The application of the FAO and US soil taxonomy systems to saline soils in relation to halophytic vegetation in SE Spain

Twenty-three pedons from six salt marshes in SE Spain, occurring under a semiarid Mediterranean climate, were classified according to various FAO and USDA Soil Survey Staff (SSS) systems. In each salt marsh, the sampling sites were selected to represent seven different plant communities. For the plant communities studied, less diversity of soil classes was observed at the Unit level using the 1998 version of the FAO soil classification system than the 1994 edition and less at the Great Group level for the 1996, 1998 and 1999 versions of the USDA system than the 1992 version. The FAO 1988 version defines the characteristics of these soils better than the 1994 edition because the former includes the possibilities of classifying at the third level and of using salic and sodic phases. The 1998 version offers greater possibilities for expressing the characteristics of these soils, but two considerations would improve the results: (i) the use of the term Hyposalic instead of Endosalic in the Calcisols group; (ii) the possibility of using the petrocalcic horizon in the Solonchak group. The main shortcomings of the 1996 and 1998 versions of the USDA system for classifying these soils are: (i) the lack of a class to indicate a high concentration of salts in the Mollisol Order independently of the presence of a natric horizon and/or aquic conditions; (ii) failure to indicate the existence of a petrocalcic horizon at the Salids Great Group level. These two problems can be overcome in the 1999 version by the use of the adjectives Halic and Petrocalcic, respectively.