spodic horizon

spodic horizon

[′späd·ik hə′rīz·ən]
(geology)
A soil horizon characterized by illuviation of amorphous substances.
References in periodicals archive ?
One of the Podzols is on the upper slope and has a dominant E horizon; the other is on the footslope and has a dominant spodic horizon.
The spodic horizon represents an accumulation of illuviated organic matter and iron and aluminum oxides lying underneath a bleached horizon.
The spodic horizon, immediately beneath this bleached zone, consists of accumulated organic matter and amorphous aluminum and/or iron.
As they precipitate and polymerize in the deeper horizons, these compounds create a darker horizon, representing the humus, iron, and aluminum and known as spodic horizon (Bh).
A soil pit excavated in Wageningen (the Netherlands) shows a thick and blackish plaggen horizon over a spodic horizon with a sandy texture, with darker streaks and spots corresponding to the accumulation of iron oxide and organic matter.
If the topsoil is thinned by erosion, the spodic horizon may be mixed into the topsoil by tillage.
Extinction of the oxalate extract was measured at 472 nm (optical density of oxalate extract, ODOE) according to Daly (1982); a spodic horizon must be [is greater than] 250 (FAO 1994; Soil Survey Staff 1996).
A previous study reported that the soil development grades from undifferentiated parent material at the Lake Michigan shoreline to soils with well-defined albic and spodic horizons (Lichter 1998a).
In previous work, the soil organic matter (SOM) of the spodic horizons was characterised by a narrow C/N ratio ([is less than] 10) with potentially high bioavailability, probably derived from amino acids, other organic acids, and oxidised carbohydrates (Beyer et al.