(a) Fig. 1 shows a disc plough being used to prepare land on a large commercial farm. (i) State two advantages of a disc plough compared with a mouldboard p...

Labelled answer diagram:

(a)(i) Two advantages of a disc plough over a mouldboard plough in stony or root-filled soil (any two for [2]):

1. The rotating discs roll over stones and roots instead of jamming or breaking, making the disc plough more durable and less prone to damage in these conditions [1].
2. Disc ploughs require less draught force in hard or dry soils because the discs cut through a rolling action rather than the sliding friction of a mouldboard [1].

Also acceptable: disc ploughs work in sticky clay soils where a mouldboard would clog; they are more durable in abrasive conditions.

(a)(ii) Another primary tillage implement and a suitable situation:

Chisel plough / subsoiler / ripper [1]. This is preferred when the farmer needs to break a hardpan or compacted layer deep in the soil without inverting the topsoil, or in conservation tillage systems where crop residues on the surface should remain undisturbed [1].

(b) Importance of ploughing at the correct depth (3 marks):

1. Ploughing too shallow fails to break up compacted layers below the surface, leaving a barrier that restricts root penetration and water movement downward [1].
2. Ploughing too deep brings infertile subsoil to the surface, diluting the nutrient-rich topsoil layer that crops depend on [1].
3. The correct depth ensures adequate loosening of the soil within the rooting zone for the specific crop while keeping fertile topsoil where roots can access it [1].