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Misconception Number 14: OA focuses on “not using chemicals.” For example, OA research tries to develop “physical” mechanisms for weed control. However, physical techniques can be even more damaging to the soil ecology than chemical techniques. For example, thermo-weeding “sterilizes” the soil by injecting high pressure vapor, killing not only weed seeds, but also insects, worms, and bacteria of the soil.
Summary of Counter-Arguments:
- Apart from mechanical techniques, flaming is the only physical technique that is used by a significant number of organic farmers, is mainly used in a targeted way, with very low impact on non-targeted species.
- Soil sterilization is against the principles of Organic Agriculture and should not be used on organic farms.
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Details of Counter-Arguments:
Some organic farmers do use techniques such as
flame weeding as a non-chemical weed control method. Flame weeding is generally a targeted technique with low impact on the
temperature of the soil itself. It uses propane gas burners to produce a
carefully controlled and directed flame that briefly passes over weeds, searing
the leaves and causing the weed to wilt and die after its cell contents—plasma
and proteins—are disrupted. It is sufficient to heat parts of the plant
especially the leaves up to 100 ºC in order to boil the water within the cells
and ultimately destroy them. It is also used to kill crops (e.g., potato
plants) when they are infected with phytophtora, so as to avoid further spread
of such infestations. Flaming is a technique that can also be used for pest
control. For example, potato plants up to eight inches (20.3 cm) tall can be
flamed to kill Colorado
potato beetles, Leptinotarsa decemlineata,
without causing undue damage to the potato plants. Again, in this case, the technique
is used in a targeted way and has very low impact on non-targeted species.
That said, it is possible that some farmers use
these techniques in a manner that is not conducive to the soil’s biological
activity. However, the general
principles of Organic Agriculture include sustaining and enhancing the health
of all ecosystems, and especially the soil. As a result, sterilization of
soils shouldn’t happen in organic farming. This is made clear in the IFOAM
Basic Standards for Organic Production and Processing, which state that:
“Standards shall require that:…physical methods for pest, disease, and weed
management are permitted, including the application of heat. Thermal sterilization of soils to
combat pests and diseases is restricted.”
Thermo-weeding is by far the most widespread of all physical techniques used by organic farmers for weed-control. However, it is still much less widespread than mechanical weeding. To date, other physical methods (UV and laser) are very rarely used on organic farms.
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