The analyses and diagnostic features for spodic horizon were changed in 1992 with the release of the 5th Edition of the Keys to Soil Taxonomy. The changes were a result of the recommendations of the International Committee on the Classification of Spodosols (ICOMOD). The ICOMOD committee functioned from 1984 through 1991 receiving input and recommendations pedologists in US and internationally. Numerous proposals and reviews of requirements and procedures were published periodically in ten Circular Letters.
The NRCS has published on these Circular letters and the proceedings of the Fifth International Soil Correlation Meeting (on Spodosols) in 1990. These can be viewed on the NRCS web site at https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/class/taxonomy/?cid=stelprdb1262263
ICOMOD Circular Letter 10 (1991) summarizes the recommendations of the committee that were integrated into the 5th Edition of the Keys to Soil Taxonomy. These were later integrated into the Second Edition of Soil Taxonomy, 1999.
It appears the primary reasons for the changes in chemical analytical procedures was to obtain more reliable results (reduce false positives and false negatives) for Spodosols from other areas (differing ages/degree of development), and to take advantage of evolving analytical techniques and improvements in equipment used for analyses. Circular Letter 7 (October 1988) and its attachments include the most comprehensive discussion of the comparison of analytical methods.
Edited 4 time(s). Last edit at 03/29/2017 03:40PM by Ken Scheffe.
