Describe soil permeability, factors affecting it, identify soil types by drainage, and explain soil horizons and their importance for crops.

Here are the answers to the questions:

i) Identify the physical property of soil being investigated above. (1 mark)
The physical property being investigated is soil permeability (or drainage rate).

ii) State two factors influencing the above factor. (2 marks)

1. Soil texture (the proportion of sand, silt, and clay particles).
2. Soil structure (the arrangement of soil particles into aggregates).

iii) Identify the soils labelled XYZ. (3 marks)

• X: Sandy soil (or Coarse Sand) - drains fastest.
• Y: Silt soil - drains moderately.
• Z: Clay soil - drains slowest.

c) Using a well-labeled diagram, illustrate a soil profile and explain the importance of ANY TWO horizons in crop production. (3 marks)

A soil profile is a vertical cross-section of the soil, showing its different layers or horizons.

$$\begin{array}{l} \text{O - Organic horizon (humus, leaf litter)} \\ \text{A - Topsoil (dark, rich in organic matter, roots)} \\ \text{B - Subsoil (lighter, accumulation of clay, minerals)} \\ \text{C - Parent material (weathered rock)} \\ \text{R - Bedrock (unweathered rock)} \end{array}$$

• A Horizon (Topsoil): This horizon is crucial for crop production because it is rich in organic matter and nutrients, which are essential for plant growth. It also has the highest concentration of microorganisms and is where most plant roots grow and absorb water and nutrients.
• B Horizon (Subsoil): The subsoil is important for water storage and provides anchorage for deeper roots. It can also contain accumulated nutrients leached from the topsoil, which plants can access.