Does Thermal weed control affect microbial biomass in soil?

I heard an interesting question today about the effects of alternative weed control methods on microbial biomass in soil. It's interesting to consider this and other ecological impacts of different

 · 2 min read

There has in fact been research into this subject, which highlights that even with intense treatment, far beyond what we are likely to apply in an amenity setting, effects on microbial biomass from hot air weed burners or flamers are small.


Below is a section of a paper regarding the microbial effect of flaming, which would be the most similar to hot air.  The table also gives the source for that information, which may be of further help.


The full paper can be read here;

https://www.researchgate.net/publication/319505488_Flaming_and_Burning_as_Thermal_Weed_Control_Methods_A_Review


When assessing appropriate tools for weed control on different surfaces, it is important to understand the impact of the product. Not only on the weed you are targeting, but also on other aspects of the environment we are trying to conserve, so it was a good question to raise.  


I am pleased to present the following findings.  


Rahkonen et al. 1999.Soil microbial effect.FlamingFlaming have little effect on microbial biomass deeper in the soil (5–10 mm). The soil temperature at 5 mm depth was raised by 4.0°C and at 10 mm by 1.2°C. It is concluded that the threat that flaming poses to soil microorganisms is small.


I have found an abstract from this source, which might be useful.


"The effects of liquefied petroleum gas (LPG) flaming on soil microbial biomass and soil temperature were studied in a laboratory trial. The trial was arranged to imitate the most common weed flaming practice, non-selective flaming pre-emergence of the crop. Soil samples were taken, without disturbing the soil surface, before the germination of the crop from a field cultivated and sown in the spring. The microbial biomass in the 0–5 mm depth, measured by substrate induced respiration (SIR), was decreased by 19% when the soils were flamed with open flame burners using a flaming intensity of 4600 MJ ha−1. The treatment was quite extreme, corresponding to a propane dose of 100 kg ha−1, while the usual dose in practice is 20–80 kg ha−1. Flaming had little effect on microbial biomass deeper in the soil (5–10 mm). The soil temperature at 5 mm depth was raised by 4.0°C and at 10 mm by 1.2°C. It is concluded that the threat that flaming poses to soil microorganisms is small."


Other important considerations might be how the run off from applied products might affect water courses for instance.  Which is an area that hot air weed control has a clear advantage over certain plant protection products applied to the weed, especially on hard surfaces near drains, or directly next to a body of water.


For much more information on weed prevention please take a look at our new Weed Prevention Guide for the Amenity Sector

You should also check out our 4 step plan to phase out glyphosate.


For more information on reducing or eliminating your reliance on chemicals to deal with weeds, please get in touch.



1 comment
Good information March 10, 2022

It is interesting to to find research regarding using heat as a weed control method.

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