Book reÕiews336

Soil taxonomy—a basic system of soil classification for making and interp-reting soil surveysSecond edition, by Soil Survey Staff, 1999, USDA–NRCS, Agriculture Hand-book number 436, Hardbound

This edition weighs almost 1 kg and will take up 7 cm of shelfspace in theŽ .library. The days of the Seventh Approximation 1960 and the first official

Ž .publication of Soil Taxonomy 1975 are over and now we have reached the 8thedition, which includes some major changes.

Over the years, major changes include the development of the kandic horizonand taxa to accommodate soils with low cation exchange capacities and high orlow base saturations. Meaningful taxa for Oxisols have also been developed and

Ž .an 11th order Andisols was created to for soils whose colloidal fraction isdominated by short-range-order minerals or Al–humus complexes. The conceptof hydromorphic conditions was reviewed and aquic conditions defined in termsof saturation, reduction and redox features, in addition to the concepts ofendosaturation, episaturation, anthraquic conditions and oxyaquic subgroupshave been developed. The Vertisol order now accommodates soils with cryictemperature regimes and soils with water tables at or near the surface. TheSpodosol order has been redefined primarily on the basis of field morphologyand, when necessary, on data obtained by oxalate extraction. New subdivisionswere created for the Aridisols. A 12th order, the Gelisols, was created to captureall soils with permafrost within 100 cm or permafrost within 200 cm and gelicmaterials. This new soil order is second in terms of extent to the Aridisols.There has also been a refinement in the mineralogy classes at the family level.The apparent cation exchange capacity of the clay fraction was accepted as analternative to qualitative clay mineralogy in mixed and siliceous families.

This new edition is well illustrated with 25 pages of colour photographs.There are two maps, one of global soil regions, another with dominant soilorders and sub-orders in the United States. It is regrettable that the book doesnot include a table giving the correlation with other major classification systems,and lacks documented analyzed and fully described soil profile examples. On

Žfundamental grounds, the heaviness of the system and not only the actual.weight of the book and its reliance on expensive analytical procedures com-

pares unfavourably to the World Reference Base for Soil Resources. Further-more, Soil Taxonomy fails to tackle soils fundamentally influenced by humanactivities, and the link with soil genesis remains patchy and it is debatable if asystem focusing explicitly on soil characteristics is to be preferred. Unless bothissues are faced, it will probably remain a system that cannot fully satisfymodern needs of soil interpretation given the growing extent of soils strongly

Book reÕiews 337

influenced by human activities. In spite of these disadvantages, Soil Taxonomyremains a standard for any national soil classification system.

Freddy NachtergaeleLand and Water DeÕelopment DiÕision,

FAO, Via delle Terme di Caracalla,00100 Rome, Italy

E-mail address: freddy.nachtergaele@fao.org

Ž .PII: S0016-7061 00 00097-5