Table 11. The cation and anion exchange capacities of common soil minerals and organic matter. As weathering intensity increases (2:1-->1:1-->oxides/hydroxides), the CEC of clay minerals decreases and the AEC increases. The cation and anion exchange capacities will vary appreciably with soil pH.
| Soil Component | CEC (cmol/kg) | AEC (cmol/kg) |
|---|
| Illite(2:1) | 10-40 | 1 |
|---|
| Smectite (2:1) | 90-120 | 1 |
|---|
| Vermiculite(2:1) | 100-150 | 1 |
|---|
| Kaolinite (1:1) | 3-15 | 3-5 |
|---|
| Oxides/Hydroxides | below 5 | 5 |
|---|
| Organic Matter | 200-400 | 0 |
|---|