No abstract

Deficit irrigation (DI) strategies using moderately saline waters save water, but may enhance soil salinization.Based on data gathered during years 2007-2012 in three drip-irrigated grapevine, peach and nectarine crops subject to several irrigation and soil mulching treatments, we assessed trends in root-zone soil salinity (saturation extract electrical conductivity, ECe), related the changes in soil salinity (ΔECe) to field-wide leaching fraction (LF), evaluated management strategies for soil salinity control, and examined the sustainability of DI strategies under present and expected climate change scenarios in the Middle Ebro River Basin (ERB, Spain). ECe increased in 82% of the irrigation seasons and decreased in 75% of the nonirrigation seasons examined. Soil salinization trends were not apparent during the study years due to these annual salt accumulation-salt leaching cycles. ECe increases were higher in the more severe DI treatments and in the geotextile-mulched soil, and lower in the full and less severe irrigation treatments and in the organic-mulched soil. As expected, ΔECe and LF were linearly and negatively correlated (P < 0.01), indicating that soil salinization increased with decreasing LF. These linear relationships provided a way to evaluate best management strategies (increased irrigation, rainfall harvesting and soil mulching) for soil salinity control. These strategies decreased soil salinization, but did not guarantee the sustainability of severe deficit irrigations in the study area. The application of these relationships to the climate change precipitation and crop evapotranspiration projections in the ERB shows that the examined DI strategies will be unsustainable due to soil salinization.

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 grapevine's 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 water