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HALVES THE HERBICIDE REQUIRED
They are known as foxtail grass, dead nettle or goose grass, and are fairly unpopular among farmers, since the battle against these persistent weeds swallows up a sizeable sum of money: every year the use of herbicides in farming gobbles up as much as 200 euros per hectare. On a large farm of several thousand hectares this adds up to a considerable amount, quite apart from the fact that even modern herbicides represent a threat to the environment. Yet more accurate spraying of fields could save a large amount of chemicals, as Dr. Roland Gerhards from the Bonn Institute of Plant Cultivation realised almost a decade ago. The situation with crop weeds is comparable to athlete's foot: only rarely is the whole area affected, with most of these unwelcome guests being concentrated in specific places, from which it is often difficult to remove them even with herbicides. Dr. Gerhards has therefore developed a spraying machine which detects such concentrations of weeds while moving across the field and attacks them. The heart of this hi-tech sprayer is three digital cameras which photograph the field while crossing it and send the pictures to a computer. The latter extracts the contours of the plants which have been photographed and removes flaws; a second computer compares the pictures which have been processed in this way with sample plants in a data bank. It thereby recognises not only whether the plant is a weed or not, but also, if need be, what sort of weed it is. "There are herbicides which are only effective against types of grass, others can only be used for dicotyledonous plants like heart's-ease or for special problem weeds," Dr. Gerhards explains. Up to now farmers have therefore been spraying a cocktail of different herbicides on their fields. "Our machine selects the correct herbicide from a choice of three different ones," he adds. The machine also selects the correct dosage: where no weeds are growing nothing is sprayed; where there are only a few weeds, only a little herbicide is sprayed. The engineer Dr. Rolf-Dieter Therburg developed the camera technology. He is justifiably proud of the result: the automatic image recognition, difficult enough even under laboratory conditions with optimum light, works in the field in all kinds of weather. And it works pretty fast: the sprayer trundles across the field at a speed of up to ten kilometres an hour, with each of the three cameras taking two photos per second. In the field trials being carried out at the University's experimental farm near Wesseling the programme currently identifies the weeds in an initial stage and on the basis of this produces a GPS-supported "spray map", on which it enters the amounts of herbicide required. Then, in a second stage, the 21 metre wide sprayer uses this map to spray the herbicides, in principle, however, this would be possible in a single operation. "Field trials have already shown that by using our method over 50% of the herbicides normally used can be saved," Dr. Gerhards says. "And this is not detrimental to the successful eradication of weeds: even after several years the amount of infestation with weeds does not normally increase." At present there is only one prototype of the sprayer, which was constructed and tested in field trials by Gerd Beckers, a member of the technical staff of the Dikopshof experimental farm, and the agricultural scientist Reiner Lock. The Norwegian company Kverneland, one of the leading manufacturers of herbicide spraying equipment worldwide, recognised the potential of the new technology years ago and is involved in the project. The Norwegians are now planning to mass-produce Bonn's spraying machine. The marketing prospects are not bad in view of the increasingly stringent regulations on the use of herbicides, especially since there are not likely to be any quantum leaps in making herbicides more environment-friendly and effective. As Dr. Gerhards puts it: "The next revolution will be technological, not chemical."
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