SA Graan Oktober 2018

Population shifts, on the basis of survival of the fittest, might

have accordingly already occurred in our soils over the past couple

of decades as a result of extensive usage of various herbicides.

A USA research group

similarly concluded that shifts in subpop

ulations of particularly the

Xanthamonadales

and

Acidobacteria

bacterial groups are possible under long-term glyphosate toler

ant cropping. Their study suggested that bacteria from the family

Xanthomonadacea

are better adapted to and/or enriched by envi

ronments containing glyphosate.

On the other hand,

Acidobacteria

which is highly involved in bio

geochemical processes, such as cellulose degradation (process in

volved with breaking down of cell walls of plant material), decreased

in response to glyphosate application.

Decreases in the abundance of these bacteria over the long-term

could impair the ability of soil to perform certain biogeochemical

reactions performed by these organisms.

Interestingly they found the reduction effect to be more dramatic in

maize as opposed to what was observed in soybean, suggesting that

any subsequent effects on biogeochemical processes due to this

bacterial group would be more pronounced in maize. The authors

concluded by stating that it is still unknown whether this shift affects

functional capacity of the soil under glyphosate tolerant cropping

systems

The question we should be asking is whether we are accordingly

still seeing or measuring today what was present before we became

so reliant on not only herbicides but pesticides in general, or are

we actually looking at adapted communities, that continue to evolve

based on what we expose them to?

If the latter is the case, how efficient are these newly adapted

communities compared to their ‘predecessors’, and does that have

any effect at all on our current agricultural outputs?

In Part 3 of this series, focus will be placed on research findings

published on the impact of glyphosate and other herbicides on

pathogenic fungi.

Readers are welcome to contact the authors at

ARC-Grain Crops with any enquires they might have

at 018 299 6100.

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The effects of herbicides on soil life

On farm level

Integrated pest control

Oktober 2018