Agronomic effects of reclaimed water used for tomato (Solanum lycopersicum L.) and lettuce (Lactuca sativa L.) irrigation

Due to the global warming, a reduction of the availability of water is expected everywhere around the world. To face this challenge, it is necessary to develop strategies for saving and reusing treated wastewater. This is a priority especially in agriculture, one of the human activities that requires the biggest amount of water. During 2021, reclaimed water of a hybrid constructed wetland (horizontal subsurface unit followed by free water surface unit), used for tertiary treatment of effluents from a farmhouse located in Eastern Sicily, was reused by micro-irrigation techniques to irrigate vegetable crops. In this experiment the effects of domestic wastewater treated with a hybrid constructed wetland (CW) was evaluated on tomato (Solanum lycopersicum L.) and lettuce (Lactuca sativa L.) in a split-plot experimental design for each crop. For the tomato crop the main experimental factor was the irrigation water type, the second one the dripline type, and the third one the genotype. The main plot was splitted in reclaimed water and ground water plots, each of them was splitted in two sub-plots represented by the type of dripline utilized: the driplines "blue" and "yellow" were treated with two different antimicrobial compounds (provided by Irritech®). Finally, the sub-sub-plot was represented by the genotype, ‘Big Rio' and ‘SV8840MT'. For the lettuce was adopted the same experimental design as for tomato utilizing only one cultivar, represented by ‘Gretta Erre'. For both crops all the combination of the experimental factors were replicated three times. Due to the experimental design the experimental field was subdivided in 36 plots (24 for tomato and 12 for lettuce). For lettuce, a slight but not significant higher yield was recorded in plants irrigated by the CW system compared to ground water (GW), and yield of plants irrigated with the "blue" dripline(BD) was significantly higher than that of the "yellow" one (YD). The yield of the tomato crop was similar among irrigation water types, whereas the highest fruit yield was recorded in plants irrigated by "blue" dripline compared to those irrigated with "yellow" ones. From the crop yield data and other bio-morphometric parameters recorded and evaluated in this trial, it is possible to state that domestic wastewater treated by a CW system is suitable for agricultural use.