CROPS AND
METHODS FOR SOIL
IMPROVEMENT
By
ALVA AGEE, M.S.
HEAD OF DEPARTMENT OF AGRICULTURAL EXTENSION
ACTING DEAN AND DIRECTOR OF THE SCHOOL OF
AGRICULTURE AND EXPERIMENT STATION OF
THE PENNSYLVANIA STATE COLLEGE
ILLUSTRATED
New York
THE MACMILLAN COMPANY 1912
All rights reserved
Copyright, 1912,
By THE MACMILLAN COMPANY.
Set up and electrotyped. Published November, 1912.
Norwood Press
J. S. Cushing Co.—Berwick & Smith Co.
Norwood, Mass., U.S.A.
CONTENTS
CHAPTER I
Pages Introduction 1-11 In lieu of preface 1 Natural strength of land 2 Plant constituents 2 Organic matter 4 Drainage 6 Lime 7 Crop-rotation 8 Fertilizers 9 Tillage 10 Control of soil moisture 11CHAPTER II
The Need of Lime 12-22 The unproductive farm 12 Soil acidity 13 The rational use of lime 14 Where clover is not wanted 16 Determining lime requirement 17 The litmus-paper test 19 A practical test 20 Duration of effect 21CHAPTER III
Applying Lime 23-35 Forms of lime 23 Definitions 24 The kind to apply 26 The fineness of limestone 27 Hydrated lime 27 Stone-lime 28 Ashes 30 Marl 31 Magnesian lime 31 Amount per acre 32 Time of application 34CHAPTER IV
Organic Matter 36-45 Office of organic matter 36 The legumes 38 Storing nitrogen 39 The right bacteria 41 Soil inoculation 42 Method of inoculation 43CHAPTER V
The Clovers 46-58 Red clover 46 Clover and acid soils 47 Methods of seeding 48 Fertility value 49 Taking the crops off the land 51 Physical benefit of the roots 52 Used as a green manure 52 When to turn down 53 Mammoth clover 54 Alsike clover 55 Crimson clover 56CHAPTER VI
Alfalfa 59-70 Adaptation to eastern needs 59 Fertility and feeding value 60 Climate and soil 61 Free use of lime 62 Inoculation 62 Fertilization 63 A clean seed-bed 64 Varieties 65 Clean seed 65 The seeding 66 Seeding in August 67 Subsequent treatment 68CHAPTER VII
Grass Sods 71-79 Value of sods 71 Prejudice against timothy 72 ObjectCHAPTER VIII
Grass Sods (Continued) 80-89 Seeding in late summer 80 Crops that may precede 81 Preparation 83 The weed seed 84 Summer grasses 85 Sowing the seed 85 Deep covering 86 Seed-mixtures 88CHAPTER IX
Sods for Pastures 90-97 Permanent pastures 90 Seed-mixtures 91 Blue-grass 91 Timothy 92 Red-top 92 Orchard grass 93 Other seeds 93 Yields and composition of grasses 93 Suggested mixtures for pastures 94 Renewal of permanent pastures 96 Destroying bushes 96 Close grazing 97CHAPTER X
The Cowpea 98-107 A southern legume 98 Characteristics 99 Varieties 99 Fertilizing value 100 Affecting physical condition 101 Planting 101 Inoculation 103 Fertilizers 103 Harvesting with livestock 104 The cowpea for hay 104 As a catch crop 106CHAPTER XI
Other Legumes and Cereal Catch Crops 108-119 The soybean 108 Fertility value 109 Feeding value 109 Varieties 110 The planting 111 Harvesting 112 The Canada pea 113 Vetch 113 Sweet clover 115 Rye as a cover crop 116 When to plow down 117 Buckwheat 118 Oats 119CHAPTER XII
Stable Manure 120-128 Livestock farming 120 The place for cattle 121 Sales off the farm 122 The value of manure 124 The content of manure 125 Relative values 126 Amount of manure 127 Analysis of manure 128CHAPTER XIII
Care of Stable Manure 129-138 Common source of losses 129 Caring for liquid manure 130 Use of preservatives 131 Spreading as made 132 The covered yard 133 Harmless fermentation 135 Rotted manure 135 Composts 136 Poultry manure 137CHAPTER XIV
The Use of Stable Manure 139-148 Controlling factors 139 Direct use for corn 140 Effect upon moisture 141 Manure on grass 142 Manure on potatoes 143 When to plow downCHAPTER XV
Crop-rotations 149-158 The farm scheme 149 Value of rotation 150 Selection of crops 151 An old succession of crops 152 Corn two years 153 The oat crop 154 Two crops of wheat 154 The clover and timothy 154 Two legumes in the rotation 155 Potatoes after corn 156 A three-years' rotation 157 Grain and clover 158 Potatoes and crimson clover 158CHAPTER XVI
The Need of Commercial Fertilizers 159-170 Loss of plant-food 159 Prejudice against commercial fertilizers 160 Are fertilizers stimulants? 161 Soil analysis 162 Physical analysis 163 The use of nitrogen 164 Phosphoric-acid requirements 165 The need of potash 166 Fertilizer tests 167 Variation in soil 168CHAPTER XVII
Commercial Sources of Plant-food 171-187 Acquaintance with terms 171 Nitrate of soda 171 Sulphate of ammonia 178 Dried blood 173 Tankage 174 Fish 175 Animal bone 175 Raw bone 177 Steamed bone 178 Rock-phosphate 178 Acid phosphate 180 Basic slag 183 Muriate of potash 184 Sulphate of potash 185 Kainit 185 Wood-ashes 185 Other fertilizers 186 Salt 186 Coal-ashes 187 Muck 187 Sawdust 187CHAPTER XVIII
Purchasing Plant-food 188-197 Necessity of purchase 188 Fertilizer control 189 Brand names 191 Statement of analysis 191 Valuation of fertilizers 193 A bit of arithmetic 194 High-grade fertilizers 196CHAPTER XIX
Home-mixing of Fertilizers 198-208 The practice of home-mixing 198 Effectiveness of home-mixing 198 Criticisms of home-mixing 199 The filler 202 Ingredients in the mixture 203 Materials that should not be combined 207 Making a good mixture 207 Buying unmixed materials 208CHAPTER XX
Mixtures for Crops 209-219 Composition of plant not a guide 209 The multiplication of formulas 209 A few combinations are safest 210 Amount of application 211 Similarity of requirements 213 Maintaining fertility 215 Fertilizer for grass 216 All the nitrogen from clover 218 Method of applying fertilizers 218CHAPTER XXI
Tillage 220-229 Desirable physical condition of the soil 220 The breaking-plow 221 Types of plows 221 Subsoiling 223 Time of plowing 223 Method of plowing 224 The disk harrow 225 Cultivation of plants 227 Controlling root-growth 227 Elimination of competition 228 Length of cultivation 229CHAPTER XXII
Control of Soil Moisture 230-236 Value of water in the soil 230 The soil a reservoir 231 The land-roller 232 The plank-drag 233 The mulch 233 Mulches of foreign material 234 Plowing straw down 235 The summer-fallow 235 The modern fallow 236CHAPTER XXIII
Drainage 237-246 Underdrainage 237 Counting the cost 238 Where returns are largest 239 Material for the drains 239 The outlet 240 Locating main and branches 240 The laterals 241 Size of tile 241 Kind of tile 242 The grade 243 Establishing a grade 243 Cutting the trenches 244 Depth of trenches 245 Connections 245 Permanency desired 246
ILLUSTRATIONS
Alfalfa and Corn in Indiana Frontispiece Facing Page A Good Crop for a Poor Soil 4 Red Clover on Limed and Unlimed Land 20 Turning down Organic Matter with a Gang Plow 36 Red Clover on the Farm of P. S. Lewis & Son, Pt. Pleasant, W. Va. 51 Alfalfa on the Ohio State University Farm 61 Curing Alfalfa at the Pennsylvania Experiment Station 68 A Heavy Grass Sod in New York 73 Good Pasture Land in Chester County, Pa. 90 Sheep on a New York Farm 96 The Cowpea Seeded at the Last Cultivation of Corn in the Great Kanawha Valley, W. Va. 106 Texas Calves on an Ohio Farm 121 In the Fertile Miami Valley, Ohio 126 Concrete Stable Floors 131 Corn in the Ohio Valley 140 Penn's Valley, Pennsylvania 151 In the Shenandoah ValleyCROPS AND METHODS FOR SOIL IMPROVEMENT
CHAPTER I
INTRODUCTION
In Lieu of Preface.—This book is not a technical treatise and is designed only to point out the plain, every-day facts in the natural scheme of making and keeping soils productive. It is concerned with the crops, methods, and fertilizers that favor the soil. The viewpoint, all the time, is that of the practical man who wants cash compensation for the intelligent care he gives to his land. The farming that leads into debt, and not in the opposite direction, is poor farming, no matter how well the soil may prosper under such treatment. The maintenance and increase of soil fertility go hand in hand with permanent income for the owner when the science that relates to farming is rightly used. Experiment stations and practical farmers have developed a dependable science within recent years, and there is no jarring of observed facts when we get hold of the simple philosophy of it all.
Natural Strength of Land.—Nearly all profitable farming in this country is based upon the fundamental fact that our lands are storehouses of fertility, and that this reserve of power is essential to a successful agriculture. Most soils, no matter how unproductive their condition to-day, have natural strength that we take into account, either consciously or unconsciously. Some good farm methods came into use thousands of years ago. Experience led to their acceptance. They were adequate only because there was natural strength in the land. Nature stored plant-food in more or less inert form and, as availability has been gained, plants have grown. Our dependence continues.
Plant Constituents.—There are a few technical terms whose use cannot be evaded in the few chapters on the use of lime and fertilizers. A plant will not come to maturity unless it can obtain for its use combinations of ten chemical elements. Agricultural land and the air provide all these elements. If they were in abundance in available forms, there would be no serious soil fertility problem. Some of their names may not interest us. Six or seven of these elements are in such abundance that we do not consider them. A farmer may say that when a dairy cow has luxuriant blue-grass in June, and an abundance of pure water, her wants are fully met. He omits mention of the air because it is never lacking in the field. In the same way the land-owner may forget the necessity of any kind of plant-food in the soil except nitrogen, phosphoric acid, potash, and lime. Probably the lime is very rarely deficient as a food for plants, and will be considered later only as a means of making soils friendly to plant life.
Nitrogen, phosphoric acid, and potash are the three substances that may not be in available form in sufficient amount for a growing crop. The lack may be in all three, or in any two, or in any one, of these plant constituents. The natural strength of the soil includes the small percentage of these materials that may be available, and the relatively large stores that nature has placed in the land in inert form as a provision against waste.
The thin covering of the earth that is known as the soil is disintegrated rock, combined with organic matter. The original rock "weathered," undergoing physical and chemical change. A long period of time was required for this work, and for the mixing and shifting from place to place that have occurred. Organic matter has been a factor in the making of soils, and is in high degree a controlling one in their production of food.
Organic Matter.—Nature is resourceful and is constantly alert to repair the wastes and mistakes of man. We may gain fundamental truth about soil fertility through observance of her methods in restoring land to a fertile condition. Our best success comes only when we work with her. When a soil has been robbed by man, and has been abandoned on account of inability to produce a profitable crop, the first thing nature does is to produce a growth of weeds, bushes, briers, or aught else of which the soil chances to have the seeds. It is nature's effort to restore some organic matter—some humus-making material—to the nearly helpless land. Vegetable matter, rotting on and in the soil, is the life-giving principle. It unlocks a bit of the great store of inert mineral plant-food during its growth and its decay. It is a solvent. The mulch it provides favors the holding of moisture in the soil, and it promotes friendly bacterial action. The productive power of most farming land is proportionate to the amount of organic matter in it. The casual observer, passing by farms, notes the presence or absence of humus-making material by the color and structure of the soil, and safely infers corresponding fertility or poverty. Organic matter is the life of the soil.
A good crop for a poor soil.
A great percentage of the food consumed by Europe and the Americas continues to come out of nature's own stores in the soil, organic and inorganic, without any assistance by man except in respect to selection of seeds, planting, and tillage. The percentage grows less as the store of original supplies grows less and population increases. Our science has broadened as the need has grown greater. We have relatively few acres remaining in the United States that do not require intelligent treatment to insure an adequate supply of available plant-food. The total area that has fallen below the line of profitable productiveness is large. Other areas that never were highly productive must supplement the lands originally fertile in order that human needs may be met.
When soils have been robbed through the greed of man, nature is handicapped in her effort to restore fertility by the absence of the best seeds. Man's intelligent assistance is a necessity. Successful farming involves such assistance of nature that the percentage of vegetable matter in the soil
Drainage.—Productive soils are in a condition to admit air freely. The presence of air in the soil is as necessary to the changes producing availability of plant-food as it is to the changes essential to life in the human body. A water-logged soil is a worthless one in respect to the production of most valuable plants. The well-being of soil and plants requires that the level of dead water be a considerable distance below the surface.
When a soil has recently grown trees, the rotting stump roots leave cavities in the subsoil that permit the removal of some surplus water, and the rotted wood and leaves that give distinctive character to new land are absorbents of such water. As land becomes older, losing natural means of drainage and the excellent physical condition due to vegetable matter in it, the need of drainage grows greater. The tramping of horses in the bottoms of furrows made by breaking-plows often makes matters worse. The prompt removal of excessive moisture by drains, and preferably by underdrains, is essential to profitable farming in the case of most wet lands. The only exception is the land on which may be grown the grasses that thrive fairly well under moist conditions.
Lime.—The stores of lime in the soil are not stable. The tendency of lime in most of the states between the Missouri River and the Atlantic seaboard is to get out of the soil. There is no evidence that lime is not in sufficient quantity in most soils to feed crops adequately, but within recent years we have learned that vast areas do not contain enough lime in available form to keep the soil from becoming acid. Some soils never were rich in lime, and these are the first to show evidence of acidity. In our limestone areas, however, acid soil conditions are developing year by year, limiting the growth of clover and affecting the yields of other crops.
The situation is a serious one just in so far as men refuse to recognize the facts as they exist, and permit the limiting of crop yields, and consequently of incomes, through the presence of harmful acids. The natural corrective is lime, which combines with the acid and leaves the soil friendly to all plant life and especially to the clovers and other legumes that are necessary to profitable farming. Nature is largely dependent upon man's assistance in the correction of soil acidity.
Crop-rotation.—A good crop-rotation favors high productiveness. One kind of crop paves the way nicely for some other one. The land can be occupied by living plants without any long intermissions. Organic matter can be supplied without the use of an undue portion of the time. The stores of plant-food throughout all the soil are more surely reached by a variety of plants, differing in their habits of root-growth. The injury from disease and insects is kept down to a minimum. There is better distribution of the labor required by the farm, and neglect of crops at critical times is escaped. The maintenance of fertility is dependent much upon the use of a legume that will furnish nitrogen from the air. A permanently successful agriculture in our country must be based upon the use of legumes, and crop-rotations would be demanded for this reason alone if none other existed.
Fertilizers.—When a crop is fed to livestock, and all the manure is returned to the land that produced the crop without loss by leaching or fermentation, there is a return to the land of four fifths of the fertility, and a good form of organic matter is supplied. A portion of the crops cannot be fed upon the farm, or otherwise the human race would have only animal products for food. The welfare of the people demands that a vast amount of the soil's crops be sold from the farms producing them. This brings about a dependence upon the natural stores of plant-food in the soil, which become available slowly, and upon commercial fertilizers.
There has been a disposition on the part of many farmers to regard fertilizers only as stimulants, due to the irrational use of certain materials, but a good commercial fertilizer is a carrier of some or all of the necessary elements that we find in stable manures. They may carry nitrogen, phosphoric acid, or potash,—any one or two or the three,—and the three are the constituents that usually are lacking in available forms in our soils. Examples of the best modern skill in farming may be found in the rational selection and use of commercial fertilizers.
Tillage.—Man's ability to assist nature in the work of production finds a notable illustration in the matter of tillage. Its purpose is to provide right physical condition of the soil for the particular class of plants that should be produced, while destroying the competition of other plants that are for the time only weeds. Most soils become too compact when left unstirred. The air cannot enter freely, plant-roots cannot extend in every direction for food, the water from rains cannot enter easily, there is escape of the moisture in the ground, and weathering of the soil proceeds too slowly. The methods used in plowing, harrowing, and later cultivations fix the productive power of a soil for the season in large measure.
Control of Soil Moisture.—The water in the soil is a consideration that has priority over plant-food in the case of agricultural land. The natural strength of the soil is sufficient to give some return to the farmer in crops if the moisture content is right throughout the season. The plant cannot feed unless water is present; the process of growth ceases in the absence of moisture. One purpose of plowing is to separate the particles of soil to a good depth so that water-holding capacity may be increased. When the soil is compact, it will absorb and hold only a very limited amount of moisture. We harrow deeply to complete the work of the plow, and the roller is used to destroy all cavities of undue size that would admit air too freely and thus rob the land of its water. Later cultivations may be given to continue the effect of the plow in preventing the soil from becoming too compact, but usually should be required only to make a loose mulch that will hold moisture in the ground, and to destroy the weeds that would compete with the planted crop for water, food, and sunshine.
CHAPTER II
THE NEED OF LIME
The Unproductive Farm.—When a soil expert visits an unproductive farm to determine its needs, he gives his chief attention to four possible factors in his problem: lack of drainage, of lime, of organic matter, and of available plant-food. His first concern regards drainage. If the water from rains is held in the surface by an impervious stratum beneath, it is idle to spend money in other amendments until the difficulty respecting drainage has been overcome. A water-logged soil is helpless. It cannot provide available plant-food, air, and warmth to plants. Under-drainage is urgently demanded when the level of dead water in the soil is near the surface. The area needing
Soil Acidity.—Lime performs various offices in the soil, but farmers should be concerned chiefly about only one, and that is the destruction of acids and poisons that make the soil unfriendly to most forms of plant life, including the clovers, alfalfa, and other legumes. Lime was put into all soils by nature. Large areas were originally very rich in lime, while other areas of the eastern half of the United States never were well supplied. Within the last ten years it has been definitely determined that a large part of this vast territory has an actual lime deficiency, as measured by its inability to remain alkaline or "sweet." Many of the noted limestone valleys show marked soil acidity. There has been exhaustion of the lime that was in a state available for union with the acids that constantly form in various ways. The area of soil thus deficient grows greater year by year, and it can be only a matter of time when nearly all of the eastern half of this country will have production limited by this deficiency unless applications of lime in some form are made. When owners of soil that remains rich in lime do not accept this statement, no harm results, as their land does not need lime. On the other hand are tens of thousands of land-owners who do not recognize the need of lime that now exists in their soils, and suffer a loss of income which they would attribute to other causes.
Irrational Use of Lime.—Some refusal to accept the facts respecting soil acidity and its means of correction is due to a prejudice that was created by an unwise use of lime in the past. Owners of stiff limestone soils learned in an early day that a heavy application of caustic lime would increase crop production. It caused such flocculation of the fine particles in their stiff soils that physical condition was improved, and it made the organic matter in the soil quickly available as plant-food. The immediate result was greater crop-producing power in the soil, and dependence upon lime as a fertilizer resulted. The vegetable matter was used up, some of the more available mineral plant-food was changed into soluble forms, and in the course of years partial soil exhaustion resulted. The heavy applications of lime, unattended by additions of organic matter in the form of clover sods and stable manure, produced a natural result, but one that was not anticipated by the farmers. The prejudice against the use of lime on land was based on the effects of this irrational practice.
There are land-owners who are not concerned with present-day knowledge regarding soil acidity because they cannot believe that it has any bearing upon the state of their soils. They know that clover sods were easily produced on their land within their remembrance, and that their soils are of limestone origin. As the clovers demand lime, these two facts appear to them final. The failures of the clovers in the last ten or twenty years they incline to attribute to adverse seasons, poor seed, or the prevalence of weed pests. They do not realize that much land passes out of the alkaline class into the acid one every year. The loss of lime is continuous. Exhaustion of the supply capable of combining with the harmful acids finally results, and with the accumulation of acid comes partial clover failure, a deficiency in rich organic matter, a limiting of all crop yields, and an inability to remain in a state of profitable production.
Lime deficiency and its resulting ills would not exist as generally as is now the case if the application of lime to land were not expensive and disagreeable. These are deterrent features of wide influence. There continues hope that the clover will grow successfully, as occasionally occurs in a favorable season, despite the presence of some acid. The limitation of yields of other staple crops is not attributed to the lack of lime, and the proper soil amendment is not given to the land.
Where Clover is not Wanted.—The ability to grow heavy red clover is a practical assurance that the soil's content of lime is sufficiently high. When clover fails on account of a lime deficiency, the work of applying lime may not be escaped by a shift in the farm scheme that permits the elimination of clover. The clover failure is an index of a condition that limits the yields of all staple crops. The lack of lime checks the activity of bacteria whose office it is to prepare plant-food for use. The stable manure or sods decompose less readily and give smaller results. Soil poisons accumulate. Mineral plant-food in the soils becomes available more slowly. Physical condition grows worse.
The limitations of the value of manure and commercial fertilizers applied to land that has a lime deficiency have illustration in an experiment reported by the Cornell station:
The soil was once a fertile loam that had become very poor. A part was given an application of lime, and similar land at its side was left unlimed. The land without lime and fertilizer of any kind made a yield of 1824 pounds of clover hay per acre. A complete fertilizer on the unlimed land made the yield 2235 pounds, and 15 tons of manure on the unlimed land made the yield 2091 pounds.
Where lime had been applied, the unfertilized land yielded 3852 pounds per acre, the fertilized, 4085 pounds, and the manured, 4976 pounds. The manure and fertilizer were nearly inactive in the acid soil. The lime enabled the plants to obtain benefit from the plant-food.
Determining Lime Requirement.—It is wasteful to apply lime on land that does not need it. As has been said, the man who can grow heavy clover sods has assurance that the lime content of his soil is satisfactory. This is a test that has as much practical value as the analysis of a skillful chemist. The owner of such land may dismiss the matter of liming from his attention so far as acidity is concerned, though it is a reasonable expectation that a deficiency will appear at some time in the future. Experience is the basis of such a forecast. Just as coal was stored for the benefit of human beings, so was lime placed in store as a supply for soils when their unstable content would be gone.
The only ones that need be concerned with the question of lime for soils are those who cannot secure good growths of the clovers and other legumes. Putting aside past experience, they should learn whether their soils are now acid. Practical farmers may judge by the character of the vegetation and not fail to be right nine times out of ten. Where land has drainage, and a fairly good amount of available fertility, as evidenced by growths of grass, a failure of red clover leads immediately to a strong suspicion that lime is lacking. If alsike clover grows more readily than the red clover, the probability of acidity grows stronger because the alsike can thrive under more acid soil conditions than can the red. Acid soils favor red-top grass rather than timothy. Sorrel is a weed that thrives in both alkaline and acid soils, and its presence would not be an index if it could stand competition with clover in an alkaline soil. The clover can crowd it out if the ground is not too badly infested with seed, and even then the sorrel must finally give way. Where sorrel and plantain cover the ground that has been seeded to clover and grass, the evidence is strong that the soil conditions are unfriendly to the better plants on account of a lime deficiency. The experienced farmer who notes
The Litmus-paper Test.—A test of fair reliability may be made with litmus paper. A package of blue litmus paper can be bought for a few cents at any drug store. This paper will turn pink when brought into contact with an acid, and will return to a blue if placed in lime-water. A drop of vinegar on a sheet of the paper will bring an immediate change to pink. If the pink sheet be placed in lime-water, the effect of the lime in correcting the acidity will be evidenced by the return in color to blue.
To test the soil, a sample of it may be put into a basin and moistened with rain-water. Several sheets of the blue litmus paper should be buried in the mud, care being used that the hands are clean and dry. When one sheet is removed within a few seconds and rinsed with rain-water, if any pink shows, there is free acid present. Another sheet should be taken out in five minutes. The rapidity with which the color changes, and the intensity of the color, are indicative of the degree of acidity, and aid the judgment in determining how much lime should be used. If a sheet of the paper retains its blue color in the soil for twenty minutes, there probably is no lime deficiency. The test should be made with samples of soil from various parts of the field, and they should be taken beneath the surface. One just criticism of this test is that while no acidity may be shown, the lime content may be too low for safety.
Red clover on limed and unlimed land.
A Practical Test.—The importance of alkalinity in soils is so great, and the prevalence of acidity has such wide-spread influence to-day, limiting the value of the clovers on a majority of our farms, that a simple and more convincing test is suggested here. Every owner of land that is not satisfactorily productive may learn the state of his soil respecting lime requirement at small expense. When a field is being prepared for seeding to the grain crop with which clover will be sown, a plat containing four square rods should be measured off, and preferably this should be away from the border to insure even soil conditions. A bushel of lump-lime, weighing eighty pounds, should be slaked and evenly distributed over the surface of the plat of ground. It can be broadcasted by hand if a spreader is not available, and mixed with the surface soil while in a powdered state. The plat of ground should be left as firm as the remainder of the field, so that all conditions may be even for the test. The appearance of the clover the following year will determine whether lime was needed or not. There is no reason why any one should remain in doubt regarding the lime requirement of his fields. If income is limited by such a cause, the fact should be known as soon as possible.
Duration of Effect.—Soil acidity is not permanently corrected by a lime application. The original supply failed to prove lasting, and the relatively small amount given the land in an application will become exhausted. The duration depends upon the degree of acidity, the nature of the soil and its crops, and the size of the application. Experiments at the Pennsylvania experiment station have shown that an application only in sufficient amount to correct the existing acidity at the time of application will not maintain an alkaline condition in the soil, even for a few months. There must be some excess at hand to unite with acids as formed later in the crop-rotation, or limings must be given at short intervals of time to maintain alkaline conditions.
Experience causes us to assume that enough lime should be applied at one time to meet all requirements for a single crop-rotation of four, five, or six years, and, wherever lime is cheap, the unpleasant character of the labor inclines one to make the application in sufficient amount to last through two such rotations. It is a reasonable assumption, however, that more waste results from the heavier applications at long intervals than from light applications at short intervals. In any event need will return, and soil acidity will again limit income if applications do not continue to be made.
CHAPTER III
APPLYING LIME
Forms of Lime.—There is unnecessary confusion in the mind of the public regarding the forms of lime that should be used. If amounts greatly in excess of needs were being applied, the form would be a matter of concern. There would arise the question of soil injury that might result from the use of the lime in caustic form. Again, if pulverized limestone were used, a very heavy application would bring up the question of coarseness in order that waste by leaching might be escaped. Most farms needing lime do not have cheap supplies, and the consideration is to secure soil alkalinity at a cost that will not be excessive. Freight rates and the cost of hauling to the fields, added to first cost of the lime, limit applications on most farms to the necessities of a single crop-rotation which includes clover, or, at the most, to two crop-rotations. Under these circumstances it is best to let cost of correction of soil acidity determine the form of lime to be used.
The material that will render the soil friendly to clover for the least money is the right one to select. We need to be concerned only with the relative efficiencies of the various forms of lime, as measured in terms of money. That which will most cheaply restore heavy clover growths to the land is the form of lime to be desired. The contentions of salesmen may well be disregarded as they produce confusion and delay a work that is important to the farmer.
Definitions.—The use of the various forms of lime will become general, and the terms employed to designate them should be understood. They vary in their content of acid-correcting material, and their correct names should be used with accuracy.
Stone-lime, often called lump-lime or unslaked lime, or calcium oxide or CaO, is a form widely known, and may be taken as a standard. It is the ordinary lime of commerce, and is obtained by the burning of limestone. One hundred pounds of pure limestone will produce 56 pounds of stone-lime (CaO).
Pulverized lime, often called ground lime, is stone-lime after being pulverized to permit even distribution. When it is fully exposed to the air or moisture, it slakes and doubles in volume.
Hydrated lime, often called slaked lime, is a combination of stone-lime and water. The water causes an increase in weight of 32 per cent, 56 pounds of stone-lime becoming 74 pounds of the hydrate.
Pulverized limestone, often called carbonate of lime, is the unburned limestone made fine so that good distribution may be possible.
Air-slaked lime, often called carbonate of lime, is stone-lime or hydrated lime combined with carbonic acid from the air, and thereby increased in weight. Fifty-six pounds of stone-lime, or 74 pounds of hydrated lime, become 100 pounds of air-slaked lime.
Agricultural lime, or land-lime, may embrace anything that the manufacturer of lime chooses to market. It may be reasonably pure unslaked lime, or it may have less value than a finely pulverized pure limestone. There is a custom of grinding the core, or partially burned limestone of the kiln, together with impurities removed from builders' lime, and with this may be put some air-slaked lime. Some manufacturers market under this name a lime of excellent value. There is no standard, and one should not pay more than a finely pulverized pure limestone would cost unless he knows that the content of
The element with which we are concerned in any of these forms of lime is calcium. It is the base whose union with the acids destroys the latter. It should be obvious that the addition of water to stone-lime, which adds weight and causes 56 pounds of the stone-lime to become 74 pounds of hydrated lime, adds no calcium. Likewise the change to the air-slaked condition adds no calcium, but again adds weight.
The Kind to Apply.—If a soil contains free acid, the amount of calcium needed is definite. The form of lime that can supply the need in that particular field at least expenditure of money and trouble is the one to be selected. A ton of stone-lime, or pulverized lime, can correct as much acid as 2640 pounds of hydrated lime or 3570 pounds of pulverized limestone, if all the original material was pure.
In other words, if the value of a given weight of pulverized limestone is placed at 100, the value of the same weight of hydrated lime would be 132 and the value of stone-lime would be 180, when each was finely divided and distributed throughout the surface soil.
The Fineness of Limestone.—Experiments at the Pennsylvania experiment station have shown that limestone has practically immediate availability in an acid soil if all of it has ability to pass through a screen having 60 meshes to the linear inch. Much of the limestone meeting this test doubtless is fine enough to pass through an 100-mesh screen. The requirement that a 60-mesh screen be used in testing is a satisfactory one to the buyer that wants immediate results in the field. A coarser product must be used in larger amount per acre, as only the fine particles are available at once, and the object of the application is to correct all the acidity. Where a coarse product, containing some fine particles, can be used at such a low price per ton that the application may consist of a large number of tons per acre, the practice may be commended, but the essential thing is immediate results, and only finely divided limestone can give them. Any long railway or wagon haul makes a heavy application of coarsely pulverized limestone inexpedient.
Hydrated Lime.—Many salesmen are too enthusiastic in their claims for hydrated lime. It has advantages over pulverized limestone, stone-lime, and pulverized lime, and there are disadvantages. The buyer of pulverized limestone pays for the haul on 100 pounds of material to get the 56 pounds of lime carried, while 74 pounds of the hydrate furnish the same amount of actual lime, if all of it is a hydrate. While the hydrate contains less strength than the stone-lime, it is in good physical condition for distribution, and the stone-lime must be slaked. The buyer will bear in mind, moreover, that much of the stone-lime which is burned on farms comes from limestone that is not very pure, and all impurity is waste. Most manufacturers of the hydrate locate their costly plants where the limestone is relatively pure. Prudent business reasons dictate such a course. A careful manufacturer of hydrated lime takes out imperfectly burned and other faulty material with screens. These advantages have some weight, but the fact remains that a ton of pure stone-lime has considerably more acid-correcting power than a ton of the hydrate.
Stone-lime.—Stone or lump-lime is composed of the 56 per cent of a pure limestone that gives value to the limestone. Forty-four pounds of waste material were driven off in the burning. Where railway or wagon hauls are costly, the purchase of stone-lime is indicated. There is advantage in getting this lime in pulverized form, provided it can be distributed in the soil before moisture from the air induces slaking and consequent bursting of the packages. The necessity of rapid handling has limited the popularity of pulverized unslaked lime, but no other form is equal to it when it is wholly unslaked. Some manufacturers grind the partially burned limestone often found in kilns, and furnish goods little better than pulverized limestone.
The slaking of stone-lime should be done in a large pile, and the distribution may be made with lime-spreaders. When the application is fairly heavy, a manure-spreader does satisfactory work. A good lime-spreader is to be desired, but care must be used to remove any stones or similar impurities in the slaked lime when filling it. Such spreaders are on the market.
The practice of slaking lime in small piles in the field is wasteful. It is difficult to reduce all the lime to a fine powder and to make even distribution over the surface. Any excess of water from rains puddles some of the lime, destroying practically all its immediate effectiveness. Distribution with shovels is necessarily imperfect.
The labor of slaking stone-lime and the difficulty in distribution are two factors to be considered when selecting the form of lime to be used. They may counter-balance in some instances the higher percentage of actual lime when comparison is made with the hydrate. That is a question to be decided by the buyer. He must be willing to use methods that will secure even distribution. The prevailing practice, however, of marketing the hydrate at a much higher price per ton than the stone-lime should prevent sales to farmers. The price paid for ease of handling is too great when purchase of the hydrate is made under such circumstances. It is better to do the slaking at home, furnishing the added weight of 32 per cent in water on the farm.