Small-Grain Cover Crops Have Limited Effect on Neonicotinoid Contamination from Seed Coatings

Area of Science:

• Agricultural Science
• Environmental Science
• Ecotoxicology

Background:

• Neonicotinoids from insecticidal seed coatings contaminate soil, risking non-target organisms and ecosystem health.
• Understanding mitigation strategies for pesticide contamination is crucial for sustainable agriculture.

Purpose of the Study:

• To assess the efficacy of small grain cover crops in mitigating neonicotinoid contamination in agricultural soils.
• To investigate neonicotinoid dissipation and movement in no-till corn-soybean rotations.

Main Methods:

• Field study over three years in a no-till corn-soybean rotation.
• Comparison of plots with and without neonicotinoid seed coatings.
• Inclusion of small grain cover crops in some plots.
• Measurement of neonicotinoid concentrations in soil and cover crops.

Main Results:

• Neonicotinoids were detected in cover crops, but early dissipation limited residue absorption.
• Small grain cover crops did not mitigate neonicotinoid contamination in treated or untreated plots.
• Neonicotinoid residues dissipated rapidly post-planting, remaining below 5 ppb, but persisted due to historical and adjacent use.
• Significant interplot movement of neonicotinoids was observed, with higher contamination in less isolated untreated plots.

Conclusions:

• Small grain cover crops are ineffective at mitigating neonicotinoid contamination from seed coatings.
• Neonicotinoid residues persist in soil at low concentrations and exhibit significant local movement.
• Management practices should consider historical pesticide use and plot proximity to minimize contamination risks.