Ionic composition and hazards of poor quality waters for irrigation in southwestern part of Punjab

The quality of water is of immense important because poor quality of ground water is not only a limiting factor in crop production but also its constant and indiscriminate use causes secondary salinization. Therefore, a qualitative water quality survey was carried out to diagnose the salinity or sodicity hazards in ground waters in relation to their suitability for irrigation in Faridkot district (Punjab) having two blocks namely Faridkot and Kotkapura. The total concentration of soluble salts in ground waters varied from 0.31–7.53 dS m⁻¹. On splitting the analytical data block wise, it was observed that ground waters of Faridkot block pose high salinity hazards than that of Kotkapura block. Among the anions, concentration of HCO₃⁻ varied from 0.5–21.5 me l⁻¹, whereas that of Cl⁻ and SO₄²⁻ ranged from 1.00–51.30 and 0.83–48.33 me l⁻¹, respectively. The highly saline waters were dominant in SO₄²⁻ and Cl⁻ ions rather than CO₃²⁻ and HCO₃⁻ ions. Na⁺ was the dominant cation and its value ranged from 1.74–83.93 me l⁻¹. The mean sodium adsorption ratio (SAR) of Kotkapura block (17.53 me l⁻¹)^0.5 was higher than that of Faridkot block (15.06 me l⁻¹)^0.5 indicating more sodicity hazards. The mean residual sodium carbonate (RSC) of ground water indicated that Kotkapura block (4.96 me l⁻¹) had more alkalinity hazard than Faridkot block (2.55 me l⁻¹). The continuous use of such waters can cause secondary salinization/sodification. At any particular salinity, sodium was always more than other cations and the slope values for Na⁺ for the district revealed that increase in concentration of Na⁺ was steeper than other ions. Regression equations were used to predict salinity by using ion concentration as independent variables. Multiple regression analysis indicated that predictability of the relationships between EC and ion concentration improved when Ca+Mg was included along with Na. Among anions, dominance of SO₄²⁻ ion was found in under ground waters. Keeping in view the quality of ground water and site specific salinity and sodicity, improved cultural practices including land and water management have been recommended which have direct and positive impacts on the yield of crops.