The Elements of Agriculture Part 31

TILE DRAINING.

The best under-drains are those made with tiles, or burnt clay pipes.

The first form of these used was that called the _horse-shoe tile_, which was in two distinct pieces; this was superseded by a round pipe, and we have now what is called the _sole tile_, which is much better than either of the others.

[Ill.u.s.tration: Fig. 4--Sole Tile.]

[Why is the sole tile superior to those of previous construction?

How are these tiles laid?

How may the trenches be dug?]

This tile is made (like the horse-shoe and pipe tile) of common brick clay, and is burned the same as bricks. It is about one half or three quarters of an inch thick, and is so porous that water pa.s.ses directly through it. It has a flat bottom on which to stand, and this enables it to retain its position, while making the drain, better than would be done by the round pipe. The orifice through which the water pa.s.ses is egg-shaped, having its smallest curve at the bottom. This shape is the one most easily kept clear, as any particles of dirt which get into the drain must fall immediately to the point where even the smallest stream of water runs, and are thus removed. An orifice of about two inches is sufficient for the smaller drains, while the main drains require larger tiles.

These tiles are laid, so that their ends will touch each other, on the bottoms of the trenches, and are kept in position by having the earth tightly packed around them. Care must be taken that no s.p.a.ce is left between the ends of the tiles, as dirt would be liable to get in and choke the drain. It is advisable to place a sod--gra.s.s side down--over each joint, before filling the trench, as this more effectually protects them against the entrance of dirt. There is no danger of keeping the water out by this operation, as it will readily pa.s.s through any part of the tiles.

In _digging the trenches_ it is not necessary (except in very stony ground) to dig out a place wide enough for a man to stand in, as there are tools made expressly for the purpose, by which a trench may be dug six or seven inches wide, and to any required depth. One set of these implements consists of a long narrow spade and a hoe to correspond, such as are represented in the accompanying figure.

[Ill.u.s.tration: Fig. 5.

Upton tool.

Spade and hoe.]

With these tools, and a long light crowbar, for hard soils, trenches may be dug much more cheaply than with the common spade and pickaxe. Where there are large boulders in the soil, these draining tools may dig under them so that they will not have to be removed.

When the trenches are dug to a sufficient depth, the bottoms must be made perfectly smooth, with the required descent (from six inches to a few feet in one hundred feet). Then the tiles may be laid in, so that their ends will correspond, be packed down, and the trenches filled up.

Such a drain, if properly constructed, may last for ages. Unlike the stone drain, it is not liable to be frequented by rats, nor choked up by the soil working into it.

The position of the tile may be best represented by a figure, also the mode of constructing stone drains.

[Why are small stones better than large stones in the construction of drains?

On what must the depth of under-drains depend?]

It will be seen that the tile drain is made with much less labor than the stone drain, as it requires less digging, while the breaking up of the stone for the stone drain will be nearly, or quite as expensive as the tiles. Drains made with large stones are not nearly so good as with small ones, because they are more liable to be choked up by animals working in them.[AK]

[Ill.u.s.tration: Fig. 6.

_a_--Tile drain trench.

_b_--Stone drain trench.

_c_--Sod laid on the stone.]

[Describe the principle which regulates these relative depths and distances. (Blackboard.)

Which is usually the cheaper plan of constructing drains?]

The _depth_ of the drains must depend on the distances at which they are placed. If but _twenty_ feet apart, they need be but _three_ feet deep; while, if they are _eighty_ feet apart, they must be _five_ feet deep, to produce the same effect. The reason for this is, that the water in the drained soil is not level, but is higher midway between the drains, than at any other point. It is necessary that this highest point should be sufficiently far from the surface not to interfere with the roots of plants, consequently, as the water line between two drains is _curved_, the most distant drains must be the deepest. This will be understood by referring to the following diagram.

[Ill.u.s.tration: Fig. 7.

_aa_--5 feet drains, 80 ft. apart. _bb_--3 feet drains, 20 ft. apart.]

The curved line represents the position of the water.

In most soils it will be easier to dig one trench five feet deep, than four trenches three feet deep, and the deep trenches will be equally beneficial; but where the soil is very hard below a depth of three feet, the shallow trenches will be the cheapest, and in such soils they will often be better, as the hard ma.s.s might not allow the water to pa.s.s down to enter the deeper drains.

By following out these instructions, land may be cheaply, thoroughly, and permanently drained.

FOOTNOTES:

[AK] It is probable that a composition of hydraulic cement and some soluble material will be invented, by which a continuous pipe may be laid in the bottoms of trenches, becoming porous as the soluble material is removed by water.

CHAPTER III.

ADVANTAGES OF UNDER-DRAINING.

The advantages of under-draining are many and important.

1. It entirely prevents drought.

2. It furnishes an increased supply of atmospheric fertilizers.

3. It warms the lower portions of the soil.

4. It hastens the decomposition of roots and other organic matter.

5. It accelerates the disintegration of the mineral matters in the soil.

6. It causes a more even distribution of nutritious matters among those parts of soil traversed by roots.

7. It improves the mechanical texture of the soil.

8. It causes the poisonous excrement.i.tious matter of plants to be carried out of the reach of their roots.

9. It prevents gra.s.ses from running out.

10. It enables us to deepen the surface soil.

By removing excess of water--

11. It renders soils earlier in the spring.