A packing pressure adjustment assembly for a ground opener unit of an agricultural implement includes a spring interconnected between a rotatable pressure adjustment arm and a trailing arm to which a packer wheel is rotatably mounted. The pressure adjustment arm is centered about an axle of the ground opener unit and is movable between a set of mounting positions that are defined by a set of teeth spaced and arced from one another along a frame portion of the ground opener unit. As the pressure adjustment arm is rotated, the amount of force exerted by the spring on the trailing arm is varied. The packing pressure adjustment assembly is relatively compact and is useful in providing high packing forces, such as a packing force in excess of 100 lbs.