Project Gutenberg's Right Use of Lime in Soil Improvement, by Alva Agee This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org Title: Right Use of Lime in Soil Improvement Author: Alva Agee Release Date: May 8, 2008 [EBook #25389] Language: English Character set encoding: ISO-8859-1 *** START OF THIS PROJECT GUTENBERG EBOOK RIGHT USE OF LIME IN SOIL *** Produced by Steven Giacomelli, Janet Blenkinship and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images produced by Core Historical Literature in Agriculture (CHLA), Cornell University) Applying Lime Applying Lime Right Use of Lime In Soil Improvement By ALVA AGEE Secretary New Jersey State Department of Agriculture Formerly director of agricultural extension in the Pennsylvania State College and New Jersey State College of Agriculture. Illustrated NEW YORK ORANGE JUDD COMPANY LONDON KEGAN PAUL, TRENCH, TRUBNER & CO., LIMITED 1919 Copyright 1919, by ORANGE JUDD COMPANY All Rights Reserved Printed in U. S. A. CONTENTS CHAPTER PAGE 1. Introduction 1 2. The Lime in Soils 4 3. Sour Soils 10 4. Evidences of Acidity 15 5. Tests for Acidity 20 6. Sources of Lime 24 7. Definitions 28 8. Ground Limestone 33 9. Storing Lime in the Soil 38 10. Fresh Burned Lime 44 11. Burning Lime 49 12. Lime Hydrate 53 13. Other Forms of Lime 57 14. Magnesian Lime 64 15. What Shall One Buy? 68 16. Methods of Application 78 17. Amount of Lime per Acre 82 18. Special Crop Demands 86 ILLUSTRATIONS Applying Lime Frontispiece 1. Clover and Timothy Unfertilized at the Pennsylvania Experiment Station Yielded 2,460 pounds per acre 10 II. Clover and Timothy with Lime alone at the 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 (Courtesy of the Michigan Limestone Company.) 33 XI. A Limestone Pulverizer for Farm Use (Courtesy of the Jeffrey Manufacturing Company, Columbus, Ohio.) 38 XII. A Lime Pulver in Operation (Courtesy of the Jeffrey Manufacturing Company.) 39 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 (Courtesy of the Palmer Lime and Cement Company, York, Pa. 53 XVII. Filling the Lime Spreader at the Ohio Experiment Station 78 XVIII. Lime Distributors 79 XIX. Remarkable Effect of Lime on Sweet Clover at the Ohio Experiment Station 86 XX. Sweet Clover Thrives When Lime and Manure are Supplied, Ohio Experiment Station 87 CHAPTER 1 INTRODUCTION There is much in the action of lime in the soil that is not known, but all that we really need to know is simple and easily comprehended. The purpose of this little book is to set down the things that we need to know in order that we may make and keep our land friendly to plant life so far as lime is necessarily concerned with such an undertaking. Intelligent men like to reason matters out for themselves so far as practicable, taking the facts and testing them in their own thinking by some truth they have gained in their own experience and observation, and then their convictions stay by them and are acted upon. The whole story of the right use of lime on land is so simple and reasonable, when we stick only to the practical side, that we should easily escape the confusion of thought that seems to stand in the way of action. The experiment stations have been testing the value of lime applications to acid soils, and the government has been finding that the greater part of our farming lands is deficient in lime. Tens of thousands of farmers have confirmed the results of the stations that the application of lime is essential to profitable crop production on their farms. The confusion is due to some results of the misuse of lime before the needs of soils were understood, and to the variety of forms in which lime comes to us and the rather conflicting claims made for these various forms. It is unfortunate and unnecessary. The soil is a great chemical laboratory, but exact knowledge of all its processes doubtless would enrich the farmer's vocabulary more than his pocketbook. We are concerned in knowing that lime's field of usefulness is broad in that it is an essential plant food and provides the active means of keeping the feeding ground of plants in sanitary condition. We want to know how it comes about that our soils are deficient in lime, and how we may determine the fact that they are deficient. We wish to know the relative values of the various forms of lime and how we may choose in the interest of our soil and our pocketbook. The time and method of application are important considerations to us. There are many details of knowledge, it is true, and yet all fit into a rational scheme that shows itself to be simple enough when the facts arrange themselves in an orderly way in our minds. Lime cannot take the place of nitrogen, nor phosphorus, nor any other of the essential plant foods. It is not a substitute for any other essential factor in plant growth. It would be folly to try to depend upon lime as a sole source of soil fertility. On the other hand, we have learned very definitely within the last quarter of a century that it is foolish to depend upon commercial fertilizers and tillage and good seeds for full production of most crops from great areas of our farming [Pg 1] [Pg 2] [Pg 3] country that have a marked lime deficiency. The obvious need of our soils is the rich organic matter that clover and grass sods could furnish, and their fundamental need is lime. Most farms cannot possibly make full returns to their owners until the land's hunger for lime has been met. The only question is that regarding the best way of meeting it. CHAPTER II THE LIME IN SOILS Limestone Land. Soil analyses are serviceable only within certain limits, and in the case of the normal soils that comprise the very great part of the entire humid region of the United States the practical man gives little heed to what special analyses might show him when deciding upon the purchase of a farm. He does know, however, that a limestone soil has great natural strength, and recovers from mistreatment more readily than land low in lime. It has staying powers, and is dependable, unless through natural processes the lime leaches out or loses availability. All limestone areas have gained reputation for themselves as producers of grain and grass. Other Calcareous Soils. It is not only the limestone areas that stand high in esteem. There are types of soil with every varying percentage of lime down to clear sand or to peat, and some of the types are finely calcareous, containing such a high percentage of lime that nothing more could be desired. The actual percentage is not the determining factor, a clay soil needing greater richness in this material than a loam, and a sandy soil giving a good account of itself with an even less total content of lime, but in its way the particular soil type must be well supplied by nature with lime if its trees and other vegetation bear evidences of its strength and good agricultural value. Natural Deficiency. It is interesting to note the differences in evidences of prosperity that are associated with lime percentages. The areas that are able to produce the vegetation characteristic of calcareous soils are obviously the most prosperous. The decidedly lime-deficient sections, advertising their state by the kind of original timber, and later by unfriendliness to the clovers, do not attract buyers except through relatively low prices for farms. Such areas are extensive and have well marked boundaries in places. It does not follow that every farm in such limestone valleys as the Shenandoah, Cumberland, and Lebanon, or in the great corn belt having a naturally calcareous soil, is prosperous, or that a multitude of owners of such lime-deficient areas as the belt in a portion of southern New York and northern Pennsylvania, or the sandstone and shale regions of many states, have not overmatched natural conditions with fine skill. We treat only of averages when saying that a "lime country" shows a prosperity in its farm buildings and general appearance that does not come naturally and easily to any lime-deficient territory. In the latter a man rows against the current, and if livestock farming is not employed to furnish manure, and if the manure is not supplemented by tillage and drainage to secure aeration, or if lime is not applied, the land reaches such a degree of acidity that it loses the power to yield any profit. Nature's Short Supply. The total area of lime-deficient soil is large, comprising certainly much more than half of all the land east of the semi-arid belt of the United States. No small part of this area was not deficient at one time, as the nature of the original timber indicates, and it is well within the knowledge of practical men that land which once produced the walnut and ash and shellbark hickory can be brought back to productivity with reasonable ease after very hard usage. It has a good inheritance. It is a disconcerting fact in our American agriculture that, fertile as our country is as a whole, very great areas were so deficient in lime before they came under man's control that the chestnut, pine, and the oaks of mean growth were fully at home. The gradation from low lime content to high, and its relation to soil type, give us all sorts of mixtures of lime-loving and acid-resistant varieties of trees in original forests, but our agriculture is hampered by the high percentage of land for which nature made no great provision of lime, and on this land farming lags. Effect of Irrational Farming. Interest in liming might well have been due to the amendment of all this soil, but the rational use of lime that has been the subject of much study in the last quarter of a century concerns chiefly great areas that probably could have been kept in alkaline condition and friendly to the clovers for a long time despite a short natural supply as compared with the content of our limestone lands. The success of individual farmers in areas now admittedly acid as a whole is convincing on this point. Nature tries constantly to cure the ills of her soil through the addition of vegetable matter. An excess of water or a deficiency is atoned for in a degree by the leaves and rotted wood of her forests. Aeration is kept possible. The lime in the product of the soil goes back to it. A system of farming that involves the application of manure, thorough tillage, drainage where needed, and the free use of sods in some way, has kept portions of these non-calcareous soils out of the distinctly acid class. Clover grows satisfactorily, grass sods are heavy, and there is no acute lime problem. Such farms are relatively few in the great stretches of land now classed as acid soil, and probably the most of the lime that is being applied goes only on ground that once was sufficiently alkaline to grow the clovers. The loss of organic matter through failure to use the best methods of farming is responsible for no small part of the widespread need of lime today. This subtracts nothing from the urgency of its use to restore a condition favoring clover and grass sods, but it does teach a lesson of the highest value. The day of destructive soil acidity can be retarded by good farming, but in the long run the inevitable losses of lime from most soils must be met by [Pg 4] [Pg 5] [Pg 6] [Pg 7] [Pg 8] [Pg 9] applications. Limestone Soils. The old-time practice of making heavy applications of fresh burned lime to stiff limestone soils to make them friable, and to make their plant food available, led to disuse of all lime in some sections on account of the exhaustion that followed dependence upon these large amounts as a manure. Queerly enough, these original limestone soils have latterly been going into the acid class through loss of their distinctive elements, and they, too, have become dependent upon means for the correction of acidity. CHAPTER III SOUR SOILS Loss of Lime. Nature made the value of land as a producer of food utterly dependent upon the activity of lime, and at the same time gave it some power to shirk its work. In a normal soil is a percentage of lime that came from the disintegration of rock of the region or was transported by action of water on a huge scale. Possibly rarely would it be in insufficient amount to keep a soil in a condition friendly to plant life, and to feed the plant, if it stayed where nature placed it and kept in form available for the needs it was intended to meet. There is land that always was notably deficient in this material, and there is land that was known in the early history of the world's agriculture to be "sour," but the troubles of our present day in the case of the farming country in the humid region of the United States is less due to any natural absolute shortage than to combination that destroys value and to escape by action of water. Clover and Timothy Unfertilized at the Pennsylvania Experiment Station Yielded 2460 Pounds per Acre [Pg 10] Clover and Timothy with Fertilizer alone at the Pennsylvania Experiment Station Yielded 3900 Pounds per Acre Prevalence of Acidity. The results of experiment station and farm tests are conclusive that the soils of the greater part of all the humid region of the United States show lime deficiency. Formerly, acidity was associated in our minds with wet, low-lying land, but within the last twenty years we have learned that it prevails in light seashore sands along the Atlantic shore, in clays, loams and shales stretching to the Appalachian system of mountains, on top of mountain ranges and across foothills to our central states, and through them in stretches to the semi-arid lands of the west. While not all this land has fallen into the lime-deficient class, and the great part of some states remains alkaline, the tendency toward acidity is continuous. Crop production in great portions of the Mississippi valley is restricted by lack of lime in the soil, and some states to the eastward have one-half to nine-tenths of their acreage too low in lime for the best results. Calcareous soils have been losing their distinctive feature, and the immense areas of land naturally low in lime have remained hampered in ability to make full returns for labor, fertilizer and seed. It is this situation that brings the right use of lime on land to the front as a matter of fundamental importance to the farmer. Causes of Soil Acidity. If any discussion of the causes of soil acidity would delay a decision to apply lime where needed, the time given to such discussion would be worse than wasted. It is much more important to be able to detect the presence of harmful acids and to neutralize them than it is to know why the soil should be in such plight that it could not supply the required lime and had become dependent upon its owner for assistance. On the other hand, some of us find it difficult to accept a fact without seeing a reason for it, and we may do well to consider several causes that may be at work to put a soil out of the alkaline class. Leaching. One cause that appears obvious and easy of acceptance is leaching. In the case of one Pennsylvania farm, lying in a limestone valley, the lime had been washed out by action of water so freely that caverns formed under the surface, and a test showed a marked deficiency in the top soil. This land ceased to grow clover, and plantain and sorrel abounded. This case, which is not an isolated one, showed an unusually rapid loss, but we always expect to find the water from wells and springs in a limestone country strongly impregnated with lime. Drainage waters contain it. The draft by action of water is continuous, and in some types could easily account for sufficient loss to change the nature of the soil. We may place undue emphasis upon this factor, as other causes are at work, but leaching is a leading source of loss. Chemical Compounds. A serious cause of lime exhaustion that is being studied by soil chemists is the presence of compounds in the soil that combine with the lime and rob it of ability to serve the soil when new acids form. The practical farmer accepts the statements of the chemists on this point, and probably would not have his interests served by any exact knowledge of the nature of these agents. Decaying Vegetation. A cause of acid conditions that is widely known and accepted, and that may therefore stand out in our thinking with undue prominence, is connected with the decay of green vegetable matter in the soil. Many of us have seen fields rendered temporarily unproductive by the plowing down of a mass of immature plants in midsummer. All organic matter, indeed, in its decay makes a draft upon the lime content of the soil in which it may be buried. Removal in Crops. Lime is taken out of land by plants, and the loss is a considerable item, but our interest is in the form of lime that can correct soil acidity, and we know that compounds of lime that are worthless for this purpose may be the chief source of the lime in our crops. A determination of the lime in the ash of a crop does not give data of much practical value. Clover and Timothy with Lime Alone at the Pennsylvania Experiment Station Yielded 4900 [Pg 11] [Pg 12] [Pg 13] [Pg 14] Pounds per Acre Clover and Timothy with Fertilizer and Lime at the Pennsylvania Experiment Station Yielded 6290 Pounds per Acre CHAPTER IV EVIDENCES OF ACIDITY Character of Vegetation. The character of the original forests is determined much by the lime-content, and the practical man, when buying a farm, rates its productive power by the kinds of timber it has produced. The black walnut, ash, shellbark hickory, black and white oak, sturdily grown, evidence a soil rich in lime, while the pines, small blackjack and post oaks, and the chestnut are at home in non-calcareous soils. The latter class of lands gains nothing in lime as time passes, and the timber continues to be a sure index, but in the former class the surface soil may have lost enough lime to limit crop production materially while the trees continue to find in the subsoil all that they need. It does not follow that the land has gone down in value to the naturally lime-deficient class, but its power to produce is impaired, and will remain so until there has been restoration of its original alkaline state. Sorrel and Plantain. We determine quite surely the state of the soil by observance of the vegetation that roots in the surface soil and the immediate subsoil. Sorrel is a plant popularly associated with soil acidity, but this is not through any dislike for lime. It has been observed growing in the edge of a heap. Its presence suggests acidity because it can thrive in a sour soil that will not produce plants of value which on even terms could crowd the sorrel out. There is constant competition among plants for food and water and space, and some of our worst weeds are not strong competitors of clover and grass where soil conditions are not unfavorable to the latter. Blue grass, the clovers and timothy give a good account of themselves in a contest with sorrel and plantain where lime is abundant. This does not mean that the seeds of these weeds may not be so numerous that an application of lime cannot cause the clover and grasses immediately to take the ground to the exclusion of other plants, but it is true that the crowding process will continue until the time comes in the crop rotation that these weeds cease to be feared, and clean sods can be made. It is the absence of lime that permits such weeds to maintain their reputation for good fighting qualities. [Pg 15] [Pg 16] [Pg 17] Limed and Unlimed Ends of a Plot at the Ohio Experiment Station Limed and Unlimed Ends of a Plot at the Ohio Experiment Station Effect of Finely Pulverised Limestone on Clover in a Soil Having a Lime Requirement of 5200 Pounds of Limestone per Acre at the Pennsylvania Experiment Station The Clovers. Red clover can make growth in some soils that have a lime deficiency. If all other conditions are favorable, the lime requirement may exceed one-half a ton per acre of fresh burned lime and not affect the clover adversely, but farm experience throughout the country has demonstrated that when soil acidity is only slight and clover grows with difficulty, an application rarely fails to favor the clover in a marked degree. Experience has taught the land owners to fear soil acidity when red clover does not thrive where formerly it made good growth. The prevalence of alsike clover in a farming region is indicative of lack of lime. This clover thrives in a calcareous soil, but is more indifferent to a small lime supply than is the red clover. As red clover seedings begin to fail, the alsike gains in popularity, and where a soil is decidedly sour the alsike is most in evidence. The latter has less value to the farmer, rooting nearer the surface of the soil, and making less growth of top, but it has gained in favor with farmers as soil acidity has increased. The Grasses. Timothy is more resistant to acidity than red clover, but often fails to make a heavy sod where the deficiency in lime is marked. Rhode Island Bent, known as redtop, is less exacting, and where it thrives to the exclusion of timothy, or is in evidence in grass lands, the inference is fairly safe that a test would show that the soil is sour. When Production Decreases. It is not a matter of any moment to the owner of a productive soil whether or not his soil would give an acid or an alkaline reaction under test. Returns from his labor are satisfactory. Some land in this class is not strictly alkaline. The man most interested in the effects of lime applications is the one who is not satisfied with yields. The tests for acidity have been so many throughout our eastern and central states that the owner of land which is not productive has reason for the presumption that its percentage of lime is too low. There is danger of error, and a scientific test is surer, but in most cases the land which has been reduced from a fertile to an unproductive state has lost its alkaline nature. Naturally Thin Soils. Nature may be prodigal in supplies of nearly all the elements of plant food to land and yet skimp its supply of lime, but naturally poor soils are quite surely in the acid class. The exceptions in our humid region are not [Pg 18] [Pg 19] extensive. When improvement is planned for, involving additions of organic matter and plant food, the application of lime to correct acidity is the first requirement. If such land could be given the characteristics of a limestone soil so far only as the lime factor is concerned, the building up of fertility would be relatively easy. Liming must form the foundation of a new order of things. The ability to grow the clovers and to furnish rich vegetable matter to the soil, which naturally is poor in humus, rests upon lime application first, and then upon any supply of plant food that may continue to be lacking. CHAPTER V TESTS FOR ACIDITY The Litmus Paper Test. A method of testing soils for acidity, which has been in use for many years, is the simple litmus paper method. Because of its simplicity and fair degree of accuracy, the litmus paper test is still used to a considerable extent in estimating the degree of acidity of certain soils. The best manner of using litmus is to place a strip of the blue paper in the bottom of a glass saucer, covering it with filter paper or other paper which is neutral—that is, paper which is neither acid nor alkaline. A small quantity of the soil to be tested is moistened with rain or distilled water and placed on this paper. If the acid is present the blue paper will be changed to a reddish color, varying in intensity according to the degree of acidity in the soil. Two objections to the use of litmus paper are to be noted: One of these is that the red color may be produced by carbonic acid gas without a trace of more powerful acids being present, and this may give a wrong impression to the operator. Another objection to the use of litmus is that the degree of acidity is not accurately indicated, and therefore the farmer is sometimes at a loss to know just how much lime should be applied to make soil conditions favorable for growing crops. A More Accurate Method. Within the last few years improved methods for determining the presence of acidity in soil have been developed. Some of these are suitable only for the chemist with his complete laboratory equipment, while others are more simple and can be used by anyone willing to exercise reasonable care. One of the simplest and most accurate tests to date is that devised by Professor E. Truog of the agricultural experiment station of the University of Wisconsin. This test not only detects positively the presence of soil acidity, but also gives definite information as to the degree of acidity. The test is based upon the principle that when zinc sulfid comes in contact with the acid, hydrogen sulfid gas is formed, and when this gas comes in contact with lead acetate, lead sulfid, a black chemical, is formed. The method of making this test is simple, and consists in placing a measured quantity of soil in a flask, to which is added a solution composed of 20% calcium chlorid and 2% zinc sulfid. The mixture of soil and chemical solution is heated to the boiling point by means of an alcohol lamp, and the boiling continued for a minute for the purpose of driving off the carbonic acid gas, which is liberated first. The boiling is continued and a piece of moistened paper, previously impregnated with lead acetate, is placed over the mouth of the flask. If the soil contains acid, a chemical reaction occurs between it and zinc sulfid, and hydrogen sulfid gas is liberated. The quantity of acidity in the soil determines the quantity of gas which comes in contact with the lead acetate paper, and this determines the depth of color produced on the paper. A slight brownish color indicates the presence of very little acidity, while an intense black signifies the presence of injurious amounts of acidity. There are various degrees of coloration between these two extremes, and each gives an accurate indication as to the quantity of lime required to correct the acidity. This test is simple and inexpensive, and at the present time most county agent offices are equipped with this apparatus or a similar one for testing soils for farmers. Some newer methods are being devised, and doubtless this method will be improved upon as time passes, but the Truog test has qualities of accuracy and simplicity which will always make it valuable. CHAPTER VI SOURCES OF LIME Nature's Provision. Soils are composed of pulverized stone and organic matter. Much of the original stone contained little lime, and the human race would become nearly helpless if there were no stores of supply in the form of limestone, chalk, marl, etc. The day would come when the surface soil could not produce our staple crops if its loss of lime continued, and a means of replenishing the stock were not at hand. The huge deposits of limestone that have not been disintegrated by processes of weathering are assurance that the soil's need can be met forever. The calcium and magnesium in the stone are in chemical combination with carbonic acid forming carbonates, and there is an additional mixture of other earthy material that was deposited by the water when the stone was being formed, but much limestone [Pg 20] [Pg 21] [Pg 22] [Pg 23] [Pg 24] possesses an excellent degree of purity. Lime Favors Clover at the Ohio Experiment Station Lime Favors Clover at the Ohio Experiment Station Lime Affects Growth of Corn at the Ohio Experiment Station Lime Affects Growth of Corn at the Ohio Experiment Station Confusion Respecting Forms. In the public mind there is much confusion respecting the sources and forms of lime most to be desired. Wood ashes appealed to people, especially in an early day in our agriculture, partly because the ashes were so universally present that tests had been made voluntarily and otherwise in millions of instances. The value of such tests had been obscured by the fact that the ashes contained potash, and much of the credit of any good effect was attributed to that fact. It has been generally known, however, that lime in peculiarly effective form is in wood ashes, and the favor in which ashes have been held rested not a little upon the curious preference for an organic source of all soil amendments. This is seen in the case of direct fertilizers. Dealers' Interests. The doubts regarding the wisdom of selecting any one form of lime for the betterment of soil conditions have been promoted very naturally by the conflicting interests of men who would furnish the supply. Some dealers in fresh burned lime have asserted that it was folly to expect any appreciable result from the use of unburned limestone. The manufacturer of ground limestone has pointed out the possibility of injuring a soil by the use of caustic lime, and oftentimes has so emphasized his point that farmers have become unwilling to apply fresh or water-slaked lime to their land. Manufacturers of hydrated lime in some instances have made a confused situation worse by insisting upon the claim that there was a fertilizing quality in their goods. Some dealers in lime marls have been unwilling to have the value of their goods rated according to the content of carbonate of lime, and have emphasized the value of fine division of the particles and the absence of any caustic properties. The presence of shells, evidencing an organic source of the material, has helped in the appeal to buyers. The rightful place of magnesia, and the possible danger of injury from its use, have been a fruitful cause of perplexity, making price per ton only a secondary consideration to the man wanting to supply his soil's needs. Scientists' Failure to Agree. It is only fair to say that much of the doubt and indecision on the part of the public is [Pg 25] [Pg 26] directly attributable to the conflicting statements of our scientists. It should be borne in mind that careful investigation in respect to the relative values of the various forms and sources of lime has been confined largely to the short period of time that has elapsed since recognition of the lime deficiency of our country's soils. Our agricultural literature contained little about soil acidity 20 years ago, and our experiment station tests afford only relatively recent results. Some knowledge of sour soils and the efficacy of lime in their amendment is nearly as old as the history of agriculture, it is true, but answers to the questions uppermost in the minds of men wanting to apply lime to land have been sought only within recent years. The variation in soil types, and in sources of lime, and in preconceived ideas of men drawing conclusions from incomplete data may easily account for failure of our soil scientists to be in the close agreement in statement that would remove all confusion in the public mind. However, the agreement respecting the facts is becoming better assured with every added year of investigation, as a study of station bulletins shows. CHAPTER VII DEFINITIONS Technical Terms. The practical man uses a great number of technical terms in his own field of labor, and often fails to recognize the fact that they are technical, and may be puzzling to many other people. He uses such terms for the sake of accuracy, desiring to express to his fellow-workmen exactly what he means. The farmer, stockman, carpenter, banker —all have command of such terms, and need them, but the chemist who, in a way, must come even nearer to accuracy in expression, finds that many people who want his assistance do not care to master and use any of his terms. Failure to do so compels misunderstanding. Anyone who is interested in the right use of lime should be willing to add a few of the chemists' technical terms to the scores in his own line of work that he uses constantly, and thus let the whole matter of liming land come to appear more simple to him. Acquaintance with a few terms is necessary to any understanding of statements of analyses upon which purchase should be made. An Element is a substance that cannot be divided into simpler substances. The number of elements necessary to the growth of plants is small, and of this number calcium is one and magnesium is another. Compounds. We do not find these elements merely mixed with other elements to form a soil. They unite in definite proportions by weight to form chemical compounds. As conditions change, many of these compounds undergo change, giving up one element, or group of elements, and uniting with another element or group from a different compound. Heat, moisture and the action of bacteria are factors in promoting the changes. There is no more restless activity than may be found among the elements composing a productive soil. Calcium is an element which will unite with oxygen and carbon dioxide to form a compound known as calcium carbonate. The chemist's symbol for calcium is Ca. Calcium Oxide is a compound left after the burning of limestone, and is known as fresh burned lime, or quick lime. Its formula is CaO. It contains, when pure, 40 parts of calcium and 16 parts oxygen by weight. Carbon Dioxide is a compound whose formula is CO2. Calcium Carbonate, known also as carbonate of lime, has a definite composition, containing, when pure, 56 parts CaO and 44 parts CO2. It is known to the chemist as CaCO3, and forms practically all of very pure limestones. Impure limestones contain some earthy materials that became mixed with the lime carbonate when the rock was being formed. Calcium Hydroxide is a compound made by permitting calcium oxide to combine with water, and is known as lime hydrate. It contains 56 parts by weight CaO and 18 parts water, and has the formula Ca(OH)2. Magnesium is an element, and is found in magnesium carbonate, a compound that is effective in correcting soil acidity. Magnesian Limestone. Magnesium carbonate is usually found in combination with calcium carbonate, and when about 47 per cent of the total carbonates is magnesium carbonate, the limestone is known as dolomite. Ground Limestone is the stone pulverized so that it can be distributed. It is carbonate of lime (CaCO3), or a combination of calcium and magnesium carbonate, and in a way has a right to be designated as "lime," but such use leads to confusion. Fresh Burned Lime. Calcium oxide (CaO) formerly was accurately designated as "lime," but the words "fresh burned" are often prefixed to prevent confusion with lime carbonate or the hydrate. It is known as "lump lime," "caustic lime" and "stone lime." Ground or Pulverized Lime. Fresh burned lime may be ground fine, so that it can be spread on land without slaking. This product should not be confused with ground limestone or hydrated lime. Fresh ground lime is worth nearly twice as much per ton as ground limestone, but some of the product on the market is far from pure. There is opportunity to grind up unburned and waste material with the caustic lime, and this form of lime usually contains some hydrated material. [Pg 27] [Pg 28] [Pg 29] [Pg 30] [Pg 31] Hydrated Lime is the compound formed by the action of water or steam on fresh burned lime. Air-Slaked Lime is a compound formed by the action of carbon dioxide from the air on hydrated lime, and its formula is CaCO3, which is that of pure limestone. An Indiana Limestone Quarry An Indiana Limestone Quarry A Limestone Plant (Courtesy of the Michigan Limestone Company) A Limestone Plant (Courtesy of the Michigan Limestone Company) CHAPTER VIII GROUND LIMESTONE Variation in Quality. Limestones vary widely in purity. They were formed under water, and clay and sand were laid down with the lime in such quantity in some cases that the resulting stone is not worth handling for soil improvement. A stone that is practically all carbonate of calcium, or a combination of calcium and magnesium, is wanted because it is these two elements that give value to the material. If a poor stone is used, too much waste matter must be handled. Twenty-five per cent more ground limestone of 80% purity must be applied than would be required in the case of an absolutely pure limestone. Any stone above 90% pure in carbonate of lime and magnesia is rated as good, but the best stone runs from 96% to 99%. Limestones vary greatly in ability to resist disintegration, and this variation is a big factor in determining the agricultural value of ground limestone that has not been reduced to a fine powder. Particles of a hard limestone may lie inert in the soil for many years. Hardness also affects the cost of grinding. A Matter of Distribution. Nature has used various agencies in reducing limestone for the making of soils. The stone [Pg 32] [Pg 33] [Pg 34] contained its lime in carbonate form, and when reduced to good physical condition for distribution it helped to make highly productive land. We know that lime carbonate does the needed work in the soil so far as correction of acidity is concerned, but in the form of blocks of limestone it has no particular value to the land. Burning and slaking afforded to man a natural means of putting it into form for distribution, and it is only within recent years that the pulverization of limestone for land has become a business of considerable magnitude. The ground limestone used on land continues to be in part a by-product of the preparation of limestone for the manufacture of steel, glass, etc., and the making of roads, the fine dust being screened out for agricultural purposes. These sources of supply are very inadequate, and too remote from much land that requires treatment. Large plants have been established in various parts of the country for the purpose of crushing limestone for use on land, and quite recently low-priced pulverizers for farm use have come upon the market and are meeting a wide need. Low-Priced Pulverizers. A serious drawback to the liming of land is the transportation charge that must be paid where no available stone can be found in the region. Great areas do have some beds that should be used, and a low-priced machine for pulverizing it is the solution of the problem. Such a machine must be durable, have ability to crush the stone to the desired fineness and be offered at a price that does not seem prohibitive to a farmer who would meet the demands of a small farming community. In this way freight charges are escaped, and a long and costly haul from a railway point is made unnecessary. The limestone of the locality will be made available more and more by means of this type of machine, and the inducement to correct the acidity of soils will be given to tens of thousands of land-owners who would not find it feasible to pay freight and cartage on supplies coming a long distance. There should be a market many times greater than now exists for the product of all large plants, while the number of small pulverizers multiplies rapidly. The very large areas that have no limestone at hand must continue to buy from manufacturers equipped to supply them, and farmers within a zone of small freight charges should be able to buy from such manufacturers more cheaply than they could pulverize stone on their own farms. An individual, or a group of farmers, will buy a machine for pulverizing limestone at a cost of a few hundred dollars when costly equipment would be out of the question. If he has a bed of limestone of fair quality, and the soil of the region is lacking in lime, an efficient grinder or pulverizer solves the problem and makes prosperity possible to the region. Within the last few years much headway has been made in perfecting such machines, and their manufacturers have them on the market. Any type should be bought only after a test that shows capacity per hour and degree of fineness of the product. As a high degree of fineness is at the expense of power or time, and as the transportation charge on the product to the farm is small, there is no requirement for the fineness wanted in a high-priced article that must be used sparingly. The aim should be to store in the soil for a term of years, and the coarse portion is preferable to the fine for this purpose because it will not leach out. The heavy application will furnish enough fine stuff to take care of present acidity. If nearly all the product of such a pulverizer will pass through a 10-mesh screen, and the amount applied is double that of very fine limestone, it should give immediate results and continue effective nearly twice as long as the half amount of finer material. There could hardly be a practical solution of the liming problem for many regions without the development of such devices for preparing limestone for distribution, and it is a matter of congratulation that some manufacturers have awakened to the market possibilities our country affords. CHAPTER IX STORING LIME IN THE SOIL Liberal Use of Limestone. Land never does its best when skimped in any way. As we raise the percentage of carbonate of lime in land that naturally is deficient, we give increasing ability to such land to take on some of the desirable characteristics of a limestone soil. It is poor business to be making a hand-to-mouth fight against a state of actual acidity unless the cost of more liberal treatment is prohibitive. The most satisfactory liming is done where the expense is light enough to justify the free use of material. When this is the case, extreme fineness of all the stone is undesirable. There is the added cost due to such fineness and no gain if the finer portion is sufficient to correct the acidity, and the coarser particles disintegrate as rapidly as needed in later years. Loss by Leaching. Another valid argument against extreme fineness of the stone used in liberal applications is the danger of loss by leaching. Soils are so variable in their ability to hold what may be given them that it is idle to offer any estimate on this point. The amount of lime found in the drainage waters of limestone land teaches no lesson of value for other land, the excessive loss in the former case being due oftentimes to erosion that creates channels through the subsoil, through which soil and lime pass. [Pg 35] [Pg 36] [Pg 37] [Pg 38] [Pg 39] A Limestone Pulverizer for Farm Use (Courtesy of the Jeffrey Manufacturing Company, Columbus, Ohio) A Lime Pulver in Operation (Courtesy of the Jeffrey Manufacturing Company) A Lime Pulver in Operation (Courtesy of the Jeffrey Manufacturing Company) But we do know the tendency of lime to get away, and the use of several tons of fine stone per acre may easily be followed by loss in many types of soil. It is wholly reasonable to believe that some portion of such an application should be coarse enough to stay where put until needed by exhaustion of the finer portion. It is upon this theory that coarser material often is preferred to the very finest. What Degree of Fineness? Assuming that the farmer is in a position to store some carbonate of lime in his land for future use, giving the soil an alkaline character for five or 10 years, the degree of fineness of the stone is important, partly because there will be distinct loss by leaching from many types of soils if all the material is fine as dust, and specially because less finely pulverized material can be supplied him at a lower price per ton. Much by-product in the manufacture of coarse limestone for other purposes contains a considerable percentage of material that would not pass through a 60-, or 40-, or 10-mesh screen, but it does contain a big percentage of immediately available lime, and a more complete pulverization of this by-product would add greatly to its cost. It is quite possible that a ton of such stone may be bought at a price that would cover the value only of the fine portion, estimated on the basis of the prevailing price of finely ground material, the coarse material being obtained without any cost at all. It is this situation, or an approach to it, that leads some authorities to become strenuous advocates of the use of coarsely pulverized stone. The advice is right for those who are in a position to accept it. If the money available for liming an acre of land can buy all the fine stone needed for the present and some coarser stone mixed with it for later use by the soil, the purchase is much more rational than the investment of the same amount of money in very fine stone that has no admixture of coarser material. If the investment in the former case is larger than in the latter, it continues to be good business up to a certain point, and the room for some uncertainty is wide enough to provide for much difference in judgment. Quality of the Stone. Another factor of uncertainty is the hardness of the stone. A limestone may have such flinty characteristics that a piece barely able to pass through a 10-mesh screen will not disintegrate in the soil for years, and there are other types of limestone that go into pieces rapidly. The variation in quality of stone accounts for no little [Pg 40] [Pg 41] difference in opinion that is based upon limited observation. Using One's Judgment. It is evident that no hard and fast rule respecting fineness may be laid down, and yet a rather definite basis for judgment is needed. There is much good experience to justify the requirement that when all ground lime is high-priced in any section for any reason, and the amount applied per acre is thereby restricted, the material should be able to pass through a screen having 60 wires to the linear inch, and that the greater part should be much finer. Usually some part of such stone will pass through a 200-mesh screen. When a limestone on the market will not meet this test, some concession in price should be expected. If the stone is not very flinty, a 40-mesh screen may be regarded as affording a reasonably satisfactory test. An increasing percentage of coarser material makes necessary an increase in amount to meet the lime deficiency, and a distinct concession in price is to be expected when a 10-mesh screen is used in testing. At the same time a careful buyer will use a 60-mesh screen to determine the percentage that probably has availability for the immediate future. A coarsely ground article, containing any considerable percentage that will not pass through a 10-mesh screen, must sell at a price justifying an application sufficient to meet the need of the soil for a long term of years, as the greater part has no immediate availability, and only a heavy application can provide a good supply for immediate need. New York State Experience. A bulletin of the New York agricultural experiment station, published early in 1917, calls attention to the rapid increase in demand for ground limestone in New York. Within the last five years the number of grinding plants within the state had increased from one to 56, and more than a dozen outside plants are shipping extensively into the state. The bulletin says: "Farmers who have had experience with the use of ground limestone are as a rule satisfied with only a reasonable degree of fineness, and are able to judge the material by inspection. When limestone is ground so the entire product will pass a 10-mesh (or 2 mm.) sieve, the greater part of it will be finer than a 40-mesh (or ½ mm.) sieve.... There are now in operation in this State more than a dozen small portable community grinders; they are doing much to help solve the ground limestone problem and their use is rapidly increasing. In the practical operation of these machines they grind only to medium fineness (2 mm.). To insist upon extreme fineness is to discourage their use." This State experiment station is only one of many scientific authorities approving the use of limestone reduced only to such fineness that it will pass through a 10-mesh screen, the cost of the grinding being sufficiently small to permit heavy applications. CHAPTER X FRESH BURNED LIME An Old Practice. The beneficial effect of caustic lime on land is mentioned in some ancient writings. Burning and slaking afforded the only known method of reducing stone for use in sour soils. Lime in this form not only is an effective agent for correcting soil acidity, but it improves the physical condition of tough and intractable clays, rendering them more friable and easy of tillage. Caustic lime also renders the organic matter in the soil more quickly available, an increase in yield quickly following an application. These three effects of burned lime brought it into favor, and a rational use would have continued it in fav...