Management of irrigation water and nutrient demands of tomato (Lycopersicon esculentum Mill.) using urban treated wastewater from a pilot-scale horizontal subsurface flow system constructed wetland in Sicily (Italy)

The reuse of treated wastewater (TWW) in crop irrigation is an advanced and rational approach to water resource management in agriculture. Results would seem to demonstrate that it could be an extremely important tool in the reduction of freshwater (FW) consumption in agriculture, at the same time helping to increase crop yields through the transfer of nutrients required for crop growth. In arid and semi-arid areas of the Mediterranean, constructed wetlands can play a key role in the treatment and reuse of wastewater due to their multifunctional nature. The aim of this study was to manage water and nutrient requirements of tomato (Lycopersicon esculentum Mill.) using TWW from a pilot-scale horizontal subsurface flow system (HSSFs) in a comparative study with traditional agronomic management methods. Research was carried out in 2015 at a pilot-scale HSSFs test area in West Sicily. Tomato plant plots were irrigated with both FW and with TWW from 2 planted-units and an unplanted-unit. Results showed that the pilot system was efficient in the treatment of wastewater and FW saving was high: approx. 90 m3 of water per t of total tomato yield. The TWW affected the productive, biometric and qualitative parameters of the tomato fruits considerably. The increase in total tomato fruit yield using TWW compared to FW was found to be 4 t ha–1 regarding water from unit A, 6 t ha–1 from unit B, and 7 t ha–1 from unit C of the HSSFs. Escherichia coli concentrations were not always within the threshold limits required by Italian law concerning the reuse of TWW in irrigation. Maximum microbial contamination was found in the fruit skin (106 CFU 100 g–1 on average) and in those fruits which were in contact with bare soil. No significant variation of soil pH was found but an increase in organic matter content and salinity was recorded in TWW-irrigated plots. Results confirm that TWW can provide an additional source of water and fertilizer in areas where FW supply is limited.