Soil

Soil science

Soil is a living layer with horizons, a texture, and a limit to how much abuse it can take before the crop fails.

CAPS

Grade 10 · Agricultural Sciences · Soil

Agricultural Sciences splits animals from plants, soil and management.

The papers
Paper 1 is animal nutrition, animal production, reproduction and protection. Paper 2 is soil science, plant studies, and agricultural management. Each paper is 150 marks.
How to write it
Use the farming term, then the reason: a deficient mineral, a symptom, a management practice, and why it changes the yield or the health of the animal. A list with no cause does not explain.
How a marker reads it
A common mix-up is to call any dark soil fertile, or to think clay is always better because it holds water.

Data-response questions want you to read the table first. A general paragraph about farming that ignores the numbers scores as if you did not see them.

Diagram

Worked theory

Worked theory. A handful from a landsand a handful from a cattle path. The land, if it is loam and still has the dark top horizon, holds moisture and crumbles. The path is capped, pale, and hard, because the topsoil has gone and hooves have sealed what remains. A donga is that loss cut deep enough to see the horizons in the wall. Planting on the donga floor without stopping the water that cut it simply feeds the donga. The theory is the horizon you are trying to keep.

More worked examples

A jar of soil and a donga wall
Shake soil in a jar of water and let it settle. Sand drops in a minute. Silt takes longer. Clay is still cloudy the next morning. A loam leaves a mixed layer, not a jar of pure sand. In a donga wall you can see the dark top horizon thinning toward the gully and gone at the edge. The jar tells you the texture you still have. The wall tells you the horizon you have already lost.
Lime on an acid land
A soil test reads pH 4.8. Maize on that land germinates poorly and the leaves look unhappy even when water is there. The farmer spreads agricultural lime. Lime does not feed the plant the way nitrogen does. It raises the pH so nutrients already in the soil become usable and aluminium is less toxic. Spreading more fertiliser on the same acid soil wastes the bag. The pH was the lock.

In ordinary words

A profile shows horizons: organic litter on top, a darker topsoil mixed by roots and organisms, a subsoil, and parent material below. Texture is the share of sand, silt and clay. Sand drains fast and holds little water or nutrient. Clay holds water and nutrients but can waterlog. Loam is the workable mixture. Erosion is the loss of that topsoil to wind or water. Cover, contours and fewer animals per hectare slow it.

In South Africa

A soil pit on the school farm, or a donga wall, shows the horizons in order.

Part 1 / 4

What it is

Soil is a living layer with horizons, a texture, and a limit to how much abuse it can take before the crop fails.

More worked examples

Board walkthroughs on this topic. Open one, copy the working, then try the next.

Example 1 / 20

A soil sample has 40% sand, 40% silt and 20% clay. Name the texture class and describe its properties.

How we got there

Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.

Explain in another language · 11

1. What is the question asking?

Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: A soil sample has 40% sand, 40% silt and 20% clay. Name the texture class and describe its properties.

In other words — as if you have never seen this before

If you have never seen this before: This mixture is a loam. We will name a method in words, write the formula with no numbers, then substitute one line at a time.

2. What do we already know?

40 : 40 : 20.

3. Which method — and why this one?

This mixture is a loam.

4. Step-by-step working

01 / 05
Identify the given
Loam.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
02 / 05
Explain
Good drainage and aeration from sand, plus water and nutrient holding from silt and clay — ideal for most crops.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
03 / 05
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
04 / 05
Step F — Box the answer with its unit
Loam — balanced drainage and water holding.
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
05 / 05
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.

5. The answer

Loam — balanced drainage and water holding.

Copy onto your answer sheet — in this order

Answer: Loam — balanced drainage and water holding.

6. Check it like a marker

Check: 40+40+20=100%.

7. A trap first-timers fall into

First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”

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