Simple predictive tool estimates sodium adsorption ratio for evaluation of potential infiltration problems using reclaimed wastewater

The physical and chemical characteristics of irrigation water are of particular importance. Sodium (Na) is one of the most problematic ions present in excessive concentrations causes specific toxicity. In addition, another indirect affect of high sodium content is the deterioration of the physical condition of soil such as formation of crusts, water logging and reduced soil permeability. If the infiltration rate is greatly reduced, it may be impossible to supply the crop or landscape plant with sufficient water for good growth. In this work, a simple predictive tool, which is easier than existing approaches, less complicated with fewer computations is formulated to accurately predict the sodium adsorption ratio as a function of concentration of Na⁺ magnesium (Mg²⁺ ), calcium ( Ca²⁺ ), salinity of applied water and the ratio of bicarbonate (HCO_{3^_} ) over Ca²⁺ for interpretations of water quality for irrigation. The proposed method showed consistently accurate results for salinity of applied water up to 8 dS m⁻¹ and ratio of HCO₃^_ over Ca²⁺ up to 20. Predictions showed an excellent agreement with the reported data with an average absolute deviation being less than 3%. This proposed simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on sodium adsorption ratio at wide range of conditions without the necessity of any time consuming experimental runs. In particular soil scientists and agricultural engineers would find the proposed approach to be user friendly involving transparent calculations with no complex expressions.