Soil microorganisms thrive on organics

New research from Stellenbosch University demonstrates that
organic management practices really do help soil microorganisms thrive.

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Ecotoxicologists from Stellenbosch University have added local scientific evidence that organic farming is better for the long-term health of agricultural land. researchers demonstrated that soil organisms in a Western Cape vineyard, such as earthworms, mites and fungi, were more active in soil under organic management practices than conventional chemical treatment. A microcosm laboratory test was also done.

The study, by husband-and-wife team Prof Koot and Prof Sophié Reinecke and doctoral student Randal Albertus of the Department of Botany and Zoology, in conjunction with Prof Otto Larink of the Institute of Zoology at the Technical University of Braunschweig in Germany, was published in the scientific journal African Zoology. Prof Reinecke says the protection of soil biodiversity and its functions is a vital goal for soil ecotoxicologists and conservationists, who want to provide ecologically relevant, economically realistic solutions to agroecological problems.

Stop poisoning soil microorganisms
Soil organisms are, amongst other things, important for the decomposition of plant matter and for making nutrients available to plants. They also help improve soil aeration and structure. In developing countries, agriculture has increasingly turned to chemical biocides to manage pests such as weeds and fungal disease. Research shows this can accidentally poison beneficial non-target organisms, especially soil organisms, including earthworms. The concept of organic farming has been developed and popularised in an effort to reduce or even eliminate the use of chemical pesticides and fertilisers. Organic farming aims to revitalise soils by adding organic matter. Farmers are expected to rely on local biological resources and environmentally friendly techniques to combat pests and fertilise the soil. The aim is to prevent poisoning beneficial organisms and promote natural soil processes.

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In the study, experimental plots received either pesticides and full chemical weed control or organic treatment according to the Organic Standards of the British Soil Association. The bait-lamina test, used to measure the feeding activity of soil organisms, assessed the activity and abundance of soil life in the plots. researchers compared feeding activity and moisture content, and showed that soil organisms were substantially more active in the organically treated plots than the conventionally treated ones. “We must be careful when drawing conclusions because of the many variables involved, but we believe this study provided some evidence that organic management promoted higher soil organism feeding activity in the short term, shortly after treatment, compared to conventional practices,” Prof Koot Reinecke summarises. “Organic management practices could contribute to the sustainable use of soil.”

More and more support for organics
The organic management concept is widely accepted in many circles despite limited scientific evidence. Already, soil biologists widely agree that adding organic material can, within limits, increase populations of various beneficial organisms, especially in poor soils. It seems to follow that this improves fertility and sustainability, though more sound evidence is still required. Sustainable agriculture relies on biological activity, but so far direct practical evidence for organic management’s real field value in this regard has been scarce. Relevant local research is even harder to come by.
Other South African research includes studies in sugarcane fields, where green cane harvesting with trash retention, a form of organic treatment, instead of burning, increased earthworm numbers and beneficial microbial biomass. – Staff reporter
Contact Prof Koot Reinecke on (021) 808 2861 or e-mail [email protected]. |fw