After more than 20 years of treated wastewater irrigation, no
negative changes have been observed in the evaluated soil properties
of the island of Mallorca, with the exception of an increase in
soil pH caused by greater sodium supply. The enhancement in soil
microbial biomass, b-glucosidase activity and alkaline phosphatase
activity, in addition to relatively higher values of water-soluble
organic carbon and available phosphorus, can be attributed to
a combination of the irrigation regime and the agricultural management at each location. Thus, treated wastewater use in
irrigation can have positive effects, not only in aspects of soil
quality, but also in social terms, as it allows the maintenance of
irrigated agriculture in areas where groundwater has been polluted
by seawater intrusion.