Short-term effects of treated wastewater irrigation on Mediterranean calcareous soil

Water shortage and soil degradation are the two most important environmental problems in the Mediterranean area. For this reason, strategies for soil and water conservation are necessary. Our objective was to evaluate the use of treated wastewater as an irrigation source to help alleviate these problems. Short-term effects on several soil fertility properties were evaluated in an agricultural area located at Biar (Alicante, SE Spain), where grapes (Vitis labrusca) are grown. Three treatments: fresh water (control), and treated wastewaters from secondary and tertiary treatment were evaluated for 2 years. We found a slight increase in soil organic carbon content in plots irrigated with the secondary treatment. These plots also had increased electrical conductivity (EC) and increased available Na content due to the high values of EC in wastewater. Laboratory analyses also show a decrease in aggregate stability for all treatments, presumably due to the wetting and drying (WD) cycles associated with each irrigation dose. These WD cycles may also explain changes in microbial biomass carbon and basal soil respiration. We recommend modifying the dose of irrigation in order to reduce the quantity applied and to increase the frequency of application to avoid the loss of aggregation. We also suggest long-term studies to assess the feasibility of wastewater reuse.

Research highlights▶ This study reports on the short-term effects of irrigation with treated wastewater. ▶ These effects were measured on a Mediterranean agricultural soil, during more than 2 years. ▶ Basal soil respiration changed when the dose and frequency of irrigation were modified. ▶ Disaggregation of soil was detected due probably to wetting and drying cycles. ▶ A study of medium or long-term is necessary to ascertain the impact of irrigation on the soil.