Abstract: A device is provided for diffusing volatile treatment products into the soil. The device includes a mount frame. Pumps are provided on the mount frame for pumping the products contained in storage compartments. Feeding circuits are arranged with the pumps and connect the storage compartments to a manifold. A diffusing tube is formed on a coulter of a tractor and is connected to the outlet of the manifold to diffuse in the soil a gas stream derived from the reaction of the treatment products when the coulter is introduced into the soil.