Stagnic colour pattern (WRB)
Stagnic colour pattern is one of the diagnostic properties used, in the WRB system, to discriminate some soils from others.
Description
The term "Stagnic colour pattern" (from Latin stagnare, to stagnate) refers to soils that are, at least temporarily, saturated with surface water (or were saturated in the past, if now drained) for a period long enough that allows reducing conditions to occur (this may range from a few days in the tropics to a few weeks in other areas).
Criteria
A stagnic colour pattern shows mottling in such a way that the surfaces of the peds (or parts of the soil matrix) are lighter (at least one Munsell value unit more) and paler (at least one chroma unit less), and the interiors of the peds (or parts of the soil matrix) are more reddish (at least one hue unit) and brighter (at least one chroma unit more) than the non-redoximorphic parts of the layer, or than the mixed average of the interior and surface parts.
Additional characteristics : if a layer has a stagnic colour pattern in 50 percent of its volume the other 50 percent of the layer are non-redoximorphic (neither lighter and paler nor more reddish and brighter).
RSG in which stagnic colour pattern can be observed
See also
- The FAO reference text, (2007 version)
