The Evening Star TUESDAY, FEBRUARY 21, 1928. “EDUCATION” IN IRRIGATION.

Evening Star, Issue 19796, 21 February 1928, Page 6

The Evening Star TUESDAY, FEBRUARY 21, 1928. “EDUCATION” IN IRRIGATION.

In t lig year 1924 there run through the ‘New Zealand Journal of Agriculture ’ a series of articles written jointly by Mr R. R. Tenncnt, N.D.D., Instructor in xigriculture, Dunedin, and Mr J, h. Marks, A.M.lnst.C.E., M.N.Z.Soc.C.E., then Resident Engineer, Public Works Department, Alexandra. The series was entitled ‘ Irrigation and its Practice,’ and in tho Juno issue of tho journal the methods of applying water and preparation of the land' were dealt with. One of the methods described was the border-dyke system, it was described as undoubtedly the most cllicient for Hat land, and though expensive in first cost, «s in the long run tho most economical from every point of view. In order to outline the system brief extracts from the article will serve; “Tho head ditches should be formed almost on a dead fiat, across the upper end of a field and at further intervals of 10 chains, and, being flat in gradient, must bo fairly large, as the method involves the rapid use of a comparatively large How ol water.

Small levees, ridges, or ‘ borders ’ run down the direct slope of tho land,

dividing it into strips

direction of the borders follows tho steepest direction of fall at each point in their progress from tho head ditch, to ensure that each strip will be perfectly level in cross-sections at every point. For operating a largo How is let into the top end of a ‘ land.’ The water spreads into an even film a few inches deep confined between the borders, and travels rigid clown the full length of the strip, watering the land in that strip evenly and thoroughly.

, . , Enough water to irrigate a whole strip must bo allowed to run into the head of it in thirty minutes” (that being the time officially calculated to satisfy average porous Central Otago land). . . . “Tho supply is then

cut olf at the head ditch and trans-

ferred to another strip. . . . The volume of water used should bo adjusted by trial. For land with a gradient of 3ft per chain a flow of about J cusecs (or heads) should be used, increasing to G cusecs when tho gradient reduces to Jin per chain.

. The whole essence of this system is speed and precision, therefore a wooden gate should he set in tho side of the head ditch leading to each ‘ check ’ or strip. Also a gate will bo necessary in the branch ditch leading from one head ditch to the next. These gates should be about Git wide and one board deep, the movable part consisting of one board, with handle to lift it by, set in a simple frame. . . . Tho

land must be smoothed perfectly, tho main levelling, such as cutting off decided hummocks and filling into hollows, being done in the first place with horse scoops and -scrapers, and tho finer levelling by special implements.

. . . The initial cost of preparation for the border-dyke system (though non-recurring) is much higher than any of the others ” (being set down at £5 per acre). . . . “By this method one man can irrigate 10 acres in eight hours. It is the only really scientific method known, and settlers should bo prepared to undertake very considerable grading and levelling work to adapt even very uneven land to its use."

Settlers in Central Otago are prepared to do nothing of the kind. In the vast majority of cases the addition of £5 per acre (too low an estimate, we are assured) to the capital cost of their land is utterly 7 beyond them. Heavy land requires no such treatment —unless it is under the most intensive culture for “small truck,” which again requires heavy capital expenditure in other directions. As to the light land, the condemnation of the system by those few who have experimented with it is general and emphatic. What happens in practice is that nearly all the top soil containing any humus is scraped off the plot to form the border-dykes which contain the water. Tims there is nothing left for the seeds sown to root in but gravel, and the application of even unlimited water will not induce the growth of a satisfactory or a payable crop. The Public Works Department has itself proved this. It has experimental or demonstration border-dyke plots at Springvale and Galloway (on opposite sides of the Manuherikia River), at Earnscleugh (fed by the Fraser River

system), and at Tarras (watered from the Lindifl race). At Earnsclough the only growth visible on one plot was thistles, and the other plot showed a moderate growth of clover. On the Springvalo plot tliere was a sparse growth of lucerne, fairly well-grown clumps standing out here and there in the bare patches. Certainly this Government demonstration 'area, depending for water on the Manuherikia main race, bad suffered from the same Sep-tembcr-January water famine as the rest of the sections dependent on this, the most important water-artery in Central Otago. But whenever water was available tho Government’s borderdyke area got it—and got it to the exclusion of the neighbors, who had to pay for their water. The comments of an irrigator who adjoins the plot were caustic and illuminating. He said that, ns an object-lesson to the Government’s customers, the experiment was ,not only worthless, but worse than worthless. The settlers can get only what water is given them; when the race is running the Government plot can get all the water in the race to the exclusion of those who pay for what they (mostly) do not get. When, on the raceman giving notice that water will be available on a certain day, the settler goes to his section to distribute it, he is often rendered vocationless by the Government demonstrator arriving to water the border-dyke demonstration plot. The plot is blessed with a flow of four or five heads, an amount never allowed to bona fide customers lest they “wax fat and kicking.” In short, the demonstration plots are an absolute laughing-stock. They command water which rouses envy among the neighbors —who have to go short to provide it; they are carefully nursed and fed with artificial manure; they require an initial expenditure which is not chargeable, being mot out of the Consolidated Fund; and the produce they yield per acre is the reverse of encouraging to lookers-on who know something about irrigating for a living. The plight of irrigators who depend for water on Government systems is bad enough. When time and space permit something must be said about those who slave under the local body system at Bannockburn and the company system at llipponvale. For it is slavery; and that slavery has been legalised by Parliament in its lack of knowledge.