The unknown underworld: Understanding soil health in South Africa

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1Volume 110 | Number 5/6
May/June 2014
South African Journal of Science
http://www.sajs.co.za
News & Views Understanding soil health in South Africa
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The unknown underworld:
Understanding soil health in South Africa
The need to provide food security to a growing human population in the face of global threats such as climate
change, land transformation, invasive species and pollution1 is placing increasing pressure on South African soils.
South Africa is losing an estimated 300–400 million tonnes of soil annually2, while soil degradation is a major threat
to agricultural sustainability3. In spite of these problems, treatment of soil health in biodiversity assessment and
planning in South Africa has been rudimentary to date.4,5
Defining soil health
Soil is a crucial component of the pedosphere, which sustains life, and should therefore be regarded as one of the
most important assets held by South Africans. However, in South Africa, soil is a highly neglected research focus
in ecosystem service delivery. Studies of ecosystem services often focus on more elegant and tractable systems,
such as pollination networks.6 Currently in South Africa, soils are viewed in certain sectors as resources that can
be used to generate short-term gains, rather than assets to be protected and developed. Soils form the basis for
food security through agriculture, where processes taking place in the pedosphere result in water retention, nutrient
augmentation and soil biodiversity proliferation.
In an effort to facilitate research on soil health, or at least stimulate debate on the topic, we propose that soil
health be measured by a combination of abiotic (A) and biotic (B) and socio-economic (S) aspects relative to a
benchmark measure, i.e.
Soil health = ∑A. ∑B. ∑S
benchmark
where A is measured by a subset of soil physicochemical indicators (with subsets determined on the basis of
variable thresholds relating to soil type and soil usage); B is determined by standard biodiversity metrics (e.g.
species richness, abundance, network or species assemblage connectedness), incorporating biodiversity in
the context of applied strategies (e.g. agricultural push–pull systems and mixed cropping) and S is determined
by socio-economic values (e.g. monetary value, equity, human well-being). In order to scale each component,
benchmark values will also have to be determined that will serve as the denominator for calculation of changing
component values over time.7,8
Here we use a similar model to that used in above ground environmental analyses (e.g. the IUCN’s system analysis
in Leverington et al.9), but we recognise that the below ground ‘closed’ medium functions at different tempos
and scales. As such, this model is simplistic, yet a degree of ignorance exists about ‘understanding’ soils,10
strengthening the notion that soils need to be elevated to mainstream research foci where interactions among
the physical, chemical and biological components of soils receive precedence and serve as a point of departure.
For soils to operate in a complex, interacting total system manner, biodiversity in different environments serving
different socio-economic requirements can potentially be temporally and spatially separated, e.g. hydroponic farms
and conservation areas or an ecological network in which all aspects are incorporated. In some cases this can
lead to an overall greater soil health set-up than if all elements were combined in one area at a specific time period
(e.g. debate on conservation versus agriculture, or conservation and agriculture11 and landscape-scale analysis
over seasons12).
The three components of soil defined here all contribute to ecosystem services and intersect to provide healthy
soils. The model for this soil health index (Figure 1), supported by intersection descriptions and more detailed
relevant examples (Figure 2), serves to emphasise that soils are extremely complex and function in multiple
roles, and as such have a pivotal role in ecological function. Based on this framework, we formulated several key
research questions (Table 1).
The need for foundational work on soil organisms
In the last decade, the diverse roles of soil communities in the ecological function of soils has gained global
recognition.13 Several large multidisciplinary projects in Europe (such as ENVASSO and EcoFINDERS) now
focus on soil organisms using holistic approaches incorporating traditional taxonomy14 and modern molecular
techniques15. However, in South Africa, like elsewhere in the world, research in the field of soil biology has been
neglected compared with research in soil chemistry or soil physics. This scenario has started to change over the
past decade or two and South Africa is no exception in this regard. Research on a broad biological basis regarding
South African soils has increased since the mid-1990s and these outcomes are published in journals such as the
European Journal of Soil Science, Soil Biology and Biochemistry, Biogeochemistry, Soil Research, Geoderma and
the South African Journal of Plant and Soil. Sadly, however, this cannot be said of pure foundational research on
soil organisms and, despite some notable pioneering experts (e.g. Lawrence16), our knowledge of South African
soil organisms is largely restricted to taxonomically well-known groups such as ants17-19 and spiders20, and even
then this knowledge is often fragmented and poorly documented. The need to integrate existing research initiatives
was unanimously expressed at a Soil Health Workshop at the XVII Congress of the Entomological Society of
Southern Africa in July 2011. This expression led to the formation of SERG (Soil Ecosystem Research Group) – a
soil biodiversity research group that provides a platform for linking and promoting research on soil organisms.
AUTHORS:
Schalk v.d.M. Louw1
John R.U. Wilson2,3
Charlene Janion3
Ruan Veldtman2,4
Sarah J. Davies3
Matthew Addison4,5
AFFILIATIONS:
1Department of Zoology and
Entomology, University of
the Free State, Bloemfontein,
South Africa
2South African National
Biodiversity Institute,
Kirstenbosch National
Botanical Gardens, Cape Town,
South Africa
3Centre for Invasion Biology,
Department of Botany and
Zoology, Stellenbosch University,
Stellenbosch, South Africa
4Department of Conservation
Ecology and Entomology,
Stellenbosch University,
Stellenbosch, South Africa
5Hortgro Science, Stellenbosch,
South Africa
CORRESPONDENCE TO:
Schalk Louw
EMAIL:
louws@ufs.ac.za
POSTAL ADDRESS:
Department of Zoology and
Entomology, University of
the Free Sate, PO Box 339,
Bloemfontein 9300, South Africa
KEYWORDS:
soil signature; edaphic factors;
sustainability; food security;
sustainable agriculture
HOW TO CITE:
Louw SvdM, Wilson JRU,
Janion C, Veldtman R, Davies
SJ, Addison M. The unknown
underworld: Understanding soil
health in South Africa. S Afr J Sci.
2014;110(5/6), Art. #a0064, 4
pages. http://dx.doi.org/10.1590/
sajs.2014/a0064
© 2014. The Authors.
Published under a Creative
Commons Attribution Licence.

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South African Journal of Science
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News & Views Understanding soil health in South Africa
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Conceptual model Area Definition Examples
A∩B∩S
Happy healthy soils – production landscapes
where the inputs are minimal and biodiversity
is maintained through sustained soil ecosystem
service delivery
• Sustainable flower har vesting from the wild
(Figure 2)
• Mixed cropping system with conservation tillage
A∩B
Ecological function – natural ecosystems with
significant functional roles. Ecological processes
and physicochemical cycles are maintained; soil
condition is preserved
• Wetlands
• Unfarmed Succulent Karoo ecosystems –
dry low primary productivity regions with
low or no animal stocking (Figure 2)
B∩S
Beneficial organisms – soil organisms are used
by humans for utilitarian purposes
• Biological control (e.g. entomo-pathogenic
nematodes) and vermi-composting
• Bio-prospecting
A∩S
Input production – production systems
where physical and chemical properties are
manipulated to maintain production
• Mono-cultural intensive agriculture
B
Biotic – soil biodiversity, including organisms
of all different taxonomic and functional groups,
which together result in multi-trophic interactions
• Maputo-Pondoland Centre of Endemism
AAbiotic – physical and chemical properties of soil • Iron oxide rich Kalahari sandy soils
SSocio-economic – encompasses ownership and
land use and subsequent production
• Hydroponics (Figure 2)
Figure 1: Proposed conceptual scheme for defining soil. We consider healthy soils as those that provide abiotic, biotic and socio-economic services.
Hydroponics Nature reserves in the Succulent Karoo Sustainable harvesting of wild flowers
Approximately 800 ha of hydroponics in RSA in 200221 Knersvlakte Nature Reserve: 24 058 ha22 South Africa’s Agulhas Plain: 30 597 ha23
S
B
AA∩B
B∩S
B
A∩B
B∩S
A∩B∩S
Productivity via hydroponics, means there is no ‘soil’
at all.24 However, such systems have no ecosystem
functionality. A neighbouring/interlinked soil system
is required for soil processes to continue. System will
require continual inputs.
Succulent Karoo soils are likely to harbour many
endemic species,25 although they have been poorly
studied to date. There are some important functions,
e.g. reducing erosion, but very little productive value
exists, and in many cases such soils are sensitive
to disturbance.26
Several initiatives are in place to combine economic
value with biodiversity conservation. The selling
of flowers (particularly Proteaceae) from nature
reserves as ‘green’ products raises money for
environmental restoration and management, as well
as local development.
Figure 2: Case studies highlighting how ‘soils’ differ in abiotic, biotic and socio-economic aspects (based on examples from Figure 1).
Socio-economic
(S)
Beneficial
organisms
Happy
healthy soils
Input
production
Abiotic
(A)
Ecological
function
Biotic
(B)

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South African Journal of Science
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One of the first priorities identified by SERG was the need to collate and
mobilise data and collections to consolidate and compare the state of
knowledge of each group.
Conclusion
We anticipate that research on soils will be a major initiative linking
fundamental and applied research endeavours in the times ahead,
especially in the context of climate smart management strategies.
Having said this, we do recognise that the establishment of thresholds
for biological indicators of soil health is a far greater challenge than the
establishment of thresholds for either chemical or physical indicators of
soil health, simply because biological indicators are too variable over
short periods. Future research endeavours will therefore have to breach
this complication.
Acknowledgements
We thank our respective institutions and departments for suppor t in
terms of funding and facilities. We also thank the NRF for funding. An
anonymous reviewer is gratefully acknowledged for providing many
positive and thought-provoking comments which helped improve
the manuscript.
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Table 1: Key research questions/topics in soil ecology in South Africa
1. What are the underlying interactions and independent values of sustainable agriculture and intensive agriculture (A∩B∩S & A∩S), taking cognisance that
intensive agriculture might not necessarily be unsustainable?
2. What is the human carrying capacity of a functional, healthy soil, irrespective of whether it is used for crop farming or stock farming?
3. How much of soil biodiversity is resistant, or resilient or incompatible with disturbance?
4. How can natural benchmarks for soils in South Africa be determined?
5. Can the interactions within the total system, e.g. those among production systems, soil organisms and water-based soil nutrient cycling, be analysed? Such
analysis could include the following:
• Interaction and feedback loops between soil organisms and nutrient cycling.
• Interaction and feedback loops between plants and soil organisms that affect nutrient cycling.
• Interaction and feedback loops between soil nutrient cycling processes and crop yield.
• Identification of soil organisms and their nutrient processing qualities.
• Quantification of nutrient cycles.
• Identification of species assemblages most beneficial to soil processes and crop yield.
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4Volume 110 | Number 5/6
May/June 2014
South African Journal of Science
http://www.sajs.co.za
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