Agriculture Reference
In-Depth Information
weathered parent rock is evident with some illuvial accumulation of sesquioxides and
amorphous organic matter. Finally, at the toeslope location, the organic horizons overlie
an horizon of weathering parent rock.
The changes in profile morphology illustrated and described above are paralleled by
similar differences in the suites of clay minerals present; allophane and sometimes
gibbsite are features of the Bw and Bs horizons, particularly. All subsoils are acid,
deficient in a number of nutrient elements and have limited cation exchange capacities.
4.6
Classification of soils
4.6.1
INTRODUCTION
As with the study of all natural phenomena, there is a need to group or classify soils into
meaningful categories. That is, into groups that possess an internal homogeneity with
respect to those not so included, for some defined combination of characteristics.
This need arises from the enormous variety and complexity of natural materials and
environmental conditions which is expressed in the wide diversity of soils that exist on
the surface of the earth: natural, influenced or formed by humankind. Appropriate soil
classifications are indispensable to the acquisition, organisation and dissemination of
knowledge about soils and in defining their capabilities and limitations in many aspects
of their use and function.
