CHAPTER XIV
THE USE OF STABLE MANURE
Controlling Factors.—The farm supply of stable manure is a carrier of plant-food, returning to the soil four fifths of all the fertility removed in the crops fed, but it is much more than this. Land which receives only plant-food, as may be the case when fertility is supplied in commercial fertilizers, loses good physical condition. Organic matter is needed for maintenance of physical condition, the retention of soil moisture, the freeing of inert minerals in the land, and the promotion of bacterial life in the soil. No small share of the value of a ton of manure is due to its organic matter. This is a factor in the problem when deciding what disposition of the manure will pay best. One field may be in condition to respond fully to the use of commercial fertilizers, while another is too deficient in humus for best results. Some crops are more insistent upon supplies of organic matter than others.
Again, the disposition of the manure depends upon the supply. If most crops are fed on the farm, the manure is a leading source of fertility for all fields and crops, and may be used once or twice in the crop-rotation on every field. If the manure is in small amount, due to a scheme of farming involving the growing of crops for market, the function of the manure may be only to encourage the starting of sods, in which legumes are a leading factor.
Direct Use for Corn.—The practice of spreading manure on grass land for corn is based upon much good experience. The custom is nearly universal in regions where corn is an important part of a four, five, or six years' rotation, and all of the corn and hay is fed on the farm. This disposition of the manure permits the handling at times when other work does not rush. The supply carried over from the spring is put on in late summer, and the manure made in the early part of the winter can be drawn to the field fast as made. Manure spread immediately before the sod is broken is less effective, as no leaching of soluble elements into the surface soil occurs before the coarse material is buried in the bottom of the furrow.
Corn in the Ohio Valley.
Corn in the Ohio Valley.
The use of fresh manures for corn is rational, because corn is a gross feeder and requires much nitrogen. All plants having heavy foliage can use nitrogen in large amounts. It is possible to apply manure in excessive amount for this cereal, the growth of stalk becoming out of proportion to the ear, but the instances are relatively few. Ordinarily corn suffers from lack of nitrogen. When the farm manure is in large amount, its direct use for corn is good practice.
Effect upon Moisture.—Coarse manures should not be plowed down late in the spring, as they increase the ill effects of drouth. Decayed vegetation, well mixed with the soil, increases the soil's water-holding capacity, but undecayed material in the bottom of the furrow is harmful. Fresh, strawy manure, made immediately before the time for breaking a sod, is preferably carried over in a covered shed until a later season of the year.
When manure has been spread upon a sod in the fall or early winter, it decays quickly after the plowing, and aids in resistance to drouth. When it is plowed down, the ground is kept more porous, and the presence of plant-food and moisture at or near the depth of plowing encourages deeper rooting of plants, and thus indirectly assists them to withstand dry weather. If the plowing is good in character, leaving the furrow-slice partly on edge, and permitting the harrow to mix part of the turf and the manure with the remainder of the soil, the best conditions respecting moisture are secured.
Manure on Grass.—When the crop-rotation embraces two or more years of grass, or one of clover followed by only one of grass, it is better practice to use the manure to thicken the sod. The object in view is the largest possible amount of crops, and the maximum amount of organic matter for the soil. Grass is a heavy feeder, like corn, and makes good use of nitrogen. Its roots fill the soil so that no loss attends the use of manure. When the supply is given the grass, after the harvest of the second crop of clover and during the winter, the timothy can make a rank growth. The part of the plant above ground has corresponding development below ground. Not only does a large increase in the hay crop result, but the heavy mass of grass roots, the aftermath, and the remains of the manure provide a great amount of fertility for the corn which follows. The increase in hay permits a corresponding increase in the manure supply the next year, if it is fed, and if it is sold on account of a market price greater than its value for feed and manure, it adds to income materially—and that is one reason for farming.
Manure on Potatoes.—There are excellent cash crops that may get more than their fair share of the farm supply of fertility, and against the interest of fields in the farm not adapted to cash crops. The justification is found in the farm ledger. In some regions potatoes are the best crop in point of net income per acre, where the acreage is kept restricted so that there may be plenty of organic matter to help in conserving moisture. It is not good practice to use fresh manure, and especially that from horse-stables, for potatoes. A heavy application makes an excessive growth of vine, and the yield of tubers suffers. A stronger deterrent is the effect that fresh manure has on the development of the spores that produce the disease known as potato-scab. Rotted manure is less dangerous, and few crops repay its use in higher degree than the potato. Some growers prefer to make heavy application of fresh manure to grass for corn, and follow with potatoes so that they can profit by the rotted organic matter that remains. In this way the physical condition is made excellent, moisture is well held in a dry season, and commercial fertilizers can supplement the plant-food left in the manure.
When to plow Down.—Excellent farmers differ regarding the relative efficiencies of manure plowed down and that mixed with the top soil. Both classes may be right for their individual instances. The plowing down of manure helps to deepen the soil, and that always is desirable. It causes plants to root deeply, and that is a distinct benefit in a drouthy season, and always desirable. When a soil is in such tilth that the breaking-plow always brings fertile soil to the surface, the plowing down of manure gives excellent results, though it should be permitted to leach at the surface for a few weeks before being turned under. When land is being prepared for a seeding to grass or clover, the supply of manure should not be plowed down wherever the breaking-plow brings soil to the surface that is deficient in humus. In the latter case the manure always should be used as a top-dressing, and should be evenly spread and well mixed with the surface soil. It is needed there far more than it can be needed farther down. The surface soil always should have a high content of organic matter.
Heavy Applications.—When the farm supply of manure is small, applications should be light. The manure should not be the dependence for plant-food on a part of a field, or a single field of the farm, under such circumstances. It is more profitable to give a light dressing to a larger area. The manure is needed to make a fertilizing crop grow, and a very few tons per acre can assist greatly, when rightly used. The manure is needed to furnish bacteria to the soil, and a small amount per acre is useful for this purpose. Always there is temptation to use all the manure on a field convenient to the barn, and to concentrate it on a sufficiently small area to make a good yield sure. The loss to the farm in this method is heavy. The thin spots and the thin fields have first right to the manure as a top-dressing, and six tons per acre will bring larger returns per ton than twelve tons per acre. At the Pennsylvania experiment station the land receiving ten tons of manure per acre in the common four years' rotation of corn, oats, wheat, and mixed clover and grass gives added returns of $1.63 a ton, while an application of eight tons pays $1.85 a ton, and a six-ton application brings the value per ton up to $2.41. These applications are made twice in the four years.
Reënforcement with Minerals.—A ton of mixed manure in the stable contains about ten pounds of nitrogen, five pounds of phosphoric acid, and ten pounds of potash. This makes the percentage of nitrogen and potash the same, while the percentage of phosphoric acid is only half as high. A commercial fertilizer of such percentages would be esteemed a badly balanced one. Certainly the phosphoric acid should be relatively high, as this constituent of plant-food runs low in the soil. If 50 pounds of 14 per cent acid phosphate were added to each ton of manure while it is being made in the stable, seven pounds of phosphoric acid would be added, making the percentage in the manure a little higher than that of the nitrogen and the potash. A better balance is given to the fertility. There cannot be any loss in this purchased plant-food, if the stable floor is tight. Fermentation cannot drive it off, and when applied to the soil it is tightly held. Practically no phosphoric acid is found in drainage waters. Eight tons of manure thus reënforced would contain the same amount of plant-food as a ton of fertilizer having 4 per cent nitrogen, 5 per cent phosphoric acid, and 4 per cent potash. The addition of the 50 pounds of acid phosphate per ton does not bring the phosphoric acid content up as high relatively as in most commercial fertilizers, but it helps. The total amount in the eight tons manure may be sufficient, and the greater part of the total has sufficiently immediate availability, while the manure must undergo decomposition, and some of the nitrogen and potash does not become available within the year.
Durability of Manure.—Tests of the durability of manure in the soil involve some uncertain factors, but we are interested only in the effects of applications. These effects may continue for a long term of years, and an example will illustrate. Land may be too infertile to make a good clover sod. If a good dressing of manure be given half the land, affording proper conditions for making a sod, the result will be a heavy growth of clover, while the seeding on the unmanured half will be nearly a failure. If no manure or fertilizer be used in the crop-rotation, the probability is the manured portion of the field will again make a fairly good sod. How much this success may be due to the remains of the manure, and how much is attributable to the effect of the clover and to better bacterial life introduced and favored by the manure, no one knows. Probably the greater part of the benefit comes only indirectly from the manure applied three or four years previously. Half of the field may thus be lifted out of a helpless state and remain out of it for a long term of years, while the other half grows only poorer. A probable illustration of this lasting indirect effect may be seen in one of the plats in the soil fertility experiments on the Pennsylvania experiment station farm.
Experiments at the Rothamstead station, England, show some lasting results from applications of manure. Director Hall cites the case of one plat of grass land which was highly manured each year from 1856 to 1863, and has since been left unmanured. In 1864 this plat gave double the yield of an adjoining plat which had been left unmanured during the eight years. In 1865 the plat, last manured in 1863, gave over double the yield of the unmanured. In the following ten years its yield was a half more than that of the unmanured. In the next ten years the yield was a quarter more. In the next ten years it fell to 6 per cent more than the plat that had received no manure in the beginning of the experiment. In the following ten years it rose to 15 per cent. Here is a lasting effect of manure for over forty years where grass was grown continuously.
CHAPTER XV
CROP-ROTATIONS
The Farm Scheme.—Notwithstanding some of the theorizing that does not commend itself to the practical man, farm management is taking on the form of a science. It involves the organization of a farm for best results, and in the scheme that should be worked out for any particular farm the most important feature is the crop-rotation. The selection of crops is controlled by so many local considerations, including the personal likes and dislikes of the farmer, that very rightly the kinds of rotation are innumerable. The order in which crops may be grown with most profit is less variable, and yet even here local conditions may quickly derange the scheme of a theorist. There is, however, such right relation of facts to each other that we are getting a working philosophy, and the individual farmer can bend practice to his own liking in considerable degree, and yet not compel plants to do their part at a disadvantage. He has much liberty in the order of their growing, without endangering profits materially. Theoretically, this is not true, and the factors of production on any farm are such that the largest return is obtainable in only one scheme of farming. Practically there is rather wide liberty.
Value of Rotation.—Experience has shown the benefit of variety in crops grown on land. Among the advantages of crop-rotation are the following:
1. It enables the farmer to maintain the supply of organic matter in his soil. The roots and stubble of a grain crop are insufficient for this purpose, and the introduction of a sod or cover crop is helpful.2. It permits the use of legumes to secure cheap supplies of nitrogen.3. Some plants feed near the surface of the ground, and the use of other plants which send roots deeper adds to the production.4. Some crops leave the soil in bad physical condition, and the use of other crops in the rotation serves as a corrective.5. The keeping of livestock is made more feasible and profitable, and this leads to increase in farm manures.6. In a proper succession of crops the soil is covered with living plants nearly all the time, and thus is prevented from washing or leaching.7. In addition to these influences upon soil fertility, crop-rotation assists in control of insect and fungous foes and of weeds; it permits such distribution of labor on the farm that the largest total production may be secured by its employment; and it saves the farmer from sole dependence upon a single crop.
1. It enables the farmer to maintain the supply of organic matter in his soil. The roots and stubble of a grain crop are insufficient for this purpose, and the introduction of a sod or cover crop is helpful.
2. It permits the use of legumes to secure cheap supplies of nitrogen.
3. Some plants feed near the surface of the ground, and the use of other plants which send roots deeper adds to the production.
4. Some crops leave the soil in bad physical condition, and the use of other crops in the rotation serves as a corrective.
5. The keeping of livestock is made more feasible and profitable, and this leads to increase in farm manures.
6. In a proper succession of crops the soil is covered with living plants nearly all the time, and thus is prevented from washing or leaching.
7. In addition to these influences upon soil fertility, crop-rotation assists in control of insect and fungous foes and of weeds; it permits such distribution of labor on the farm that the largest total production may be secured by its employment; and it saves the farmer from sole dependence upon a single crop.
Penn's Valley, Pennsylvania.
Penn's Valley, Pennsylvania.
Selection of Crops.—The natural inclination of the farmer is a consideration that cannot be ignored. If a man does not like certain kinds of animals or crops, his farm or market must possess an unusual advantage to counter-balance. Illustration of this truth may be seen in every farming community.
As a rule, the crops should be those that are well adapted to the particular soils upon which they are grown. It is up-hill work to compete with producers whose soils have far better adaptation, unless the local markets equalize conditions.
The crops should follow each other in such succession that each crop naturally paves the way for the next one in the succession, or at least does not place its successor at a disadvantage.
When it is feasible, a rather large proportion of the entire produce of the rotation should be feeding-stuff for livestock, as soil fertility is most easily guarded by livestock farming. This is desirable when consistent with profit, but, as we have seen, it is not an absolute essential.
An Old Succession of Crops.—In the corn belt of the northern states some time-honored crop-rotations have been formed by corn, oats, wheat, clover, and timothy. The number of years devoted to the grain and to the sod has varied with the soil and the desire of its owner. A common succession is corn one year, oats one year, wheat one year, clover and timothy one year, timothy one year—a five years' rotation that has much substantial success behind it. Such a rotation is wholly reasonable and in accord with the nature of things. Every year furnishes some organic matter for the soil in roots and stubble, and all the produce of four years out of the five may be fed on the farm. There is one cash crop, or two if the price of the clear timothy hay justifies sale.
The manure may be hauled upon the sod when other work does not press, and it goes where the crop is one that prefers fresh manure, be that the grass or the corn. There is plenty of time after the corn to prepare for oats, and after the oats to prepare for wheat. The preparation for the wheat is sufficient for the clover and timothy. The seedings come only in the spring and the fall, when rainfall is more abundant and effective than in mid-summer. The danger of failure in case of this rotation is relatively small.
Corn Two Years.—Hunt says that the prosperity of the east, as a whole, would be greatly increased if the rotations of crops were so modified as to increase the corn acreage. He suggests the four rotations given in the table below, which is taken from Bulletin 116 of the Pennsylvania experiment station. The fertilizers recommended should maintain fertility.
Corn in Crop-rotations
The Oat Crop.—In the northern part of the corn belt the oat crop is profitable. In the southern half of Ohio and regions of like temperature the oat crop rarely pays. The heat, when the oat is in the milk stage, usually is too great. The tendency there is to eliminate this crop. Where silage is wanted, the stubble-land can be seeded directly to wheat with good results. A common practice is to seed to wheat between the shocked corn, and the wheat does poorly unless the soil is quite fertile.
Two Crops of Wheat.—A common practice has been to grow two crops of wheat, seeding first in the corn stubble-land, and plowing the ground for the second wheat crop, making a smooth surface for mowing. This method ceased to pay well when wheat became low in price. It has the advantage of giving two cash crops to the rotation.
Where winter wheat does not thrive in the north, it is dropped out, and the seeding to clover and grass is with the oat crop. There is the compensation of a large oat yield where the climate is too cold for a good crop of wheat.
In the Shenandoah Valley.
In the Shenandoah Valley.
The Clover and Timothy.—The timothy and clover sod is made inexpensively so far as labor is concerned. The first crop of hay is chiefly clover, and the soil is enriched by the roots and stubble, while the hay is converted into manure.
The second year the hay is nearly clear timothy. The sod should not be left until it becomes thin, but should be turned under while heavy, no matter if this must be after one season's harvest, or two. A sod stands three or four years for harvest on some farms, and without heavy fertilization there is decrease in fertility.
Two Legumes in the Rotation.—If all the crops of this five years' rotation, excepting wheat, were fed on the farm, and if all the manure were saved and rightly applied, there would be little or no difficulty in maintaining fertility, provided the soil were friendly to clover. The fact is that much such land has grown poorer, and it is known that another legume is needed in the rotation. The substitution of the soybean or cowpea for the oat crop gives excellent results. It makes a large supply of rich hay, and it fits the soil nicely for winter grain. The use of the breaking-plow is escaped. The surface of the land is in good tilth, especially if the legume was planted in rows so that cultivation could be given. A cutaway harrow, run shallow, and a roller make the seed-bed. Near the southern edge of the oat belt this substitution gives more value in the crop following corn, and at the same time conserves soil fertility.
Where land is thin, a four years' rotation of corn, soybeans or cowpeas, wheat, and clover is one of the best, because it contains two leguminous crops, and because one of them favors the wheat which follows and the clover seeded in the wheat.
Potatoes after Corn.—When potatoes are grown in the corn belt, a five years' rotation of corn, potatoes, oats, wheat, and clover, or corn, potatoes, wheat, clover, and timothy, is one of the best. When a late potato crop is grown, there is not time for seeding to wheat in cool latitudes, and the oat crop, or the soybean, fits in best. Farther south, where the oat crop is less profitable, there usually is time to go directly to wheat.
The advantage in this rotation is that the fresh manure can be used on the sod for the corn, and the potato thrives in the rotted remains of the sod and manure. Corn leaves the soil in good physical condition for the potato. Commercial fertilizer is used freely for the potato, which repays fertilization in higher degree than most other staple crops. The land can be prepared for seeding to wheat and grass with a minimum amount of labor. The rotation is excellent where there is enough fertility for the potato, which usually can be by far the most profitable crop in the entire rotation.
A Three Years' Rotation.—Farm conditions may require that certain fields in the farm go under a crop-rotation covering three years. In the winter wheat belt this may be clover, corn, and wheat, or clover, potatoes, and wheat. It is an excellent rotation when early planted potatoes or silage corn follows the sod, favoring the wheat in which the clover again is seeded. The ground is plowed only once in three years. The clover furnishes hay for the farm, and organic matter with nitrogen for the land. There are two cash crops in the rotation when potatoes are grown, and that makes a heavy draft upon fertility. Experience has demonstrated that commercial fertilizers or manure become necessary as a supplement to clover in a three years' rotation embracing potatoes. This rotation gives good control of most weeds and insect enemies.
Where wheat is unprofitable, the oat crop is used in its stead. If mixed hay is wanted, timothy is sown with the clover. This is poor practice from the standpoint of soil fertility because the draft upon humus is heavy in a close rotation embracing a tilled crop and small grain. The sod should be chiefly clover, or manure should be used in connection with commercial fertilizer.
Grain and Clover.—In the case of some soils it is possible to grow a wheat or corn crop each year, clover being grown as a catch crop. In the long run, this practice will fail because the clover will cease to make a thrifty growth when grown so nearly continuously. It succeeds best on fertile land.
Potatoes and Crimson Clover.—In some potato-producing sections in warm latitudes it is a not uncommon practice to grow potatoes year after year on the same land, seeding to crimson clover after the removal of the crop in August, and plowing the clover down early in the spring. Rye has been similarly used farther north. In each instance available plant-food must be freely supplied. The practice is a temporary expedient of value, but probably cannot be pursued indefinitely with profit. This is likewise true of similar close rotations.
CHAPTER XVI
THE NEED OF COMMERCIAL FERTILIZERS
Loss of Plant-food.—The soil is composed chiefly of material that never will enter into the structure of plants, but that serves us by affording a congenial place for plant-roots. It anchors the plants, holds moisture for them, and offers opportunity for all the processes necessary to the preparation of plant-food and to its use. In this material are the abundant supplies of such plant-food as silica, but, as has been previously stated, their very abundance leads us rightly to disregard them in our thinking. Our interest is only in the very small percentage of material that is composed of the four constituents which may be lacking in available form in the soil: nitrogen, phosphoric acid, potash, and lime. We believe that the only consideration that now need be given lime is as a soil-corrective and, when there is no acidity, we may assume that there is plenty of lime present. When yields of crops tend to decrease, the only plant-foods with which we are concerned are nitrogen, phosphoric acid, and potash.
The materials were stored in all agricultural land, and much of the supply is in inert forms. They help to make what we call the natural strength of the land. The rotting of organic matter, tillage, and many other agencies bring about some availability. The removal of crops, leaching, etc., reduce the supply. The right use of commercial fertilizers involves the addition of some plant-food when the available supply in a particular soil is inadequate.
Prejudice against Commercial Fertilizers.—The owner of land that was made very fertile by nature, and that has not been cropped long enough to reduce the supply of available fertility to the danger-point, rarely fails to entertain a prejudice against commercial fertilizers. It is the rule that he refuses to consider their use until the decrease in crop yields becomes so serious that necessity drives. If his land is not contributing its fair share of grain, vegetables, etc., to the markets, but has all its products converted into meat or milk, the supply of available plant-food may remain sufficient for so long a time that the matter cannot have any interest for him. If the land is producing some crops for market, there is reduction in its mineral store. It is the rule that the boundary of profitable use of commercial fertilizers pushes westward from the older and naturally poorer seaboard states about one generation after need shows in the crop yields. Lack of knowledge, the association of the use of commercial fertilizers with poor land, and some observation of the unwise use of fertilizers, combine to create a lively prejudice. They are viewed as stimulants only, and costly ones at that.
Are Fertilizers Stimulants?—Some words carry with them their own popular condemnation. We are accustomed to draw a sharp line between foods and stimulants, and to condemn the latter. To stimulate is to rouse to activity. Tillage does not add one pound of plant-food to the soil, and its office is to enable plants to draw material out of the soil. It makes activities possible that convert soil material into crops. Fertilizers add plant-food directly to the soil, and it is also to their credit that their judicious use favors increased availability in some of the compounds already in the soil. The greater part of the labor put on land is designed to make plant-food available, either by providing moisture, or ease of penetration of plant-roots, or activity of bacteria, or other means that will permit plants to remove what they need for growth. Fertilizers supply fertility directly and indirectly, but it is their direct service in meeting a deficiency in plant-food that affords all needed justification for their use by practical farmers.
Referring to the thirty years' soil fertility experiments of the Pennsylvania station, Hunt says that they "show that there is nothing injurious about commercial fertilizers. For thirty years certain plats in this experiment have received no stable manures. No organic matter has been added to the soil except that which was furnished by the roots and stubble of plants grown. These plats are not only as fertile as they were thirty years ago, but they have yielded, and continue to yield, as good crops as adjacent plats which have received yard manure every two years in place of commercial fertilizer."
Soil Analysis.—There is wide misconception regarding the value of chemical analysis of the soil as an aid in making choice of a fertilizer. Analysis has shown that some soil types are relatively richer in plant-constituents than are others, and it has shown abnormal deficiency in some types of limited area. It has given us more knowledge of soils, but as a guide to fertilization in particular instances it usually has no value. The samples used by an analyst are so small that the inaccuracy in his determination may easily be greater than the total amount of plant-food in a very heavy application of commercial fertilizer. A field that has been reduced to temporarily low productive power by heavy cropping or bad farming methods may show a greater content of plant-food than another field that is in a highly productive condition. This is a fact difficult of acceptance by some who want the aid of science, but such are the present limitations. The weight of a fertilizer application is so small in comparison with the weight of the surface part of an acre of land that the use of a ton of fertilizer may not be detected in the analyst's determinations, and moreover his determinations of actual availability in the soil's supplies are not serviceable in the selection of a fertilizer for any particular field and crop.
Physical Analysis.—Chemical analysis is costly and unsatisfactory as a guide to fertilization. Physical analysis by a competent man may have distinct value, and especially to one lacking experience with his soil. The mapping of soils by national and state authorities has given pretty accurate knowledge of hundreds of soil types, their location and characteristics, and when a soil expert obtains a sample of soil and the history of its past treatment, he can assign it to its type and give to its owner dependable advice regarding its crop-adaptation and probable fertilizer requirements.
The Use of Nitrogen.—There is no fully satisfactory way of determining the kind and amount of fertilizer that should be used at any particular time for any one crop. Perfection in this respect is no easier in attainment than in other matters. There are, however, means of arriving at conclusions that are a valuable guide.
In a general way, nitrogen is in scant supply in all worn soils. Wherever the cropping has been hard, and manure has not gone back to the land, the growth in stalk and leaves of the plant is deficient. The color is light. Inability of a soil to produce a strong growth of corn, a large amount of straw, or a heavy hay crop, is indicative of lack of nitrogen in nearly every instance.
The legumes, such as clover, and the stable manures are rich in nitrogen, and when the scheme of farming involves their use on all the land of the farm, no need of purchased nitrogen may arise in the production of staple crops. In the black corn soils the nitrogen content originally was high.
Lands that naturally are not very fertile rarely have enough available nitrogen. Where timothy is a leading crop, the demand for nitrogen is heavy. A cold spring or summer, checking nature's processes in the soil, may cause a temporary deficiency in available nitrogen in land that usually has a sufficient supply. Associating a rank growth of stalk and leaf with an abundance of nitrogen, the experienced man can form a pretty safe opinion regarding the probable profitableness of an investment in this element. It costs nearly four times as much per pound as either of the two other constituents of a fertilizer, and so far as is feasible it should be obtained through the legumes and stable manure.
Phosphoric-acid Requirements.—Soil analyses show that the content of phosphoric acid in most soils of this country is relatively small. The results of experiments with the various constituents of fertilizers are in accord with this fact. Fertilizer experiments at the various stations and on farms are nearly a unit in showing that if any need in plant-food exists, phosphoric acid is deficient. When crop-producing power decreases, and the farmer begins to seek a commercial fertilizer to repair the loss, he finds that bone-dust or acid phosphate is serviceable. The resulting increase in yield often leads to such sole dependence upon this fertilizer that clover and manure are disregarded, the percentage of humus is allowed to drop, and finally the fertilizer is brought into disrepute. The need of phosphoric acid is so common that it is the sole plant-food in much fertilizer, and the dominant element in practically all the remainder on the market.
Plat experiments.
Plat experiments.
The Need of Potash.—Land which is deficient in organic matter ordinarily is lacking in available potash, and responds with profit to applications, provided the nitrogen and phosphoric-acid requirements have been met. Clay soils contain far more potash than sandy soils, and in a farming scheme for them that permits the use of manure and clover, it may not become necessary to buy much potash. The liberal use of straw in the stables, and the saving of all the liquid manure, are helps. Farms from which the hay and straw have been sold for a long period of time develop an urgent need of potash. Much muck land is very deficient in this constituent.
Fertilizer Tests.—Every farmer should conduct some fertilizer tests for himself. It is only the soil itself that can make an adequate reply to a question regarding its needs. The test should be made under conditions furnishing evenness in the soil, and it should be continued for years. There is pleasure to an intelligent farmer in such questioning of his soil, and only in this way can assurance be obtained that the investment in fertilizers is the wisest that can be planned for the farm.
There are only three plant constituents to be tested, but they must be used in combination as well as singly. A soil that is deficient in the three may not give any return from potash alone, and usually does not, although it may give a marked increase from use of phosphoric acid alone. The plats may be eight rods long and one rod wide, containing each one twentieth of an acre, and having strips two feet wide separating them. The following chart suggests quantities of fertilizers to be used on the one-twentieth acre plats, 10 in number:
Variation in Soil.—The difficulty in determining the character of fertilizer for a field, due to variation in the soil, is overestimated. Very often a land-owner says, "I have a dozen kinds of soil in every field." This is true in a way, it may be, but if all the field has had the same treatment in the past, the probability is that the fertilizer which is best for one part of the field will be quite good for the other parts. The likeness in characteristics that permits the land to be cropped as one field gives some assurance of likeness in plant-food needs, even where the proportion of clay and sand varies and the color is not the same.
There may be wide variation in the productive power of the fields of a farm, due to the treatments they have received. The land that grows heavy clover in a close rotation, or receives all the stable manure, may need neither nitrogen nor potash, while another field, hard-run by timothy and corn, may need a complete fertilizer. When a careful fertilizer test on land of only average productive power has been made, the owner has some definite knowledge of his soil that enables him to give more intelligent treatment to all his fields than was possible before the test had been made. He observes the appearance and yield of plants where the plant-food requirement was fully met, and makes allowance in other fields for gains or losses in the soil due to different treatment. It is out of the question to become discouraged before a beginning has been made. If yields are limited by absence of plant-food, fertilizers must be used. If money must be expended for fertilizers, it is only good business to know that the money is expended to the best advantage.
CHAPTER XVII
COMMERCIAL SOURCES OF PLANT-FOOD
Acquaintance with Terms.—The hesitation of many users of commercial fertilizer to master the few technical terms used in analyses of the goods, for which over one hundred million dollars annually are expended in this country, is to be deplored. The number of the materials available for any large use as sources of plant-food in a commercial fertilizer is small, and something of their characteristics should be known. Every farmer should have a working knowledge of these materials—their sources, the percentage of plant-food carried by them, and their probable availability. He should know in a general way their advantages and disadvantages in comparison with each other.
Nitrate of Soda.—One of the best carriers of nitrogen is nitrate of soda, which is imported from Chili, South America, where great beds exist. The most of the impurities are removed, and the nitrate of soda comes to us in bags holding 200 pounds, and looks much like discolored salt. It is easily soluble in water, and usually contains a little over 15 per cent of nitrogen, which is in a very available form. Its immediate availability brings it into use by gardeners and truckers, and it is an excellent source of nitrogen for grass fertilizers to be used in the early spring. It was formerly advised that nitrate of soda should not form part of a fertilizer for use before plant-roots had filled the ground, its high availability being supposed to lead to heavy loss by leaching. The Pennsylvania experiment station uses it as its sole source of nitrogen in fertilizers for staple crops on its 900 acres of farm land. It is effective in fertilizers for corn, wheat, potatoes, and grass, as well as for special crops.
The warnings regarding loss by leaching should not be disregarded, however. If the price of nitrogen in an organic form were as low as it has been in nitrate of soda, and if the soils of the Pennsylvania station farms were sandy, the use of nitrate of soda as the sole carrier of nitrogen would be inadvisable. The only fact of consequence is that the danger of loss has been over-stated, turning some farmers away from the use of a good and relatively cheap carrier of nitrogen.
Sulphate of Ammonia.—This is a by-product in the manufacture of coke and also of illuminating gas. Hunt estimates that the amount of nitrogen lost annually in Pennsylvania's coke industry would be sufficient, if recovered by proper type of ovens, to furnish every acre of land under cultivation in the state with four fifths of all the nitrogen needed to keep it in a maximum state of fertility.
Sulphate of ammonia contains about 20 per cent of nitrogen, which is in a quite available form. It has a tendency to exhaust the lime in the soil, producing an acid condition. Some plats in the fertilizer experiment at the Pennsylvania station have received their nitrogen in the form of sulphate of ammonia for 30 years, and are now in such acid condition that no crops thrive upon them. The corrective, of course, is lime, and if ammonium sulphate were somewhat lower in price, its use would be profitable, justifying cost of correction of acidity if it should occur. It is used by manufacturers of commercial fertilizers, and is well adapted to mixtures on account of its physical condition.
Dried Blood.—There is no more satisfactory source of organic nitrogen than dried blood of high grade. The best blood, red in color, contains nearly as much nitrogen as nitrate of soda, running from 13 to 15 per cent. The nitrogen is not as quickly available as that in the nitrate, but is more so than that in any other form of organic nitrogen. One would rarely go amiss in the purchase of dried blood as a carrier of nitrogen if the price were relatively as low as in the case of nitrate of soda, but he should not let any prejudice in favor of animal origin of fertilizers lead him to pay an excessive price per pound for the nitrogen contained in it. Such a prejudice has caused the nitrogen in a good red blood to sell for one half more per pound than in nitrate of soda, and it is not a good purchase on that basis.
The lower grades of dried blood on the market contain as low as 6 per cent of nitrogen, and the animal refuse put into it gives it a content of a few per cent of phosphoric acid. This black blood is very variable in composition, and should always be accompanied by a guaranteed analysis.
Tankage.—The waste from the slaughter of animals goes into a product called tankage. The refuse is cooked for removal of the fat, and then ground. It may run high in nitrogen on account of the amount of meat in the mixture, and it may be low in nitrogen and very high in phosphoric acid by reason of the large amount of bone in the mixture. Only a guarantee of analysis affords safety to the buyer. It is a relatively slow and good fertilizer, and is used usually in connection with forms of plant-food that are more quickly available.
Fish.—Near the Atlantic coast a large quantity of ground fish, after the extraction of oil, is used as a fertilizer, but the cost of the nitrogen and phosphoric acid in this carrier is relatively too high to justify its free use. Like dried blood, its organic character gains for it a popularity that does not have full justification in fact.
Animal Bone.—The original source of phosphoric acid as a fertilizer was animal bone, just as hard-wood, unleached ashes were the source of potash. The organic character of the animal bone made it appear more truly a manure than could any rock or other inorganic substance. There is no more satisfactory source of phosphoric acid than animal bone, and if it were in full supply for the needs of soils, there would be little occasion to discuss the merits of rock-phosphate and other similar materials. The supply is a small fraction of the need. If all animal bone were carefully saved and returned to the land that produced all of our animals, it would return to the soil only what those animals carried away in their bones, and that is indeed a small fraction of all the draft our crops make upon the soil's supply of this one substance. Some of the best animal bone goes into the manufacture of articles that never contribute anything to the soil, and there are other sources of loss. The supply of phosphoric acid from bone is too small, when compared with the land's need, to deserve more than a small fraction of the consideration it receives by users of commercial fertilizers.
The peculiar situation respecting animal bone has come about through a form of deceit. The demand for bone existed, and there was no legal restraint in the matter of branding phosphatic rock as "bone," "bone-phosphate," etc. In the past, nearly all forms of rock-phosphates have carried the word "bone" on the bag to quiet the apprehension of those who entertained a prejudice against anything other than animal bone. Nearly all the phosphoric acid has come from rock, and its use has been necessary and profitable, but the misrepresentation fostered the old-time prejudice. Within recent years some manufacturers have tired of the seeming deceit that served no purpose with many customers, and have placed acid phosphate and mixed goods upon the market without the intimation that the phosphoric acid was derived from animal bone.
The demand for bone makes prices high for the very limited amount upon the market, when availability is taken into account, and the advice that such goods be used would be valueless if it had any general acceptance. Prices would go higher, and the amount in the world would remain wholly inadequate.
Raw Bone.—Stable manure lasts several years in the soil because decay is slow. Raw bone has appealed to many because its action is likewise necessarily slow. The fat in it prevents fine grinding and protects the coarse particles from decay. It is known as bone-meal or coarse ground-bone. A good quality of raw bone may contain 4 per cent of nitrogen, while the phosphoric-acid content is 20 to 25 per cent. The bones of old animals is less rich in nitrogen. The age of the animals, and the sorting for manufactures of various kinds, cause variation in quality, and the purchase of raw bone should be made on guaranteed analysis just as surely as the purchase of bone that has been treated in any way for removal of various substances in it.
Steamed Bone.—When animal bone is boiled or steamed under pressure for removal of the fat and the cartilage, the content of nitrogen is reduced, and the percentage of phosphoric acid is increased by this removal of fat and nitrogenous substance. The nitrogen in steamed bone may run as low as 1 per cent, and the phosphoric acid may go up to 30 per cent. The composition of steamed bone is so widely variable that the name means little, and purchase should be made only on guaranteed analysis. Some grades run very low both in nitrogen and phosphoric acid, due probably to adulteration.
The boiling or steaming of bone makes fine grinding possible, and the fineness and absence of fat permit quick decay in the soil. Steamed bone is an excellent source of phosphoric acid. The availability is less immediate than that of acid phosphate, but much greater than that of raw bone.
Rock-phosphate.—While the greater part of our soils contain relatively scant stores of phosphoric acid, the deposits of this plant constituent in combination with lime are immense. The rock now chiefly used in this country is found in South Carolina, Tennessee, and Florida. It varies greatly in content of phosphoric acid. When pulverized for direct use on land, without treatment with sulphuric acid to make the plant-food available, a grade running 28 per cent phosphoric acid, or less, usually is selected, the higher grades being reserved for treatment with acid or for export. This untreated rock, pulverized exceedingly fine, often is known as floats.
The value of a pound of phosphoric acid in floats, as compared with that of a pound in the treated rock, known as acid phosphate, is a matter upon which scientists differ widely. Only a small percentage of the plant-food is immediately available, and the question of wise use hinges upon the degree of availability gained later, and the time required. The large amount of experimental work that has been done affords data that causes the following opinion to be stated here: Rock-phosphate, known as floats, is not a profitable source of plant-food for soils deficient in organic matter, when compared with acid phosphate. It is more nearly profitable in an acid soil than in one that has no lime deficiency. It gives more satisfactory results when mixed intimately with stable manure than when used upon land that remains deficient in organic matter. Applications should be in large amount per acre—500 to 1000 pounds—in order that the amount of readily available phosphoric acid may meet the immediate need of plants. Dependence should be placed upon the readily available acid phosphate in all instances until experiment on the farm shows that the rock-phosphate is a cheaper source of plant-food than the acid phosphate.
Acid Phosphate.—When animal bone is treated with sulphuric acid, the result is an acid phosphate, but treated animal bone is so rare on the market that it may be ignored. The acid phosphate on the market is rock-phosphate treated with sulphuric acid to render its plant-food available. The content of phosphoric acid varies because the original rock-phosphate varies, but the most common grade on the market is guaranteed to contain 14 per cent available phosphoric acid, and 1 to 2 per cent insoluble. Some acid phosphate is guaranteed to contain 16 per cent available phosphoric acid, and some runs down to 10 per cent available.
An acid phosphate contains quickly available plant-food. A prejudice exists against it on account of its source, and it has been a common practice to label the bags "bone-phosphate," or "dissolved bone," or such other designation as would imply an organic source, but the acid phosphate is made out of rock-phosphate, regardless of the name given. The prejudice against the rock as a source of plant-food is giving way. It is our chief and cheapest source of supply. The combination of sulphuric acid with rock-phosphate in the production of acid phosphate produces sulphate of lime, known as gypsum or land-plaster. The amount of gypsum in a ton of acid phosphate varies, but may be roughly estimated by the buyer as two thirds of the total weight of the acid phosphate.
The tendency of gypsum is, in the long run, to make a soil acid, and its use necessarily hastens rather than retards the day when a lime deficiency will occur. The influence in this direction is not great enough to be a very material factor in deciding upon a carrier of phosphoric acid. If a soil has little lime in it, a state of acidity soon will come anyway, and the increase in amount of required lime will be small. The cheapness of acid phosphate, as compared with animal bone, is the decisive factor.
The ill-effects usually attributed to acid phosphate are not due in any great degree directly to the sulphuric acid used in its making, but to the bad farming methods that so often attend its use. When the need of commercial fertilizers is first recognized, acid phosphate seems to meet the need. The soil's store of available phosphoric acid gives out first, and this fertilizer brings a new supply. If the available potash is in scant amount, the acid phosphate helps in this direction by freeing some potash. The phosphoric acid has peculiar ability in giving impetus to the growth of a young plant, and that enables it to send its roots out and obtain more nitrogen than it otherwise would do. The farmer thus may come to regard it as a means of securing a crop, and there is neglect of manure and clover. If a field is thin and fails to make a sod, there is no immediate compulsion to use manure or to grow a catch crop to get organic matter, but the field is cropped again with grain. Soon the supply of humus is exhausted, the soil lies lifeless, and the stores of available nitrogen and potash are in a worse depleted state than formerly.
The fault lies with the method. The phosphoric acid in the acid phosphate was needed. Profit from its use was legitimate, but the necessity of supplying organic matter became even greater than it would have been otherwise. Tens of thousands of our most successful farmers use heavy applications of acid phosphate, but they keep their soils in good physical condition by the use of manure or clover, and they apply potash and nitrogen when needed. The clover is assured by using lime wherever it is in too limited supply, and that is the case in most instances, regardless of the use of any kind of commercial fertilizer.
Basic Slag.—When iron ores contain much phosphorus, its extraction by use of lime gives a by-product in the making of steel that has agricultural value. The ores of the United States usually do not give a slag sufficiently rich in phosphorus to be valuable. Nearly all the basic slag used as a fertilizer is imported from Germany, and usually contains 17 to 18 per cent of phosphoric acid. The availability of the plant-food in this fertilizer has been the subject of much discussion. The chemist's test which is fair for acid phosphate is admittedly not fair when used for basic slag. Field tests, at experiment stations and on farms, are our best sources of knowledge. When the soil is slightly acid, each 1 per cent of phosphoric acid in the slag appears to be about as valuable as each 1 per cent of the available phosphoric acid in an acid phosphate. Some of the effectiveness may be due to the lime, although very little of it is in forms regarded as valuable for the correction of soil acidity. There is evidence that basic slag favors clover. It has not been found feasible to ship this material many hundreds of miles inland from the seaboard to compete with acid phosphate, but it is an excellent source of phosphoric acid for soils that are not rich in lime.
Muriate of Potash.—The mines of Stassfurt, Germany, contain an inexhaustible supply of potash in various compounds. Muriate of potash is prepared from the crude salts, and the commercial product on our markets has the appearance of a coarse and discolored salt. It is handled in large bags, and inclines to become moist by absorption of water from the air. It contains some common salt. The content of actual potash is about 50 per cent. The potash is readily available, but the loss from leaching out of the soil is very small. Muriate of potash is our cheapest source of potash, and should be used for all staple crops except tobacco, sugar beets, and, possibly, the potato. Tests even on heavy soils fail to show any injury to the quality of the potato, and on light soil the muriate may always be used.
Sulphate of Potash.—Some sulphate of potash is imported into this country. Its content of potash may vary 1 or 2 per cent below or above 50. Its physical condition favors mixing more than does the muriate. It usually costs several dollars a ton more than the muriate, and the fact that it is known to favor quality in tobacco, and is popularly supposed to do so in the potato, creates demand at the higher price. It is soluble in water, and quickly available. As a rule, it has no higher agricultural value than the muriate.
Kainit.—Unlike muriate and sulphate of potash, kainit is a crude product of the German mines, having received no treatment to remove impurities. It contains 12 to 13 per cent of potash, and is rated as a sulphate, but one third of it is common salt, and in effect upon quality it should be classed with muriate and not sulphate. Its low content of plant-food should confine its use to regions relatively near the seaboard. When shipped far inland, the price becomes too high to give a reasonably cheap pound of potash.
Wood-ashes.—Wood-ashes contain lime and potash, with a small percentage of phosphoric acid. The market price is above agricultural value, and any needed potash should be obtained from the German potash salts.
Other Fertilizers.—Manufacturers of commercial fertilizer make use of other materials, some of which, like manufactured nitrogen, are excellent, and others are low in quality and slow in action. The sources of plant-food that have been described form the great bulk of all fertilizers on the market, and from them may be selected all the materials a farmer needs to use on his land, either singly or home-mixed. In most instances the selection will embrace only four or five of these fertilizing materials.
Salt.—Salt is not a direct fertilizer, and its use is not to be advised unless it can be secured at a very low price per ton. Some soils have been made more productive by the application of 200 to 300 pounds per acre, and chiefly in case the salt was mixed well with the soil when the seed-bed was made. The practice of using salt as a top-dressing on wheat in the spring gives less effectiveness it is believed. Salt frees potash in the soil, and may have some practical effect upon soil moisture. As a soil amendment, salt has had more reputation than its performance justifies. If land is infertile, it is better, as a rule, to apply actual plant-food.
Coal-ashes.—There is no plant-food of value in coal-ashes. The physical condition of heavy soils is improved by an application, and their use may be quite profitable in this way if cost of application is small. When used as a mulch, ashes conserve moisture.
Muck.—The use of muck pays in stables, as it is a good absorbent and contains some nitrogen which gains in availability by mixture with manure. Its direct application to land as a fertilizer does not pay the labor bill under ordinary circumstances.
Sawdust.—As a fertilizer, sawdust does not have much value, but serves as an excellent absorbent in stables. Its presence in manure need not cause fear of injury to the soil. When fresh sawdust is applied in large quantity to a sandy soil, the effect upon physical condition is bad, increasing drouthiness.