Water & Soil
- 1. Water & Soil Assessment Statements E.12.2 State what is meant by the term cation-exchange capacity (CEC) and outline its importance E.12.3 Discuss the effects of soil pH on cation-exchange capacity and availability of nutrients
- 2. E.12.2 Cation-exchange capacity (CEC) is the capacity of a soil for ion exchange of cations between the soil and the soil solution. Cation is a positively charged ion CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect groundwater from cation contamination The two main particles in the soil are clay and humus
- 3. The CEC of the soil is determined by the amount of clay and/or humus that is present. Cation warehouse Nutrient and water holding capacity Sandy soils with very little organic matter have a low CEC Heavy clay soils with high levels of organic matter have a much greater capacity to hold cations.
- 4. E.12.3 Rise in pH = rise in CEC油 Acidic soil will have high concentrations of H+ and Al3+ In neutral to moderately alkaline soils, Ca2+ and Mg2+ will be prevalent Exchangeable cations are available to plants pH can have the following effects: K uptake by plants is limited by high levels of Ca in some soils.油 High levels of K can in turn, limit Mg uptake even if Mg levels in soil are high.