As a food, asparagus can trace an illustrious lineage back 20,000 years to Egypt; it features in the world's oldest surviving cook book, Apicius's third century 'De re coquinaria'; it is packed with vitamins, and a very good source of dietary fibre. No wonder the asparagus is such a prized food. But its reputation as the ultimate gourmet vegetable is also reflected in its delicate cultivation, with white asparagus in particular requiring labour intensive hilling. And in Europe, this dedicated nurturing is threatening the crop as farmers struggle to find the manpower needed to harvest asparagus.
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Now, however, a German engineer is developing a machine to take the burden out of the harvesting process. Mathias Kück has been perfecting an automated asparagus plucker that gently cuts and removes the asparagus stalk using an innovative image recognition system. "It does everything that a human does, only more precisely," says Kück, who has led the project, named AutoSpar.
Europe accounts for almost one third of the world's asparagus market. Asparagus is difficult to harvest: most plants are ready to be picked only three years after planting, and they have to be removed with a serrated knife, cutting them off 20 cm beneath the soil. About 70% of the European crop is white or violet asparagus, which is obtained through hilling cultivation, a technique in agriculture and horticulture of piling soil up around the base of a plant. The cultivation process is backbreaking and the workforce – particularly in Germany, Europe's biggest asparagus producer – has been draining away. Manual labour is also clumsy: even experienced workers accidentally cut neighbouring stalks, with losses typically amounting to 15% or €20,000 per hectare.
Hence the need for a continuous, fully automatic harvesting machine. Backed by a €927,560 grant from the European Commission, AutoSpar is designed for white and violet asparagus. The four German, three Spanish, Romanian and Dutch partners in the consortium have been tackling a number of technological challenges: designing an asparagus detection system, building cutting and lifting tools, and creating a motion controlled system. "If we can roll out this technology, it could revive the European asparagus sector and help us compete on the world market," says Kück.
AutoSpar is in the prototype stage, but it has already demonstrated the gentle cutting and removal of the asparagus stalk on the basis of image recognition and processing system. Kück says the team still faces a number of issues, including redesigning it so that the driving wheel is at the front rather than the back. Another issue is to simply speed it up: it is currently able to cut eight stalks per minute, while humans can do up to 14.
But he is confident he can overcome these issues so that the machine can be rolled out over the next few years. There is a huge market available: asparagus is one of the most expensive vegetables in Europe, with prices reaching up to €10 per kilogram. Some 35 to 50% of the production cost is in labour.
Kück says AutoSpar could halve harvesting costs while avoiding the current problem of seasonal labour shortages. With an anticipated price of €40.000, the AutoSpar machines would have a relatively low investment cost. Kück is aiming for less than 1% of broken and undersized asparagus during harvesting, reducing losses per hectare and season from 700 to 1,000kg to below 100kg. And if perfected, the machines could harvest two hectares a day, up from less than one per day for manual harvesting.