Abstract
The interest in “urban agriculture”, i.e. the production of food next to place of consumption/sales, where the availability of soils suitable for agriculture is scarce, give an important opportunity for the development of soilless cultural systems. In this context, soilless floating system where plants are fed on a nutrient solution is a common alternative to traditional agriculture. In this research, the growth conditions in a closed-loop hydroponic system of a salad, Valerianella locusta, were studied in order to increase yield, shelf life and food quality. In particular, the composition of the growth solutions was carefully studied in order to adapt it to this cultivation system and this plant species. Moreover, in order to improve further the quality of the edible product, some non-nutritive elements were added to the composition of the hydroponic solution. Results showed that the composition of the often-used solutions is not well equilibrated. In particular, the N content is high in order to achieve high yield but this often unbalances the overall nutrient content. To improve the composition, the concentrations of S and Fe were increased. This resulted in higher yields, up to +40%, and lower nitrate content, which is a critical factor for salad in this cultivation system, where plants have tendency to accumulate this anion in leaves up to a level that is considered to become a potential health risk factor for the consumer. The addition of non-nutritive elements, e.g. Silicon, induces also an increase of the edible yield (up to +60%) and the quality level reducing the nitrate concentration in edible tissues. Moreover this supplementation resulted in a prolongation of the shelf life of the product. In conclusion, there is ample room for improvement of the soilless cultivation techniques and minor adjustments can substantially increase yield and quality of the obtainable edible product. Research was supported by the grant Novel strategies meeting the needs of the fresh-cut vegetable sector - STAYFRESH from AGER foundation.