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

 

[Give an instance of such change.

How do plants and animals benefit each other?

Describe the experiment with the glass tube.]

The blood of animals contains carbon derived from their food. This unites with the oxygen of the air drawn into the lungs and forms carbonic acid. Without this process, animals could not live. Thus, while by the natural operation of breathing, they make carbonic acid for the uses of the vegetable world, plants, in taking up carbon, throw off oxygen to keep up the life of animals. There is perhaps no way in which we can better illustrate the changes of form in carbon than by describing a simple experiment.

Take a glass tube filled with oxygen gas, and put in it a lump of charcoal, cork the ends of the tube tightly, and pass through the corks the wires of an electrical battery. By passing a stream of electrical fluid over the charcoal it may be ignited, when it will burn with great brilliancy. In burning it is dissolved in the oxygen forming carbonic acid, and disappears. It is no more lost, however, than is the carbon of wood which is burned in a stove; although invisible, it is still in the tube, and may be detected by careful weighing. 

SECTION 1 (THE PLANT) CHAPTER II (ATMOSPHERE) Pg 12

A more satisfactory proof of its presence may be obtained by decomposing the carbonic acid by drawing the wires a short distance apart, and giving a spark of electricity.This immediately separates the oxygen from the carbon which forms a dense black smoke in the tube. By pushing the corks together we may obtain a wafer of charcoal of the same weight as the piece introduced. In this experiment we have changed carbon from its solid form to an invisible gas and back again to a solid, thus fully representing the continual changes of this substance in the destruction of organic matter and the growth of plants.

SECTION 1 (THE PLANT) CHAPTER III (HYDROGEN, OXYGEN AND NITROGEN)_HYDROGEN AND OXYGEN Pg 13

[What is water composed of?

If analyzed, what does it yield?

How do plants obtain their hydrogen and oxygen?]

Let us now consider the three gases, hydrogen, oxygen and nitrogen, which constitute the remainder of the organic part of plants.

Hydrogen and oxygen compose water, which, if analyzed, yields simply these two gases. Plants perform such analysis, and in this way are able to obtain a sufficient supply of these materials, as their sap is composed chiefly of water. Whenever vegetable matter is destroyed by burning, decay, or otherwise, its hydrogen and oxygen unite and form water, which is parted with usually in the form of an invisible vapor. The atmosphere of course contains greater or less quantities of watery vapor arising from this cause and from the evaporation of liquid water. This vapor condenses, forming rains, etc.

Hydrogen and oxygen are never taken into consideration in manuring lands, as they are so readily obtained from the water constituting the sap of the plant, and consequently should not occupy our attention in this book.

SECTION 1 (THE PLANT) CHAPTER III (HYDROGEN, OXYGEN AND NITROGEN)__NITROGEN Pg 14

[If vegetable matter be destroyed, what becomes of these constituents?

What is the remaining organic constituent?

Why is it worthy of close attention?

Do plants appropriate the nitrogen of the atmosphere?]

Nitrogen, the only remaining organic constituent of vegetable matter, is for many reasons worthy of close attention.

It is necessary to the growth and perfection of all cultivated plants. It is necessary to the formation of animal muscle. It is often deficient in the soil. It is liable to be easily lost from manures.

Although about four fifths of atmospheric air are pure nitrogen, it is almost certain that plants get no nutriment at all from this source.

SECTION 1 (THE PLANT) CHAPTER III (HYDROGEN, OXYGEN AND NITROGEN)__NITROGEN Pg 15

 

It is all obtained from some of its compounds, chiefly from the one called ammonia. Nitric acid is also a source from which plants may obtain nitrogen, though to the farmer of less importance than ammonia.

AMMONIA.

[What is the principal source from which they obtain nitrogen?

What is ammonia?

How is it formed?

Where does it always exist?

How do plants take up ammonia?]

Ammonia is composed of nitrogen and hydrogen. It has a pungent smell and is familiarly known as hartshorn. The same odor is perceptible around stables and other places where animal matter is decomposing. All animal muscle, certain parts of plants, and other organized substances, consist of compounds containing nitrogen. When these compounds undergo combustion, or are in any manner decomposed, the nitrogen which they contain usually unites with hydrogen, and forms ammonia. In consequence of this the atmosphere always contains more or less of this gas, arising from the decay, etc., which is continually going on all over the world.

This ammonia in the atmosphere is the capital stock to which all plants, not artificially manured, must look for their supply of nitrogen.

SECTION 1 (THE PLANT) CHAPTER III (HYDROGEN, OXYGEN AND NITROGEN)__NITROGEN Pg 16

 

As they can take up ammonia only through their roots, we must discover some means by which it may be conveyed from the atmosphere to the soil.

[Does water absorb it?

What is spirits of hartshorn?

Why is this power of water important in agriculture?

What instance may be cited to prove this?]

Water may be made to absorb many times its bulk of this gas, and water with which it comes in contact will immediately take it up. Spirits of hartshorn is merely water through which ammonia has been passed until it is saturated.[A] This power of water has a direct application to agriculture, because the water constituting rains, dews, &c., absorbs the ammonia which the decomposition of nitrogenous matter had sent into the atmosphere, and we find that all rain, snow and dew, contain ammonia. This fact may be chemically proved in various ways, and is perceptible in the common operations of nature. Every person must have noticed that when a summer's shower falls on the plants in a flower garden, they commence their growth with fresh vigor while the blossoms become larger and more richly colored. This effect cannot be produced by watering with spring water, unless it be previously mixed with ammonia, in which case the result will be the same.

Although ammonia is a gas and pervades the atmosphere, few, if any, plants can take it up, as they do carbonic acid, through their leaves. It must all enter through the roots in solution in the water which goes to form the sap. Although the amount received from the atmosphere is of great importance, there are few cases where artificial applications are not beneficial.

SECTION 1 (THE PLANT) CHAPTER III (HYDROGEN, OXYGEN AND NITROGEN)__NITROGEN Pg 17

 

The value of farm-yard and other animal manures, depends chiefly on the ammonia which they yield on decomposition. This subject, also the means for retaining in the soil the ammoniacal parts of fertilizing matters, will be fully considered in the section on manures.

[Can plants use more ammonia than is received from the atmosphere?

On what does the value of animal manure chiefly depend?

What changes take place after ammonia enters the plant?

May the same atom of nitrogen perform many different offices?]

After ammonia has entered the plant it may be decomposed, its hydrogen sent off, and its nitrogen retained to answer the purposes of growth. The changes which nitrogen undergoes, from plants to animals, or, by decomposition, to the form of ammonia in the atmosphere, are as varied as those of carbon and the constituents of water. The same little atom of nitrogen may one year form a part of a plant, and the