Different amendments for combating soil sodicity in an olive orchard

Abstract

Sodic soil formation, following irrigation with saline-sodic water has become a major concern due to its negative impact on soil structure, crop growth and yield. However, specifically in orchards, little knowledge exists regarding the reclamation of sodic soils. Our objective was to examine the effects of different amendments on soil reclamation and crop performance of olive grove. The study was conducted in a 14 years old olive grove, grown in a clayey soil, in which irrigation started in 2008 using saline-sodic water resulting in sodium adsorption ratio (SAR) ranging from 22 to 40 (mmol_c L⁻¹)^0.5. Six treatments were studied: control (no amendments applied), CaCl₂, MgCl₂ and H₂SO₄ that were added to the irrigation water, and gypsiferous material (GM) that was added to the soil surface prior to the rainy season and either left spread or tilled into the upper soil layer. Soil samples were analyzed for selected saturated extract properties and for aggregate stability. Additionally, plant parameters including yield, trunk expansion, fruit oil content, and tree nutritional status were measured. The results showed that the lowest SARs were observed in the GM and GM till treatments at 0–30 cm [5.0 and 3.3 (mmol_c L⁻¹)^0.5, respectively], while CaCl₂ and MgCl₂ treatments had the lowest SARs at 30–90 cm [16.2 and 17.1 (mmol_c L⁻¹)^0.5, respectively]. GM and CaCl₂ application raised the electrical conductivity (EC) levels to 6.9 and 7.6 dS m⁻¹ respectively. GM addition resulted in the most stable aggregates which was associated with a significant improvement in average tree productivity of 33 kg/tree. Conversely, MgCl₂ had the lowest average yield, of 21.3 kg/tree, which was attributed to the high concentration of Mg that led to some nutrient imbalances. In conclusion, the current study showed the efficacy of different amendments based on Ca for remediating sodic soil in drip-irrigated orchards.