Cation Exchange Capacity of Acid Forest Humus Layers1
- P. J. Kalisz and
- E. L. Stone2
Cation exchange capacities (CEC's) of acid forest humus layers and mineral soils were measured at the pH of air-dried samples (CEC [field pH]) using a neutral salt procedure. The values obtained were ¼ to ½ those measured by NH4OAc at pH 7 (CEC [pH 7]). Organic matter was the chief source of exchange capacity at all localities studied. CEC (field pH) of mors from the Adirondack Mt. area (pH ≤4.1) and mulls from central New York (pH 4.9–5.4) averaged 52 and 123 meq/100 g OM (organic matter), respectively, as compared with 183 and 236 meq/100 g when determined at pH 7. Base saturation calculated from the lower CEC measured at field pH may range from 15 to 30% for H layers below pH 4, and from 81 to 94% for mull layers at pH 5.4. At one location where the pH of a mor layer varied naturally from 3.2 to 5.6, CEC (field pH) was linearly correlated with pH; CEC increased about 30 meq/100 g OM per pH unit. CEC (field pH) was unrelated to total N over the range 1.6–2.6% N, ash-free. Estimates of total forest floor CEC (field pH) for seven Adirondack and New England localities with mor layers ranged from 10 to 165 keq/ha.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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