Soil has traditionally been seen as a "dead" agricultural medium – something to keep crops upright. Soil physicochemical analyses were conducted to determine the application rate of chemical fertilizers to sustain/increase the season's yields. Soils were injudiciously ploughed, drenched in herbicides and pesticides, crop residues were burned, and fields were left bare and vulnerable to nature's elements, with precious fertile topsoil being blown away or carried off during wind and rainstorms. The vital role of soil microorganisms in agriculture have only recently gained popularity with South African farmers after they experimented with various agricultural practices in an effort to increase their yields and soil's health/fertility in a sustainable way. Before this paradigm shift, we never realized that only 6-8 cm of fertile soil was naturally formed over a period of 2000 years; that soil-life consisted of thousands of different insects, earthworms, mites, nematodes, fungi, yeasts, and single-cell organisms; that a teaspoon of fertile soil could contain a billion bacteria and almost 5,000 different species of bacteria per gram of soil.
Since less than 1% of all microbes can be cultured on artificial media, numerous alternative techniques had to be developed to overcome the limitations frequently associated with conventional techniques. Most of the latest available techniques are independent of cell culturability, and circumvent the numerous problems associated with conventional methods. The Soil Microbiology Laboratory ARC-PPRI, Roodeplaat, provides services based on two such techniques namely
soil microbial functional profiles and enzyme activity, to characterize microbial ecosystems.
Soil microbial functional profiles measure the ability of soil microbial populations to utilise specific carbon sources, i.e. food sources. These profiles are essential components of monitoring and managing depleted soils, since food availability is the main factor that influences both size and activities of microbial populations. Microbial ecologists have developed several techniques attempting to reveal more closely the functional role the community plays in nature. One approach to translate the information in a microbial ecosystem, would be to determine the microbial metabolic diversity (functional diversity) by analysing community-level physiological profiles (CLPPs). The utilisation of various substrates by soil microorganisms will give a characteristic reaction pattern, called a metabolic fingerprint, which is comparable to the cumulative metabolic ability of the soil microbial community through CLPPs as determined by the Biolog EcoPlate system.
Soil microbial enzymatic activity viz. microbial activity, fulfil absolutely critical soil biogeochemical processes in soil ecosystems. The activity of any enzyme assayed in a soil sample, is the sum of active and potentially active enzymes from all the different sources. Enzymatic activities in relation to the cycling of carbon, nitrogen or release of inorganic phosphorus in soil, have been used to evaluate the fertility of the soil or to describe the functioning of the ecosystem.
By correlating this data with production practises, the management of land can be improved and eventually provide healthy soils for sustainable agriculture. It is advisable to conduct soil microbial analyses at least twice per season over a period of 3-5 years. PPRI's Soil Microbiology Laboratory consists of adequate facilities and knowledge to determine soil microbial diversity and activity as indicators of soil health. These analyses could be implemented by commercial and smallholder farmers to monitor the impact of their agricultural practices on soil microbial populations, soil health, and yield. These services are available to any persons concerned about the health of their soils.
We were appointed as curators of our soils. Let's act accordingly, because when our soils collapse, it will take all living beings with it. No soil, no agriculture, no producers, no life.
The Soil Microbiology Laboratory is proudly associated with:
ARC-Vegetable and Ornamental Plants: Medicinal plants
ARC-Soil, Climate & Water
AgriLibrium: Sustainable Agriculture
ESKOM: Biodiversity Assessment
GrainSA: Conservation Agriculture
North-West University (Potchefstroom and Mafikeng Campus)
Stellenbosch University – Department of Agronomy
Tshwane University of Technology: Department of Crop Sciences
Western Cape Government Department of Agriculture: Directorate: Plant Sciences
Contact: Dr Ahmed Hassen or Dr Elna van der Linde
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