A suspension assembly for an agricultural implement having a carrier frame, an implement support frame pivotally connected to the carrier frame, and a rubber torsion spring having a drive shaft disposed coaxially within a square tubular housing, with an elastic rubber element captured within the housing and the shaft embedded in and adhered to the elastic rubber element. The torsion spring is connected to the implement support frame. An externally threaded screw has an internally threaded member engaged therewith, the screw being connected to the carrier frame. An adjusting arm has a first portion in driving engagement with the drive element, and has a second portion connected to the threaded member. Displacing the threaded member along the screw provides selectable spring force that adjustably biases the implement support frame away from the carrier frame such that an implement connected to the support frame is pressed against the soil with a selected force.
