Crops and Methods for Soil Improvement Part 8

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 subst.i.tution 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 subst.i.tution 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 lat.i.tudes, 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 gra.s.s 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 lat.i.tudes 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 const.i.tuents 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 a.s.sume 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 a.s.sociation 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 a.n.a.lysis.--There is wide misconception regarding the value of chemical a.n.a.lysis of the soil as an aid in making choice of a fertilizer. a.n.a.lysis has shown that some soil types are relatively richer in plant-const.i.tuents 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 a.n.a.lyst 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 a.n.a.lyst'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 a.n.a.lysis.--Chemical a.n.a.lysis is costly and unsatisfactory as a guide to fertilization. Physical a.n.a.lysis 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 a.s.sign 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. a.s.sociating 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 const.i.tuents of a fertilizer, and so far as is feasible it should be obtained through the legumes and stable manure.

Phosphoric-acid Requirements.--Soil a.n.a.lyses show that the content of phosphoric acid in most soils of this country is relatively small. The results of experiments with the various const.i.tuents 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.

[Ill.u.s.tration: 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 const.i.tuent.

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 furnis.h.i.+ng 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 a.s.surance be obtained that the investment in fertilizers is the wisest that can be planned for the farm.

There are only three plant const.i.tuents 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 quant.i.ties of fertilizers to be used on the one-twentieth acre plats, 10 in number:

+---------------------------------------+ | Nothing. | +---------------------------------------+ | 5 pounds nitrate of soda. | +---------------------------------------+ | 18 pounds 14 per cent acid phosphate. | +---------------------------------------+ | 4 pounds muriate of potash. | +---------------------------------------+ | Nothing. | +---------------------------------------+ | 5 pounds nitrate of soda. | | 18 pounds 14 per cent acid phosphate. | +---------------------------------------+ | 5 pounds nitrate of soda. | | 4 pounds muriate of potash. | +---------------------------------------+ | 18 pounds 14 per cent acid phosphate. | | 4 pounds muriate of potash. | +---------------------------------------+ | 5 pounds nitrate of soda. | | 18 pounds 14 per cent acid phosphate. | | 4 pounds muriate of potash. | +---------------------------------------+ | Nothing. | +---------------------------------------+

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 a.s.surance 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 a.n.a.lyses 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 gra.s.s 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 gra.s.s, 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 c.o.ke and also of illuminating gas. Hunt estimates that the amount of nitrogen lost annually in Pennsylvania's c.o.ke 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 a.n.a.lysis.

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 a.n.a.lysis 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 quant.i.ty 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.