The Elements of Agriculture Part 13

CHAPTER I.

CHARACTER AND VARIETIES OF MANURES.

[What must a farmer know in order to avoid failures?

Can this be learned entirely from observation?

What kind of action have manures?

Give examples of each of these.

May mechanical effects be produced by chemical action?

How does potash affect the soil?]

To understand the science of _manures_ is the most important branch of practical farming. No baker would be called a good practical baker who kept his flour exposed to the sun and rain. No shoemaker would be called a good practical shoemaker, who used morocco for the soles of his shoes, and heavy leather for the uppers. No carpenter would be called a good practical carpenter, who tried to build a house without nails, or other fastenings. So with the farmer. He cannot be called a good practical farmer if he keeps the materials, from which he is to make plants, in such a condition, that they will have their value destroyed, uses them in the wrong places, or tries to put them together without having every thing present that is necessary. Before he can avoid failures _with certainty_, he must know what manures are composed of, how they are to be preserved, where they are needed, and what kinds are required. True, he may from observation and experience, _guess_ at results, but he cannot _know_ that he is right until he has learned the facts above named. In this section of our work, we mean to convey some of the information necessary to this branch of _practical farming_.

We shall adopt a cla.s.sification of the subject somewhat different from that found in most works on manures, but the _facts_ are the same. The action of manures is either _mechanical_ or _chemical_, or a combination of both. For instance: some kinds of manure improve the mechanical character of the soil, such as those which loosen stiff clay soils, or others which render light sandy soils compact--these are called _mechanical_ manures. Some again furnish food for plants--these are called _chemical_ manures.

Many mechanical manures produce their effects by means of chemical action. Thus _potash_ combines chemically with sand in the soil. In so doing, it roughens the surfaces of the particles of sand, and renders the soil less liable to be compacted by rains. In this manner, it acts as a _mechanical_ manure. The compound of sand and potash,[U] as well as the potash alone, may enter into the composition of plants, and hence it is a _chemical_ manure. In other words, potash belongs to both cla.s.ses described above.

It is important that this distinction should be well understood by the learner, as the words "mechanical" and "chemical" in connection with manures will be made use of throughout the following pages.

[What are absorbents?

What kind of manure is charcoal?]

There is another cla.s.s of manures which we shall call _absorbents_.

These comprise those substances which have the power of taking up fertilizing matters, and retaining them for the use of plants. For instance, _charcoal_ is an absorbent. As was stated in the section on soils, this substance is a retainer of all fertilizing gases and many minerals. Other matters made use of in agriculture have the same effect.

These absorbents will be spoken of more fully in their proper places.

TABLE.

MECHANICAL MANURES are those which improve the mechanical condition of soils.

CHEMICAL " are those which serve as food for plants.

ABSORBENTS are those substances which absorb and retain fertilizing matters.

[Into what cla.s.ses may manures be divided?

What are organic manures?

Inorganic? Atmospheric?]

Manures may be divided into three cla.s.ses, viz.: _organic_, _inorganic_, and _atmospheric_.

ORGANIC manures comprise all _animal_ and _vegetable_ matters which are used to fertilize the soil, such as dung, muck, etc.

INORGANIC manures are those which are of a purely _mineral_ character, such as lime, ashes, etc.

ATMOSPHERIC manures consist of those organic manures which are in the form of gases in the atmosphere, and which are absorbed by rains and carried to the soil. These are of immense importance. The ammonia and carbonic acid in the air are atmospheric manures.

FOOTNOTES:

[U] Silicate of potash.

CHAPTER II.

EXCREMENTS OF ANIMALS.

[Of what is animal excrement composed?

Explain the composition of the food of animals.

What does hay contain?

To what does Liebig compare the consumption of food by animals, and why?]

The first organic manure which we shall examine, is animal _excrement_.

This is composed of those matters which have been eaten by the animal as food, and have been thrown off as solid or liquid manure. In order that we may know of what they consist, we must refer to the composition of food and examine the process of digestion.

The food of animals, we have seen to consist of both organic and inorganic matter. The organic part may be divided into two cla.s.ses, _i.

e._, that portion which contains nitrogen--such as gluten, alb.u.men, etc., and that which does not contain nitrogen--such as starch, sugar, oil, etc.

The inorganic part of food may also be divided into _soluble_ matter and _insoluble_ matter.

DIGESTION AND ITS PRODUCTS.

[Of what does that part of dung consist which resembles soot?

What else does the dung contain?

In what manner does the digested part of food escape from the body?]

Let us now suppose that we have a full-grown ox, which is not increasing in any of his parts, but only consumes food to keep up his respiration, and to supply the natural wastes of his body. To this ox we will feed a ton of hay which contains organic matter, with and without nitrogen, and soluble and insoluble inorganic substances. Now let us try to follow it through its changes in the animal, and observe its destination. Liebig compares the consumption of food by animals to the imperfect burning of wood in a stove, where a portion of the fuel is resolved into gases and ashes (that is, it is completely burned), and another portion, which is not thoroughly burned, pa.s.ses off as _soot_. In the animal action in question, the food undergoes changes which are similar to this burning of wood. A part of the food is _digested_ and taken up by the blood, while another portion remains undigested, and pa.s.ses the bowels as solid dung--corresponding to soot. This part of the dung then, we see is merely so much of the food as pa.s.ses through the system without being materially changed. Its nature is easily understood. It contains organic and inorganic matter in nearly the same condition as they existed in the hay. They have been rendered finer and softer, but their chemical character is not materially altered. The dung also contains small quant.i.ties of nitrogenous matter, which _leaked out_, as it were, from the stomach and intestines. The digested food, however, undergoes further changes which affect its character, and it escapes from the body in three ways--_i. e._, through the lungs, through the bladder, and through the bowels. It will be recollected from the first section of this book, p. 22, that the carbon in the blood of animals, unites with the oxygen of the air drawn into the lungs, and is thrown off in the breath as carbonic acid. The hydrogen and oxygen unite to form a part of the water which const.i.tutes the moisture of the breath.

[Explain the escape of carbon, hydrogen and oxygen.