Agriculture Reference
In-Depth Information
Table 16.6
Family Matrix for the Hutton Form in “Soil Classification: A Taxonomic System for
South Africa”
1000 Dystrophic B1 horizon
Nonluvic B1 horizon
1100
LILLIEBURN
Luvic B1 horizon
1200
KELVIN
2000 Mesotrophic B1 horizon
Nonluvic B1 horizon
2100
HAYFIELD
Luvic B1 horizon
2200
SUURBEKOM
3000 Eutrophic B1 horizon
Nonluvic B1 horizon
3100
STELLA
Luvic B1 horizon
3200
VENTERSDORP
Adapted from Soil Classification Working Group, 1991.
made clear what exactly was meant with natural bodies, and no guidelines were given about how
to Ýnd and deÝne these natural bodies. Furthermore, no institution/organization was given the
responsibility or the funding to give the necessary guidance or to do the coordination and
correlation needed to avoid chaos. The consequence is that from 1983 to 2001, no progress was
made on this issue. At the 1992 Congress of the Soil Science Society of South Africa, Duvenhage
et al., (1992) already highlighted the problem that there were no guidelines in the 1991 classi-
Ýcation system to guide scientists on how to deÝne series. They emphasized that the information
provided by series was essential for any land user, and therefore guidelines for series differen-
tiation should be a high priority.
Yet it was only at the meeting of the new soil classiÝcation working group in January 2001
(nearly 10 years later), under the agenda point ÑSoil series/Natural soil bodies,Ò that the chairman
(Lambrechts) Ñinvited discussion by asking the question: How should this issue be tackled?Ò
(Soil ClassiÝcation Working Group, 2001). He further added: ÑThe issue of unclear concepts is
still not resolved. We have a responsibility to deÝne what we want to establish locally as a series
concept.Ò It was decided that ÑWe need a concept deÝnition of what we want soil series to be
in South Africa. It should be understandable by all and within the context of the Blue Book.Ò
(The ÑBlue BookÒ is the 1991 South African soil classiÝcation system.) Turner was given the
task of writing the Ýrst draft, because he recently completed a comprehensive study on the
recognition of natural soil bodies in two of South AfricaÔs nine provinces under my supervision,
studying data of over 4000 proÝles in the process (Turner, 2000).
Ever since the natural soil body issue was raised in 1983, I could not agree with the idea
that series should be deÝned in terms of natural soil bodies. I agree with the series concept
explained in Soil Taxonomy (Soil Survey Staff, 1975):
The function of the soil series is pragmatic, and differences within a family that are important to use
the soil should be considered in classifying the soil series. Differences in particle size, texture,
mineralogy, amount of organic matter, structure, and so on that are not family differentiae should be
considered at series level.
Duvenhage et al. (1992) compared soils of the Avalon form (Orthic A/Yellow-brown apedal
B/Soft plinthic B), one of the most important soils for rainfed cropping in the maize quadrangle,
in two districts in the somewhat drier western part of the quadrangle. In the 1977 system, they
were placed in two different series on the basis of clay content of the B21 (now B1) horizon,
one falling in the 6Ï15% clay range, and the other in the 15Ï35% clay range. The management
techniques applied by farmers differ in at least nine respects between the two series: crop
selection, type of cultivation, depth of cultivation, tractor power used, planting density, planting
depth, row width, weed control measures, and fertilizer placement. The fertilizer advisors,
extension ofÝcers, farmers, etc., knew the names of the series and the management requirements
of each. In the natural soil body approach, the big question will be how to handle this type of
