Kale (Brassica oleracea L. var acephala) production in soilless systems in the Mediterranean region

The challenges faced by traditional agriculture led to the development of alternative agricultural systems such as soilless systems. The aim of this work was to assess the growth and yield components of kale under three soilless growing systems: Nutrient film technique set up vertically (T-vertical); Nutrient film technique set up horizontally (T-horizontal) and substrate coco bags (T-coco). The trials were conducted for two consecutive growing seasons (S1: Spring 2018 and S2: Fall 2019) in an unheated greenhouse. Irrigation supply, maximum plant uptake of water and radiation use efficiency were evaluated for both seasons. The quantitative and qualitative parameters of the production were assessed in terms of yield ( kg per plant and kg per m2), number of leaves per plant, dry matter, protein content, nitrates level and leaf mineral composition. The main results showed that the maximum plant uptake was 0.30 L m-2 day-1, 0.30 L m-2 day-1 and 0.20 L m-2 day-1 respectively for T-vertical, T-horizontal and T-coco while the actual supply of water was 62.4 L m-2 day-1, 32.28 L m-2 day-1 and 3.27 L m-2 day-1, respectively. A significant difference was recorded for the number of leaves, yield components, dry matter, proteins level, Radiation Use Efficiency and mineral composition of kale leaves that were higher during fall than in the spring season. However, the nitrates level was much higher in spring than fall. T-vertical soilless system showed better yield (6.83 ± 2.27 kg per m2), more proteins (2.53 ± 0.31 g in 100 g FW) and higher amounts of calcium (Ca), total nitrogen (N), manganese (Mn) and iron (Fe) than the other systems. The study demonstrated the potential of soilless production technologies in the coastal Mediterranean areas.