Influence of wastewater vs groundwater on youngCitrus trees

The use of wastewater as an alternative water resource for irrigation needs specific studies to evaluate its effect on different soils and crops. Young Citrus trees have been irrigated with wastewater from a sewage treatment plant during three consecutive seasons and the growth, leaf mineral status and fruit quality measured. Some differences have been found between groundwater and wastewater composition. Sodium ion, chloride ion, organic matter and boron concentrations were always higher in wastewater. In contrast, high nitrate levels were found in groundwater, probably due to aquifer contamination. In all seasons the values of soil-analysed elements were within the optimal ranges for this kind of crop and soil. Levels of sodium, chloride and boron in leaf tissue were below the toxic levels for Citrus. Leaf nitrogen content was in the optimal nutrition range and no significant difference was observed between samples from trees irrigated with wastewater and groundwater. Both growth and fruit quality parameters were unaffected by the high levels of sodium, chloride and boron in wastewater. Collectively our data show that no detrimental effects are found after using wastewater for irrigation of young Citrus trees. More importantly, fertiliser rates could be lowered significantly without reducing yields or affecting leaf nutrient levels when using reclaimed wastewater. Thus reclaimed wastewater appears to be a suitable alternative water resource for irrigation of Citrus trees. © 2000 Society of Chemical Industry