A WIDE FIELD FOR DRAINAGE

Press, Volume XCVIII, Issue 28896, 16 May 1959, Page 8

A WIDE FIELD FOR DRAINAGE

Department’s Advisory Service

As Mr Bruce Harvey, a town milk supply dairy farmer at Styx, watched a trench being dug for a tile and mole drainage system on a nine acre paddock last week, he told students from Canterbury Agricultural College, who were studying the operation as part of their agricultural engineering course, that he expected to recoup in little more than a year the cost of the work—£2o to £25 an acre.

The paddock has never been ; cropped before and it has not been possible to cut hay from it. ' It is Mr Harvey’s intention to . plough it for a crop of peas for , freezing which will at the same ; time provide him with a supply . of silage, to have a crop of green- ( feed on it next winter and subsequently to sow it down to pasture. He expects ultimately to carry an extra cow to the acre with additional pasture and hay, , raising his herd from 47 or 48 to • 60. This scheme, involving the lay- 1 ing of 25 chains of tile drains, , has been planned by the Depart- . ment of Agriculture, which is ■ also supervising its installation. : With drainage instructors j stationed in Auckland, Palmerston ( North*, Christchurch and In vercar- ( gill, the department is prepared to discuss drainage problems with farmers free of charge. . Generally instructors in agricul- ; ture in the course of their duties ; observe where drainage is most ] acutely needed and through them 1 the specialist instructors—in the ] case of Canterbury, Marlborough, 1 Nelson and the West Coast, Mr J. i F. Scott—visit these farms and i discuss with their owners what is ; involved in the alleviation of j their. particular problem. If the : farmer is still interested the de- ; partment will make a survey, take levels, investigate the soils : and sub soil, the source of the water and outlet arrangements for a drainage scheme and forward to the farmer an estimate survey report setting out the cause of the problem, a drainage plan, tile requirements and estimate of the cost and information about the quality of materials which should be used and the standards ’ to which the drains should be laid. Charge For Service Should the farmer decide to proceed from this stage a charge is made for services at 15s an hour for an instructor and 10s an hour for a technician. The department will peg out the scheme and supervise its construction and finally prepare a plan of the scheme. To minimise costs the department may lay out the scheme pegging the tile lines and the farmer may then proceed without further help, but the department prefers to see the job through to the end so that it can be sure that the work it has started is carried through faithfully to the end and so no blame can be attached to it for a failure for which it may not be genuinely responsible. Just lately with drought conditions and changing economic fortunes farmers, apart from those on the West Coast and in Nelson, have been showing less interest in drainage, according to Mr Scott, but the swing to cropping will again focus more attention on it as yields can drop off sharply where drainage is inadequate. There is no lack of drainage work in Canterbury and the other districts in which Mr Scott works. In 1952 a survey showed that in Canterbury, Nelson, Marlborough and the West Coast there were 1,710,000 acres in need of drainage. On most of this, including 450,000 acres in Canterbury, Mr Scott said that drainage was probably warranted. Generally speaking he said that a doubling of production could be expected from . drainage, but sometimes the benefits accruing from drainage are not fully realised as they are masked by other farm practices. Liming and topdressing may not give full responses until drainage is improved, but responses then obtained are due not only to the drainage. On a paddock in the Murchison district on the West Coast where half of the area was drained completely by mole drains at a cost of only £2 an acre there was a 500 per cent, inincrease in pasture production as disclosed by hay cut off it. At the department’s Invermay research . station a trial is now in progress to assess the increase in pasture production which may be attributed to drainage. Mole Draining But not all, land can be drained so economically as that at Murchison. Straight mole draining is confined to the clay foothills and downs where there is no problem of fall. On the flatter clay country although it is suited to moling tiles are also generally necessary and depending on the degree of flatness drainage on this basis may cost from £l5 to £2O an acre. On the silt where the problem is a rising water table and the solution lies in open drains or tiles, if it is a tile project the cost may range from £l5 to £25 an acre. The department also undertakes sports field drainage planning and supervision and here where a higher standard of drainage is required so water may be moved off the ground more qv.ickly and tile drains are situated at a chain or half a chain apart instead of an average of two chains the cost may be £l5O or £l6O an acre. Such drainage may also be justified on market garden, nursery or orchard land where the gross return per acre runs into hundreds of pounds. A big farm drainage scheme which the department has planned and which is under consideration provides for the laying of 19,000 ft of 4in pipe and 6000 ft of 6in pipe with outlets from the

pipe lines into grassed waterways to let the water away in periods of heavy rainfall. This scheme would cost £3OOO to install to serve an area of 300 acres on a property on the Inland road, Kaikoura. This scheme has been stimulated by successful drainage on a, neighbouring property. High Standard A high standard of workmanship is a vital aspect of drainage. Where tiles were laid before the turn of the century they have been found to be still functioning perfectly, and if a cost of £2O to £25 an acre is spread over a ( life of 40 years a very worthwhile return over and above interest and principle payments can be . envisaged when in some cases recovery of all costs is expected in ' the first year. In tile drainage, where the ' system is ccvered in, good work is particularly desirable and Mr 1 Scott says that points to watch : here are that there is a firm bed for the tiles, that they are laid to specified grade, butted 1 tightly together and that first ' grade pipes are used. Such refinements might also be incorporated as silt traps at grade changes and 1 placing soil by hand to stop tiles falling out of line when trenches are being filled in. An important point is that a plan should be prepared indicating the depth and direction of tile lines. Mr Scott says that where a property changes hands the production of such’ a plan represents a tangible asset, but where a claim is made to drainage but no plan can be produced it is open to some suspicion. In a few areas where machinery can be used only with great difficulty a spectacular yet practical method of constructing short lengths of ditches instead of hand digging is the use of gelignite. It has been used bn the West Coast, at Takaka, Kaikoura, on Banks Peninsula, and in North Canterbury, but it is emphasised that this sort of work should not be undertaken without guidance from men well versed in the use of explosives. Mr Scott foresees the need for some type of drainage service in the South Island on the lines of that operated by Massey Agricultural College for the work that is being done now is merely [ scratching the surface of the possibilities of drainage in the 1 South Island. Even the Massey service in its first three years i drained only 2000 acres of wet country. In the northern part of the South Island in 1952 there were 1,700,000 acres in need of drainage.