(a) Explain the following terms: (i) primary tillage implement; (ii) secondary tillage implement. (b) (i) State three reasons why disc ploughs are better su...

(a) Explanation of terms:

• (i) Primary tillage implement: This is a heavy implement used for the first, deep opening and breaking of the soil to loosen and turn it before planting, for example the disc plough or mouldboard plough.
• (ii) Secondary tillage implement: This is a lighter implement used after primary tillage to break the large clods into a fine, level seedbed and to control weeds, for example the harrow, ridger and cultivator.

(b)(i) Three reasons why disc ploughs are better suited to West African soils than mouldboard ploughs:

1. The disc plough rolls over stumps, roots and stones without being damaged, whereas the mouldboard plough would be broken by them.
2. It works well in hard, dry and sticky soils common in the tropics because the rolling disc scours and does not clog easily.
3. It is not easily worn out by the abrasive tropical soils, so it lasts longer and needs less repair.

(b)(ii) Six major parts of a disc plough:

• Disc (concave steel plate)
• Disc bearing / hub
• Standard (frame arm carrying the disc)
• Scraper
• Beam or main frame
• Furrow wheel and hitch (linkage to the tractor)

(c) Three reasons why secondary tillage is necessary before sowing:

1. To break the large clods left by ploughing into a fine tilth suitable for good seed germination.
2. To level the field and make ridges or beds for easy planting and drainage.
3. To destroy weeds and incorporate manure and crop residues into the soil.

(d) Three precautions when spraying chemicals:

1. Wear protective clothing such as overalls, hand gloves, nose mask and goggles.
2. Spray along the direction of the wind (down-wind), not against it, to avoid drift onto the operator.
3. Do not eat, drink or smoke while spraying, and wash the body and equipment thoroughly after use.