EBB-AND-FLOW AND FLOATING SYSTEMS TO GROW LEAFY VEGETABLES: A REVIEW FOR ROCKET, CORN SALAD, GARDEN CRESS AND PURSLANE

The interest for functional foods and the consumption of fresh-cut vegetables are rising in many EU countries and in the USA. The intensive winter season cultivation of vegetable crops causes more sensitive and hence disease-prone plants. This leads to an intensified application of pesticides, increasing chemical residue risks. Vegetable crops are facing the banning of fumigant methyl bromide application for ground disinfections. Furthermore, chain quality production has become crucial in terms of food safety and environmental impact. Thus, protected cultivation is increasingly shifting from Traditional Culture System (TCS) in soil to Soilless Culture System (SCS). The SCS allows to control growth factors and to obtain clean raw material at harvest improving its safety and quality. Among the SCSs, Ebb-and-Flow (EF) and Floating (FL) Systems are relatively cheap and easyto-use hydroponic systems. They are suitable to produce vegetables both with a short cultural cycle and with a high plant density, and can be considered as an efficient system to produce leafy vegetables, either baby leaves or baby bushes. Controlling the nutrient solution and managing plant growth according to environmental conditions allow decreasing nitrate content in the edible product. Nitrate accumulation, however, is very variable among species. The full control of the inputs that SCS provides should reduce the environmental impact and contribute to product quality standardization. Different irrigation systems (EF and FL), nutrient solutions (N levels and NO3/NH4 ratios), culture systems (SCS and TCS) were investigated from years 2000 to 2005. Were considered species commonly cultivated (rocket and corn salad) and minor species, important for their functional content or traditional use (purslane, garden cress) and those with potentiality to be introduced in the fresh-cut supply chain. CULTURAL SYSTEMS Protected cultivation is nowadays shifting from Traditional Culture System (TCS) in soil to Soilless Culture System (SCS), based on growing media. The goals of this change are to obtain higher qualitative and quantitative standards, to standardize cultural techniques and to reduce both production costs and environmental impact (Sambo et al., 2001). According to Santamaria and Valenzano (2001), many studies have compared TCS to SCS, indicating that SCS allowed to increase earliness and to reduce nitrate content of leafy vegetables. SCS is a valid alternative to TCS to avoid soil born diseases, to control mineral plant nutrition for standardizing qualitative characteristics of the final product (Incrocci et al., 2001); thus, using mineral and sterile media with a low environmental impact may be an alternative to the practice of soil disinfection. SOILLESS CULTURE IRRIGATION SYSTEMS In the SCSs, Ebb-and-Flow (EF) and Floating (FL) systems are relatively cheap and easy-to-use irrigation systems. Vavrina and Hochmuth (1996) showed how using a sub-irrigation system increases fertilizer application precision to the plants by reducing water leaching during irrigation. The EF system may allow a 50 to 60% reduction in