Weed killing sledge a 'knock-out'

Waimarino Bulletin, Volume 2, Issue 25, 20 November 1984, Page 11

Weed killing sledge a 'knock-out'

Like many a good invention, it is the sheer simplicity of the Knock Out system that makes it such a major advance in weed control. "I liken it to putting the wrinkle in a woman's hair clip to stop it falling out," claims its inventor Lindsay Cockburn. "That's how simple it is." The idea for the sledge came to Lindsay from a simple observation he made while watching a wick boom conventionally mounted on a three-wheeled trike. "I found where the trike had been running over thistles the resultant kill in the wheel tracks was terrific," he said. The wheels knocked the plant down, bruising and cracking the stem, but the thistles still had enough resilience to spring back to receive a lick of the herbicide. The principle of the better kill is that the herbicide penetrates the waxy stem of the thistle quicker through the damaged surface and is taken into the plant's sap stream. Lindsay, who has been in the stock and station business "pretty well all my life" took his idea along to an engineer at Rakauhauka, Murray Heenan, who admits he was just a shade sceptical at first. Construction Murray set to work on the prototype model of a twometre sledge unit, using long skids or skis designed to give smooth travel over most types of terrain. The skis were preferable to wheels for two reasons — firstly because they are cheaper but more importantly because they make the sledge more stable than one mounted on wheels, which would be more likely to bounce around on lumpy ground. The plane of the ski can be adjusted and the operator has full control over the height setting, which can be adjusted according to the height of the weed being treated and the length of the pasture. The frame for bending the thistles over is angled forward at something like 30 degrees. Originally a canvas cover was used on the prototype but this was later replaced with lightweight

steel bars which do the job more efficiently and eliminate the problems of sagging which were evident with the canvas covered model. Another improvement was the addition of a bruising bar, which is mounted on the frame just in front of the boom. The bar is crafted from high carbon steel and its leading edge scrapes along the stem of the thistle, exposing the damaged stem to the herbicide. Double unit The next step was to design a double unit with a span of four metres. This model is based on the single unit with a second sledge that folds up onto the first for transportation and clearing gateways. An ingenious hinge has been designed to allow the double unit to bend up and down. This allows the whole unit to follow the contours of the ground and maintain a constant height, preventing damage to pasture. This innovation eliminates the problems experienced with fully mounted wick booms where there is no control over the varying height of the outer edges of the booms on rough ground. Field trials The system has given excellent results in the control of Californian and Scotch thistles, rushes, ragwort and cutty grass. As yet it has not been tried on winged, variegated or nodding thistles, but Lindsay says the prospects look very exciting. He says it could also be used to control wild turnips in swedes, barley grass and goose grass — "in fact anything that exposes itself above the pasture." In January the sledge was put to the test in field trials on Mr Bruce Caldwell's property at Roslyn Bush under the supervision of a representative of the company that supplied the chemical. Four plots were marked out in a paddock with an infestation of Californian thistles. Single and two-way runs were done with and without the bruising bar attached. Lindsay Cockburn estimates a kill of 80 percent of the thistles on the one-way plot, 90 percent on the twoway run and between 30 and

40 percent on the two plots when the bruising bar was removed. This result was achieved despite a heavy fall of rain just one and a half hours after the trial was completed. Lindsay Cockburn says they can't claim the chemical used is rainfast — not yet anyway. "We're not recommending that the sledge is used in the rain, but we believe it minimises the risk of a failure," he said. The trials will be repeated this year, including an extra trial to monitor weed numbers on a marked plot. Twice as fast In the past the use of the wick boom has been a painfully slow job if operated correctly at three or four miles an hour. But Lindsay Cockburn and Murray Heenan claim their Knock Out system can at least double the speed of application in areas of lighter weed infestations, which farmers would frequently not even bother about. The design of the frame reduces the whipping effect common when the boom is used on its own and at a faster speed than it was designed for. The faster sppeds called for heavier materials than used on the original prototype model, so Murray has "beefed up" the new models. Southern debut Trials done in JanuaryFebruary 1983 at 10 kph resulted in a 92 percent reduction in Californian thistle when inspected 12 months later. In the same trial the areas treated at 5 kph only achieved a 66-70 percent reduction. Both areas received a two-way pass. The results of this trial clearly show the importance of the extra bruising attained with increased speed. In January-February further trials were set down using the new Stafix wick boom which features a greater wick area and a built-in header tank which combine to give a greater flow of chemical. At this stage the results look even better than with the older type of wick boom but final results will not be known until January-February 1985. From the results of many trials Murray Heenan says the two most important factors in control of Californian thistles are firstly, getting sufficient bruising, and secondly, not

commencing treatment until the thistles are at the right stage of growth which is when 10-20 percent have started flowering. The sledge made its debut at the Invercargill show in 1981 and the double unit first appeared at the Southern Field Days at Waimumu early in 1982. To date over 400 sledges have been sold. An essential part of the sledge 's development has been feedback from clients and the subsequent modifications. They admit that they have not actively pushed the marketing side of the operation yet but once patents are completed they intend to market them in both New Zealand and Australia, where they see an immense export potential. In fact they say the technique could be applied worldwide. Not surprisingly, thes partnership has been successful in the past. Four years ago the pair developed pig tail electric fencing standards for sheep and deer using a high density plastic insulator. Murray Heenan has manufactured about 100,000 of the standards, which were marketed exclusively by J.E. Watsons and have been sold as far north as Hamilton. Engineering runs strongly

in the Heenan blood. Murray trained as an engineer, working for his father's business at South Hillend but gave it up to go farming on his own account. But the challenge of the workshop proved too strong and he later sold the farm to concentrate on his present business, which specialises. in farm machinery. Reprinted from the Southland Times