Geoscience Reference
In-Depth Information
FAO lists 40 diagnostic horizons. The US Soil Taxonomy distinguishes as many as
30 surface horizons (epipedon) and subsurface horizons.
When we summarize this chapter on soil horizons, we have to accentuate that
individual horizons differ one from another by characteristics readily visible while
looking at soil profi les in the fi eld. They are color, structure, texture, resistance to
rupture, and deformation. We can also detect the presence or absence of carbonates
and obtain reliable estimates of pH. The fi eld detection of soil morphology is then
completed by laboratory analysis. But the fi rst step in our study of the soil is in the
fi eld where we describe the soil profi le and all observed features (Fig.
12.1
).
Fig. 12.1
Studies of the soil in the soil pit. Soil faces differ from one location to another and are
not uniform. We show the variability of some of them. The soil profi les demonstrated here reach
roughly to a depth 1 m below the surface. The type of each soil is in the US classifi cation at the
level of order and suborder. In the World Reference Base, WRB, the Reference Soil Group, RSG,
is indicated
