A supplemental down force system for a ground working implement (10) is provided where the supplemental downforce system groups the row units (16A, ..., 16P) into at least two groups and provides a different supplemental down force (F D ) to the row units (16A, ..., 16P) in each group. This enables the row unit (16A, ..., 16P) to have a supplemental down force (F D ) closer to the desired down force (F D ) recognizing that the row units (16A, ..., 16P) do not all operate in the same conditions. A controller (82) periodically regroups the row units (16A, ..., 16P) into the at least two groups and readjusts the down force (F D ). Futhermore, a ground working implement (10) with such down force system and a method of operating a supplemental down force system is disclosed.
