|18 December 2018
THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE
Dear Friends and Colleagues
The Impact of Glyphosate on Soil Health
Soils are the foundation of our food security and yet a recent global scientific assessment found that 33% of land is degraded due to the erosion, salinization, compaction and acidification and chemical pollution of our soils. Over the last decade, about 6.1 billion kilograms of the herbicide glyphosate have been sprayed on the world’s farms, gardens and public spaces.
The Soil Association has reviewed the scientific evidence on the impact of glyphosate on soils and soil life. The key findings are as follows:
- Leaching into water: Glyphosate’s ability to leach deeper into the soil or groundwater, rivers or lakes was low due to its ability to attach to soil particles. In particular types of soil or weather conditions, however, glyphosate can leach out and pose a potential pollution threat to water courses.
- Impact on soil micro-organisms that are vital to soil health: Glyphosate has been shown to negatively affect the abundance of the culturable bacterial community, and the total bacterial composition. For example, a study found that the relative abundance of Acidobacteria decreased in response to glyphosate exposure. Decreases in the abundance of these bacteria over the long-term could impair the ability of soil to perform certain biogeochemical reactions performed by them.
- Impact on fungi:Beneficial fungi that live near plant roots have been found to be harmed by glyphosate. For example, studies found 40% reduction of mycorrhization after the application of glyphosate in soils.
- Severity and occurrence of crop diseases:Using glyphosate has increased the severity or the re-emergence of crop diseases, potentially by changing the balance between beneficial and harmful microbes in the soil. Increased frequency of soil-borne pathogens and reduced ability of crops to defend against them, are both reported to result from glyphosate use. In one study, the colonisation of roots by Fusarium fungi increased steadily as soybean growth progressed and as the rate of glyphosate increased.
- Impact on earthworms:Glyphosate showed a negative impact on the reproduction, growth, movement or activity of different species of earthworms. A study also found that earthworms avoided soil treated with the herbicide.
The report recommends further research to examine the impact of glyphosate on other soil fauna and microflora. Research should also consider the differences between the impact of glyphosate on soils as an active ingredient only, and when it is combined with other ingredients in a range of commercial products.
With best wishes,