CHAPTER IX
DEFICIENCIES OF SOILS, MEANS OF RESTORATION, ETC
As will be seen by referring to the analyses of soils on p. 72, they may be deficient in certain ingredients, which it is the object of mineral manures to supply. These we will take up in order, and endeavor to show in a simple manner the best means of managing them in practical farming.
ALKALIES
POTASH
Do all soils contain a sufficient amount of potash?
How may its deficiency have been caused?
How may its absence be detected?
Does barn-yard manure contain sufficient potash to supply its deficiency in worn-out soils?
Potash is often deficient in the soil. Its deficiency may have been caused in two ways. Either it may not have existed largely in the rock from which the soil was formed, and consequently is equally absent from the soil itself, or it may have once been present in sufficient quantities, and been carried away in crops, without being returned to the soil in the form of manure until too little remains for the requirements of fertility.
In either case, its absence may be accurately detected by a skilful chemist, and it may be supplied by the farmer in various ways. Potash, as well as all of the other mineral manures, is contained in the excrements of animals, but not (as is also the case with the others) in sufficient quantities to restore the proper balance to soils where it is largely deficient, nor even to make up for what is yearly removed with each crop, except that crop (or its equivalent) has been fed to such animals as return all of the fertilizing constituents of their food in the form of manure, and this be all carefully preserved and applied to the soil. In all other cases, it is necessary to apply more potash than is contained in the excrements of animals.
What is generally the most available source from which to obtain this alkali?
Will leached ashes answer the same purpose?
How may ashes be used?
Unleached wood ashes is generally the most available source from which to obtain this alkali. The ashes of all kinds of wood contain potash (more or less according to the kind—see analysis section V.) If the ashes are leached, the potash is removed; and, hence for the purpose of supplying it, they are worthless; but unleached ashes are an excellent source from which to obtain it. They may be made into compost with muck, as directed in a previous chapter, or applied directly to the soil. In either case the potash is available directly to the plant, or is capable of uniting with the silica in the soil to form silicate of potash. Neither potash nor any other alkali should ever be applied to animal manures unless in compost with an absorbent, as they cause the ammonia to be thrown off and lost.
From what other sources may potash be obtained?
How may we obtain soda?
In what quantities should pure salt be applied to the soil?
Potash sparlings, or the refuse of potash warehouses, is an excellent manure for lands deficient in this constituent.
Potash marl, such as is found in New Jersey, contains a large proportion of potash, and is an excellent application to soils requiring it.
Feldspar, kaolin, and other minerals containing potash, are, in some localities, to be obtained in sufficient quantities to be used for manurial purposes.
Granite contains potash, and if it can be crushed (as is the case with some of the softer kinds,) it serves a very good purpose.
SODA
If applied in large quantities will it produce permanent injury?
In what quantities should salt be applied to composts? To asparagus?
Soda, the requirement of which is occasioned by the same causes as create a deficiency of potash, and all of the other ingredients of vegetable ashes, may be very readily supplied by the use of common salt (chloride of sodium), which consists of about one half sodium (the base of soda). The best way to use salt is in the lime and salt mixture, previously described, or as a direct application to the soil. If too much salt be given to the soil it will kill any plant. In small quantities, however, it is highly beneficial, and if six bushels per acre be sown broadcast over the land, to be carried in by rains and dews, it will not only destroy many insects (grubs, worms, etc.), but will, after decomposing and becoming chlorine and soda, prove an excellent manure. Salt, even in quantities large enough to denude the soil of all vegetation, is never permanently injurious. After the first year, it becomes resolved into its constituents, and furnishes chlorine and soda to plants, without injuring them. One bushel of salt in each cord of compost will not only hasten the decomposition of the manures, but will kill all seeds and grubs—a very desirable effect. While small quantities of salt in a compost heap are beneficial, too much (as when applied to the soil) is positively injurious, as it arrests decomposition; fairly pickles the manures, and prevents them from rotting.
What is generally the best way to use salt?
What is nitrate of soda?
What plants contain lime?
For asparagus, which is a marine plant, salt is an excellent manure, and may be applied in almost unlimited quantities, while the plants are growing, if used after they have gone to top, it is injurious. Salt has been applied to asparagus beds in such quantities as to completely cover them, and with apparent benefit to the plants. Of course large doses of salt kill all weeds, and thus save labor and the injury to the asparagus roots, which would result from their removal by hoeing. Salt may be used advantageously in any of the foregoing manners, but should always be applied with care. For ordinary farm purposes, it is undoubtedly most profitable to use the salt with lime, and make it perform the double duty of assisting in the decomposition of vegetable matter, and fertilizing the soil.
Soda unites with the silica in the soil, and forms the valuable silicate of soda.
Nitrate of soda, or cubical nitre, which is found in South America, consists of soda and nitric acid. It furnishes both soda and nitrogen to plants, and is an excellent manure.
LIME
The subject of lime is one of most vital importance to the farmer; indeed, so varied are its modes of action and its effects, that some writers have given it credit for every thing good in the way of farming, and have gone so far as to say that all permanent improvement of agriculture must depend on the use of lime. Although this is far in excess of the truth (as lime cannot plow, nor drain, nor supply any thing but lime to the soil), its many beneficial effects demand for it the closest attention.
Do all soils contain enough lime for the use of plants?
What amount is needed for this purpose?
What is its first-named effect on the soil?
Its second? Third? Fourth? Fifth?
How are acids produced in the soil?
As food for plants, lime is of considerable importance. All plants contain lime—some of them in large quantities. It is an important constituent of straw, meadow hay, leaves of fruit trees, peas, beans, and turnips. It constitutes more than one third of the ash of red clover. Many soils contain lime enough for the use of plants, in others it is deficient, and must be supplied artificially before they can produce good crops of those plants of which lime is an important ingredient. The only way in which the exact quantity of lime in the soil can be ascertained is by chemical analysis. However, the amount required for the mere feeding plants is not large, (much less than one per cent.), but lime is often necessary for other purposes; and setting aside, for the present, its feeding action, we will examine its various effects on the mechanical and chemical condition of the soil.
1. It corrects acidity (sourness).
2. It hastens the decomposition of the organic matter in the soil.
3. It causes the mineral particles of the soil to crumble.
4. By producing the above effects, it prepares the constituents of the soil for assimilation by plants.
5. It is said to exhaust the soil, but it does so in a very desirable manner, the injurious effects of which may be easily avoided.
How does lime correct them?
How does it affect animal manures in the soil?
1. The decomposition of organic matter in the soil, often produces acids which makes the land sour, and cause it to produce sorrel and other weeds, which interfere with the healthy growth of crops. Lime is an alkali, and if applied to soils suffering from sourness, it will unite with the acids, and neutralize them, so that they will no longer be injurious.
2. We have before stated that lime is a decomposing agent, and hastens the rotting of muck and other organic matter. It has the same effect on the organic parts of the soil, and causes them to be resolved into the gases and minerals of which they are formed. It has this effect, especially, on organic matters containing nitrogen, causing them to throw off ammonia; consequently, it liberates this gas from the animal manures in the soil.
3. Various inorganic compounds in the soil are so affected by lime, that they lose their power of holding together, and crumble, or are reduced to finer particles, while some of their constituents are rendered soluble. One way in which this is accomplished is by the action of the lime on the silica contained in these compounds, forming the silicate of lime. This crumbling effect improves the mechanical as well as the chemical condition of the soil.
4. We are now enabled to see how lime prepares the constituents of the soil for the use of plants.
Inorganic compounds?
How does lime prepare the constituents of the soil for use?
What can you say of the remark that lime exhausts the organic matter in the soil?
By its action on the roots, buried stubble, and other organic matter in the soil, it causes them to be decomposed, and to give up many of their gaseous and inorganic constituents for the use of roots. In this manner the organic matter is prepared for use more rapidly than would be the case, if there were no lime present to hasten its decomposition.
By the decomposing action of lime on the mineral parts of the soil (3), they also are placed more rapidly in a useful condition than would be the case, if their preparation depended on the slow action of atmospheric influences.
Thus, we see that lime, aside from its use directly as food for plants, exerts a beneficial influence on both the organic and inorganic parts of the soil.
5. Many contend that lime exhausts the soil.
If we examine the manner in which it does so, we shall see that this is no argument against its use.
How can lime exhaust the mineral parts of the soil?
Must the matter taken away be returned to the soil?
It exhausts the organic parts of the soil, by decomposing them, and resolving them into the gases and minerals of which they are composed. If the soil do not contain a sufficient quantity of absorbent matter, such as clay or charcoal, the gases arising from the organic matter are liable to escape; but when there is a sufficient amount of these substances present (as there always should be), these gases are all retained until required by the roots of plants. Hence, although the organic matter of manure and vegetable substances may be altered in form, by the use of lime, it can escape (except in very poor soils) only as it is taken up by roots to feed the crop, and such exhaustion is certainly profitable; still, in order that the fertility of the soil may be maintained, enough of organic manure should be applied, to make up for the amount taken from the soil by the crop, after liberation for its use by the action of the lime. This will be but a small proportion of the organic matter contained in the crop, as it obtains the larger part from the atmosphere.
The only way in which lime can exhaust the inorganic part of the soil is, by altering its condition, so that plants can use it more readily. That is, it exposes it for solution in water. We have seen that fertilizing matter cannot be leached out of a good soil, in any material quantity, but can only be carried down to a depth of about thirty-four inches. Hence, we see that there can be no loss in this direction; and, as inorganic matter cannot evaporate from the soil, the only way in which it can escape is through the structure of plants.
If this course be pursued, will the soil suffer from the use of lime?
Is it the lime, or its crop, that exhausts the soil?
Is lime containing magnesia better than pure lime?
What is the best kind of lime?
If lime is applied to the soil, and increases the amount of crops grown by furnishing a larger supply of inorganic matter, of course, the removal of inorganic substances from the soil will be more rapid than when only a small amount of crop is grown, and the soil will be sooner exhausted—not by the lime, but by the plants. In order to make up for this exhaustion, it is necessary that a sufficient amount of inorganic matter be supplied to compensate for the increased quantity taken away by plants.
Thus we see, that it is hardly fair to accuse the lime of exhausting the soil, when it only improves its character, and increases the amount of its yield. It is the crop that takes away the fertility of the soil (the same as would be the case if no lime were used, only faster as the crop is larger), and in all judicious cultivation, this loss will be fully compensated by the application of manures, thereby preventing the exhaustion of the soil.
Is the purchase of marl to be recommended?
How is lime prepared for use? (Note.)
Describe the burning and slaking of lime.
Kind of lime to be used. The first consideration in procuring lime for manuring land, is to select that which contains but little, if any magnesia. Nearly all stone lime contains more or less of this, but some kinds contain more than others. When magnesia is applied to the soil, in too large quantities, it is positively injurious to plants, and great care is necessary in making selection. As a general rule, it may be stated, that the best plastering lime makes the best manure. Such kinds only should be used as are known from experiment not to be injurious.
Shell lime is undoubtedly the best of all, for it contains no magnesia, and it does contain a small quantity of phosphate of lime. In the vicinity of the sea-coast, and near the lines of railroads, oyster shells, clam shells, etc., can be cheaply procured. These may be prepared for use in the same manner as stone lime.31
The preparation of the lime is done by first burning and then slaking, or by putting it directly on the land, in an unslaked condition, after its having been burned. Shells are sometimes ground, and used without burning; this is hardly advisable, as they cannot be made so fine as by burning and slaking. As was stated in the first section of this book, lime usually exists in nature, in the form of carbonate of lime, as limestone, chalk, or marble (being lime and carbonic acid combined), and when this is burned, the carbonic acid is thrown off, leaving the lime in a pure or caustic form. This is called burned lime, quick-lime, lime shells, hot lime, etc. If the proper quantity of water be poured on it, it is immediately taken up by the lime, which falls into a dry powder, called slaked lime. If quick-lime were left exposed to the weather, it would absorb moisture from the atmosphere, and become what is termed air slaked.
What is air slaking?
If slaked lime be exposed to the air, what change does it undergo?
What is the object of slaking lime?
How much carbonic acid is contained in a ton of carbonate of lime?
How much lime does a ton of slaked lime contain?
What is the most economical form for transportation?
When slaked lime (consisting of lime and water) is exposed to the atmosphere, it absorbs carbonic acid, and becomes carbonate of lime again; but it is now in the form of a very fine powder, and is much more useful than when in the stone.
If quick-lime is applied directly to the soil, it absorbs first moisture, and then carbonic acid, becoming finally a powdered carbonate of lime.
One ton of carbonate of lime contains 11¼ cwt. of lime; the remainder is carbonic acid. One ton of slaked lime contains about 15 cwt. of lime; the remainder is water.
Hence we see that lime should be burned, and not slaked, before being transported, as it would be unprofitable to transport the large quantity of carbonic acid and water contained in carbonate of lime and slaked lime. The quick-lime may be slaked, and carbonated after reaching its destination, either before or after being applied to the land.
What is the best form for immediate action on the inorganic matter in the soil?
For most other purposes?
As has been before stated, much is gained by slaking lime with salt water, thus imitating the lime and salt mixture. Indeed in many cases, it will be found profitable to use all lime in this way. Where a direct action on the inorganic matters contained in the soil is desired, it may be well to apply the lime directly in the form of quick-lime; but, where the decomposition of the vegetable and animal constituents of the soil is desired, the correction of sourness, or the supplying of lime to the crop, the mixture with salt would be advisable.
The amount of lime required by plants is, as was before observed, usually small compared with the whole amount contained in the soil; still it is not unimportant.
[AH] The straw producing the grain and the turnip and potato tops contain more lime than the grain and roots.
What is the best guide concerning the quantity of lime to be applied?
What is said of the sinking of lime in the soil?
What is plaster of Paris composed of?
Why is it called plaster of Paris?
The amount of lime required at each application, and the frequency of those applications, must depend on the chemical and mechanical condition of the soil. No exact rule can be given, but probably the custom of each district—regulated by long experience—is the best guide.
Lime sinks in the soil; and therefore, when used alone, should always be applied as a top dressing to be carried into the soil by rains. The tendency of lime to settle is so great that, when cutting drains, it may often be observed in a whitish streak on the top of the subsoil. After heavy doses of lime have been given to the soil, and have settled so as to have apparently ceased from their action, they may be brought up and mixed with the soil by deeper plowing.
Lime should never be mixed with animal manures, unless in compost with muck, or some other good absorbent, as it is liable to cause the escape of their ammonia.
PLASTER OF PARIS
Plaster of Paris or Gypsum (sulphate of lime) is composed of sulphuric acid and lime in combination. It is called 'plaster of Paris,' because it constitutes the rock underlying the city of Paris.
Is it a constituent of plants?
What else does it furnish them?
How does it affect manure?
How does it produce sorrel in the soil?
How may the acidity be overcome?
It is a constituent of many plants. It also furnishes them with sulphur—a constituent of the sulphuric acid which it contains.
It is an excellent absorbent of ammonia, and is very useful to sprinkle around stables, poultry houses, pig-styes, and privies, where it absorbs the escaping gases, saving them for the use of plants, and purifying the air, thus rendering stables, etc., more healthy than when not so supplied.
It has been observed that the extravagant use of plaster sometimes induces the growth of sorrel. This is probably the case only where the soil is deficient in lime. In such instances, the lime required by plants is obtained by the decomposition of the plaster. The lime enters into the construction of the plant, and the sulphuric acid remains free, rendering the soil sour, and therefore in condition to produce sorrel. In such a case, an application of lime will correct the acid by uniting with it and converting it into plaster.
CHLORIDE OF LIME
What does chloride of lime supply to plants?
How does it affect manures?
How may it be used?
How may magnesia be supplied, when wanting?
What care is necessary concerning the use of magnesia?
Chloride of lime is a compound of lime and chlorine. It furnishes both of these constituents to plants, and it is an excellent absorbent of ammonia and other gases arising from decomposition—hence its usefulness in destroying bad odors, and in preserving fertilizing matters for the use of crops.
It may be used like plaster, or in the decomposition of organic matters, where it not only hastens decay, but absorbs and retains the escaping gases. It will be recollected that chloride of lime is one of the products of the lime and salt mixture.
Lime in combination with phosphoric acid forms the valuable phosphate of lime, of which so large a portion of the ash of grain, and the bones of animals, is formed. This will be spoken of more at length under the head of 'phosphoric acid.'
MAGNESIA
Magnesia is a constituent of vegetable ashes, and is almost always present in the soil in sufficient quantities. When analysis indicates that it is needed, it may be applied in the form of magnesian lime, or refuse epsom salts, which are composed of sulphuric acid and magnesia (sulphate of magnesia).
The great care necessary concerning the use of magnesia is, not to apply too much of it, it being, when in excess, as has been previously remarked, injurious to the fertility of the soil. Some soils are hopelessly barren from the fact that they contain too much magnesia.
ACIDS
SULPHURIC ACID
What is sulphuric acid commonly called?
How may it be used?
How does it prevent the escape of ammonia?
Sulphuric acid is a very important constituent of vegetable ashes, especially of oats and the root-crops.
It is often deficient in the soil, particularly where potatoes have been long cultivated. One of the reasons why plaster (sulphate of lime) is so beneficial to the potato crop is undoubtedly that it supplies it with sulphuric acid.
Sulphuric acid is commonly known by the name of oil vitriol, and may be purchased for agricultural purposes at a low price. It may be used in a very dilute form (weakened by mixing it with a large quantity of water) to the compost heap, where it will change the ammonia to a sulphate as soon as formed, and thus prevent its loss, as the sulphate of ammonia is not volatile; and, being soluble in water, is useful to plants. Some idea of the value of this compound may be formed from the fact that manufacturers of manures are willing to pay seven cents per lb., or even more, for sulphate of ammonia, to insure the success of their fertilizers. Notwithstanding this, many farmers persist in throwing away hundreds of pounds of ammonia every year, as a tax for their ignorance (or indolence), while a small tax in money—not more valuable, nor more necessary to their success—for the support of common schools, and the better education of the young, is too often unwillingly paid.
What is the effect of using too much sulphuric acid?
If a tumbler full of sulphuric acid (costing a few cents), be thrown into the tank of the compost heap once a month, the benefit to the manure would be very great.
Where a deficiency of sulphuric acid in the soil is indicated by analysis, it may be supplied in this way, or by the use of plaster or refuse epsom salts.
Care is necessary that too much sulphuric acid be not used, as it would prevent the proper decomposition of manures, and would induce a growth of sorrel in the soil by making it sour.
In many instances, it will be found profitable to use sulphuric acid in the manufacture of super-phosphate of lime (as directed under the head of 'phosphoric acid,') thus making it perform the double purpose of preparing an available form of phosphate, and of supplying sulphur and sulphuric acid to the plant.
PHOSPHORIC ACID
How large a part of the ashes of grain consists of phosphoric acid?
Of what other substances does it form a leading ingredient?
How many pounds of sulphuric acid are contained in one hundred bushels of wheat?
We come now to the consideration of one of the most important of all subjects connected with agriculture, that is, phosphoric acid.
Phosphoric acid, forming about one half of the ashes of wheat, rye, corn, buckwheat, and oats; nearly the same proportion of those of barley, peas, beans and linseed; an important ingredient of the ashes of potatoes and turnips; one quarter of the ash of milk and a large proportion of the bones of animals, often exists in the soil in the proportion of only about one or two pounds in a thousand. The cultivation of our whole country has been such, as to take away the phosphoric acid from the soil without returning it, except in very minute quantities. Every hundred bushels of wheat sold contains (and removes permanently from the soil) about sixty pounds of phosphoric acid. Other grains, as well as the root crops and grasses, remove likewise a large quantity of it. It has been said by a contemporary writer, that for each cow kept on a pasture through the summer, there is carried off in veal, butter and cheese, not less than fifty lbs. of phosphate of lime (bone-earth) on an average. This would be one thousand lbs. for twenty cows; and it shows clearly why old dairy pastures become so exhausted of this substance, that they will no longer produce those nutritious grasses, which are favorable to butter and cheese-making.
How much phosphate of lime will twenty cows remove from a pasture during a summer?
What has this removal of phosphate of lime occasioned?
How have the Genesee and Mohawk valleys been affected by this removal of phosphoric acid?
That this removal of the most valuable constituent of the soil, has been the cause of more exhaustion of farms, and more emigration, in search of fertile districts, than any other single effect of injudicious farming, is a fact which multiplied instances most clearly prove.
It is stated that the Genesee and Mohawk valleys, which once produced an average of thirty-five or forty bushels of wheat, per acre, have since been reduced in their average production to twelve and a half bushels. Hundreds of similar cases might be stated; and in a large majority of these, could the cause of the impoverishment be ascertained, it would be found to be the removal of the phosphoric acid from the soil.
How may this devastation be arrested?
Is any soil inexhaustible?
What is usually the best source from which to obtain phosphoric acid?
The evident tendency of cultivation being to continue this murderous system, and to prey upon the vital strength of the country, it is necessary to take such measures as will arrest the outflow of this valuable material. This can never be fully accomplished until laws shall be made preventing the wastes of cities and towns. Such laws have existed for a long time in China, and have doubtlessly been the secret of the long subsistence and present prosperity of the millions of people inhabiting that country.
We have, nevertheless, a means of restoring to fertility many of our worn-out lands, and preserving our fertile fields from so rapid impoverishment as they are now suffering. Many suppose that soils which produce good crops, year after year, are inexhaustible, but time will prove to the contrary. They may possess a sufficiently large stock of phosphoric acid, and other constituents of plants, to last a long time, but when that stock becomes so reduced, that there is not enough left for the uses of full crops, the productive power of the soil will yearly decrease, until it becomes worthless. It may last a long time, a century, or even more, but as long as the system is—to remove every thing, and return nothing,—the fate of the most fertile soil is evident.
The source mentioned, from which to obtain phosphoric acid, is the bones of animals. These contain large quantities of phosphate of lime. They are the receptacles which collect nearly all of the phosphates in crops, which are fed to animals, and are not returned in their excrements. For the grain, etc., sent out of the country, there is no way to be repaid except by the importation of this material; but, all that is fed to animals, or to human beings, may, if a proper use be made of their excrement, and of their bones after death, be returned to the soil. With the treatment of animal excrements we are already familiar, and we will now turn our attention to the subject of
BONES
Of what do dried bones consist?
What is the organic matter of bones?
The inorganic?
What can you say of the use of whole bones?
Bones consist, when dried, of about one third organic matter, and two thirds inorganic matter.
The organic matter consists chiefly of gelatine—a compound containing nitrogen.
The inorganic part is chiefly phosphate of lime.
Hence, we see that bones are excellent, as both organic and mineral manure. The organic part, containing nitrogen, forms ammonia, and the inorganic part supplies the much needed phosphoric acid to the soil.
Liebig says that, as a producer of ammonia, 100 lbs. of dry bones are equivalent to 250 lbs. of human urine.
How does the value of bone dust compare with that of broken bones?
What is the reason of the superiority of bone dust?
How is bone-black made?
Of what does it consist?
Bones are applied to the soil in almost every conceivable form. Whole bones are often used in very large quantities; their action, however, is extremely slow, and it is never advisable to use bones in this form.
Ten bushels of bones, finely ground, will produce larger results, during the current ten years after application, than would ensue from the use of one hundred bushels merely broken, not because the dust contains more fertilizing matter than the whole bones, but because that which it does contain is in a much more available condition. It ferments readily, and produces ammonia, while the ashy parts are exposed to the action of roots.
Should farmers burn bones before using them?
How would you compost bones with ashes?
In what way would you prevent the escape of ammonia?
Bone-black. If bones are burned in retorts, or otherwise protected from the atmosphere, their organic matter will all be driven off, except the carbon, which not being supplied with oxygen cannot escape. In this form bones are called ivory black, or bone-black. It consists of the inorganic matter, and the carbon of the bones. The nitrogen having been expelled it can make no ammonia, and thus far the original value of bones is reduced by burning; that is, one ton of bones contains more fertilizing matter before, than after burning; but one ton of bone black is more valuable than one ton of raw bones, as the carbon is retained in a good form to act as an absorbent in the soil, while the whole may be crushed or ground much more easily than before being burned. This means of pulverizing bones is adopted by manufacturers, who replace the ammonia in the form of guano, or otherwise; but it is not to be recommended for the use of farmers, who should not lose the ammonia, forming a part of bones, more than that of other manure.