Degradation of soil physical and chemical properties, and subsequently a decrease in crop growth and yield, in soils subjected to long term irrigation with poor quality water (e.g., saline-sodic water and treated wastewater [TWW]) has become a major concern worldwide. Soils in orchards are especially sensitive to such degradation due to (i) the absence of soil cultivation and (ii) concentration of a large volume of irrigation water in a small fixed area along the tree line. We hypothesized that use of amendments containing Ca and/or Mg ions in drip-irrigated orchards may alleviate the danger to thus related soil degradation. Our objective was to examine the effects of different types and modes of applications of amendments on soil reclamation and crop performance of a 16 years old olive grove. The study was conducted in an intensive olive grove grown on a clayey soil with a sodium adsorption ratio (SAR) ranging from 22 to 40 at a depth of 0-90 cm. This high soil SAR resulted from irrigation with low quality water reaching SAR that peaked 14 (mmolc L−1)0.5 over a long period of time. Six treatments were studied: control (no amendments applied), CaCl2, MgCl2 and sulphuric acid (H2SO4) that were added repeatedly to the irrigation water, and gypsiferous material (GM) that was added to the soil surface prior to the rainy season and either left spread on the soil surface or was tilled into the upper soil layer (0-10 cm). Soil samples were taken twice a year and analyzed for selected saturated extract properties and for aggregate stability. In addition, plant parameters including yield, fruit oil content and tree nutritional status (by leaf samples), were measured. The results showed that GM, CaCl₂, and MgCl₂ consistently reduced soil sodicity and sodium concentrations over time. Physiological assessments showed an increase in leaf potassium and magnesium content in MgCl₂-treated trees, with a general trend of improved yields in gypsum-treated plots. However, no statistically significant differences were observed in cumulative yield, oil content, or ripening indices. In conclusion, inorganic soil amendments demonstrated the potential to enhance soil properties and, to a lesser extent, tree performance in olive groves. Further investigation is warranted to solidify conclusions and refine recommendations for practical applications.
