An agricultural implement (100) is disclosed. The agricultural implement (100) is adapted to be moved by a vehicle, the agricultural implement (100) comprising: a plurality of ground-engaging tools； a plurality of wheels (110)； a sensor (122) configured to provide a signal indicative of a rotational speed of at least one of the ground-engaging tools； and a controller (132) configured to determine a ground speed of the agricultural implement (100), characterized in that the controller (132) is further configured to: calculate a ratio of the rotational speed to the ground speed； compare the ratio to a threshold ratio； and send an alert signal if the ratio is below the threshold ratio and/or determine a threshold rotational speed by multiplying the threshold ratio by the ground speed； compare that threshold rotational speed with the actual rotational speed from first speed sensor (122)； and send an alert signal if the actual rotational speed is below that threshold rotational speed.
