Palexeralfs (Keys to Soil Taxonomy 11 vs. 12)

This topic may apply to other "Pale" great groups, but for simplicity lets focus solely on Palexeralfs. The newest Keys to Soil Taxonomy changed the requirements for Palexeralfs. In short, item JDF 3 on page 79 was changed to clarify position in the profile for criterion on clay content and to add to add a new criterion for the abrupt textural change.

In the previous version, it was required to have 35 percent or more of noncarbonate clay within 15 cm of the upper boundary of the argillic or kandic horizon. In the new version it says 35 percent or more clay throughout one or more subhorizons in the upper part of the argillic or kandic horizon.

My question for the forum is what is the upper part?

I found an official soils description for a tentative series (Motherlode) where this new definition causes issues.
Link: https://soilseries.sc.egov.usda.gov/OSD_Docs/M/MOTHERLODE.html This soil was classified in 2009 and did not meet the requirements for Palexeralfs. With this new definition, is this soil a Palexeralf? The horizon with greater than 45% clay (2Bt3) comes in a 74 cm and the argillic extends from 7- 140 cm.



Edited 1 time(s). Last edit at 08/27/2015 11:47AM by ttcf.