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

Sodium (Na + ) dominated soils reduce saturated hydraulic conductivity ( K s ) by clay dispersion and plugging pores, while gypsum (CaSO 4 •2H 2 O) 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 K s , leach Na + and salts. This study comprised loamy‐sand (LS), sandy loam (SL), and clay loam (CL) soils with electrical conductivity of saturation extract (EC e ) of ~8 dS m −1 , sodium adsorption ratio (SAR) of ~44 (mmol L −1 ) 1/2 and exchangeable sodium of ~41%, receiving no gypsum (G 0 ), gypsum at 25% (G 25 ), 50% (G 50 ) and 75% (G 75 ) 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 mmol c  L −1 ]. It proved that a rise in gypsum rate amplified K s of LS ≫ SL > CL. However, K s of LS soil at G 25 and others at G 75 remained efficient for salts and Na + removal. Retention of calcium with magnesium (Ca 2+  + Mg 2+ ) by LS and SL soils increased by G 50 and decreased in G 75 , while in CL, it also increased with G 75 . The enhanced Na + leaching efficiency in LS soil with G 25 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 G 25 , SL at G 50 and CL at G 75 predicted cost‐effective soil reclamation with a decrease in EC e and SAR below 0·97 dS m −1 and 5·92 (mmol L −1 ) 1/2 , respectively. Copyright © 2015 John Wiley & Sons, Ltd.