Sweet potatoes are very sensitive to the cold, but resistant to intense heat. Their optimum temperature ranges between 21 and 29° C, whilst they have trouble withstanding temperatures under 10° C. Growing sweet potatoes out of doors at Swiss latitudes therefore represents a major technical challenge. In response to this challenge, Agroscope has set up so-called ‘acclimatisation’ trials for adapting the sweet potato to Swiss production conditions. These trials compare different techniques enabling us to limit the risks of loss associated with low spring temperatures, and guaranteeing an optimum harvest in terms of both quantity and quality. The trials have shown that it is possible to grow sweet potatoes outdoors in Switzerland, and are currently being pursued to further improve the performances of these techniques. They also compare two different technical planting itineraries – the taking of cuttings and transplantation – in order to determine if one of them enables the growing season to be shortened, thereby limiting the risks of loss associated with the cold.
So far, Swiss sweet-potato yields have been free from disease. This makes them an attractive option for organic growers, since the crop need not be treated over the course of the season. Weed control, however, remains a major challenge for this crop, as the still-chilly spring nights mean that the crop struggles to become established and compete with the weeds. The licensing of herbicides for conventional agriculture is underway, but no solution is yet available for organic farmers. In order to find organic solutions, Agroscope is carrying out trials with different (artificial and natural) mulches intended to curb weed development.