Treated wastewater irrigation of Rosmarinus officinalis in arid regions: enhancing yield and soil health

Abstract

Hybrid MSL treatment reduces pollutants and microbial contamination while retaining nutrients. MSL treated wastewater supports optimal rosemary growth and soil fertility, with moderate salinity and lower oxidative stress. Water scarcity in arid and semi-arid regions necessitates sustainable alternatives for irrigation. This study assessed the effects of raw wastewater (RWW), treated wastewater (TWW) produced by a hybrid multi-soil-layering (MSL) system, and well water (WW) on soil properties and the physiological, biochemical, and oxidative stress responses of Rosmarinus officinalis. The MSL system achieved high removal efficiencies for total suspended solids (97%), chemical oxygen demand (88.6%), total phosphorus (79.9%), and total nitrogen (88.5%), and significantly reduced pathogenic indicators. The resulting TWW met Moroccan irrigation standards while retaining essential nutrients (N, P, K, Ca, and Mg). Soils irrigated with RWW showed elevated electrical conductivity, sodium accumulation, and organic matter, indicating potential salinity and sodicity risks. In contrast, TWW irrigation maintained moderate salinity and improved nutrient availability without exceeding safety limits. RWW enhanced chlorophyll and carbohydrate contents but induced pronounced oxidative stress, as evidenced by increased malondialdehyde, hydrogen peroxide, and superoxide dismutase activity. TWW promoted superior plant growth (dry biomass and shoot height) while maintaining lower oxidative stress levels. WW irrigation resulted in the lowest growth, likely due to nutrient deficiencies. Overall, TWW represents a safe and nutrient-rich irrigation source for rosemary in arid regions, improving soil fertility and plant performance while minimizing stress.