LO 4.2 - Cation exchange capacity – definition

Question 1

Question

What is Cation Exchange Capacity (CEC)?

Cation exchange capacity (CEC)

Answer 1

• Cation exchange capacity is the ability of a soil to hold onto nutrients and prevent them being leached. High values indicate a fertile soil.

Cation exchange capacity (CEC)

Question 2

Question

How is CEC expressed?

Cation exchange capacity (CEC)

Answer 2

• CEC is expressed in milligram equivalents (meq) per 100 g of soil.

Cation exchange capacity (CEC)

Question 3

Question

What does the meq figure refer to?

Cation exchange capacity (CEC)

Answer 3

• The meq figure is an estimate of the number of negatively charged sites available to hold cations.

Cation exchange capacity (CEC)

Question 4

Question

Which types of soils have higher CEC?

Cation exchange capacity (CEC)

Answer 4

• Finer textured soils have a higher CEC (review soil texture – clay particles are the finest ones)
• This is partly because of the higher surface area (relative to volume) of smaller particles, and partly because the clay particles have a negative charge.
• Organic matter also has a high CEC.

Cation exchange capacity (CEC)

Question 5

Question

What is important about soils with a high CEC?

Cation exchange capacity (CEC)

Answer 5

Soils with a high CEC provide a nutrient reserve for plant uptake between fertiliser applications.

Cation exchange capacity (CEC)