Land Drainage.

Te Aroha News, Volume II, Issue 57, 5 July 1884, Page 5

Land Drainage.

Whatever the composition or natural capability of soil, its fertility depends materially upon its relation to the water which falls upon it. If the rain water has free access throughout it— a free passage through it— not only are ingredients added which the roots absorb for the nourishment of the plant, but these ingredients are available in the laboratory of the soil for those purposes by which plant food is manufactured from the material of soil itself, and from the manure added to it; and, above all, the full use is obtained of a necessary carrier of plant-food by the hungry mouths, the absorbent ends of root fibres to which it must be brought. Upon the permeability, as well as on the composition of a soil, its fertility is thus very materially dependent ; and land drainage, either natural or artificial, is essential to it. When there is an excess of water in the soil, and no provision exists for withdrawing it, the interstitial canals become completely filled, to the exclusion of the necessary amount of air on which the activity of the soil considered as a laboratory for the provision of plant food depends. When the soil is drained, the superfluous water flows off through the air canals, and only so much moisture is retained as can be absorbed by the minuter pores within the small particles of earth ; and as there is, then, free communication through these canals between the pores and the drains, it is evident that the water will be withdrawn from the soil, except that which is held by capillary attraction. Thus the rain, which falls upon and is absorbed by the surface ground, percolates towards the drainage level, flushing every crevice and canal in its descent, leaving behind. it the nutritive ingredients which it carries in suspension or in solution, and on which the plants can feed as it passes by their roots, or which the soil, acting as a filter, extracts and appropriates. The object of land drainage is not merely to render wet ground sufficiently dry for tillage operations, but so to regulate the passage of moisture that, while the soil shall have every facility for absorbing the necessary quantity, stagnation, and the consequent starvation of the plants, shall be prevented. Almost all lands require it, in whole or in part, and there are few fields which can be economically cultivated with out draining pome part of them. The causes which wet the soil of any field requiring drainage must first be considered. When these arc understood, it will be easy to decide upon the best mean,s of providing a remedy. But in this consideration the strata of the district must be taken into account, as well as the contour of the surface, and the texture of the soil and subsoil of the particular field. If the bin face of the ground be level, ami the structure of the soil uniform, the drain. 1 ; may be arranged at regular intervals apart, witli the feeders at right angles to the mains, and the necessary slope must be gained by cutting upwards horn a sufficiently deep outfall. In any case the mains must bo placed at the lowest level, delivering into a ditch or brook, and the minor drains should run into them in the direction of the inclination of the ground. When the inclination of the surface varies, though there should be biiilicient fall for discharge if the drains weije cut thioughout to a uniform depth, yet it is necessary to observe a sufficient uniformity of fall in the pipes to hinder any risk of a deposit of mud in any part of their course. If the substrata consist of layers of various retentive power, their relative positions must be regarded in the arrangement of the drains. Instead of following rigid rules for fixing the proportionatedepthsand distances of drains in light and heavy soils, we must determine these points by reference to the thickness and order of the substrata no less than by the character or texture of the soil itself. Practically these are determined by digging holes? four feet deep here and there in a field, and taking a drain of the intended depth up the field in their neighbourhood. The holes m ill fill m ith water if the land needs draining ; and the efl'cct of the drain in emptying them at distances of three, five, and .seven yards, etc., will indicate twice that measure as the proper interval to be adopted between the drains. If the upper bed bo retentive, and of such depth that the drains cannot be cut completely through it, the best system to adopt will be that ot comparatively shallow drains at close intervals ; and, on the contrary, a pervious material should have deeper drains at wider intervals. If a thin bed of clay rests upon a porous substratum, the drains may be cut into the latter, or through it, according to its depth, and they must then be laid at frequent intervals. When the case occurs, as it sometimes does, that a free supersoil, about three feet in depth, overlies a comparatively thin bed ot clay, it is often advisable to limit the depth of the drains to that of the porous bed. When springs, which are fed fiom a higher level, lie immediately below a clay substratum which exceeds the practicable depth of the drains, recourse may be had to tapping, by means of an auger-hole or vertical bore, w Inch will open communication to the drains by >\ Inch the contents of the springs may be carried oft", and the liability to mischief caused by their bursting forth at a lower level "w ill be prevented The drainayc of wet and deep boggy land is a gradual process, requiring sometimes years of patience before success is attained. Frequent open ditches should, at first, be cut as deep as the sides w- ill stand, and then gradually deepened as the land subsides, taking care always to keep them well cleaned out. When the land has become sufficiently consolidated, the usual pipe drains may be put in, but they should be laid rather beyond the depth which would be thought necessary in a firmer soil of the same nature. If the moss will not carry the ordinary pipes, it will be advantageous to use collars with them, in order to prevent their displacement. Marshes, and even lakes, which occupy a bowl-shaped cavity, rendering drainage by the ordinary means impracticable, have often been successfully drained by boring or digging through the impermeable surface layer where it is not thick, and rests upon a porous substratum of sufficient depth to receive the water and drain it from the surface. But this method must not be tried without due attention to the disposition of the sectional strata of the district, for the porous soil may be surcharged >\ ith water from a higher level, and the pioposcd cure might only prove an aggravation of the existing evil. In that case the object may be obtained by cutting a deep ditch or canal through the bank on a level with the bottom of the lake. In ordinary practice it is the texture of the soil and subsoil, and the nature of the lope, which determine the proper depth and distance of drains. Deep drains are longer in beginning to flow ; but, if the soil is porous, they will carry off the surface water, after heavy rains, sooner than shallow drains. They also drain a greater bulk of the soil, and allow the water time to deposit the particles of mould and manure, which it carries down from the surface of the ground. In an open soil, which the water penetrates freely, the drain will draw from long distances, if the depth is great; but

in stiff, compact soils, percolation is more difficult, and the drains will draw from a smaller distance than in free and open soils where the water finds a ready escape. No amount of depth will compensate for excessive distance on compact soil, because the material either resists the passage of the water altogether, or the removal is so slow that the drainage is worthless. The requirements of vegetation must also bo considered in determining the proper depths of drains, and the depths to which the rootlets of the plants penetrate may afford some indication of how far the free subjacent water should be permitted below the surface. As its availability for their supply -win be regulate! by the porosity of the soil, the bottom of the drains may be at a less distance from the roots on a heavy soil than on a light one. In dry summers, grass land especially is sometimes liable to injury, owing to the land being dried below the rootlets, which the capillary power of [ the soil is thus unable to feed. | Another circumstancewhich will occasionI ally have an influence in regulating the depth is the degree of slope which can be [ obtained, according to the surface levels of the district. Theoretically, water will flow if there is but the smallest possible deviation from a horizontal line ; but, in practice, this is not sufficient, for it supplier a perfectly smooth and regular bed, a condition which cannot be expected to exist in land drains. The water should not pass too quickly through the soil before it has time to deposit its nutritrive ingredients, but neither should it be allowed to stagnate, as it will do if the drains are deeper than^ it can readily permeate, or if the fall is insufficient to induce a free discharge. When the drains are sufficiently active they will not allow the water to stand for any length of time on the surface after the most heavy rains. For purposes of cultivation the drains should seldom, if ever, be laid at a less depth than throe feet from the surface of the ground. In grass lands two and a half feet may be sufficient, but where all other circumstances are favourable, three feet should be the minimum depth. The dimensions found most efficient in actual practice vary from three feet to five feet in depth, and from fifteen feet to thirtysix feet apart, according to the closeness or porosity of the soil, and the cost of cutting, placing the tiles, and refilling, varies from scl. to 1 Od. per rod, according to the depth of the drain and the hardness ot the substratum. Thelayingof the pipes should be entrusted, to a careful workman, who is paid day's wages, as more attention in the performance of the work is thus insured than when it is done by the drainer at piece-work. It is very important that the pipes should be large enough for the quantity of water they have to discharge. It the fall is considerable, a pipe ot less dimensions will suffice than where the inclination is smaller. In practice, after the depth and interval of the intended drainage have been determined by trial holes in tho manner described, and after tiny particular springs of -water have been dealt witli by special conduits taken through the wet spots thus created, and after all old water channels have been furnished with pipes laid at sufficient depths, and properly filled in, the systematic drainage of n Held which ncedn tho operation is begun at the lowest lc\el in it. Tho ditch is cleaned out by A\hich the Avator is to escape. The main drain is dug from a point six to eight inches above the bottom of the ditch along the lower edge of the field, parallel with its side, from which it may be distant five yards or more, and a deep (to at least four feet) as possible. Into this drain the minor drains deliver over the top of the four to six-inch pipes, which are placed in it. These minor drains, at a depth which has been resolved upon, are taken right up the slope, unless it be very steep, and frno-inch pipes are placed in them. If the field is more than two hundred yauls long, there should be a second main drain crossing it midway of its length, into which the upper series of minor drains deliver. The pipes should be carefully placed and carefully covered with the earth taken out. It is not necessary to put straw or turf over them before the earth which has been taken out is replaced. If there is any considerable remainder of the earth, it should be spread on the land, all stones being removed ; and tho turf, which in pastures has been first dug out, should, as soon as the earth has settled sufficiently, be replaced and rolled down ; and the work may then be considered complete. It will often be possible to economize the labour by sending a plough along the line of each drain to turn out the first six inches by horse power. A double furrow will be necessary to open up the work efficiently ; and in the case of grass lands the ploughing will be more effective if it be not too deep. And then these furrow slices, thrown out on cither side without being detached from the land, can be brought together over the finished drain and rolled down. But the operation cannot be considered complete without careful provision for its permanence by a properly built outfall. The last pipe of the main should pass through brickwork aa hose foundation is laid below the level of the bottom of the ditch, and it should be protected by a flap or grid. And the exitwater should fall from this opening on a slab of stone laid on the bottom of the ditch, so as to hinder any risk of undermining the brickwork by its continual fall. The cost per acre of land-draining is more generally covered by the consequent increased value of the land than that ot any other agricultu ral im pro vement. Whatever tho interval or depth, the expense depends on the character of the soil or subsoil, the local rate of wages, the cost of the tiles and the distance oi the kiln. — The Soil of the Farm.

"Oh, will he bite?" exclaimed one of Liverpool's sweetest, girls, with a look of alarm, when she &a\v one of the dancing bears in the street the other day. "No," said her escort, "lie cannot bite, he is muzzled. But he can hug." "Oh," she said, with a distracting smile, "I don't mind that !" A young man dressed in the height of fashion, and with a poetic turn of mind, was driving along a country road, and, upon gazing at a pond which skirted the highway, said, " Oh, how I would like to lave my hoated head in those cooling waters !" An Irishman, ovorhearing the exclamation, remarked, " Bcdad, you might lave it there, and it wouldn't sink !" A collision between a butcher's cart; and one of Smith's Mount Eden omnibusses took place in Upper Queen-street about a week ago, and was the subject of the action Smith v. Lupton, heard in the R.M. Court last Thursday. It appears that as the 6 o'clock 'bus from Auckland was proceeding up Upper Queen-street, a cab and a butcher's cart were observed racing down the street ata furious pace. The butcher's cart, driven by Roger Lupton, had no lights, and was on the wrong side of the road, and when near the Turkish Baths came violently into collision with the 'bus, breaking the pole, knocking down the horses, and doing some damage to the body of the 'bus. The 'bus was filled with passengers at the time, and the collision caused no little consternation among them. Fortunately, however, no one was injured. Judgment was given by the Resident Magistrate for the full 1 amount claimed for the damage done, and costs. Mr W. J, Napier appeared for the plaintiff.