POLYCARBOXVLIC ACIDS EXTRACTED BY WATER AND BY ALKALI FROM AGRICULATURAL TOP SOILS OF DIFFERENT DRAINAGE STATUS |
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Authors: | D.J. LINEHAN |
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Affiliation: | (The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, AB9 2QJ) |
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Abstract: | Water-ex tractable poly carboxy lie acids and alkali-extractable humic acids and fulvic acids, were isolated from agricultural top-soils of two soil associations. Samples from four soil series from each association were selected with drainage status varying from well-drained to very poorly-drained. The amounts of atkali-extractable humic acid and water-ex tractable polycarboxylic acids were highest in the very poorly-drained soils whilst the amounts of alkali-extractable fulvic acid were generally similar in all the soils, although the fulvic acid accounted for a lower proportion of the total organic matter in the poorly-drained soils. Oxalate-extractable aluminium decreased with increased drainage impedance, whilst no such trend was observed for oxalate-extractable iron. It is suggested that the fulvic acid-like polycarboxylic acids are removed from the soil solution by adsorption onto sesquioxides; so that the lower content of aluminium oxides in the very poorly-drained soils results in depressed levels of fulvic acid and increased concentrations of water-extractable polycarboxylic acids. |
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