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 .