Environmental Engineering Reference
In-Depth Information
Fig. 4.11 Impact of structure on percolation of water through soil (Published with kind permis-
sion of US Department of Agriculture, Natural Resources Conservation Service (
2010b
). Figure is
public domain in the USA. All Rights Reserved)
By definition, organic soil material is saturated with water for long periods or is
artificially drained and, excluding live roots, has an organic C content
18 %
with
12 % organic C with 0 % clay (Soil Survey Staff
1999
). Soils
with an intermediate amount of clay have an intermediate amount of organic
C. Three types of organic soil materials are recognized and distinguished by the
degree of decomposition: muck (highly decomposed), peat (very little decomposi-
tion), and mucky peat (intermediate decomposition).
To distinguish mineral soil materials that are highly enriched with organic
matter, a “mucky” modifier is added to its mineral texture designation; for example,
mucky sand. Mucky modified mineral soil with 0 % clay has 5-12 % organic
C. Mucky modified mineral soil with 60 % clay has 11-18 % organic C (Soil
Survey Staff
1999
). Soils with an intermediate amount of clay have intermediate
amounts of organic C. The Field Indicators in this category are: A7 5 cm Mucky
Mineral, S1 Sandy Mucky Mineral, and F1 Loamy Mucky Mineral.
60 % clay, or
4.8.2 Field Characterization of Soil Materials High
in Organic Carbon
Material high in organic C could fall into three categories: (1) organic, (2) mucky
mineral, or (3) mineral. In lieu of laboratory data, the following estimation method
can be used for soil material that is wet or nearly saturated with water. The first step
is to determine whether the material is mineral or organic. If organic, the second
step is to determine the type of soil organic material.
These soil material categories can be determined by gently rubbing wet soil
material between forefinger and thumb. For sandy textured soils, if upon the first or
second rub the material feels gritty, it is mineral soil material. If after the second rub
