Reclaimed Water Use in Agriculture: Effects on Soil Chemical and Biological Properties in a Long-Term Irrigated Citrus Farm

In Mediterranean regions, the scarcity of freshwater for agricultural purposes is leading to the use of alternative water sources. This study aimed to evaluate the effects of long-term irrigation with reclaimed water on chemical and biological soil properties. On a mandarin tree orchard (Citrus clementina, cv. Orogrande), freshwater (FW) and tertiary reclaimed water (RW) were supplied for irrigation. In spring 2017, a soil sampling was carried out, collecting from each experimental plot four samples at 0-0.20 m depth. Chemical and biochemical soil properties were determined on air dried and sieved soil and on fresh and field-moist soil, respectively. The irrigation with reclaimed water significantly increased the soil water extractable organic carbon (WEOC), available P, Mg, and Na content, and the electrical conductivity (EC). Although not significant, the respiration rates and enzymatic activities were higher in RW treatment. The results of this research highlighted that the irrigation with reclaimed water, providing organic carbon and other nutrients, could have, in the long-term, beneficial effects on soil microorganism and their activities. In any case, especially in arid and semi-arid environments, a proper management of wastewater should be recommended to avoid soil degradation due to salt accumulation in the rootzone.

Automated summary

This study evaluated the effects of long-term irrigation with reclaimed water on soil chemical and biological properties. The results showed that reclaimed water irrigation significantly increased the water extractable organic carbon, available phosphorus, magnesium, sodium content, and electrical conductivity in the soil. Although not statistically significant, the rates of respiration and enzymatic activities were higher in the reclaimed water treatment. This suggests that reclaimed water irrigation, while providing nutrients, may have beneficial effects on soil microorganisms and their activities in the long-term. However, proper management of wastewater should be recommended, especially in arid and semi-arid environments, to prevent soil degradation from salt accumulation.