Layer (from bottom) Particle type Depth of layer (mm) 1 Sand 36 2 Silt 24 3 Clay (suspended) 20 4 Table 4.1 shows the results of a sedimentation test carrie...

(a) Why the soil sample was shaken with water [1]

Shaking separates the different-sized particles from each other by breaking up soil aggregates (clumps). [1] This allows each particle type to settle individually according to its size and weight when the cylinder is left undisturbed.

(b) Particle that settled first, and why [2]

Sand settled at the bottom of the cylinder first. [1] Sand particles are the largest and heaviest of the three mineral fractions, so they sink through the water most rapidly under gravity. Silt settles next (medium-sized), and clay particles, being the smallest and lightest, remain suspended longest and settle last at the top. [1]

(c) Textural class of the soil (45% sand, 30% silt, 25% clay) [1]

Loam (loamy soil). [1] A loam contains a relatively balanced proportion of sand, silt, and clay, without any single fraction dominating to the point where it controls all the soil's properties.

(d) Why loam is good for growing vegetables [3]

Any three of:

1. Loam has good drainage so roots do not become waterlogged, preventing root rot - an important factor for most vegetable crops. [1]
2. It retains enough moisture between waterings for steady plant uptake, reducing the need for constant irrigation. [1]
3. It is easy to cultivate and has good tilth - it breaks into a fine, crumbly structure ideal for sowing small vegetable seeds and transplanting seedlings. [1]
4. It holds nutrients reasonably well (moderate cation exchange capacity) so applied fertiliser stays in the root zone.
5. It allows good root penetration, enabling vegetables to develop strong, deep root systems.

(e) Two ways organic matter improves this soil [2]

Any two of:

1. Increases water-holding capacity by acting as a sponge that absorbs and retains moisture. [1]
2. Improves soil structure and aggregation, creating a more stable crumb structure with better aeration. [1]
3. Adds nutrients as the humus decomposes, releasing nitrogen, phosphorus, and other elements slowly.
4. Increases microbial activity, which further breaks down organic residues and cycles nutrients.
5. Improves aeration by creating more pore spaces.