Soil Taxonomy: How Have We Gotten to Where We Are?.

Following publication of the 7^th approximation and the first edition of Soil Taxonomy in 1975, and as intended in its original architecture, revisions have been made at all levels in the system, including the addition of two new orders and a multitude of classes at other categorical levels. Particularly in the 1980s, numerous international committees were charged with investigating particular taxonomic questions which resulted in significant revisions to Soil Taxonomy. Not surprisingly, most of these revisions resulted in the addition of taxonomic classes, although occasionally (especially in the 1998 KST) there were notable reductions in the number of classes within certain orders.  This paper is an attempt to document the nature and magnitude of changes that have occurred in the development of Soil Taxonomy over its 54 year history in order to better understand how we have arrived at the current state of our soil classification system.