Crops and Methods for Soil Improvement Part 12

The Modern Fallow.--The modern method of making a gra.s.s seeding in August partakes of the nature of the old-fashioned summer-fallow. The desire is to eradicate weeds, secure availability in plant-food, and fit the soil to profit by even a light rainfall. Thin soils lend themselves well to this treatment, which is described in Chapter VIII, and there is no better method for fertile land. The benefit of the fallow is obtained without serious loss of time.

CHAPTER XXIII

DRAINAGE

Underdrainage.--There are great swamps, and small ones, whose water should be carried off by open ditches. Our present interest is in the wet fields of the farm,--the cold, wet soil of an entire field, the swale lying between areas of well-drained land, the side of a field kept wet by seepage from higher land,--and here the right solution of the troubling problem lies in underdrainage. An excess of water in the soil robs the land-owner of chance of profit. It excludes the air, sealing up the plant-food so that crops cannot be secured. It keeps the ground cold. It destroys the good physical condition of the soil that may have been secured by much tillage, causing the soil particles to pack together. It compels plant-roots to form at the surface of the ground. It delays seeding and cultivation. An excess of water is more disheartening than absolute soil poverty. The remedy is only in its removal. The level of dead water in the soil must be below the surface--three feet, two and one half feet, four feet,--some reasonable distance that will make possible a friable, aerated, warm, friendly feeding-ground for plant-roots. Only under drainage can do this.

Counting the Cost.--Thorough underdrainage is costly, but it is less so than the farming of fields whose productiveness is seriously limited by an excess of water. The work means an added investment. Estimates of cost can be made with fair accuracy, and estimates of resulting profit can be made without any a.s.surance of accuracy. The farmer with some wet land does well to gain experimental knowledge, and base future work upon such experience. He knows that he cannot afford to cultivate wet land, and the problem before him is to leave it to produce what gra.s.s it can produce, sell it, or find profit in drainage. He has the experience of others that investment in drainage is more satisfactory than most other investments, if land has any natural fertility. He has a.s.surance that debt incurred for drainage is the safest kind of debt an owner of wet land can incur. He has a right to expect profit from the undertaking, and he can begin the work in a small way, if an outlet is at hand, and learn what return may be expected from further investment.

Almost without fail will he become an earnest advocate of underdrainage.

[Ill.u.s.tration: Drain tile.]

Where Returns are Largest.--The total area of land needing drainage is immense. Swamps form only a small part of this area. Yields of much old farm land are limited by the excess of water during portions of the year. As land becomes older, the area needing drainage increases.

The owner of wet land does well to gain his first experience in a field where a swale or other wet strip not only fails to produce a full crop, but limits the yield of the remainder of the field by delaying planting and cultivation. This double profit often is sufficient to repay cost in a single year.

Material for the Drains.--Doubtless there are places and times when stone, or boards, or brush should be used in construction of underdrains, but they are relatively few in number. Such underdrains lack permanency, as a rule, though some stone drains are effective for a long time. If drain tile can be obtained at a reasonable price, it should be used even in fields that have an abundance of stone. Its use requires less labor than that of stone, and when properly laid on a good bottom, it continues effective. There is no known limit to the durability of a drain made of good tile.

The Outlet.--The value of any drainage system is dependent upon the outlet. Its location is the first thing to be determined. If the land is nearly flat, a telescope level should be used to determine elevations of all low points in the land to be drained. The outlet should permit a proper fall throughout the length of the system, and it should not require attention after the work is completed. If it is in the bank of a stream or ditch, it should be above the normal level of the water in the stream. In times of heavy rainfall water may back up into the main with no injury other than temporary failure to perform its work, but continuous submersion will lead to deposits of silt that may close the tile.

Locating Main and Branches.--There are various systems of drainage.

Wherever a branch or lateral joins the main, the means of drainage is duplicated within the area that the main can drain, and the system should call for the least possible waste of this sort. It usually is best that the main take the center line of the low land, laterals being used to bring the water to the main from both sides, but there is less duplication of work when the main can be at one side of the wet land.

Branches of the main may be needed to reach remote parts of the area.

The Laterals.--Small lines of tile are used to bring the water to the main when the wet land extends beyond the influence of the main. The distance between these laterals depends upon their depth and the nature of the land. A tight clay soil will not let water pa.s.s laterally more than a rod or 20 feet, compelling the placing of the drains not over 40 feet apart, while an open soil may permit a distance of 60 or more feet between laterals.

Size of Tile.--The size of the main depends upon the area that eventually may be drained, the amount of overflow from higher land, the nature of the soil, and the grade of the drain. It is a common mistake to make the main too small because the drainage immediately contemplated is less than that which will be desired when its value is known. In the determination of the size the judgment of an expert is needed, and if this cannot be had, the error should be on the side of safety. If the main will not be required to carry overflow from other land, and has a fall of 3 inches to 100 feet, one may a.s.sume that a 6-inch main will carry the surplus water from 12 to 20 acres of land, and an 8-inch main will carry the water of twice that area. Some drainage experts figure larger areas for such mains, but there is danger of loss of crop when the rainfall is very heavy.

The laterals need not be larger than 3 inches in diameter when laid on a good bottom.

Kind of Tile.--When clay tile is used, it should be well burned. Some manufacturers offer soft tile for sale, as the loss from warping and cracking is less in case of insufficient burning. The claim may be made that the efficiency of soft tile is greater than that of the hard tile whose porosity has been destroyed. This is an error, as the water enters the drain at the joints, and not through the walls of the tile.

Underdrainage should be permanent in its character, and it is essential that every piece of tile be sound and well-burned.

Vitrified clay tile is good for drainage, but no better than common clay hard-burned.

Round or octagonal tile is the most desirable because it can be turned in laying to secure the best joints. Collars are not needed in ordinary drainage.

Cement tile is coming into general use in regions having no good clay.

Its durability has not been tested, but there is no apparent reason that it should not be a good subst.i.tute for clay.

The Grade.--The outlet may fix the grade. If it does not, the main, branches, and laterals should have a fall of 3 inches, or more, to the 100 feet. This grade insures against deposits of silt and gives good capacity to the drains. If the outlet demands less fall in the system, the main may be laid on a grade of only a half inch to the 100 feet with satisfactory results. Such a small fall should be accepted only when a lower outlet cannot be secured, and great care should be used in grading the trench and laying the tile.

Establishing a Grade.--If the grades are light, they should be established by use of a telescope level. Most of the cheap levels are a delusion. A stake driven flush with the surface of the ground at the outlet becomes the starting point, and by its side should be driven a witness stake. Every 100 feet along the line of the proposed drain and laterals similar stakes should be driven. Their levels should then be taken, and when the fall from the head of the system to the outlet is known, the required cut at each 100-feet station is easily determined.

It may be necessary to reduce or increase the grade at some point to get proper depth in a depression or to save cutting when pa.s.sing through a ridge.

Cutting the Trenches.--There are ditching-machines that do efficient work. The best are costly. Most of the work on farms will continue to be done with ditching-spades. The ground should be moved when wet, so that labor can be saved.

A line should be used to secure a straight side to the trench. The grade should be obtained by means of a system of strings. If two light poles be pushed into the ground at each 100-feet station, one on either side of the proposed trench, and a string be drawn across at a point 5-1/2 feet above the bottom of the proposed trench, these strings will be in line on a grade 5-1/2 feet above the grade the drain will have.

As the cut at the station is known, the height of the string above the top of the stake is easily determined. These strings will reveal any inaccuracy in the survey. The workman can test every part of the bottom of the trench by use of a rod 5-1/2 feet high, the top end being exactly in line with the strings when the lower end is placed on the correct grade of the trench. This device is better than running water where grades are slight.

A drain scoop should be used in bottom of the trench to make a resting place for the tile that will prevent any displacement by the soil when the trench is filled.

Depth of Trenches.--Underdrains may be placed too deep in close soils for best results. In an early day it was advised that the drains be put down 4 feet deep. We now know that a tight clay soil may give best results from a drain only 28 inches deep, or even a little less. In a looser soil 3 feet is a better depth, and in porous swamp lands the drain may well go 4 feet deep, thus permitting increase in distance between drains.

Connections.--The laterals should enter the branches and mains near the top, so that the water will be drawn out rapidly. The tile should be laid with close joints at the top, so that the water may enter more freely from the sides than the top. No covering other than moist soil is needed unless there is very fine sand, when paper over the joints will serve a good purpose. After some moist soil from the sides of the trench has been tramped upon the tile, the trench may be filled by use of a breaking-plow or winged sc.r.a.per.

Permanency Desired.--The expense of underdrainage demands care in every detail of the work. The grade of the trenches should be carefully tested. Every piece of tile should be examined. The outlet should be guarded against displacement or entrance by animals. A good plan is to lay the last few pieces of tile in a close-fitting wooden box, and to protect the end with iron rods placed 2 inches apart.

If the drain is on a true grade, so that no silt will collect, there need be no fear concerning its continued efficiency, provided water does not run in it all the time. If it carries the water from springs continuously, plant-roots may fill it, and tree roots are quite sure to do so when opportunity offers. This is notably true in case of elms and willows, but protection is afforded in such an instance by closing the joints with cement.

[Ill.u.s.tration: The lure of the country.]