Some RSGs do consider subsoil (but not specifically B2 horizon) structure and grade, such as the nitic horizon (Nitisols), whereas others, such as the natric horizon (Solonetz), consider ped shape but lack any structure grade criteria.
The natric horizon of ST requires the presence of strong blocky to prismatic peds and an ESP >15.
ST maintains structural criteria for a natric horizon, thus relegating those massive soil materials with ESP >15 to a non-sodic great group.
Argillic comes from the Latin word argilla, meaning "white clay." One type of argillic horizon is a natric horizon, which contains sodium and causes soil sealing.
The subsurface is characterized by an argillic or natric horizon. The mean soil temperature in which Alfisols form is usually > 8[degrees]C (47[degrees]F).
Others have a natric horizon
at depth and either waterlogging on top of the B-horizon (Aquic Natrixeralf), or no waterlogging (Typic Natrixeralf).
It is interesting to note that none of these soils were classified as having a natric horizon.
None of the soil mapping units in field A had natric horizons. Based on these field study results, field A did not meet the taxonomic definition of a natric horizon according to measures of central tendency for ESP (Table 2).
Other horizons that are found in arid environments include salic horizons, natric horizons, and those cemented by silica.
Natric horizons are typical of the soils known as solonetz, and are restricted to areas with semiarid to subhumid environments.