Letter | Published:

Oxidation-reduction Potentials and Capillary Activities of Humic Acids

Nature volume 204, page 581 (07 November 1964) | Download Citation



APART from the effects which humic acids have on the physical properties of the soil, such as its structure, permeability and water retention, and through which they influence the growth of plants, it has been shown that humic acids also have a directly stimulating effect on plant growth1–3. In an attempt to trace the cause of this stimulation, Flaig and Otto4 investigated the influence of quinones and other oxidation-reduction systems on the growth of plant roots, and found in many instances a favourable effect. Flaig and Beutelspacher5 found that in an acid environment and in the presence of nitrogen the rH value (redox potential) of humic acids decreased. Proper E0 values of humic acids, however, have not as yet been published and it was therefore considered to be of interest to study the oxidation-reduction humic acid system in greater detail.

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  1. Department of Zoology, Makerere University College, Kampala, Uganda.

    • S. A. VISSER


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