The Elements of Agriculture

MINERAL MANURES

How many kinds of action have inorganic manures?

What is the first of these? The second? Third? Fourth?

Do all mineral manures possess all of these qualities?

The second class of manures named in the general division of the subject, in the early part of this chapter, comprises those of a mineral character, or inorganic manures.

These manures have four kinds of action when applied to the soil.

1st. They furnish food for the inorganic part of plants.

2d. They prepare matters already in the soil, for assimilation by roots.

3d. They improve the mechanical condition of the soil.

4th. They absorb ammonia.

Some of the mineral manures produce in the soil only one of these effects, and others are efficient in two or all of them.

The principles to be considered in the use of mineral manures are essentially given in the first two sections of this book. It may be well, however, to repeat them briefly in this connection, and to give the reasons why any of these manures are needed, from which we may learn what rules are to be observed in their application.

Relate what you know of the properties of vegetable ashes?

How does this relate to the fertility of the soil?

According to what two rules may we apply mineral manures?

What course would you pursue to raise potatoes on a soil containing a very little phosphoric acid and no potash?

1st. Those which are used as food by plants. It will be recollected that the ash left after burning plants, and which formed a part of their structures, has a certain chemical composition; that is, it consists of alkalies, acids, and neutrals. It was also stated that the ashes of plants of the same kind are always of about the same composition, while the ashes of different kinds of plants may vary materially. Different parts of the same plant too, as we learned, are supplied with different kinds of ash.

For instance, clover, on being burned, leaves an ash containing lime, as one of its principal ingredients, while the ash of potatoes contains more of potash than of any thing else.

In the second section (on soils), we learned that some soils contain every thing necessary to make the ashes of all plants, and in sufficient quantity to supply what is required, while other soils are either entirely deficient in one or more ingredients, or contain so little of them that they are unfertile for certain plants.

Would you manure it in the same way for wheat?

Why?

From this, we see that we may pursue either one of two courses. After we know the exact composition of the soil—which we can learn only from correct analysis—we may manure it with a view either to making it fertile for all kinds of plants or only for one particular plant. For instance, we may find that a soil contains a very little phosphoric acid, and no potash. If we wish to raise potatoes on such a soil, we have only to apply potash (if the soil is good in other particulars), which is largely required by this plant, though it needs but little phosphoric acid; while, if we wish to make it fertile for wheat, and all other plants, we must apply more phosphoric acid as well as potash. As a universal rule, it may be stated that to render a soil fertile for any particular plant, we must supply it (unless it already contains them) with those matters which are necessary to make the ash of that plant; and, if we would render it capable of producing all kinds of plants, it must be furnished with the materials required in the formation of all kinds of vegetable ashes.

It is not absolutely necessary to have the soil analyzed before it can be cultivated with success, but it is the cheapest way.

How is the fertility of the soil to be maintained, if the crops are sold?

What rule is given for general treatment?

Give an instance of matters in the soil that are to be rendered available by mineral manures?

We might proceed from an analysis of the plant required (which will be found in Section V.), and apply to the soil in the form of manure every thing that is necessary for the formation of the ash of that plant. This would give a good crop on any soil that was in the proper mechanical condition, and contained enough organic matter; but a moment's reflection will show that, if the soil contained a large amount of potash, or of phosphate of lime, it would not be necessary to make an application of more of these ingredients—at an expense of perhaps three times the cost of an analysis. It is true that, if the crop is sold, and it is desired to maintain the fertility of the soil, the full amount of the ash must be applied, either before or after the crop is grown; but, in the ordinary use of crops for feeding purposes, a large part of the ash will exist in the excrements of the animals; so that the judicious farmer will be able to manure his land with more economy than if he had to apply to each crop the whole amount and variety required for its ash. The best rule for practical manuring is probably to strengthen the soil in its weaker points, and prevent the stronger ones from becoming weaker. In this way, the soil may be raised to the highest state of fertility, and be fully maintained in its productive powers.

2d. Those manures which render available matter already contained in the soil.

How may silica be developed?

How does lime affect soils containing coarse particles?

How do mineral manures sometimes improve the mechanical texture of the soil?

Silica (or sand), it will be recollected, exists in all soils; but, in its pure state, is not capable of being dissolved, and therefore cannot be used by plants. The alkalies (as has been stated), have the power of combining with this silica, making compounds, which are called silicates. These are readily dissolved by water, and are available in vegetable growth. Now, if a soil is deficient in these soluble silicates, it is well known that grain, etc., grown on it, not being able to obtain the material which gives them strength, will fall down or lodge; but, if such measures be taken, as will render the sand soluble, the straw will be strong and healthy. Alkalies used for this purpose, come under the head of those manures which develope the natural resources of the soil.

Again, much of the mineral matter in the soil is combined within particles, and is therefore out of the reach of roots. Lime, among other thing, has the effect of causing these particles to crumble and expose their constituents to the demand of roots. Therefore, lime has for one of its offices the development of the fertilizing ingredients of the soil.

3d. Those manures which improve the mechanical condition of the soil.

The alkalies, in combining with sand, commence their action on the surfaces of the particles, and roughen them—rust them as it were. This roughening of particles of the soil prevents them from moving among each other as easily as they do when they are smooth, and thus keeps the soil from being compacted by heavy rains, as it is liable to be in its natural condition. In this way, the mechanical texture of the soil is improved.

It has just been said that lime causes the pulverization of the particles of the soil; and thus, by making it finer, improves its mechanical condition.

Some mineral manures, as plaster and salt, have the power of absorbing moisture from the atmosphere; and this is a mechanical improvement to dry soils.

Name some mineral manures which absorb ammonia?

4th. Those mineral manures which have the power of absorbing ammonia.

Plaster, chloride of lime, alumina (clay), etc., are large absorbents of ammonia, whether arising from the fermentation of animal manures or washed down from the atmosphere by rains. The ammonia thus absorbed is of course very important in the vegetation of crops.

Having now explained the reasons why mineral manures are necessary, and the manner in which they produce their effects, we will proceed to examine the various deficiencies of soils and the character of many kinds of this class of fertilizers.

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.

ALKALIESPOTASH

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.