Effect of irrigation Waters of Varying Mg/Ca Ratios on Phosphate Adsorption by Calcareous Soil

A laboratory experiment was conducted to study the effect of different Mg/Ca ratios (8,4, 2.1. 0.5, 0.25 and 0.125) in waters on the magnitude of phosphate adsorption by calcareous soils. Increased concentration of magnesium (Mg/Ca from 0.125 to 8.0) in equilibrating waters decreased the adsorption of phosphate from 95 to 80 and 76 to 60 percent in calcareous and non-calcareous soils, respectively. However,favourable effect of higher Mg/Ca ratio on minimization of phosphate adsorption was more spectacular in highr. calcareous soil (CaCO₃ - 30%) when equilibrated with high saline water (EC - 20 dS m⁻¹) having higher initial phosphate (50 mg L⁻¹) concentratio.