Soils with a planic B horizon underlying a textural B horizon and, therefore, not regarded as Planosols in the Brazilian System of Soil Classification (SIBCS) were characterized and classified. Three representative soil profiles were selected in the county of Ouricuri, Araripina micro-region, within the Sertão Zone of Pernambuco State, an area with a high density of planossolic soils. Soil profiles were morphologically described and disturbed samples taken from each horizon for physical and chemical analyses. Undisturbed samples were collected to determine bulk density. Results showed that the soils, formed by the contribution of two parent materials (sediments and crystalline rocks), demonstrate this double origin with two distinct sections. The top on is formed by A, BA, Bt, and/or Btf horizons, and the bottom one by 2Btbn and 2BCn horizons. The topsoil horizons have colors of higher chromas, lower clay contents, smaller bulk density, higher hydraulic conductivity, and a lower clay activity compared to the subsoil horizons, characterized by high bulk density, low chromas and very low hydraulic conductivity, limiting the downward movement of water. The soils were classified in the SIBCS as: Sodic Planossolic Eutric Argiluvic Plinthosol (profile 1); Solodic Planossolic Eutric Yellow Argisol (profile 2) and Sodic Planossolic Plinthic Eutric Yellow Argisol (profile 3). Changes in the definition of the planic B horizon were suggested to allow the inclusion of the studied soils as follows: a planic B horizon must not obligatorily underlie an A or E horizon nor present an abrupt particle size alteration as long as it presents abrupt transition that is a very clear rupture with the previous A, E or Bt horizon.
Semi-arid; Yellow Argisol; Argiluvic Plinthosol; planic B horizon
