Living cover crops alter the fate of pesticide residues in soil: influence of pesticide physicochemical properties
In this new scientific article, we show that well-developed cover crops not only reduce nitrogen leaching, but also degrade over a third of pesticide residues in the soil post harvest, and that this effect can be predicted from the physicochemical properties of the pesticide molecules
Presentation
New scientific article: cover crops as a phytoremediation tool against pesticide residues
We are pleased to share the publication of our article “Living cover crops alter the fate of pesticide residues in soil: influence of pesticide physicochemical properties”, published in SOIL.
Pesticide residues that persist in soil after harvest represent a major source of diffuse contamination of groundwater, a risk that is highest during autumn and early winter, when rainfall is highest and crop uptake of water is minimal. Cover crops, already widely promoted for reducing nitrogen leaching during the fallow period, also stimulate soil microbial activity through their root systems. This raises the question: can they also accelerate the degradation of existing pesticide residues?
To answer this, we conducted a controlled greenhouse experiment in which 18 pesticide ingredients with contrasting physicochemical properties were applied to soil, followed by the establishment of two cover crop types at different densities, compared to bare soil.
Our main findings are:
- Thin cover crops (< 1 tDM ha⁻¹) reduce pesticide leaching by retaining residues in the topsoil, where microbial activity is highest, even before significant degradation can occur.
- Well-developed cover crops (> 1 tDM ha⁻¹) reduce soil pesticide residues by more than 33% for compounds with low to moderate soil mobility (Koc ≥ 160 mL g⁻¹) and low to high water solubility (s ≤ 1 400 mg L⁻¹), likely through enhanced rhizosphere-mediated biodegradation.
- These effects can be linked to key physicochemical properties of the pesticide molecules, providing new quantitative thresholds to predict which compounds are most likely to be affected.
- In Wallonia, 141 authorised active substances (including 30% of those most frequently used between 2015 and 2020) fall within all three identified thresholds, primarily in potato, sugar beet and winter cereal crops.
These results confirm that establishing dense cover crops as early as possible after harvest can play a meaningful role in limiting the transfer of pesticide residues to groundwater, as a complement to (not a substitute for) reducing pesticide use itself.
The article is available in open access at: 10.5194/soil-12-17-2026
