Integrating RO concentrate in viticultural irrigation for sustainable urban water reclamation

Abstract

Grapevines (Vitis vinifera L.) require precise irrigation to maintain yield and quality, and the increasing use of reclaimed desalinated water for irrigation raises concerns about the accumulation of reverse osmosis concentrate (ROC), a high-salinity byproduct with no sustainable disposal solution. This study explores the potential of ROC concentrates as a fertigation alternative, evaluating its effects on soil chemistry and vine adaptation. Using a CE 530 RO desalinator, we assessed grapevine responses under four irrigation treatments: tap water, tertiary-treated wastewater with low salinity and organic content, and tertiary-treated wastewater concentrated two times (2X) and four times (4X). By repurposing desalination by-products for viticulture, this study examines controlled salinity exposure to determine vine adaptation thresholds and improve irrigation sustainability. Irrigation with desalination-derived effluents significantly impacted soil chemistry and plant growth. Moderate salinity (2X Effluents) imposed the greatest stress, with the highest leachate EC in Barbera (7.35 mS/cm at 105DAT) and increased soil EC in both cultivars, leading to reduced root length density (RLD), root volume, root surface area, and root biomass. These reductions indicate that moderate salinity disrupts root development and nutrient acquisition, impairing plant vigor. In contrast, vines under 4X Effluents exhibited partial adaptation, showing improved root biomass, root volume, and shoot elongation compared to 2X Effluents. This suggests that grapevines can activate physiological responses to tolerate extreme salinity better than moderate salinity stress. Muscat exhibited greater resilience than Barbera, maintaining higher root and shoot biomass, RLD, and shoot elongation across treatments. The superior performance of Muscat suggests an inherent genetic advantage in salinity tolerance mechanisms compared to Barbera. However, 4X Effluents caused significant soil EC accumulation, particularly in Muscat (3.10 mS/cm), which raises concerns about long-term soil degradation and potential salt toxicity effects in vineyard soils. Comprehensive elemental analysis of soil and leaf tissues is underway to determine ion accumulation patterns and their role in salinity tolerance, while metabolite profiling of roots and leaves investigates biochemical pathways underlying adaptive stress responses.