Soil salt spatial variability of the Cienega de Chapala: The reason for their chemical degradation

Soil salinity threatens agricultural productivity, especially in regions such as La Ciénega de Chapala, Michoacán, where salinity problems generate important economic losses. In this study, 100 hectares of bare soil were evaluated in the municipality of Villamar, Michoacán, to identify the ionic composition and classify the soil according to different salinity indices. A simple random sampling was performed, and the following chemical parameters were determined in the saturation paste extract: Ca2+, Mg2+, Na+, K+, CO32-, HCO3-, Cl-, SO42-, pH, electrical conductivity (EC), evaporated dry residue, and calcined dry residue. EC, Sodium Adsorption Ratio (SAR), and Exchangeable Sodium Percent (ESP) were used for classification. Spatial interpolation maps using triangulated irregular networks (TIN) allowed visualization of the distribution of both ESP and SAR. The predominant ions were Na+ and SO42-, with 21.45 and 15.83 mEq/L, respectively. EC was positively correlated with Total Dissolved Solids, and the ionic strength was high. Between 50 and 60% of the samples were classified as non-sodium. High spatial heterogeneity was identified, 43% of the property was classified as high in salinity, low in sodium, however, the southern zone is the most affected.