Inclusion of pesticides using natural clays will add value to seed coating strategies.

The fungicides fludioxonil and metalaxyl were adsorbed on natural Spanish clays.

Metalaxyl, more polar, was always more strongly retained by the clays.

Clay granulometry and organic carbon content were relevant in fungicide adsorption.

Metalaxyl release from clays, at 10 and 20 °C, was stable up to 6 months.