(viii) Salic horizons (Bz or Cz) are enriched with secondary salts more soluble than gypsum. A salic horizon is 15 cm or more in thickness and contains at least 20 g/kg salt. A gypsic horizon (By or Cy) is enriched of secondary CaSO4, is > 15 cm thick, and has at least 50 g/kg more gypsum than the C horizon. High pH values (> 9) are associated with nutrient deficiencies or toxicities induced by high pH. Calcium is immobilized because high pH promotes the formation of carbonate from CO 2, and carbonated precipitates with Ca, as CaCO 3. A high pH also affects the sorption behavior of these cations in the soil.
Most Aridisols show a low permeability because of the presence of accumulated or cemented layers. The nutrient status of often low, however, supplies of micronutrients are usually abundant, although they may not be available because of the high pH.