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Water & Soil
Water & Soil
Water & Soil
Water & Soil
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Water & Soil

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Not free from errors, as student contributions

Not free from errors, as student contributions

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  • 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 <ul><li>Cation-exchange capacity (CEC) is the capacity of a soil for ion exchange of cations between the soil and the soil solution. </li></ul><ul><ul><li>Cation is a positively charged ion </li></ul></ul><ul><li>CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect groundwater from cation contamination </li></ul><ul><li>The two main particles in the soil are clay and humus </li></ul>
  • 3. … <ul><li>The CEC of the soil is determined by the amount of clay and/or humus that is present. </li></ul><ul><ul><li>Cation ‘warehouse’ </li></ul></ul><ul><ul><li>Nutrient and water holding capacity </li></ul></ul><ul><li>Sandy soils with very little organic matter have a low CEC </li></ul><ul><li>Heavy clay soils with high levels of organic matter have a much greater capacity to hold cations. </li></ul>
  • 4. E.12.3 <ul><li>Rise in pH = rise in CEC  </li></ul><ul><li>Acidic soil will have high concentrations of H+ and Al3+ </li></ul><ul><li>In neutral to moderately alkaline soils, Ca2+ and Mg2+ will be prevalent </li></ul><ul><li>Exchangeable cations are available to plants </li></ul><ul><li>pH can have the following effects: </li></ul><ul><ul><li>K uptake by plants is limited by high levels of Ca in some soils.  </li></ul></ul><ul><ul><li>High levels of K can in turn, limit Mg uptake even if Mg levels in soil are high. </li></ul></ul>

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