Dynamic depth control for precision destoning in fields for vegetables

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Any visitor to a field being planted with potatoes would be concerned at the amount of soil sieved during the destoning operation (typically 3,000 t/ha), the very slow work rates and the potential for damage to soils and exposure to oxidation of carbon. This project aims to develop a dynamic depth control system for destoners to ensure optimal bed depth and avoid excessively deep cultivation which occurs when destoning to the worst possible scenario, i.e. areas of the field with high stone or clod content.It is to be expected that many people will have considered the depth measurement problem before, yet have done little to provide a solution, perhaps because of the complexity, cost or lack of demand from growers or perhaps because of the lack of understanding of optimal conditions for crop growth and the damage that destoners can do to soil if worked at the incorrect depth or sub-optimal conditions. Current mechanisms for depth control are positioned in front of the intake share, thereby reducing the accuracy since soil loss through the machine is variable. By measuring the finished bed depth, accuracy will be improved. A number of techniques can be used to measure the large change in strength or density between the loose soil in the bed itself and the layer beneath the destoner share (e.g. physical, sonic and electromagnetic), but the differences in soil water content between contrasting layers can make it difficult to detect changes with some techniques. Machines can also move quite quickly (e.g. 4 km/h) on some soils, making rapid detection of depth paramount to effect a change in machine intake share depth settings.The consortium involved has a) experts in sensor technology and control mechanisms; b) soil scientists with understanding of optimal soil conditions for plant growth and cultivatability and c) farmers who require a practical and robust system. Any new sensor that proves successful will also need to have a control system that can integrate easily into existing destoner controller mechanisms, but the market and target area are both large (\>2000 destoners, \>100K ha).