Guidelines to growing Stevia rebaudiana Bertoni in Bragança, NE Portugal

Abstract

Stevia [Stevia rebaudiana Bertoni] is a crop expanding worldwide due to the increasing use in the food industry. The aims of this work were to check the adaptation of Stevia to the ecological conditions of the northeast of Portugal and to assess the response of the plant to the application of different rates of nitrogen, phosphorus and potassium as fertilizers and two different cutting regimes, once and twice during the growing season. The field trials were carried out in Bragança and Vilariça valley, both located in NE Portugal but in very different ecological situations, respectively in one of colder and warmer places in the region. It was assessed the winter survival of stevia plants, as well as dry matter yield, tissue elemental concentration and several vegetation indices. The results revealed that the plants did not survive the winter, with mortality exceeding 95%, meaning that Stevia can only be grown as an annual crop, which requires the installation of the new fields every year. The dry matter yield significantly increased with nitrogen rate. In the most productive treatment (100 kg N/ha), 1560 kg/ha of dry leaves and 4961 kg/ha of total aboveground dry matter (leaves + stems) were reached. Leaf nitrogen concentration did not significantly varied with nitrogen rate, despite the increase observed in dry matter production, which may mean that difficulties can arise in monitoring the nitrogen nutritional status of plants in the field and in the establishment of adequate fertilization programs for this crop.