Technology: Aerated droplets make for a lighter spray

日期:2019-02-28 05:07:03 作者:敬世 阅读:

A BRITISH firm has developed a new crop sprayer which, it claims, will save farmers money and be kinder to the environment. A new design of nozzle targets the spray onto the surfaces of plants and produces much less ‘drift’ than conventional hydraulic sprayers. The new ‘Airtec’ sprayer also demands less water and works more efficiently in higher winds than hydraulic sprayers. Hydraulic sprayers work by forcing liquid through a hole that is small enough to produce a fan of droplets of varying sizes, in much the same way as putting a thumb over the end of a hose pipe. The larger, heavier droplets tend to bounce off the plant surfaces, thereby wasting much of the spray. Cleanacres Machinery, based in Gloucestershire, designed its ‘Airtec’ nozzle to mix a stream of compressed air with a stream of the liquid to be sprayed. The result is a plume of droplets, each containing trapped air bubbles. Only a small portion of the compressed air that feeds into the nozzle ends up in the ‘Malteser’-like droplets. The rest of the air surrounds the plume, helping to focus the liquid onto the target plants. Researchers at AFRC Engineering, at Silsoe College in Bedfordshire, found last year that the droplets produced by the Airtec sprayer travel much slower than would be predicted for droplets from a conventional sprayer. Air bubbles reduce the weight of each droplet by about 30 per cent. The air-filled droplets stay on the plants’ surfaces rather than bouncing off them. The smaller droplets remain inside the ‘curtain’ of air surrounding the plume. The researchers found that the smallest Airtec nozzle produced 35 per cent less drift than did a hydraulic nozzle of the same size because more of the spray lands, and remains, on target. The Airtec sprayer uses much less water than hydraulic sprayers – a significant advantage for a farmer who must pay for transporting water as well as for the water itself. The firm claims that its sprayer can cut costs by 20 to 30 per cent. At Pounds sterling 9400 to Pounds sterling 25 000 per machine the Airtec sprayer will attract only the larger farm enterprises but, says Cleanacres Machinery,