for the purpose ofdriving off the carbonic acid gas, which is liberated first. The boilingis continued and a piece of moistened paper, previously impregnated withlead acetate, is placed over the mouth of the flask. If the soilcontains acid, a chemical reaction occurs between it and zinc sulfid, and hydrogen sulfid gas is liberated. The quantity of acidity in thesoil determines the quantity of gas which comes in contact with the leadacetate paper, and this determines the depth of color produced on thepaper. A slight brownish color indicates the presence of very littleacidity, while an intense black signifies the presence of injuriousamounts of acidity. There are various degrees of coloration betweenthese two extremes, and each gives an accurate indication as to thequantity of lime required to correct the acidity. 

This test is simple and inexpensive, and at the present time most countyagent offices are equipped with this apparatus or a similar one fortesting soils for farmers. Some newer methods are being devised, anddoubtless this method will be improved upon as time passes, but theTruog test has qualities of accuracy and simplicity which will alwaysmake it valuable. 

CHAPTER VI

SOURCES OF LIME

_Nature's Provision. _ Soils are composed of pulverized stone and organicmatter. Much of the original stone contained little lime, and the humanrace would become nearly helpless if there were no stores of supply inthe form of limestone, chalk, marl, etc. The day would come when thesurface soil could not produce our staple crops if its loss of limecontinued, and a means of replenishing the stock were not at hand. Thehuge deposits of limestone that have not been disintegrated by processesof weathering are assurance that the soil's need can be met forever. Thecalcium and magnesium in the stone are in chemical combination withcarbonic acid forming carbonates, and there is an additional mixture ofother earthy material that was deposited by the water when the stone wasbeing formed, but much limestone possesses an excellent degree ofpurity. 

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

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

_Confusion Respecting Forms. _ In the public mind there is much confusionrespecting the sources and forms of lime most to be desired. Woodashes appealed to people, especially in an early day in our agriculture, partly because the ashes were so universally present that tests had beenmade voluntarily and otherwise in millions of instances. The value ofsuch tests had been obscured by the fact that the ashes containedpotash, and much of the credit of any good effect was attributed to thatfact. It has been generally known, however, that lime in peculiarlyeffective form is in wood ashes, and the favor in which ashes have beenheld rested not a little upon the curious preference for an organicsource of all soil amendments. This is seen in the case of directfertilizers. 

_Dealers' Interests. _ The doubts regarding the wisdom of selecting anyone form of lime for the betterment of soil conditions have beenpromoted very naturally by the conflicting interests of men who wouldfurnish the supply. Some dealers in fresh burned lime have asserted thatit was folly to expect any appreciable result from the use of unburnedlimestone. The manufacturer of ground limestone has pointed out thepossibility of injuring a soil by the use of caustic lime, andoftentimes has so emphasized his point that farmers have becomeunwilling to apply fresh or water-slaked lime to their land. Manufacturers of hydrated lime in some instances have made a confusedsituation worse by insisting upon the claim that there was a fertilizingquality in their goods. Some dealers in lime marls have been unwillingto have the value of their goods rated according to the content ofcarbonate of lime, and have emphasized the value of fine division of theparticles and the absence of any caustic properties. The presence ofshells, evidencing an organic source of the material, has helped in theappeal to buyers. 

The rightful place of magnesia, and the possible danger of injury fromits use, have been a fruitful cause of perplexity, making price per tononly a secondary consideration to the man wanting to supply his soil'sneeds. 

_Scientists' Failure to Agree. _ It is only fair to say that much of thedoubt and indecision on the part of the public is directly attributableto the conflicting statements of our scientists. It should be borne inmind that careful investigation in respect to the relative values ofthe various forms and sources of lime has been confined largely to theshort period of time that has elapsed since recognition of the limedeficiency of our country's soils. Our agricultural literature containedlittle about soil acidity 20 years ago, and our experiment station testsafford only relatively recent results. Some knowledge of sour soils andthe efficacy of lime in their amendment is nearly as old as the historyof agriculture, it is true, but answers to the questions uppermost inthe minds of men wanting to apply lime to land have been sought onlywithin recent years. The variation in soil types, and in sources oflime, and in preconceived ideas of men drawing conclusions fromincomplete data may easily account for failure of our soil scientists tobe in the close agreement in statement that would remove all confusionin the public mind. However, the agreement respecting the facts isbecoming better assured with every added year of investigation, as astudy of station bulletins shows. 

CHAPTER VII

DEFINITIONS

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

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

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

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

_Calcium Oxide_ is a compound left after the burning of limestone, andis known as fresh burned lime, or quick lime. Its formula is CaO. Itcontains, 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 definitecomposition, containing, when pure, 56 parts CaO and 44 parts CO2. Itis known to the chemist as CaCO3, and forms practically all of verypure limestones. Impure limestones contain some earthy materials thatbecame mixed with the lime carbonate when the rock was being formed. 

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

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

_Magnesian Limestone. _ Magnesium carbonate is usually found incombination with calcium carbonate, and when about 47 per cent of thetotal carbonates is magnesium carbonate, the limestone is known asdolomite. 

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

_Fresh Burned Lime_. Calcium oxide (CaO) formerly was accuratelydesignated as "lime, " but the words "fresh burned" are often prefixed toprevent 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, sothat it can be spread on land without slaking. This product should notbe confused with ground limestone or hydrated lime. Fresh ground lime isworth nearly twice as much per ton as ground limestone, but some of theproduct on the market is far from pure. There is opportunity to grind upunburned and waste material with the caustic lime, and this form of limeusually contains some hydrated material. 

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

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

[Illustration: An Indiana Limestone Quarry]

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

CHAPTER VIII

GROUND LIMESTONE

_Variation in Quality. _ Limestones vary widely in purity. They wereformed under water, and clay and sand were laid down with the lime insuch quantity in some cases that the resulting stone is not worthhandling for soil improvement. A stone that is practically all carbonateof calcium, or a combination of calcium and magnesium, is wanted becauseit is these two elements that give value to the material. If a poorstone is used, too much waste matter must be handled. Twenty-five percent more ground limestone of 80% purity must be applied than would berequired in the case of an absolutely pure limestone. Any stone above90% pure in carbonate of lime and magnesia is rated as good, but thebest stone runs from 96% to 99%. 

Limestones vary greatly in ability to resist disintegration, and thisvariation is a big factor in determining the agricultural value ofground limestone that has not been reduced to a fine powder. Particlesof a hard limestone may lie inert in the soil for many years. Hardnessalso affects the cost of grinding. 

_A Matter of Distribution. _ Nature has used various agencies in reducinglimestone for the making of soils. The stone contained its lime incarbonate form, and when reduced to good physical condition fordistribution it helped to make highly productive land. We know that limecarbonate does the needed work in the soil so far as correction ofacidity is concerned, but in the form of blocks of limestone it has noparticular value to the land. Burning and slaking afforded to man anatural means of putting it into form for distribution, and it is onlywithin recent years that the pulverization of limestone for land hasbecome a business of considerable magnitude. The ground limestone usedon land continues to be in part a by-product of the preparation oflimestone for the manufacture of steel, glass, etc. , and the making ofroads, the fine dust being screened out for agricultural purposes. Thesesources of supply are very inadequate, and too remote from much landthat requires treatment. Large plants have been established in variousparts of the country for the purpose of crushing limestone for use onland, and quite recently low-priced pulverizers for farm use have comeupon the market and are meeting a wide need. 

_Low-Priced Pulverizers. _ A serious drawback to the liming of land isthe transportation charge that must be paid where no available stone canbe found in the region. Great areas do have some beds that should beused, and a low-priced machine for pulverizing it is the solution of theproblem. Such a machine must be durable, have ability to crush the stoneto the desired fineness and be offered at a price that does not seemprohibitive to a farmer who would meet the demands of a small farmingcommunity. In this way freight charges are escaped, and a long andcostly haul from a railway point is made unnecessary. The limestone ofthe locality will be made available more and more by means of this typeof machine, and the inducement to correct the acidity of soils will begiven to tens of thousands of land-owners who would not find it feasibleto pay freight and cartage on supplies coming a long distance. Thereshould be a market many times greater than now exists for the productof all large plants, while the number of small pulverizers multipliesrapidly. The very large areas that have no limestone at hand mustcontinue to buy from manufacturers equipped to supply them, and farmerswithin a zone of small freight charges should be able to buy from suchmanufacturers more cheaply than they could pulverize stone on their ownfarms. 

An individual, or a group of farmers, will buy a machine for pulverizinglimestone at a cost of a few hundred dollars when costly equipment wouldbe 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 orpulverizer solves the problem and makes prosperity possible to theregion. Within the last few years much headway has been made inperfecting such machines, and their manufacturers have them on themarket. Any type should be bought only after a test that shows capacityper hour and degree of fineness of the product. As a high degree offineness is at the expense of power or time, and as the transportationcharge on the product to the farm is small, there is no requirement forthe fineness wanted in a high-priced article that must be usedsparingly. 

The aim should be to store in the soil for a term of years, and thecoarse portion is preferable to the fine for this purpose because itwill not leach out. The heavy application will furnish enough fine stuffto take care of present acidity. If nearly all the product of such apulverizer will pass through a 10-mesh screen, and the amount applied isdouble that of very fine limestone, it should give immediate results andcontinue effective nearly twice as long as the half amount of finermaterial. There could hardly be a practical solution of the limingproblem for many regions without the development of such devices forpreparing limestone for distribution, and it is a matter ofcongratulation that some manufacturers have awakened to the marketpossibilities our country affords. 

CHAPTER IX

STORING LIME IN THE SOIL

_Liberal Use of Limestone. _ Land never does its best when skimped in anyway. As we raise the percentage of carbonate of lime in land thatnaturally is deficient, we give increasing ability to such land to takeon some of the desirable characteristics of a limestone soil. It is poorbusiness to be making a hand-to-mouth fight against a state of actualacidity unless the cost of more liberal treatment is prohibitive. Themost satisfactory liming is done where the expense is light enough tojustify the free use of material. When this is the case, extremefineness of all the stone is undesirable. There is the added cost due tosuch fineness and no gain if the finer portion is sufficient to correctthe acidity, and the coarser particles disintegrate as rapidly as neededin later years. 

_Loss by Leaching. _ Another valid argument against extreme fineness ofthe stone used in liberal applications is the danger of loss byleaching. Soils are so variable in their ability to hold what may begiven them that it is idle to offer any estimate on this point. Theamount of lime found in the drainage waters of limestone land teaches nolesson of value for other land, the excessive loss in the former casebeing due oftentimes to erosion that creates channels through thesubsoil, through which soil and lime pass. 

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

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

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

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

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

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

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

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

_New York State Experience. _ A bulletin of the New York agriculturalexperiment station, published early in 1917, calls attention to therapid increase in demand for ground limestone in New York. Within thelast five years the number of grinding plants within the state hadincreased from one to 56, and more than a dozen outside plants areshipping extensively into the state. The bulletin says: "Farmers whohave had experience with the use of ground limestone are as a rulesatisfied with only a reasonable degree of fineness, and are able tojudge the material by inspection. When limestone is ground so the entireproduct will pass a 10-mesh (or 2 mm. ) sieve, the greater part of itwill be finer than a 40-mesh (or 1/2 mm. ) sieve. . . . There are now inoperation in this State more than a dozen small portable communitygrinders; they are doing much to help solve the ground limestone problemand their use is rapidly increasing. In the practical operation of thesemachines they grind only to medium fineness (2 mm. ). To insist uponextreme fineness is to discourage their use. "

This State experiment station is only one of many scientific authoritiesapproving the use of limestone reduced only to such fineness that itwill pass through a 10-mesh screen, the cost of the grinding beingsufficiently small to permit heavy applications. 

CHAPTER X

FRESH BURNED LIME

_An Old Practice. _ The beneficial effect of caustic lime on land ismentioned in some ancient writings. Burning and slaking afforded theonly known method of reducing stone for use in sour soils. Lime in thisform not only is an effective agent for correcting soil acidity, but itimproves the physical condition of tough and intractable clays, rendering them more friable and easy of tillage. Caustic lime alsorenders the organic matter in the soil more quickly available, anincrease in yield quickly following an application. These three effectsof burned lime brought it into favor, and a rational use would havecontinued it in favor. 

_Irrational Use. _ The ability of caustic lime to improve the physicalcondition of land and to make inert plant food available has led manyfarmers to treat it as a substitute for manure, sods and commercialfertilizers. Immoderate use gave increased crop yields for a time, andthe inference was easy that lime could displace the old sources ofplant food supplies. It became the custom in some regions to apply 200to 300 bushels per acre to stiff limestone soils that had no limedeficiency, as a test for acidity would have shown. The lime not onlymade some mineral plant available, but it attacked the organic matter ofthe soil, making it ready for immediate use and leaving the landdeficient in humus. Wherever stable manure and clover sods were notfreely used, the heavy application of caustic lime was followedultimately by decline in productive power. Such practice has come underthe condemnation of people who have not seen that the ill results haveno relation to the rational use of lime. 

_What Lime Is. _ There is abundant evidence that pulverized limestone, orlime 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. , tomake a choice limestone soil, or man applied it. Fresh burned lime isonly the stone after some worthless matter has been driven off by use ofheat. The limestone, carbonate of lime, is represented by the formulaCaCO_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, 44pounds would escape in form of the carbon dioxide, which had no value, and 56 pounds would remain. The 56 pounds calcium oxide, or fresh burnedlime, have the same power to correct acidity as this same material hadwhen it was bound up in the 100 pounds of limestone. The 44 pounds weredriven off by heat, while if the limestone had not been burned the 44would have separated from the 56 pounds in an acid soil, leaving theactual lime to do the needed work of correcting acidity. 

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

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

We are naturally so lacking in judicial temper that opinion has swungviolently from favor to disfavor. As most soils need organic matter, weseize upon the thought that anything evidently inclined to use it up isan evil. The purpose of tillage is in no small degree to bring aboutdisintegration and resulting exhaustion of vegetable matter. The latteris a storehouse of plant food, and some of it is needed to feed the cropdesired. Tillage is no more to be commended for this purpose than aquantity of lime equivalent in power to do the needed work. Exceptingthe case of raw soils rich in the remains of plants, most land hardlyneeds lime for this purpose, it may be, the tillage required for makinga seed bed retentive of moisture and for control of weeds beingeffective, but the point is emphasized that the disintegration oforganic matter into available plant food is one of the chief aims of agood farmer. It is only the excessive use of caustic lime that causesloss. 

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

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

[Illustration: A Stack Nearly Completed at the Pennsylvania ExperimentStation]

CHAPTER XI

BURNING LIME

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

The devices for burning are various, a modern lime plant containingimmense kilns, cylindrical in form, the stone being fed into them at thetop continuously, and the lime removed at the bottom. A large part ofthe 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 alimestone country finds few such kilns now in use. 

_The Farm Lime Heap. _ A common method of producing lime for farm usehas been, and continues to be, a simple and inexpensive one, involvingthe use only of wood, coal and limestone, with earth as a covering. Dr. Wm. Frear, chemist of the Pennsylvania station, in Bulletin 261 of thePennsylvania department of agriculture, describes a method of burninglime on the farm as follows: "A convenient oblong piece of ground iscleared, and leveled if need be, to secure a fit platform. Upon thislevel is placed a layer or two of good cord wood, better well seasoned, arranged in such manner as to afford horizontal draught passages intothe interior of the heap. Between the chinks in the cord wood, shavings, straw or other light kindling is placed. The stone having been reducedto the size of a double fist, sometimes not so small, is laid upon thecord wood, care being taken to leave chinks between the stones just asbetween the bricks in a brick kiln. It is preferred that this layer ofstone 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 eachend, and the stone and coal are built up around them; thus, when theyare burned out, a chimney or two is secured, which may be damped bypieces of stone or sod. Upon this first layer of stone is spread a layerof 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 notnear the outside, so that they may be exposed to the highest heat. Theproportion of coal is diminished in the upper layers, the effort beingto distribute one-half of the total coal employed in the two lowerlayers, so as to secure the highest economy possible in the use of thefuel. 

"Fire is then kindled in the straw or shavings; when the flames havecommunicated themselves to the cord wood and lowermost layer of coal, and tongues of flame shoot out from the crevices in the sides of theheap, earth, previously loosened by a few turns of the plow about theheap, is rapidly spread over the entire heap, thus damping the draftsand retarding the combustion. Steam and smoke slowly escape during thefirst hours, but later the entire heap, including the outer covering ofearth, is heated to a dull red glow. The burning goes on slowly forseveral days, the interior often being hot for several weeks. When thelower portion of the heap has reached an advanced stage of calcination, a portion of the outer layer of lime sometimes slips down; if so, afresh 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 othersides will fail of proper calcination. "

[Illustration: Effect of Excessive Use of Burned Lime Without Manure atthe 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 acondition that makes even distribution upon land possible is by slaking. A few years ago considerable effort was made to create a market for limepulverized by machinery, but the difficulty in excluding the moisture ofthe air so that packages would not burst has been in the way ofdeveloping a market. Slaking, by the addition of water to the freshburned lime, is the common method of getting the required physicalcondition. When the slaking is done on the farm, the custom has been todistribute the lime in small piles in the field, placing the piles atsuch convenient distance apart that the lime, after slaking, could bespread easily with a shovel. 

The water for slaking comes from rains, or from moisture in the air andearth. The method is wasteful and can be justified, if ever, only wherefarm-burned lime costs little per ton, and the nature of the soil issuch that a relatively heavy application can be safely made. Thedistribution is necessarily uneven, and if the required amount goes uponall the surface, a great excess is sure to go upon a portion of it. Veryoften an excess of water puddles much of the lime in the pile, and lumpsmay be seen lying in ineffective form in the soil for years. Thepractice is responsible for much of the excessive application thatbrought the use of caustic lime into disrepute. 

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

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

_Degree of Purity. _ It is always a reasonable assumption that hydratedlime 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 judgmentwould erect a costly plant for burning and hydrating lime where thepurity of the stone would not afford a good advertisement in itself. 

On the other hand, we find very little hydrated lime on the market thathas not had sufficient exposure to the air to become changed in somepart 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 itcannot correct as much soil acidity, and the percentage of the formercannot be determined by the buyer. Its presence may not be due to anywrong-doing of the manufacturer, and, on the other hand, the increase inweight that attends air-slaking may be welcomed in some degree by adishonest manufacturer before the goods are shipped. The difficulty inpreventing hydrated lime from adding to its weight by becomingair-slaked is a point to be taken into consideration. 

The percentages of air-slaked material in hydrated limes are widelyvariable, and no manufacturer can standardize his product on the marketsurely for the benefit of the farmer. In some instances the product isadulterated with refuse material in finely pulverized condition. 

CHAPTER XIII

OTHER FORMS OF LIME

_Air-Slaked Lime. _ A pure limestone is a carbonate, and the chemicalformula is CaCO_3. When it is burned, the carbon dioxide (CO_2) isdriven off, leaving CaO, which is calcium oxide, called fresh burnedlime. In this process 44 pounds of a stone weighing 100 pounds passesinto the air, and there remain 56 pounds of lime. When it air-slakes, ittakes back the carbon dioxide from the air, and the new product becomesCaCO3, or carbonate of lime, and regains its original weight of 100pounds. This is what would happen if the process were complete, and itis nearly so when the exposure to the air is as perfect as possible. 

Fifty-six pounds of valuable material are in the 100 pounds ofair-slaked lime, just as is the case with limestone, and there is nodifference in effectiveness except in so far as the air-slaked materialis absolutely fine and available, while most pulverized limestone isless so. In making purchase for use of land the buyer cannot afford tomake 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 conditionslowly unless it has full exposure. Old heaps will remain in hydrateform 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 weightwould be added in the slaking, and therefore the value per ton would bereduced. The slowness with which air-slaking proceeds gives reason toexpect that any bulk of old lime may contain a considerable percentageof the hydrate, and therefore have greater strength than a truecarbonate like limestone. This is a consideration of value to a buyer. 

_Agricultural Lime. _ Some manufacturers have found in the demand forlime by farmers an opportunity of disposing of much material that wouldnot be satisfactory to manufacturers and builders. In some cases thisso-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 coresof kilns are ground up, the material simply retains the value ofunburned 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 avaluation given it that would be true for another lot. 

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

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

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

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

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

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

_Wood Ashes. _ A large supply of lime in excellent form was afforded byhardwood ashes, but this product has ceased to have any important valueto our agriculture. The chief supply on the market is low in quality, containing moisture and dirt in considerable amount, the form of limebeing 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 amixture of slaked lime, or calcium hydrate, and carbonate of lime, together with sulfites and sulfides of lime. These last are injurious toyoung plant life, and gas lime should be applied long before the crop isplanted, or at least exposed to the air some time before itsapplication. The action of air converts the poisonous substances in itinto non-injurious products. Gas lime contains on an average 40% ofcalcium oxide, and usually a small percentage of nitrogen. "

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

CHAPTER XIV

MAGNESIAN LIME

_Magnesium. _ As an element of plant food, magnesium is as essential ascalcium. It leaches out of the soil less readily, and there may be evenless need of its application as a plant food, though the need of calciumapplications for this purpose is assumed to be small. In the correctionof soil acidity magnesium is more effective than calcium, 84 pounds ofthe carbonate being equal to 100 pounds of calcium carbonate. It is acurious fact, however, that there is widespread fear of magnesium as asoil amendment. This is not traceable to any considerable experience bypractical farmers that inspires caution in its use, although immensequantities of magnesian limestone and lime have been used. Neither is itdue to any weight of evidence against it in the experience or teachingsof soil chemists and experiments. The facts of the case appear to be asfollows:

1. An investigator found in his laboratory that a plant growing in awater solution was injured when magnesium was added, and that theinjury 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 totalamount of magnesium than of calcium, and as the soil's supply of calciumtends to leach out more readily than the supply of magnesium, it wasbest to use a high-calcium lime. If this discovery of the laboratory hadbeen carried into the field, its significance would have dwindled tozero in the case of normal soils, and a lot of exploitation would havebeen rendered impossible. As it was, the discussion went merrily alonguntil it occurred to some one to test the matter in the soils whereplants grow, and one would now hear little of it if commercial interestswere not at stake. 

2. Very much of our limestone supply is high in magnesium, and some menwho have limestone very low in magnesium and high in calcium have done agood stroke of business for themselves by deepening the public'simpression, due to laboratory tests with water cultures, that magnesiumin lime is injurious. 

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

_The Fact's Importance. _ If every farm could get its supply of purecalcium lime as cheaply as it can have magnesian lime, the truthrespecting the value of the latter would have small agriculturalimportance, but as a great bulk of farm and commercial supplies of limeis magnesian, financial injury has been done consumers who have paidmore than should have been paid for relatively pure calcium lime andlimestone, being afraid to use goods whose content of magnesium was notsmall. It is poor policy to use either kind of burned lime in greatexcess, but when rationally used on all soils except sandy ones, thereis no preference to be exercised that can be based upon performance. Amagnesian lime corrects as much acidity as a high calcium lime, and alittle more, and its use is to be recommended if there is any advantagein the matter of price, except in the case of distinctly sandy soils. 

_Magnesian Limestone. _ Leading scientists making tests of limestone fornormal soils, use magnesian limestone freely. They recommend its use tofarmers wherever there is advantage in point of price. The advice issafe that the limestone of a given fineness should be chosen whose totalpercentage of carbonates of calcium and magnesium is the highest. Theexample of these scientists, buying pulverized limestone foragricultural colleges and experiment farms, and for their own farms, should loosen the curious hold that the early warnings of a laboratoryexperimenter took upon public imagination. The farmer should buylimestone on a basis of ability to correct soil acidity, and make eachdollar do the most possible toward that end. 

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

CHAPTER XV

WHAT SHALL ONE BUY?

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

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

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

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

_Even Distribution. _ The value of even distribution is not easilyoverestimated. If lime in proper amount does not go into each squarefoot of an acid soil, some of the soil will remain sour unless mixing isdone by implements of tillage. Lime is diffused laterally through thesoil in a very slight degree. If a strip of sour land is protected bycanvas, so that no dust from lime applied to uncovered land can blowupon it, a seeding to clover will show that plants a few inches from theedge of the limed area will fail to start thriftily and may die beforetheir roots reach the lime. Full effectiveness of an application ispossible only through even distribution. 

_Using Lump Lime. _ Lump lime, slaked on the farm, is difficult to applysatisfactorily. Spreading with a shovel from small heaps is badpractice, and when the lime is slaked in a large heap, it cannot behandled as well as pulverized stone or commercial hydrated lime. Thelatter two are in condition for application by means of a limedistributor, or even a fertilizer attachment of a grain drill. Thefarm-slaked lime contains impurities that interfere with distribution. 

_An Estimate. _ It is always hazardous to attempt an estimate of cost oflabor without knowing the particular farm conditions, but the expenseand discomfort attending the slaking and use of lime bought in lumpstate justify a willingness to pay as much for a ton of hydrated lime aslump lime would cost, although the former has only three-fourths as muchstrength as the latter. Some farmers pay nearly twice as much for thehydrated, partly to escape the inconvenience and partly because theyhope that the extraordinary claims for superiority made by some dealersmay prove true. They should know that it is only fresh burned limeslaked, but incline to credit a claim that special treatment enhancesvalue in some mysterious way. 

Comparing lump lime with finely pulverized limestone, the factors ofexpense and discomfort and final lack of perfect distribution of theformer remain important. The stone is relatively easy to handle, beingslightly granular and passing through a distributor without trouble. Thefact that it is not caustic, like the hydrated, is in its favor. Wheneverything is taken into account, one is justified in using limestone orair-slaked lime at a cost per ton three-fourths as great as that of lumplime. It is to be borne in mind that in these estimates the cost per tonis not that at the factory or at one's own railway station, but on thefarm. The freight and cartage to the farm are based on weight ofmaterial, and more material per acre is required when the worthlessportion has not been driven off by burning. If one must use one andthree-quarters tons of limestone to have the equivalent of one ton offresh burned lime, it is evident that the cost of freight and cartage ofthe worthless portion might make cost prohibitive if distances were verygreat. Farms lying a long distance from a railway station may easilyfind 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 timeof the year when teams are least busy upon other work, and it can beheld till wanted. In this way the cost of cartage to the farm may bekept relatively low, and the material is at hand when wanted, regardlessof rush of work or delays of railroads. This advantage is partialcounterbalance to the cost of freight on the worthless portion ofunburned stone. 

_Valuing Limestone. _ The estimates, so far as labor and convenience areconcerned, are merely suggestive, and rest upon the presumption that thestone is satisfactorily fine. It has been urged in another chapter thatimmediate effectiveness is determined by fineness, but as a workingbasis we assumed that when all the stone would pass through a screenhaving sixty wires to the inch it would give the desired results. Thecoarsest portion would not be available at once, but when an applicationis heavy enough to serve for a year or more, we have enough very finematerial in such a grade of stone to meet immediate need. Whenestimating values of such a grade and coarser grades, the amount peracre to be used is a factor. The coarse is unsatisfactory if the priceis not low enough to permit an application sufficient for a considerableterm of years, so that it will contain all the fine material needed atonce. In that case the coarser material may be expected to meet laterneed, and may be even more desirable for such purpose, as it would notbe subject to leaching. 

Coarse grinding costs much less than fine grinding, and it is theresulting low price that permits the heavy application. As stone variesin hardness and ability of the small particles to withstanddisintegrating forces in the soil, an estimate of the difference inprice between a 60-mesh limestone and a 10-mesh one could not serve as asafe guide. The buyer should know the percentages of a limestone passingthrough screens of various sizes before he makes a purchase, and shoulddemand part of the saving in cost of production that attends coarsegrinding. 

_Oyster Shell. _ Ground oyster shell should be given about the samevaluation as limestone. It is a lime carbonate, and the percentage ofworthless material in it varies somewhat It is coarsely ground, but thelarge pieces disintegrate in the soil much more rapidly than limestonewould do. It contains a little nitrogen and phosphoric acid, partiallyavailable, as an offset to coarseness and some lack of purity, ascompared with the highest grade of fine stone. It is profitable to buyoyster shell at limestone prices if used liberally enough to furnish asupply for a term of years. The oxide, or burned shell lime, would benearly the equivalent of burned stone if it did not change to hydrateand 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 tooexpensive. The composition of ashes on the market is widely variable, dirt and moisture often accounting for much of the weight. The lime infresh burned ashes is peculiarly effective, being finely divided and inoxide form, but the ashes on the market have much of the limewater-slaked and air-slaked. Unless analysis is made at time ofpurchase, a buyer should not estimate the content of lime in a ton at avalue greater than assigned to one-half of a ton of limestone. Theadditional value of the ashes, due to the potash content, is whollyanother consideration. 

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

_Agricultural Lime. _ This variable product should not be bought unlessactual composition is known, or the cost is as low as that of pulverizedlimestone, and even then it may be a bad purchase, the methods of themanufacturer being the determining factor. If such lime is chiefly adumping place for low-grade stone and forkings, it has smallagricultural value. 

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

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

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

_Lime in Other Fertilizers. _ The demand for lime is leading some men tostate a lime content for their goods that is designed to mislead. Suchlime is not in a form to combine with soil acids, and is as valueless asthe very large amount of lime in acid soils that is in compounds havingno power to affect free acids. 

CHAPTER XVI

METHODS OF APPLICATION

_A Controlling Principle. _ The chief purpose of liming land is toprovide a base with which acid may combine, so that the soil may befriendly to plant life. Lime has little power to distribute itselfthrough a soil, and harmful acid may remain only a few inches distantfrom the point where lime has been placed. In a general way, thetendency of lime is downward, especially when the application at thesurface is heavy. Economical use demands even distribution through thesoil so that a sufficient amount is in every part. Means to that end aregood means of distribution. 

_Spreading on Grass. _ Where lime is burned on the farm, and littleaccount of labor is taken, it has been a common custom to spread thelime on grass sods the year previous to breaking the sod for corn, using100 to 300 bushels per acre. Rains carried some of the lime through thesoil, and the increased yields for a few years were due to the improvedphysical condition of a stiff soil that a heavy application ofcaustic lime produces, and to the disintegration of organic matter andto change in compounds of mineral plant food. The practice is rightlygoing 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 maybe made on grass land that should not be plowed, but the fulleffectiveness of an application is not secured in top-dressings. If theland is under a crop rotation, it is better practice not to apply thelime 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 mixedwith the soil before rain puddles it. In no case should it be ploweddown. 

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

_Distributors. _ The most satisfactory means of distribution is a machinemade for the purpose. A number of good distributors are on the market. They are designed to handle a large quantity of material after thefashion of a fertilizer distributor ordinarily attached to a graindrill. A V-shaped box, with openings at the bottom, and a device toregulate the quantity per acre, enables the workman to cover the surfaceof the ground with an even coat, and the mixing with the soil is done byharrows. 

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

_Farm-Slaked Lime. _ Lime slaked on the farm must continue to be aleading source of supply to land. If there is stone on the farm, andlabor 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 insecuring even distribution. The loss from spreading with shovels fromsmall piles slaked in the field is heavy. The quantity per acre must belarge to insure sufficient material for every square foot of surface. The lime slaked in a large heap can be put through distributors onlyafter screening to remove pieces of stone, unless they are made with ascreening device, and the caustic character and floury condition makehandling disagreeable, but no other method is as economical when lime ishigh in price. 

_Use of the Manure Spreader. _ The next best device is the manurespreader. The makes on the market vary in ability to do satisfactorywork 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 othermaterial in the spreader before filling with lime helps, but somespreaders do fair work in spreading as little as 3000 pounds of slakedlime per acre, and certainly far better work than usually is done withshovels from a wagon. 

CHAPTER XVII

AMOUNT OF LIME PER ACRE

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

_A Working Basis. _ If land has once been productive and in later yearsclover has ceased to grow and grass sods are thin, there is a strongprobability that liming will pay, and the experience of farmers onnormal soils, and the tests of experiment stations, justify theestimate that two tons of fine stone, or one and a quarter tons of freshburned lime per acre, can be used with profit. This amount probably willpermit fertilizers and tillage to make their full return in heavy sodsthat will provide humus. It is a reasonable expectation that theapplication 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 fouror five years may be reduced somewhat, and even a ton of stone givenonce in the crop rotation may fully meet the requirement. 

In the case of the normal soil that has ceased to grow clover, and doesgrow plants that are acid-resistant, it is better practice to secure arelatively low-priced supply of coarsely pulverized stone and applythree or four tons per acre, and thus lengthen the interval betweenapplications to eight or 10 years. The fine material in the heavyapplication will take care of present need, and the coarser particleswill 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 thereis reason to believe that it is much better to use such quantitieswithout question than to defer liming for a year in the hope that somemore definite knowledge of a particular field's needs may be secured. 

_Small Amounts Per Acre. _ There is much experience as a basis for theclaim that a few hundred pounds of burned lime per acre may have markedresults. Fields that indicated an actual lime requirement of a ton offresh lime per acre have had a test of 500 pounds per acre made instrips, and the clover later on was so superior to that which wasstruggling to live in the untreated portion that the light applicationappeared almost to be adequate. In such land there cannot be fullbacterial activity or continuing friendliness to plants unless the needis met fully. A larger application would have paid better. It is thesoil rich in lime that can make the best response to tillage andfertilization. 

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

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

CHAPTER VIII

SPECIAL CROP DEMANDS

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

_Liming for Alfalfa. _ When all other conditions are right, alfalfathrives or fails according as a soil is rich in lime or is distinctlydeficient. It is entirely possible to get fair yields of this legume fora short time from land that is not fully alkaline, but full yields andability 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 hasbeen given some of the characteristics of such land by free use oflime. In the case of neutral or slightly acid ground it is good practiceto mix four tons of limestone per acre thoroughly with the soil. Suchtreatment gives greater permanence to the seeding, enabling the plantsto compete successfully with the wild grasses and other weeds that arethe chief obstacle to success in the humid climate of our Mississippivalley and eastern states. When this amount of stone is used, the finestgrade may not be preferred to material having a considerable percentageof slightly coarser grains. 

[Illustration: Remarkable Effect of Lime on Sweet Clover at the OhioExperiment 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 cloversatisfactorily while showing a decided lime deficiency. On the otherhand, much slightly acid land fails to grow clover, and an applicationof lime is followed by heavy growths. Red clover is most at home incalcareous soils, and lack of lime is a leading cause of clover failurein this country. Other causes may be important ones in the absence oflime and be overcome when it is present. 

_Alsike Clover. _ Most legumes like lime, and alsike clover is not anexception, but is far more acid-resistant than the red. It is lessvaluable, both for soil improvement and for forage, having an inferiorroot system, but has proved a boon to farmers in areas that have beenlosing the power to grow red clover. The custom of mixing red and alsikeseed has become widespread, and distinctly acid soils are marked in theclover flowering season by the profusion of the distinctive alsike bloomto the exclusion of the red. While there is acid-resistant power, thisclover responds to liming. 

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

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

_Crops Favored by Lime. _ Nearly all staple farm crops respond toapplications given acid soils. Corn, oats, timothy, potatoes and manyother crops have considerable power of resistance to acids, but giveincreased yields when lime is present. Liming is not recommended forpotatoes because it furnishes conditions favorable to a disease whichattacks this crop. When clover is wanted in a crop rotation withpotatoes, it is advisable to apply the lime immediately after the potatocrop has been grown, and to use limestone rather than burned lime. Mostkinds 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