Salic Horizons in Soils of the USA

The taxonomic hierarchy and nationwide distribution of soils with a salic horizon were studied using the USA Natural Resources Conservation Service Soil Survey Geographic (SSURGO) Database to provide a more holistic view of the role of soil-forming factors in pedogenesis than from isolated case studies. Soils with a salic horizon occupied an area of 11 000 km2, i.e., 0.1% of land area in the contiguous USA. These soils occur narrowly in three great groups (Aquisalids, Haplosalids and Halaquepts), 11 subgroups, and 97 soil series. Soils with a salic horizon commonly had a mesic (50% of soil series) or thermic (19%) soil-temperature class, an aquic (89%) soil-moisture class, a mixed mineral class (79%), a calcareous (52%) reaction class, a superactive (59%) cation exchange activity class, and a fine (24% of soil series), fine-loamy (24% of soil series), or fine-silty (19% of soil series) particle-size class. Soils with a salic horizon were concentrated in the Basin and Range Province of western USA. The key pedogenic processes leading to the development of salic horizons were salinization, gleization, and calcification, with some evidence for argilluviation and silicification.