Agriculture Reference
In-Depth Information
Table 16.2
Series Matrix Table for the Hutton form* in “Soil Classification: A Binomial System for
South Africa”
Clay
Content
of B21
Horizon
(%)
Noncalcareous in B Horizon
Grade of
Sand in
B21
Horizon
Calcareous in B
Horizon
Dystrophic in B21
Horizon
Mesotrophic in
B21 Horizon
Eutrophic in B21
Horizon
0 - 6
Fine
Alloway 10
Whithorn 20
Roodepoort 30
Lowlands 40
Medium
Arnot 11
Joubertina 21
Gaudam 31
Nyala 41
Coarse
Stonelaw 12
Chester 22
Moriah 32
Quaggafontein 42
6 - 15
Fine
Wakefield 13
Lichtenburg 23
Mangano 34
Maitengwe 43
Medium
Middelburg 14
Clansthal 24
Zwartfontein 35
Malonga 44
Coarse
Kyalami 15
Bontberg 25
Portsmouth 36
Vergenoeg 45
15 - 35
Undifferent-
iated
Hutton 16
Msinga 26
Shorrocks 37
Shigalo 46
35 - 55
Undifferent-
iated
Farningham 17
Doveton 27
Makatini 38
Hardap 47
* Adapted from MacVicar et al., 1977.
The main weaknesses of the system were:
¤
Each soil form had a series (with a much narrower range of properties) with the same name as
the form, e.g., the Hutton form included a Hutton series (Table 16.2). This often led to confusion
when people just talked about ÑHutton soils,Ò for example.
¤
Knowledge about the soils of the vast semiarid and arid parts of the country was very poor when
the classiÝcation system was constructed, and the system did not cater well for the classiÝcation
of these soils.
DEVELOPMENT OF “SOIL CLASSIFICATION: A TAXONOMIC
SYSTEM FOR SOUTH AFRICA”
In 1981 a new classiÝcation working group, still under chairmanship of MacVicar, started
with revision of ÑSoil ClassiÝcation: A Binomial System for South Africa.Ò Aspects initially
identiÝed for special attention included,
inter alia,
the following:
¤
Possible creation of new soil forms for soils with diagnostic horizon sequences for which provision
has not been made in the 1977 system
¤
Improved deÝnitions for some existing diagnostic horizons according to new information that has
become available
¤
More subdivisions of the podzolic soils. This was requested by the people in forestry because of
the importance of this in suitability evaluations of such soils for different
Pinus
species
¤
ClassiÝcation of the soils of the semiarid and arid regions
¤
Creation of a soil family category to Ýt in between the form and series categories
At the second meeting of the Working Group in 1983, two new (interrelated) issues came on the
agenda and would not only become controversial, but would bog down progress with regard to
important classiÝcation issues. Neither of these has thus far been resolved. The issues are these:
¤A proposal that soil series should be natural soil bodies and not artiÝcial classes. The soil textural
classes of the 1977 system were identiÝed as the ÑculpritÒ in this regard.
¤How provision should be made for silt in the use of soil texture as classiÝcation criterion. In the
1977 series classiÝcation, silt was ignored. This was because the silt content of the vast majority
of South African soils is low to very low, and can be ignored. There are soils with enough silt
(20% or more) to signiÝcantly affect soil properties, such as plant-available water capacity and
the susceptibility of the soil to compaction. Special concern was expressed with regard to the
