An agricultural implement system is provided that includes a down force cylinder configured to apply a downward force to a row unit, and a depth control cylinder configured to vary a penetration depth of a ground engaging tool of the row unit. The agricultural implement system also includes a valve assembly in fluid communication with the down force cylinder and the depth control cylinder. The valve assembly is configured to automatically adjust the downward force by varying fluid pressure within the down force cylinder based on fluid pressure within the depth control cylinder.