Reducing Labour Involved In Irrigation

Press, Volume CI, Issue 29714, 6 January 1962, Page 7

Reducing Labour Involved In Irrigation

Irrigation has come into its own again in Canterbury this season with a return to drought or near-drought conditions over a wide area. A long-standing objection of plainsland farmers to irrigation on the border dyke system has, however, been the long hours of work required in shifting sheet dams and supervising the watering of their pastures. As a consequence the Department of Agriculture’s irrigation research station at Winchmore has been devoting considerable effort to the development of a practicable system of automatic irrigation which would reduce substantially the labour element involved.

Summing up the results of work with automatic irrigation on a 160-acre farm at Winchmore, the station superintendent, Mr W. R. Lobb, said this week that provided there was a satisfactory race system it was now quite possible, with the equipment available, to irrigate fairly extensive areas, of the order of 160 acres, at a high level of efficiency. Mr Lobb explained that one of the keys to satisfactory automatic irrigation was to have races prepared specifically for this type of irrigation as it was easier to do this than to adapt equipment to established races. An important factor in this preparation was to have the fall in the race so that groups or sets of two, three, four, five or six borders could be watered at the same time. In some areas, Mr Lobb said, it might not be possible to have suitable races to operate automatic irrigation, but on most properties it should be possible to have automatic irrigation on quite substantial sections of races so that irrigation could be carried on unattended for quite long periods. On the automatic irrigation farm at Winchmore a race was put in last year specifically for automatic irrigation. It has a fall of about one and a half inches a chain, which is achieved in falls of four to six inches at the end of sections equivalent to mainly four borders. This enables four borders to be watered at once. Use By Farmers One of the systems being tested and perfected at Winchmore is now being used by a number of practical farmers. It involves irrigating back up the race, a method that is believed to be more efficient and economical in water usage. At each point where the water is to be dammed to irrigate a group of borders a metal standard is set into the race in concrete, and a timing device, an alarm clock, with release mechanism, is mounted on a stem which fits over the standard in the race. The lever which is attached to the alarm clock holds a shackle that is connected to a specially designed near triangular canvas sheet dam which is held up above the race. When the alarm goes off a string attached to the alarm knob of the clock is released, and it trips the lever holding the shackle, which drops down the standard, carrying the canvas sheet to the bottom of the race, where it is anchored on the standard as well as on a pipe across the race. The sheet is designed to give a full bottom so that it forms a fairly complete seal across the race. The water then overtops the sills at each of the borders and irrigation proceeds. The sills sit well above the

land to be irrigated, so that there is a minimum of interruption to the outflow of the water. Initially a piece of wood or a metal plate may be used at the sill to determine the appropriate point at which an even flow Is obtained down each border. Sills may then be concreted in. An important feature of this system is that it obviates •the need for head-blocks or head-gate boards. Recently a paddock shut up for hay was being irrigated by this method, and tihe the high growth at the sills was tending to restrict the This prompted Mr Lobb to advance the idea that such a race might be included in a fenced-off paddock that was at all times used for grazing to keep growth down to a desirable level. Problem A problem of some importance that has not yet been satisfactorily solved is how to recover the sheets from the race that remains full for a number of hours. A swivel has been fitted to the shackle with the idea of allowing the sheet to be detached from the bank of the race by a rope, but the pressure of the water is such that it does not always work easily. The use of two swivels looks, however, to be an improvement. It is possible that the same sort of sheet and release could be used for manual irrigation beckstream, but a satisfactory system for removing the sheets before the race is empty is awaited before the use of this system can be advocated. Mr A. D. Pollard, manager

of the automatic irrigation farm, has devised a timing and release device mounted on a standard tor using this system for downstream irrigation. Another system being tested at Winchmore is of American origin, and has been used in Otago by Mr L. H. Weston, machinery officer of the Department of Agriculture at Dunedin. This involves permanent concrete diversion blocks or shoulders at the damming site, with a metal gate that is held upright until released by the alarm clock timing device. This device is simple and inexpensive, but taking labour into account the cost would probably be similar to that involved in the system described earlier. A particular disadvantage is the silting up of the race, and the efficiency of the system can also be impaired by a stone or other obstacle lodging at the point where the gate closes so that there is a higher than normal loss of water. The Practice At Winchmore this system has been used on a practical basis in a paddock with 20 chain borders, with borders being watered in sets of four and two sets of six. Here it has been possible to water for 17 hours without manual effort. Still another system of automatic irrigation is that developed at Winchmore by Mr D. Hall. It incorporates an alarm clock and bomb release. It holds a canvas dam in place and a head gate open until a predetermined time when the gate is closed and the dam is released so that the next set of borders downstream can be watered. It also involves concrete spillways with dividing boards so that water can be diverted down two borders from the one headgate. Apart from the alarm clock, another timing device is being experimented with. It is a battery powered electric release. It does not depend on a constant flow of water in the race. It detects when the water reaches a predetermined point and then relays a message to the release mechanism. All these devices are constantly under study with the idea of improving them.