Soil management is heading in a new direction. Soil microorganisms and the role they play in enhancing soil-mineral levels, soil structure and composition is increasingly getting more attention in agriculture. Stephanus Malherbe, manager of the Soil Food Web laboratory, established by the farming company ZZ2 at the University of Limpopo, spoke to Glenneis Kriel about this new thinking.
The role of soil organisms has largely been ignored over the past 50 years. This is because the natural and biologically processes regulating soil structure, nutrient supply, and pest and disease control have largely been replaced by man-made interventions such as fertiliser, soil tillage and pesticides.
While most of these interventions give good short-term results, the long-term results can be frightening, especially in terms of environmental impact. Leaching and the build-up of pesticides and fertiliser residue because of incorrect application has polluted the soil with dire consequences for microorganisms, plants and animal and human life. And the overuse of pesticides results in pest resistance. Vast tracts of land in Australia, for instance, have been rendered worthless because of herbicide-resistant ryegrass.
Systems dependent on high levels of fertiliser and pesticides become vulnerable because their biological capacity for self-regulation and response to environmental change is destroyed.
These interventions are also dependent on external and market-related factors. Input costs interdependent on global economic fluctuations, such as the escalating crude oil price, make the viability of various crops on some farms economically unsustainable.
There has been a gradual shift in thinking to where today soil is no longer seen as merely a growth medium, but as living matter.
“There’s nothing new about this philosophy, we’re simply reverting to practices used by our great grandparents,” says Stephanus Malherbe, manager of the ZZ2 laboratory at the University of Limpopo, east of Polokwane.
However, this approach is hampered by a lack of scientific knowledge and limited recognition given to the role of soil biota in determining the physical and chemical properties of soil and its productivity.
This lack of knowledge is also caused by the huge diversity of soil organisms, as well as the difficulty of identifying them and studying their direct link to soil function.
“But farmers shouldn’t allow this to deter them from using more environmentally-friendly production methods,” says Stephanus.
“Start with what you have. Failing to do so could have dire consequences, especially in light of stricter export regulations and the long-term environmental impact use of some products on the soil.”
The role of science and nature
The ZZ2 lab was established specifically to measure soil biodiversity and identify dominant strains of microorganism species in soil.
Such results allow farmers to better manage their soil.
But while Soil Food Web analysis is one of the services the laboratory offers, their tests still don’t determine which species are beneficial or harmful to the crops a farmer wants to produce.
“The Soil Food Web lab provides a holistic picture of the microorganism population, including the levels of fungi, bacteria, nematodes and protozoa. It also determines which of these are dominant in your soil,” explains Stephanus.
“It doesn’t differentiate between “good” or “bad” species because diversity is the key to healthy soil. It makes it more resilient than systems dominated by single species, whether beneficial for the system or not.”
It all requires a mind-shift, says Stephanus. The bottomline is that fewer than 10% of all microorganisms are pathogenic.
Yet farmers in the past did everything in their power to destroy these pathogenic microorganisms – in the process also destroying beneficial ones. Now, instead their aim should be to create a soil environment where beneficial microorganisms will prosper, and so keep pathogens in check. Stephanus says soil bombarded with pesticides and fertiliser over time usually has more pathogenic microorganisms than more natural systems.
This is because pathogens are survivors and thrive under harsh and extreme conditions. “This type of soil management is like having the police clear out the Mafia in a Russian town, but not replacing them with a positive influence to prevent the town from being overrun again,” says Stephanus. “It’s much more difficult to tell people what to do than what not to do. The golden rule when building soil life is to avoid harsh chemical products. When conditions require synthetic products, a farmer should use products with the lowest environmental impact at minimum dosage, and stick to product instructions. Don’t get into a rut. You must be aware of new insight and research at the forefront of any industry.”
Developing with knowledge
At the laboratory, plants are seen as the client. “Being based at the university helps because we have access to the most recent research,” explains Stephanus. “With the proliferation in natural products there is often confusion over the benefits and quality of specific products.
The laboratory analyses and tests products on specific crops for efficacy on request by farmers. Raw sewage, organophosphates, kelp and humic acids are all organic compounds, but they can also damage ecosystems if used irresponsibly. The laboratory guides farmers in terms of product safety levels. “We don’t want to fall into the same trap as with synthetic fertiliser,” says Stephanus.
“We want to know the short and long-term effects of products on the soil, the plant and the environment, and on the people consuming the plant byproducts.”
Contact Stephanus Malherbe on (015) 268 2912 or e-mail [email protected]. |fw