(a) Define the term soil. [2 marks] (b)(i) List the four components of soil. [2 marks] (ii) State the percentage of each component by volume. [2 marks] (c) ...

(a) Definition of soil

Soil is the thin, loose, uppermost layer of the earth crust made up of weathered mineral particles, organic matter, water, air and living organisms, in which plants grow and obtain support and nutrients.

(b)(i) Four components of soil

1. Mineral matter (weathered rock particles).
2. Organic matter (humus).
3. Soil water (soil solution).
4. Soil air.

(b)(ii) Percentage of each component by volume

(c) Making compost by the pit method

(i) Materials

• Plant remains (grasses, crop residues, leaves, weeds), animal dung/droppings, wood ash, top soil, and water; a pit is dug for the process.

(ii) Preparation

• Dig a pit of a suitable size in a well-drained site.
• Spread the first layer of chopped plant materials (about 30 cm) at the bottom.
• Add a layer of animal dung, then a sprinkling of wood ash and a thin layer of top soil.
• Water each set of layers to keep it moist and repeat the layering until the pit is filled above ground level.
• Insert a stick or provide vents to aid aeration, and cover the heap.
• Turn the heap at intervals (about every two to three weeks) to aid decomposition; it is ready in about three to four months when it becomes dark, crumbly and odourless.

(iii) Storage

• The finished compost is removed, kept in a cool, shaded and dry place (or bagged) and protected from rain and sun until it is applied to the farm.