PLSC204 Chapter Notes - Chapter 9.3: Cation-Exchange Capacity, Soil Ph, Ion
4 Feb 2019
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Soils resist change in ph of soil solution - called buffering. Obtained by monitoring ph of solution as an acid or base is added in small increments. Soils most highly buffered when al compounds (low ph) and carbonates (high ph) are controlling buffer reactions. Buffered the worst at intermediate ph levels when h+ ions dissociation and cation exchange are primary buffer mechanisms. Ph levels 5-7 buffering can be explained in terms of equilibrium that exists among three principal pools of soil acidity. If enough base is applied to neutralize h+ ions - they are replenished through reactions minimizing change in soil solution ph. Due to involvement of residual and exchangeable acidity, we can see that soils with higher clay and om contents are likely to be better buffered in this ph range. Hydrolysis at of al at very low ph levels. Reactions with om at moderate ph levels. Dissociation of h+ ions from ph dependent change sites on certain days.
