Implication of Gypsum Rates to Optimize Hydraulic Conductivity for Variable‐Texture Saline–Sodic Soils Reclamation

• Published in: Land degradation & development 2016-04, Vol.27 (3), p.550-560
• Main Authors: Ahmad, Sagheer, Ghafoor, Abdul, Akhtar, Muhammad E, Khan, Muhammad Z
• Format: Article
• Language: English
• Subjects: adsorption; calcium; calcium sulfate; clay; cost effectiveness; electrical conductivity; Exchange; exchangeable sodium; Fluid dynamics; Fluid flow; Gypsum; gypsum rate; gypsum requirement; Hydraulics; land restoration; leaching; lysimeters; Magnesium; reclamation; saline sodic soils; sandy loam soils; saturated hydraulic conductivity; Sodium; sodium carbonate; Soils
• ISSN: 1085-3278; 1099-145X
• DOI: 10.1002/ldr.2413

Sodium (Na⁺) dominated soils reduce saturated hydraulic conductivity (Kₛ) by clay dispersion and plugging pores, while gypsum (CaSO₄•2H₂O) application counters these properties. However, variable retrieval of texturally different saline–sodic soils with gypsum at soil gypsum requirement (SGR) devised to define its quantity best suited to improve Kₛ, leach Na⁺ and salts. This study comprised loamy‐sand (LS), sandy loam (SL), and clay loam (CL) soils with electrical conductivity of saturation extract (ECₑ) of ~8 dS m⁻¹, sodium adsorption ratio (SAR) of ~44 (mmol L⁻¹)¹/² and exchangeable sodium of ~41%, receiving no gypsum (G₀), gypsum at 25% (G₂₅), 50% (G₅₀) and 75% (G₇₅) of SGR. Soils packed in lysimeters were leached with low‐carbonate water [EC at 0·39 dS m⁻¹, SAR at 0·56 (mmol L⁻¹)¹/² and residual sodium carbonate at 0·15 mmolc L⁻¹]. It proved that a rise in gypsum rate amplified Kₛ of LS ≫ SL > CL. However, Kₛ of LS soil at G₂₅ and others at G₇₅ remained efficient for salts and Na⁺ removal. Retention of calcium with magnesium (Ca²⁺ + Mg²⁺) by LS and SL soils increased by G₅₀ and decreased in G₇₅, while in CL, it also increased with G₇₅. The enhanced Na⁺ leaching efficiency in LS soil with G₂₅ was envisaged by water stay for sufficient time to dissolve gypsum and exchange and leach out Na⁺. Overall, the superiority of gypsum for LS at G₂₅, SL at G₅₀ and CL at G₇₅ predicted cost‐effective soil reclamation with a decrease in ECₑ and SAR below 0·97 dS m⁻¹ and 5·92 (mmol L⁻¹)¹/², respectively. Copyright © 2015 John Wiley & Sons, Ltd.