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

SECTION 2 (THE SOIL) CHAPTER I (FORMATION AND CHARACTER OF THE SOIL) Pg 60

 

[What is the general rule concerning the composition of rocks?

Do these distinctions affect the fertility of soils formed from them?

What do we mean by the mechanical character of the soil?

Is its fertility indicated by its mechanical character?]

As a general rule, it may be stated that all rocks are either sandstones, limestones, or clays; or a mixture of two or more of these ingredients. Hence we find that all mineral soils are either sandy, calcareous, (limey), or clayey; or consist of a mixture of these, in which one or another usually predominates. Thus, we speak of a sandy soil, a clay soil, etc. These distinctions (sandy, clayey, loamy, etc.) are important in considering the mechanical character of the soil, but have little reference to its fertility.

By mechanical character, we mean those qualities which affect the ease of cultivation--excess or deficiency of water, ability to withstand drought, etc. For instance, a heavy clay soil is difficult to plow--retains water after rains, and bakes quite hard during drought; while a light sandy soil is plowed with ease, often allows water to pass through immediately after rains, and becomes dry and powdery during drought. Notwithstanding those differences in their mechanical character, both soils may be very fertile, or one more so than the other, without reference to the clay and sand which they contain, and which, to our observation, form their leading characteristics. The same facts exist with regard to a loam, a calcareous (or limey) soil, or a vegetable mould.

SECTION 2 (THE SOIL) CHAPTER I (FORMATION AND CHARACTER OF THE SOIL) Pg 61

 

Their mechanical texture is not essentially an index to their fertility, nor to the manures required to enable them to furnish food to plants. It is true, that each kind of soil appears to have some general quality of fertility or barrenness which is well known to practical men, yet this is not founded on the fact that the clay or the sand, or the vegetable matter, enter more largely into the constitution of plants than they do when they are not present in so great quantities, but on certain other facts which will be hereafter explained.

[What is a sandy soil? A clay soil? A loamy soil? A marl? A calcareous soil? A peaty soil?]

As the following names are used to denote the character of soils, in ordinary agricultural description, we will briefly explain their application:

A Sandy soil is, of course, one in which sand largely predominates.

Clay soil, one where clay forms a large proportion of the soil.

Loamy soil, where sand and clay are about equally mixed.

Marl contains from five to twenty per cent. of carbonate of lime.

Calcareous soil more than twenty per cent.

SECTION 2 (THE SOIL) CHAPTER I (FORMATION AND CHARACTER OF THE SOIL) Pg 62

Peaty soils, of course, contain large quantities of organic matter.[P]

[How large a part of the soil may be used as food by plants?

What do we learn from the analyses of barren and fertile soils?]

We will now take under consideration that part of the soil on which depends its ability to supply food to the plant. This portion rarely constitutes more than five or ten per cent. of the entire soil, sometimes less--and it has no reference to the sand, clay, and vegetable matters which they contain. From analyses of many fertile soils, and of others which are barren or of poorer quality, it has been ascertained that the presence of certain ingredients is necessary to fertility. This may be better explained by the assistance of the following table:

---------------------------+--------------+-------------+---------- In one hundred pounds. | Soil fertile | Good | Barren. | without | wheat soil. | | manure. | | ---------------------------+--------------+-------------+---------- Organic matter, | 9.7 | 7.0 | 4.0 Silica (sand), | 64.8 | 74.3 | 77.8 Alumina (clay), | 5.7 | 5.5 | 9.1 Lime, | 5.9 | 1.4 | .4 Magnesia, | .9 | .7 | .1 Oxide of iron, | 6.1 | 4.7 | 8.1 Oxide of manganese, | .1 | | .1 Potash, | .2 | 1.7 | Soda, | .4 | .7 | Chlorine, | .2 | .1 | Sulphuric acid, | .2 | .1 | Phosphoric acid, | .4 | .1½ | Carbonic acid, | 4.0 | | Loss during the analysis | 1.4 | 3.6½ | .4 +--------------+-------------+---------- |100.0 |100.0 |100.0 ---------------------------+--------------+-------------+----------

[What can you say of the soils represented in the table of analyses?

What proportion of the fertilizing ingredients is required?

If the soil represented in the third column contained all the ingredients required except potash and soda, would it be fertile?

What would be necessary to make it so?

What is the reason for this?

What are the offices performed by the inorganic part of soils?]

The soil represented in the first column might still be fertile with less organic matter, or with a larger proportion of clay (alumina), and less sand (silica). 

SECTION 2 (THE SOIL) CHAPTER I (FORMATION AND CHARACTER OF THE SOIL) Pg 63

 

These affect its mechanical character; but, if we look down the column, we notice that there are small quantities of lime, magnesia, and the other constituents of the ashes of plants (except ox. of manganese). It is not necessary that they should be present in the soil in the exact quantity named above, but not one must be entirely absent, or greatly reduced in proportion. By referring to the third column, we see that these ingredients are not all present, and the soil is barren. Even if it were supplied with all but one or two, potash and soda for instance, it could not support a crop without the assistance of manures containing these alkalies. The reason for this must be readily seen, as we have learned that no plant can arrive at maturity without the necessary supply of materials required in the formation of the ash, and these materials can be obtained only from the soil; consequently, when they do not exist there, it must be barren.

The inorganic part of soils has two distinct offices to perform. The clay and sand form a mass of material into which roots can penetrate, and thus plants are supported in their position. These parts also absorb heat, air and moisture to serve the purposes of growth, as we shall see in a future chapter. The minute portions of soil, which comprise the acids, alkalies, and neutrals, furnish plants with their ashes, and are the most necessary to the fertility of the soil.

GEOLOGY.

[What is geology?

Is the same kind of rock always of the same composition?

How do rocks differ?]

The relation between the inorganic part of soils and the rocks from which it was formed, is the foundation of Agricultural Geology. Geology may be briefly named the science of rocks. It would not be proper in an elementary work to introduce much of this study, and we will therefore simply state that the same kind of rock is of the same composition all over the world; consequently, if we find a soil in New England formed from any particular rock, and a soil from the same rock in Asia, their natural fertility will be the same in both localities.

SECTION 2 (THE SOIL) CHAPTER I (FORMATION AND CHARACTER OF THE SOIL) Pg 64

 

Some rocks consist of a mixture of different kinds of minerals; and some, consisting chiefly of one ingredient, are of different degrees of hardness. Both of these changes must affect the character of the soil, but it may be laid down as rule that, when the rocks of two locations are exactly alike, the soils formed from them will be of the same natural fertility, and in proportion as the character of rocks changes, in the same proportion will the soils differ.

[What rule may be given in relation to soils formed from the same or different rocks?

Are all soils formed from the rocks on which they lie?

What instances can you give of this?]

In most districts the soil is formed from the rock on which it lies; but this is not always the case. Soils are often formed by deposits of matter brought by water from other localities. Thus the alluvial banks of rivers consist of matters brought from the country through which the rivers have passed. The river Nile, in Egypt, yearly overflows its banks, and deposits large quantities of mud brought from the uninhabited upper countries. The prairies of the West owe a portion of their soil to deposits by