1. In addition to clay minerals, what other soil constituents contribute to total CEC?
The Organic Matter present in the soil.
2. How does CEC buffer nutrient concentration in soil solution?
CEC will exchange ions continuously between the solution concentration until both of the concentration has neutralized.
3. Why does anion adsorption appear to be of little importance in most agricultural soils? Why are AECs of ultisols usually greater than those of mollisols?
CEC has a much larger impact for most agricultural soils. AEC occurs on the edges on minerals where positive charges are found.AEC is found particularly in highly weathered soils of the tropics and subtropics. Most agricultural soils have too high a pH for AEC to occur, which increases as pH in soils decreases, especially in the US and Canada. But the AEC in agricultural soil are smaller than CEC so they are repelled by the positive charge on soil. Ultisols have a lower pH than mollisols so AEC occurs more frequently in the ultisols because they occur more abundant in lower soil pH.
4. With what type of soil would the ammonium acetate method provide a good estimate of CEC? On what types would it provide a poor estimate? Explain why.
A soil that has a high base saturation (%BS), pH of 7, a 1:1 clay material, and high Organic Matter (OM). All of these provide a larger number of exchangeable cations available for the soil. Any soil differentiating from these will provide only a lower number exchangeable cations.
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