Provided is a seed treatment method, using a composition that may be obtained extemporaneously by mixing at least one powder substance and an aqueous medium. The seed treatment method may include producing the mixture in an automatic and cyclic manner, in at least one first vessel, by introducing into same first at least a portion of the aqueous medium and next the powder substance, the latter being sucked into the aqueous medium in the vessel by a vacuum created in the vessel, at least partially draining the content of the vessel, by at least one blast of compressed gas in the vessel, to a seed treatment device where the mixture may be brought into contact with the seeds.