The NCSS system of horizon designations was revised by the Soil Survey Staff in the early 1980’s. The changes are published in the Soil Science Society of America Journal, vol. 46, 1982 in a short article titled ”New Designations for Soil Horizons and Layers and the New Soil Survey Manual” authored by R.L. Guthrie and J.A. Witty. I suggest referring to this article to see the comparison of symbology before and after the changes were made. The Field Book for Describing and Sampling Soils , ver. 2.0, 2002, (available at: http://soils.usda.gov/technical/fieldbook/) also contains some conversion charts on pages 4-5 and 4-6. The concepts of the old horizon designations of A1 (accumulation of humified organic matter), A2 (eluviation of clay, iron, etc.), and A3 (transitional horizon between A and B) as used prior to 1982, all changed as a result of the new designations. The prior concepts are contained in the supplement that was issued to Agriculture Handbook No. 18 (Soil Survey Manual) in May of 1962. The 1962 supplement replaced pages 173 through 188 of the 1951 version of the Soil Survey Manual.
The NCSS system does not have a suffix symbol that connotes the accumulation of humified organic matter within surface horizons. Whether one is needed or not is debatable. We do have a suffix symbol h, but it is not used for surface horizons. It is intended to connote the illuvial accumulation of organic matter in subsurface B horizons (e.g., Bh). The FAO system also has a suffix symbol h which is defined as: “Designates the accumulation of organic matter in mineral horizons. The accumulation may occur in surface horizons, or in subsurface horizons through illuviation.” This definition is broader than the NCSS definition. As used by FAO, suffix symbol h may be used for in situ accumulation of humified organic matter within an A horizon (e.g., Ah) or for the illuvial subsurface accumulation mentioned above.
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Use of suffixes in proposed A horizon revision
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