Agriculture Reference
In-Depth Information
4.6.4
MAN-MADE AND MAN-INFLUENCED SOILS
In most parts of the world, soils increasingly occur that have been strongly influenced or
directly created by humankind. This varied group includes agricultural soils whose
original properties have been substantially modified by such practices as deep mixing,
cultivation carried out over long periods, flooding, drainage, re-contouring, large and
continued additions of organic matter and other ameliorants, and other cultural practices.
Further groups of soils include the so-called urban soils, those created from domestic and
industrial refuse, dredged materials and land-fill materials of various types.
Another class of materials is those derived from various geological strata that are
exposed on the surface as a consequence of mining operations. Depending on the type
of mining and the strata present, these may range from highly inimical materials often
extremely acid or extremely alkaline as are common in the metalliferous and coal
mining industries. Some materials, such as those derived from the mining of bauxitic lat-
erite, are relatively benign in terms of their propensities for supporting the growth of
higher plants and require little more than appropriate fertilisation and seeding (Reddell
et al
., 1992). Waste products such as the tailings created by initial ore processing may be
similarly variable.
Some of these materials scarcely qualify as soils. However, in many countries,
particularly in the case of mining spoils and wastes, there is a social or legislative
requirement to stabilise them with a vegetative cover or return them to some form of
agricultural production. Where rehabilitation procedures are successful, these materials
may develop some of the properties of incipient soils in relatively short periods
(see, for example, Reddell
et al
., 1992).
A number of classifications include categories for many of these man-influenced and
man-made soils, often at the highest level of organisation (see, for example, ISSS
Working Group RB, 1998; Hewitt, 1992; Isbell, 1996). In these systems they may be
designated as anthrosols or anthropomorphic soils. Other systems include these soils at
lower levels within existing groups; in Soil Taxonomy, for example, they may be
included among the Entisols. Because of the continuing widespread creation of these
soils, their incipient nature and their often unusual properties, these is a clear need to
develop a more effective approach to their classification.
