Quality indices of groundwater for agricultural use in the region of Tierra Nueva, San Luis Potosi, Mexico

The paper evaluates the quality of groundwater for agricultural use in Tierra Nueva, San Luis Potosi, Mexico, where the agricultural productivity zone presents problems of salinity soil. Twenty groundwater samples and 11 soil samples at 2 depths at each point were collected and analyzed. In this type of water quality study, Wilcox classification diagram and the method of Salinity Laboratory United States for the quality of agricultural land were used. However, in some cases, these rankings do not reflect the actual condition, as in the case of Tierra Nueva, where the soil is classified as normal while water is classified at intermediate good. To analyze the real conditions of soil and water quality indicators of water for agricultural use risk of salinization, sodium adsorption ratio, adsorption ratio magnesium, permeability index, sodium percentage, soluble sodium percentage, residual sodium carbonate, and Kelly ratio were used. Sodicity rates including sodium adsorption ratio indicate no problem in soil extract. However, 25% of water samples are dangerous, with levels ranging from medium to high. For indexes of sodium percentage, residual sodium carbonate, and Kelly ratio, a distribution of classes ranging from questionable to inadequate was applied. Salinity levels show that effective salinity has good classification; potential salinity (PS) is conditional and therefore not recommended; and osmotic potential and electrical conductivity are classified as high in saline water, which is an increasingly important problem. The combination of different indices emphasized serious problems of salinity conditions, particularly sodicity.