Abstract: There is disclosed a semi-mountable plough comprising an elongate plough frame having a long forward frame section (1) carrying a plurality of plough bodies (2), a short intermediate section (3) pivotally connected to the rear end of the forward section (1), and a rear frame section (5) pivotally connected at its forward end to the rear of the intermediate section (3), with the plough being of a reversible type and the section (1, 3 and 5) being pivotable relative to each other in a generally horizontal plane to take-up new positions suitable for movement of the plough in a reverse direction. The rear frame section (5) is pivotable about a horizontal pivot (11) so as to follow any unevenness in the ground, and an actuator (12) is coupled with the rear frame section (5) and is operable in a first mode to allow limited pivotal movement of the rear frame section (5) about horizontal pivot (11), and in a second mode to prevent such pivotal movement.