Given a vector or matrix of "eluvial" horizon clay contents (\ crit.clay.argillic() returns a vector or matrix of minimum clay contents (thresholds) that must be met for an argillic horizon clay increase.




A numeric vector or matrix containing clay contents of potential "eluvial" horizons. May contain NA.


A vector or matrix (input-dependent) containing minimum "illuvial" horizon clay contents (thresholds) to be met for argillic horizon clay increase.


Uses the standard equations for clay contents less than 15 \ and 40 \ the definition of the argillic horizon from 12th Edition Keys to Soil Taxonomy (Soil Survey Staff, 2014).


This function is intended for identifying clay content threshold required for an argillic horizon. These thresholds may not apply depending on the specifics of your soil. E.g. if the upper part of argillic has been plowed (has Ap immediately over upper boundary) the clay increase requirement can be waived (Soil Survey Staff, 2014).


Soil Survey Staff. 2014. Keys to Soil Taxonomy, 12th ed. USDA-Natural Resources Conservation Service, Washington, DC.

See also


Andrew Gene Brown


# crit.clay.argillic uses different equations for clay content
# less than 15 %, between 15 and 40 %, and >40 %

crit.clay.argillic(eluvial_clay_content=c(5, 20, 45))
#> [1]  8 24 53