Salinity is one of the main causes of soil degradation, which reduces the capacity for biomass production. Naturally, saline soil is related to climatic, hydrogeological, and edaphic processes. Evaporite rocks are a potential source of gypsum and anhydrite in climates where annual rainfall does not exceed 400 mm. Like any salt, anhydrite contributes to salinity processes that reduce osmotic potential in plants, giving rise to water stress that reduces turgor in plants. In the Zona Media of San Luis Potosí, soil salinity is not homogeneous but rather varies spatially and is associated with soil genesis, agricultural irrigation water quality, and climate. Water sodicity (% Na), toxicity (pH, B3+ y Cl-), and salinity hazards were evaluated by applying agricultural water quality indices. Low sodicity hazard was found at all sample points; chloride and boron did not pose toxicity hazards, but high sulfate concentrations can lead to toxicity and calcium and magnesium deficiency. The salinity hazard was high, identified using OP, EC, TDS, ES, and PS indices. This condition is related to the region's evaporite soils and semi-arid climate.
Keywords: Agricultural indexes; Gypseous soils; Osmotic pressure; Soil salinity.