The presence of rank vegetation or loose crop residue on the soil surface (straw, maize stalks etc.) is always troublesome to ploughs, cultivators, seed drills and other agricultural implements required to slice vertically through and penetrate the soil. In the illustrated embodiment of the invention (FIG. 1), the leading edge area of the knife coulter 10 of a seed drill 14 is continually cleared of trash by resilient disc-mounted cleaning members 16-18. The cleaning members comprise springs which have an outwardly positioned elongated section designed to be engaged by the ground or an abutment on the disc support structure to flex each member as the disc on which they are mounted is rotated. On losing contact with the ground or the abutment, each member will, in turn, spring back from a flexed position (member 16) to a relaxed position (member 17). During this spring back movement, the elongated section moves past or along the leading edge of the knife coulter and strikes trash therefrom.