Agriculture Reference
In-Depth Information
alternate. The parent materials are predominantly weathering hard rock. These factors have a
profound inÞuence on the nature of the soils. In the northern hemisphere, this major soil region
starts closer to the equator than in the southern hemisphere, but also extends to about 35
ο
N latitude.
Here it includes all the big deserts of the world.
HISTORICAL REVIEW OF SOIL CLASSIFICATION IN SOUTH AFRICA
MacVicar et al. (1965), MacVicar (1978), and Turner (2000) have given comprehensive
historical reviews of soil classiÝcation in South Africa. A start was made, with studies of South
AfricaÔs soils in the early 1890s, with Juritz being the pioneer in this Ýeld (MacVicar et al.
,
1965). By 1910, Vipond pointed out that chemical analyses alone were not adequate and suggested
soil surveys, recommending that these should be based on parent material (MacVicar et al.
1965).
After that, a few loose-standing small soil surveys were done by different individuals, without
any coordination or development of a soil classiÝcation system. During the same period, the Soil
Survey Section of the Division of Chemistry of the Department of Agriculture conducted various
detailed soil surveys for the development of irrigation schemes. The soils were classiÝed into
types, based on their morphology as observed in proÝle pits and some chemical analyses. SpeciÝc
attention was given to soil properties that would determine the behavior of soils under irrigation
(MacVicar
,
1965).
During these irrigation surveys, C.R. van der Merwe, as OfÝcer-in-charge of irrigation
surveys, inspected the work of Ýeld teams in various parts of the country. He identiÝed charac-
teristic soils, describing and sampling them for further analysis. On the basis of these studies,
Van der Merwe (1941; 1962) ÑclassiÝed the soils of South Africa into soil groups and subgroups
according to their characteristic morphology as inÞuenced by soil forming factorsÒ (MacVicar
et al.
et al.
,
1965). In this classiÝcation system, Van der Merwe embraced the zonality concept under
the inÞuence of the Russian pedologists and Marbut, and upon Ñobserving such large tracts of
uniform soil as the red Kalahari sands, the black clays on norite and the highly weathered soils
of the eastern escarpmentÒ (MacVicar, 1978). In many areas his system placed dissimilar soils
in the same class or put similar soils in different classes (MacVicar, (1978). Because of the
overriding effects of other factors, especially parent material, the zonality approach did not work
in many areas. ÑIts failure to group soils according to similarity in properties was the downfall
of this classiÝcation system. The units display the character of map units rather than taxonomic
unitsÒ (MacVicar, 1978). Despite these criticisms, the following must be kept in mind:
,
1.
This was the Ýrst attempt at a systematic classiÝcation of the soils of the country.
2.
It was done in line with the international views on classiÝcation at that time.
3.
The delineations of present-day generalized small-scale soil maps of the country do not differ
dramatically from those of Van der Merwe. Basically, only the terminology differs.
During the late 1930s, Rosenstrauch conducted surveys of the soils of the ÑSugar BeltÒ in
the KwaZulu-Natal lowlands, and in the process was the Ýrst to make broad series classiÝcations
of soils in South Africa (MacVicar et al.
1965). Beater continued this work and published the
Ýrst series deÝnitions of soils in South Africa (Beater, 1944). His reÝnement of the series
deÝnitions of the soils of the Sugar Belt was published in three volumes, covering the three main
sugar production regions of that time (Beater, 1957; 1959; 1962). Parent material was the
dominant factor that determined classes in BeaterÔs classiÝcation. ÑSince the effect of drift is
minimal, each rock type has its own suite of soils, due mainly to drainage differences. È These
geological groupings were in fact well deÝned and hence useful map units (associations of soils)Ò
(MacVicar, 1978). They were not taxonomic units, as most contained dissimilar soils because
of position in the landscape (MacVicar, 1978).
,
