An improved method of monitoring penetration of a planting unit into a ground surface comprising engaging a planting unit with a ground surface wherein the planting unit has a planting unit frame and the planting unit frame is cooperatively engaged with a support member by a planting frame and wherein the planting unit comprises, a seed trench opening assembly operable to create a seed trench in a ground surface, a depth regulating member having a vertical position relative to the seed trench opening assembly and monitoring penetration of the furrow forming structure into the ground surface.