Biasing system for harrows

A method of harrowing a field with a harrow implement comprising a tool bar mounted on wheels for travel along a ground surface in an operating travel direction that is perpendicular to a longitudinal axis of the tool bar, and a plurality of harrow sections movably mounted to the tool bar such that each harrow section extends rearward from the tool bar and is movable up and down with respect to the tool bar independent of adjacent harrow sections, the method comprising:

• providing a plurality of hydraulic cylinders, and connecting each hydraulic cylinder at one end to the tool bar and at an opposite end to a corresponding harrow section;
• connecting each hydraulic cylinder to an active hydraulic fluid source through a hydraulic control and operating the hydraulic control to supply pressurized hydraulic fluid to each hydraulic cylinder at a substantially constant selected bias pressure such that the hydraulic cylinders exert a substantially constant bias force on the harrow sections, wherein the hydraulic control allows hydraulic fluid to move in and out of the hydraulic cylinders as forces exerted on the harrow sections become greater or less than the bias force;
• activating the hydraulic control to direct pressurized hydraulic fluid into a first port on each hydraulic cylinder to exert a substantially constant selected downward bias force on the plurality of harrow sections, and activating the hydraulic control to direct pressurized hydraulic fluid into a second port on each hydraulic cylinder to exert a substantially constant selected upward bias force on the plurality of harrow sections.