A planting row unit is attachable to a towing frame and is movable in a forward direction on a field having soil of varying hardness conditions. The planting row unit includes an opener device forward of the towing frame for preparing the soil for receiving at least one of the fertilizer and the seeds. The opener device includes a soil-hardness sensor for detecting changes in soil-hardness conditions and an opener blade for maintaining, in response to the changes, a constant soil-penetration depth Z in the soil independent of the varying hardness conditions. A modular actuator is mounted to the opener device for applying pressure to the opener blade, the modular actuator being mountable to at least one other component of the planting row unit for applying pressure.
