A) A soil profile is a vertical cross-section of the soil, showing the different layers or horizons from the surface down to the parent material.

a) A soil profile is a vertical cross-section of the soil, showing the different layers or horizons from the surface down to the parent material.

b)

i)

• Horizon O: Organic layer (undecomposed or partially decomposed plant and animal remains).
• Horizon A: Topsoil (mineral soil with accumulated organic matter, dark in color).
• Horizon B: Subsoil (accumulation of clay, iron, and aluminum oxides, less organic matter).
• Horizon C: Parent material (partially weathered rock from which the soil developed).

ii) The horizons are important in crop production because:

• Horizon O provides organic matter that decomposes into humus, enriching the soil with nutrients and improving its structure.
• Horizon A (topsoil) is the most fertile layer, rich in nutrients and microorganisms, where most plant roots grow and absorb water and minerals essential for crop growth.
• Horizon B (subsoil) stores water and some nutrients, providing a reservoir for plant roots during dry periods and offering anchorage.
• Horizon C (parent material) is the source of minerals that become available to the upper horizons as it weathers, contributing to long-term soil fertility.

7. Sheila and Geoffrey may have discussed the following benefits of various soil properties in crop production:

• Good soil texture (e.g., loamy soil) ensures a balance of water retention and drainage, providing adequate moisture and aeration for roots.
• High organic matter content improves soil fertility by releasing nutrients, enhances water-holding capacity, and promotes good soil structure, making it easier for roots to penetrate.
• Appropriate soil pH ensures that essential nutrients are available for plant uptake, as extreme pH levels can lock up nutrients.
• Good soil structure allows for proper aeration, which is vital for root respiration, and facilitates water infiltration, reducing runoff and erosion.
• Adequate drainage prevents waterlogging, which can suffocate roots and lead to crop failure, while sufficient water retention ensures plants have access to moisture.

8. To show that soil has living organisms using the provided materials:
9. Spread the soil sample thinly on the white sheet of paper.
10. Use the stick to gently break apart any large clumps of soil.
11. Carefully observe the soil with your naked eye, then use the hand lens to magnify and examine smaller particles.
12. Look for any movement or visible organisms such as earthworms, insects, mites, or other small invertebrates within the soil sample. The white paper provides a clear contrast to easily spot these organisms.