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Subjects · Leaving Cert Agricultural Science

Leaving Cert Agricultural Science: Soil pH, liming & CEC

How often Soil pH, liming & CEC comes up on the Agricultural Science papers, every year it was asked, and questions to try.

HL Asked on 3 of the last 5 Higher Level papers, most recently in 2025. most years

OL Asked on 4 of the last 5 Ordinary Level papers, most recently in 2025. most years

Soil pH, liming & CEC, Higher Level(8 marks)

Quick ones on Soil pH, liming & CEC.

(a)Which material is most commonly spread to raise the pH of acid Irish soils?
  1. Sulfur
  2. Ground limestone
  3. Peat moss
(b)What does cation exchange capacity (CEC) measure?
  1. The rate water drains through soil
  2. The soil's ability to hold nitrate
  3. The soil's ability to hold positive ions
(c)Which soil would have the highest CEC?
  1. A clay soil rich in humus
  2. A gravelly soil
  3. A coarse sandy soil
Show the answers

(a) Ground limestone

(b) The soil's ability to hold positive ions

(c) A clay soil rich in humus

Your turn: Higher Level questions on Soil pH, liming & CEC.

Higher Level

Asked on 3 of the last 5 Higher Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2025Q9a, Q9b
2024Not asked
2023Q3, Q15
2022Not asked
2021Q17

Links open the State Examinations Commission’s paper for that year.

Ordinary Level

Asked on 4 of the last 5 Ordinary Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2025Q13, Q17
2024Not asked
2023Q1
2022Q3
2021Q16c

Links open the State Examinations Commission’s paper for that year.

More Soil pH, liming & CEC questions

Soil pH, liming & CEC, 2 marks

What is spread to raise the pH of an acidic soil?

  1. Sulphur
  2. Peat moss
  3. Ground limestone
Show the answer

Ground limestone

Ground limestone is calcium carbonate. It neutralises acidity, frees up nutrients like phosphorus and helps clover and earthworms.

Soil pH, liming & CEC, 2 marks

The target soil pH for grassland in Ireland is about?

  1. 8.5
  2. 6.3
  3. 4.0
Show the answer

6.3

Teagasc advises about pH 6.3 for grass and a little higher for clover and cereals. Below this, nutrients like phosphorus get locked up.

Soil pH, liming & CEC, 3 marks

In the soil pH test, why is barium sulphate added to the test tube?

  1. It makes clay settle so the colour is clear
  2. It raises the pH of the soil to neutral
  3. It kills the soil bacteria in the sample
Show the answer

It makes clay settle so the colour is clear

Barium sulphate flocculates the clay so it sinks. The liquid clears, and the colour of the universal indicator can be matched to the chart.

Other Agricultural Science topics

All of Leaving Cert Agricultural Science