Soil

Soil and water

Soil and water is how water sits in the soil and how irrigation gives a crop a drink without wasting the water or drowning the roots.

CAPS

Grade 11 · 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 “more water is always better”, which kills roots by filling the pores.

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 vegetable plot in a dry district. Furrow irrigation is cheap and wets the path as well as the crop, and the leaves stay wet enough for fungus. Drip on the same plot wets the root zone, leaves the leaf dry, and uses less water from a municipal trickle. The soil type decides the schedule: sand needs smaller, more frequent drinks because it does not store water; clay needs a slower drink or it puddles. The theory is the pore space, not the brand of pipe.

More worked examples

Sand bed and clay bed
A sandy bed watered on Monday is dry again by Wednesday. The pores are large and the water left. It needs a smaller drink more often. A clay bed watered the same way is still wet on Wednesday and the roots sit without air. It needs a slower, rarer drink. Drip on both beds beats a furrow, because the path between rows stays dry. Furrow on the clay bed is how you drown the crop you meant to save.
A white crust in a hot valley
A farmer in a hot valley irrigates and does not drain. Water evaporates. Salts stay. A white crust forms and the crop wilts even though the soil looks damp, because the roots cannot pull water out of a salty solution. More water without a way out makes it worse. Drainage, and sometimes a leaching irrigation that can leave the field, is the repair. The wilt looked like drought. The crust said salt.

In ordinary words

Soil holds water as a film on particles and in the pores. Too much water pushes the air out and roots suffocate. Too little and the plant wilts. Irrigation methods differ. Flood and furrow cover the surface and can waterlog and salt the soil. Sprinklers imitate rain and lose water to wind. Drip puts water at the root and wastes less. A centre pivot is a moving sprinkler for a large circle. Drainage has to be planned with the irrigation, or salts build up.

In South Africa

A bucket, a sprinkler and a drip line on three beds is the whole comparison.

Part 1 / 4

What it is

Soil and water is how water sits in the soil and how irrigation gives a crop a drink without wasting the water or drowning the roots.

Diagram

Soil erosion control on a farm — Diagram

Diagram

More worked examples

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

Example 1 / 20

A field of 2 ha needs 25 mm of irrigation. Calculate the volume of water needed in m³.

4. Step-by-step working

01
Convert units
2 ha=20 000 m²; 25 mm=0,025 m.
02
Multiply
20 000×0,025=500 m³.

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 field of 2 ha needs 25 mm of irrigation. Calculate the volume of water needed in m³.

Before any working — hunt first

Given

Numbers and units already in the sentence: 2 ha · 25 mm. Copy each one into a column. A name without a number is not given.

Missing

After you copy the given, the letter that still has no number is missing. The paper is pointing at: the volume of water needed in m³. Circle that word — that is the missing variable.

Find

We are required to find: the volume of water needed in m³. Write that as a symbol on the left, with a question mark, before you touch a formula.

Calculate

What we need to calculate: 1 mm on 1 ha = 10 m³. Then substitute the given, one line at a time, to get the volume of water needed in m³.

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

If you have never seen this before: 1 mm on 1 ha = 10 m³. 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?

2 ha; 25 mm.

3. Which method — and why this one?

1 mm on 1 ha=10 m³.

4. Step-by-step working

01 / 05
Convert units
2 ha=20 000 m²; 25 mm=0,025 m.
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
Multiply
20 000×0,025=500 m³.
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
500 m³ (500 000 ℓ).
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

500 m³ (500 000 ℓ).

Copy onto your answer sheet — in this order

Answer: 500 m³ (500 000 ℓ).

6. Check it like a marker

1 mm×1 ha=10 m³→25×2×10=500 ✓

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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Plant reproduction

Agricultural Sciences

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