An agricultural row unit for planting seeds in a furrow, comprising: a frame having (a) a gauge wheel that engages the soil to control the elevation of the frame and (b) an opening device that cuts a furrow in the soil to be planted, a gauge wheel down force control system that includes an actuator applying a controllable down pressure to the gauge wheel to control the depth of the furrow, wherein the agricultural row unit further comprises: a monitoring device for monitoring hardness or compaction of the soil that forms side walls of the furrow, the monitoring device extending into the furrow and into the side walls of the furrow and producing a signal representing the compaction of the soil in the side walls, the monitoring device including two wings (41, 42) that protrude laterally from sides of a bar, a distance between tips of the two wings (41, 42) being longer than a width of the furrow, the two wings (41, 42) being mounted on the bar near its trailing end on opposite sides of a load cell, and a controller supplying the actuator with a control signal representing a down pressure set point to form the furrow having a desired depth, the controller receiving the signal representing the compaction of the soil in the side walls and using the signal in an algorithm to determine whether the down pressure set point should be increased or decreased, and supplying the actuator with the control signal when it is determined that the down pressure set point should be increased or decreased. a frame having (a) a gauge wheel that engages the soil to control the elevation of the frame and (b) an opening device that cuts a furrow in the soil to be planted, a gauge wheel down force control system that includes an actuator applying a controllable down pressure to the gauge wheel to control the depth of the furrow, wherein the agricultural row unit further comprises: a monitoring device for monitoring hardness or compaction of the soil that forms side walls of the furrow, the monitoring device extending into the furrow and into the side walls of the furrow and producing a signal representing the compaction of the soil in the side walls, the monitoring device including two wings (41, 42) that protrude laterally from sides of a bar, a distance between tips of the two wings (41, 42) being longer than a width of the furrow, the two wings (41, 42) being mounted on the bar near its trailing end on opposite sides of a load cell, and a controller supplying the actuator with a control signal representing a down pressure set point to form the furrow having a desired depth, the controller receiving the signal representing the compaction of the soil in the side walls and using the signal in an algorithm to determine whether the down pressure set point should be increased or decreased, and supplying the actuator with the control signal when it is determined that the down pressure set point should be increased or decreased. a monitoring device for monitoring hardness or compaction of the soil that forms side walls of the furrow, the monitoring device extending into the furrow and into the side walls of the furrow and producing a signal representing the compaction of the soil in the side walls, the monitoring device including two wings (41, 42) that protrude laterally from sides of a bar, a distance between tips of the two wings (41, 42) being longer than a width of the furrow, the two wings (41, 42) being mounted on the bar near its trailing end on opposite sides of a load cell, and a controller supplying the actuator with a control signal representing a down pressure set point to form the furrow having a desired depth, the controller receiving the signal representing the compaction of the soil in the side walls and using the signal in an algorithm to determine whether the down pressure set point should be increased or decreased, and supplying the actuator with the control signal when it is determined that the down pressure set point should be increased or decreased.