Property Site X (steep hillside) Site Y (flat valley) Topsoil depth / cm 12 45 Organic matter content / % 2.8 7.5 pH 5.2 6.4 Soil colour Light brown Dark br...
Question 1 Report
| Property | Site X (steep hillside) | Site Y (flat valley) |
|---|---|---|
| Topsoil depth / cm | 12 | 45 |
| Organic matter content / % | 2.8 | 7.5 |
| pH | 5.2 | 6.4 |
| Soil colour | Light brown | Dark brown |
3 Table 3.1 shows the results of a survey comparing soil properties at two different sites on a farm. Site X is on a steep hillside and Site Y is in a flat river valley.
Table 3.1
(a) State which site has a deeper topsoil layer. [1]
(b) Suggest two reasons why the topsoil at Site Y is deeper than at Site X. [2]
(c) Explain how the movement of water through the soil at Site X could affect the mineral content of the topsoil. [3]
(d) Name the process by which soluble minerals are carried downwards through the soil by water. [1]
Answer Details
(a) Site Y has a deeper topsoil layer, at 45 cm compared to 12 cm at Site X [1].
(b) Two reasons why the topsoil at Site Y is deeper than at Site X:
- Soil eroded from the steep hillside (Site X) is carried downhill by surface runoff and deposited in the flat valley (Site Y), where it accumulates over time [1].
- Less erosion occurs on flat land because water flows more slowly across the surface, so soil particles are not removed as rapidly as they are on the slope [1].
Other acceptable reasons: water drains more slowly on flat land, allowing more weathering and organic matter accumulation.
(c) Water moving through the soil at Site X affects the mineral content of the topsoil in the following way:
- Water percolating through the soil dissolves soluble minerals (such as calcium, magnesium, and potassium) from the topsoil [1].
- These dissolved minerals are carried downwards by the water into the subsoil or lower horizons [1].
- Over time, this process depletes the mineral content and fertility of the topsoil, leaving it nutrient-poor [1].
(d) The process by which soluble minerals are carried downwards through the soil by water is called leaching [1]. Leaching is particularly rapid on slopes where rainfall is high and the soil is well-drained.
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