Regulated deficit irrigation, soil salinization and soil sodification in a table grape vineyard drip-irrigated with moderately saline waters

Irrigation with moderately saline waters may provoke soil salinization and sodification. The objectives of this three-year study were (1) to quantify these processes in two seedless table grapevines (Vitis vinifera cvs. Autumn Royal and Crimson) subject to a full irrigation and two regulated deficit irrigations (RDI, irrigated at 80% and 60% of net irrigation requirements from post-veraison till harvest) with 1.7 dS m−1 electrical conductivity irrigation waters, and (2) to assess the impact of soil salinization on grapevineʹs response. Soil samples were taken three times along each irrigation season and soil solution samples were extracted weekly by suction cups. Soil saturation extract electrical conductivity (ECe) and sodium adsorption ratio (SARe) were high in Autumn Royal (4.4 dS m−1 and 6.1 (mmol l−1)0.5) and very high in Crimson (7.0 dS m−1 and 8.6 (mmol l−1)0.5) due to relatively low leaching fractions (LF) (0.20 in Autumn Royal and 0.13 in Crimson). Soil solution salinity and sodicity were generally higher in the more severe RDI than in the full irrigation treatment. Soil salinity and sodicity generally increased along the irrigation seasons and decreased along the non-irrigation seasons. Salt accumulation or leaching and LF were significantly correlated, so that LF estimates could anticipate the required irrigation depths for soil salinity control. Grapevine yield declined with increases in soil salinity. Leaf Na concentrations were very low (<0.1%), but leaf Cl concentrations were higher and the maximum value of 0.61% measured in the more severe Crimson RDI treatment was within the interval reported as toxic in grapevine. Despite the water saving benefits of drip irrigation in combination with deficit irrigation strategies, its implementation in low-precipitation semiarid areas must be cautiously assessed and monitored because soil salinization and sodification may threaten the sustainability and profitability of these grapevine orchards irrigated with moderately saline waters.