The Elements of Agriculture A Book for Young Farmers, with Questions Prepared for the Use of Schools, George E. Waring [read aloud books TXT] 📗

mineral matters, which are contained in water. If a quantity of salt water be filtered through charcoal, the salt will be retained, and the water will pass through pure.

We are now able to see how carbon renders the soil retentive of manures.

1st. Manures, which resemble the brown liquor of barn-yards, have their fertilizing matters taken out, and retained by it.

[How does charcoal in the soil affect the manures applied?

Why does charcoal in the soil cause it to appropriate the gases of the atmosphere?

What fertilizing gases exist in the atmosphere?

How are they carried to the soil?

Does the carbon retain them after they reach the soil?

What can you say of the air circulating through the soil?

How does carbon give the soil power to absorb moisture?]

2d. The gases arising from the decomposition (rotting) of manure are absorbed by it.

3d. The soluble mineral portions of manure, which might in some soils leach down with water, are arrested and retained at a point at which they can be made use of by the roots of plants.

SECTION 2 (THE SOIL) CHAPTER II (USES OF ORGANIC MATTER) Pg 71

 

Charcoal in the soil causes it to appropriate larger quantities of the fertilizing gases of the atmosphere, on account of its power, as just named, to absorb gases.

The atmosphere contains results, which have been produced by the breathing of animals and by the decomposition of various kinds of organic matter, which are exposed to atmospheric influences. These gases are chiefly ammonia and carbonic acid, both of which are largely absorbed by water, and consequently are contained in rain, snow, etc., which, as they enter the soil, give up these gases to the charcoal, and they there remain until required by plants. Even the air itself, in circulating through the soil, gives up fertilizing gases to the carbon, which it may contain.

Charcoal gives to the soil power to absorb moisture, because it is itself one of the best absorbents in nature; and it has been proved by accurate experiment that peaty soils absorb moisture with greater rapidity, and part with it more slowly than any other kind.

[How does it render it warmer?

Is the heat produced by the decomposition of organic matter perceptible to our senses?

Is it so to the growing plant?

What is another important part of the organic matter in the soil?]

4. Carbon in the soil renders it warmer, because it darkens its color.

SECTION 2 (THE SOIL) CHAPTER II (USES OF ORGANIC MATTER) Pg 72

 

Black surfaces absorb more heat than light ones, and a black coat, when worn in the sun, is warmer than one of a lighter color. By mixing carbon with the soil, we darken its color, and render it capable of absorbing a greater amount of heat from the sun's rays.

It will be recollected that, when vegetable matter decomposes in the soil, it produces certain gases (carbonic acid, etc.), which either escape into the atmosphere, or are retained in the soil for the use of plants. The production of these gases is always accompanied by heat, which, though scarcely perceptible to our senses, is perfectly so to the growing plant, and is of much practical importance. This will be examined more fully in speaking of manures.

[How is it obtained by the soil?

What offices does the organic matter in the soil perform?]

Another important part of the organic matter in the soil is that which contains nitrogen. This forms but a very small portion of the soil, but it is of the greatest importance to vegetables. As the nitrogen in food is of absolute necessity to the growth of animals, so the nitrogen in the soil is indispensable to the growth of cultivated plants. It is obtained by the soil in the form of ammonia (or nitric acid), from the atmosphere, or by the application of animal matter. In some cases, manures called nitrates[S] are used; and, in this manner, nitrogen is given to the soil.

We have now learned that the organic matter in the soil performs the following offices:--

Organic matter thoroughly decomposed is carbon, and has the various effects ascribed to this substance on p. 79.

Organic matter in process of decay produces carbonic acid, and sometimes ammonia in the soil; also its decay causes heat.

Organic matter containing nitrogen, such as animal substances, etc., furnish ammonia, and other nitrogenous substances to the roots of plants.

FOOTNOTES Pg 73

[Q] Produce.

[R] By absorbing and retaining, we mean taking up and holding.

[S] Nitrates are compounds of nitric acid (which consists of nitrogen and oxygen), and alkaline substances. Thus nitrate of potash (saltpetre), is composed of nitric acid and potash: nitrate of soda (cubical nitre), of nitric acid and soda.

SECTION 2 (THE SOIL) CHAPTER III (USES OF INORGANIC MATTER) Pg 74

 

[What effect has clay besides the one already named?

How does it compare with charcoal for this purpose?]

The offices performed by the inorganic constituents of the soil are many and important.

These, as well as the different conditions in which the bodies exist, are necessary to be thoroughly studied.

Those parts which constitute the larger proportion of the soil, namely the clay, sand, and limy portions, are useful for purposes which have been named in the first part of this section, while the clay has an additional effect in the absorption of ammonia.

For this purpose, it is as effectual as charcoal, the gases escaping from manures, as well as those existing in the atmosphere, and in rain-water, being arrested by clay as well as charcoal.[T]

[What particular condition of inorganic matter is requisite for fertility?

What is the fixed rule with regard to this?

What is the condition of the alkalies in most of their combinations? Of the acids?

What is said of phosphate of lime?]

The more minute ingredients of the soil--those which enter into the construction of plants--exist in conditions which are more or less favorable or injurious to vegetable growth. The principal condition necessary to fertility is capacity to be dissolved, it being (so far as we have been able to ascertain) a fixed rule, as was stated in the first section, that no mineral substance can enter into the roots of a plant except it be dissolved in water.

SECTION 2 (THE SOIL) CHAPTER III (USES OF INORGANIC MATTER) Pg 75

 

The alkalies potash, soda, lime, and magnesia, are in nearly all of their combinations in the soil sufficiently soluble for the purposes of growth.

The acids are, as will be recollected, sulphuric and phosphoric. These exist in the soil in combination with the alkalies, as sulphates and phosphates, which are more or less soluble under natural circumstances. Phosphoric acid in combination with lime as phosphate of lime is but slightly soluble; but, when it exists in the compound known as super-phosphate of lime, it is much more soluble, and consequently enters into the composition of plants with much greater facility. This matter will be more fully explained in the section on manures.

[How may silica be rendered soluble?

What is the condition of chlorine in the soil?

Do peroxide and protoxide of iron affect plants in the same way?

How would you treat a soil containing protoxide of iron?

On what does the usefulness of all these matters in the soil depend?]

The neutrals, silica, chlorine, oxide of iron, and oxide of manganese, deserve a careful examination. Silica exists in the soil usually in the form of sand, in which it is, as is well known, perfectly insoluble; and, before it can be used by plants, which often require it in large quantities, it must be made soluble, which is done by combining it with an alkali.

SECTION 2 (THE SOIL) CHAPTER III (USES OF INORGANIC MATTER) Pg 76