Impact of treated wastewater agricultural reuse on orchards and irrigation systems

Treated wastewater is increasingly used for crop irrigation and fertigation as it provides essential minerals for plant nutrition. However, it also poses challenges such as high salinity, phytotoxic compounds, and biofilm formation, which can affect plant health, reduce yield, and lower irrigation efficiency. This study aimed to evaluate the impact of secondary treated wastewater (SW) on soil chemical properties, plant physiological and nutritional performances, and irrigation system efficiency. Over two irrigation seasons (i.e., 2021 and 2022), potted peach trees were irrigated with SW, with or without additional fertilization, and compared to fresh water with fertilizer. With this purpose, a smart fertigation system was employed to balance nutrient inputs based on continuous water quality monitoring. SW alone partially met plant nutrient demands, though additional fertilization was needed for optimal growth. It slightly increased soil electrical conductivity (of about 0.7 dS m⁻¹) and trace element levels, particularly late in the season, but had no adverse effects on plant water status or heavy metal accumulation in leaves. SW integrated with mineral fertigation, apart from slightly anticipating fruit ripening of about one week, generally showed similar fruit quality traits to fresh water-irrigated tree, not causing increase in heavy metals and trace element concentrations. However, the use of SW reduced dripper irrigation efficiency of about 10.5%, especially when combined with fertilization.