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Aviation History
1962
1962 - 0622.PDF
620 FLIGHT International, 19 April 1962 The loader scoops up a ton of superphosphate. Its driver, in his rear ward-facing cab (the vehicle is driven in reverse on the strip), checks from a weight-gauge dial and drops back any excess weight provement is that it is not necessary to clear the land of any dead- ground timber before proceeding—timber which would be costly to move and yet would prevent free and easy movement of tractors. Many of the strips used by top-dressing aircraft seem extremely primitive at first sight—at times indeed on a second look too. A survey conducted by the New South Wales Department of Agriculture a few years back revealed that on 68 per cent of the surveyed proper ties the strip had cost less than £A20 (£16 sterling) to prepare. The surface, by statutory regulation, "shall be such that a motor car or truck can be driven over it at a speed not less than 30 m.p.h. without undue discomfort to the occupants." This specification begs all sorts of interesting and amusing questions. Dimensional require ments laid down are more precise. The total minimum width needs to be 200ft, but the minimum width smooth for take-off and landing need only be 80ft. Length will depend on the type of aircraft being used, but strips are normally 500-700yd long. The de Havilland Beaver, which can carry a ton of fertilizer, requires a strip of some 660yd. The airstrip is sometimes gently ramped at one end to assist in braking after landing. The limits of the runway are usually marked off with old car and tractor tyres painted white and laid fiat on the ground. These are removed once a flying period is over and are AERIAL TOP-DRESSING How it is Done: An Interested Observer's Impressions By B. J. F. James THE Australian national sheep flock, which numbered less than 125m in 1944, had topped the 150m mark by 1959 and in March 1961 stood at 153m. This rise is the more astonishing when it is realized that the overall period encompassed a great drought which depleted the flock to just under 98m at March 1947. A major factor in this increase of numbers has been the improve ment of pastures and the replacement of poor-quality native species of grazing plants by specially bred clovers and grasses. There are well over 10m acres of improved pastures in New South Wales alone. To a recently arrived Britisher the feature of outstanding interest with regard to pasture improvement is the Australian, and New Zealand, method of doing the work from the air. This is a com paratively new development, but one which has expanded enor mously over the last ten years or so. In New Zealand, for instance, in 1950 15 aircraft spread a total of 5,000 tons of fertilizer over 49,000 acres; by 1956, 313 aircraft were in use and 405,000 tons were spread over 4m acres at rates of 2cwt per acre. The earliest known top-dressing and sowing of pastures from the air in Australia was done privately in 1945 and 1946 on a property in Northern NSW, some thirty miles from where this is being written. Superphosphate was applied in 1945 and subterranean clover sown a year later. Nitrogen, incidentally, is prohibitively expensive in Australia, so pasture-improvement programmes are always based on the application of superphosphate. This encour ages clovers and eventually the growth of grasses, as the latter benefit from the capacity of clovers to fix atmospheric nitrogen and so enrich the soil. But the business was slow to develop in the early fifties: the data below show the estimated tonnage spread by aircraft in NSW: (Acreage Year Tonnage approx) 1949 100 2,000 1950 250 5,000 1951 700 14,000 1952 2,500 50,000 1953 4,000 80,000 Yet by 1957-58 over a million acres in New South Wales alone were treated from the air; one-fifth of all fertilizer used annually on pastures was applied aerially and the method has expanded greatly since then. (In 1960 one firm alone put down 100,000 tons of superphosphate on 2m acres in NSW). Much of the land so treated could not have been dressed in any other way, because of steep slopes, inaccessibility to wheeled vehicles, rocky outcrops, timber and the like One advantage of the aerial method of pasture im- t0|| W'« normally stacked in a couple of high piles near the fence, where they present an odd sight to the uninitiated eye. Men are sometimes stationed to act as markers at each end of the fertilizer dropping runs, though if the pilot knows the area well their services can be dispensed with. If two marker-men are em ployed the pilot flies from one to the other, and each man moves along the appropriate distance after each "pass" by the aircraft. Usually signals are made with large white cloths or reflecting mirrors—absence of sunlight is not a problem in Australia. It is doubtful if markers are ever really necessary, as a slight unevenness in the spread of fertilizer does not appear to be critical in terms of subsequent feed production per acre. In New Zealand markers are not used; and many Australian graziers, too, dispense with them. Marking is expensive anyway, as hired labour is costly—upwards of £12 sterling a week for a station-hand. In the early days of aerial work, bagged fertilizer was often used and the bags had to be broken open by hand before being fed into the hopper of the loader used to tip the fertilizer into the aircraft However, the fertilizer itself is considerably cheaper (by about £1 per ton) in bulk than in bags, and the cost of rail freight is the same either way, so bulk delivery is now the rule. All the grazier needs to do nowadays is to place his contract with one of the aerial-spreading firms and, if thought necessary, provide men as markers; the con tractor does the rest, i.e., orders the fertilizer, has it transported from rail-head to the farm airstrip and provides the loading-lorn with driver and, of course, the aircraft plus pilot.
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