DRAINAGE OF LAND.

Otago Witness, Issue 2785, 31 July 1907, Page 8

DRAINAGE OF LAND.

_!By "Percy G. Wicken, in the Journal of Agrioulture, W.A. Before commencing to lay down a system of drains"" an outlet for the main drain Must ' be TotbmJ and the drains marked out so as to- give- the necessary fall — a- fall of 3ia^ihVlOQf t will be Sufficient; the bottom of "'the Irain should be kept smooth", J and jnusfc vi be' carefuHy graded:" '^are musfcl-'bev taken to avoid,- if possible, bringing the

Fig.l. Fig. 2. Fig. 3. Fig. 4. SLAB AND POLE DRAINS. subsidiary drains in at right angles to the main drain, as this impedes the flow of water at every junction. The main drain should' be made amply large enough to carry off the water from all the feeders. Great difference of opinion exists as to the depths of the drains — they vary from lift to 6ft. Much lepends on the nature of the soil; retentive soils require deep drainage; the deeper the drains the wider

they may be apart. All drains should be placed sufficiently deep to be out of reach of the plough and subsoiler, as one break will destroy the use of the whole drain. My experience is thai no drain should be nearer the surface than 30in. Our subeoilers often work 20in to 22in deep, and

they are not so easy to handle as a plough, and on coming to a 6oft place, such as a drain, are apt to sink in some distance and destroy the drain. Figs. 1, 2, 3, and 4 represent various ways of laying slab and pole drains. Drains constructed in these patterns are very effective and almost everlasting, and' where the

timber can be obtained easily or close at hand are the cheapest form that can be constructed ; care must be taken to place turf or some bushes over the joints to prevent the soil from leaking in and choking lhe drain. Figs. -5, 6, 7. 8, and 9 represent various ways of las'ing stone drains, according as to whether flat or round stones are available, the main object being to so pack the stones as to leave an open channel along which the water «can run. Fig. 9 represents a drain mado of small broken stones : bub this style of drain soon becomes choked, as " however carefully they are covered, the soil soon finds its way between the small stones, and the drain becomes useless. „ . . Fig. 10 is a sketch of a small triangular level, which is very useful for grading the

bottom of the drains ; butt' where a long distance has to be done, a tet of bouingrods are much easier. Fig. 11 is the ystem of plug-draining, which is only suitable for s>tiff clay soils; but is cheap and effective. The drain is opened up and the plug laid in the bottom, and, the clay well-packed round it, the plug is then withdrawn, and is available for the next length. Fig. 12 represents a simple form of the mole -plough. This implement is somewhat fimilar to the ordinary subsoil plough; but, instead of "the apparatus for breaking up the soil, a thin steel coulter is used, to the end of jvhich a round piece of steel is fixed of the required diameter, and pointed at one - end; this is let into the ground the

required depth, and drawn along by a team of bullocks or other available power. This is the cheapest form of draining, but is only useful for flat country and clajej soil. Several forms of model ploughs are put on the market by different firms of implement mokcis. Figs. 13 and 14 represent two methods of tile-draining, which consists of laying burnt clay tiles Jong the bottom of the drain, ana are very effective. Fig. 15. — Thi3 is by far and away the best system of draining land. A pipedrain properly laid is practically everlasting. The pipes are, round, and are made of burnt clay, aSaaux be obtained ia all

) diameters * from lin upwards. One side of I the pipe is made flat to enable it to be laid level. A 2in pipe is the size generally used, buit much depends on the length* of drain and the quantity of water to be

Fig. 13. Fig. 14. Fig. 15. TILE DRAINING. PIPE DRAINING. drawn off. A 2in pipe with a fall of 3in per 100 ft will discharge 10,575 gallons in 24 hotirs. In digging trenches for pipe-drains, the first spit or grass sod should be laid on the opposite of the drain to which the earth is thrown, and when the are laid the sod should be laid gTass eide downwards on the pipes, also a piece of bark or old tin should be iaid over the joints of the pipes to keep the sand, etc., from falling in. Care must be taken, that the pipes are properly graded, and they have sufficient fall to carry off the water. An average distance apart of drains may be token to be about 40ft apart; if the ground is sandy % they may be further apart, but if in olay or wet ground they must be closer. The shallower the drain the closer

they must be together; the deeper the drain the further apart tjhey may be placed. Drains should not be laid too olose to trees, -a* the roots may displace the pipes and cause the flow of water to stop. Fig. 16 ia a set of draining tools neces-

sary for digging and laying pipe-drains. A, long bitted spade; B, ordinary spade; C, half-round spade for depth ; D, a wider half-round spade ; E, pipe-layer ; F, scoop for bottoming ; G, flat-bottoming tool; H, for cleaning bottom of drain; I, for cleaning bottom of drain.