Mechanisms of fixation and release of ammonium in paddy soils after flooding III. Effect of the oxidation state of octahedral Fe on ammonium fixation |
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| Authors: | Heinrich W Scherer Yongsong Zhang |
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| Abstract: | An experiment with two typical paddy soils from China and two clay minerals was conducted to study the effect of reduction of octahedral FeIII on fixation of NH4+ ions. Reduction of octahedral FeIII was achieved by treating soils and clay minerals with dithionite‐citrate‐bicarbonate (DCB) followed by dialyzing the samples under oxygen free conditions. Reduction of FeIII increased the negative charge of interlayers and resulted in a significantly higher ammonium fixation. Close positive correlations were found between the Fe2+ concentration or the ratio of Fe2+/Fe3+ and non‐exchangeable NH4+‐N. Therefore, it is concluded that the reduction of octahedral Fe induced by flooding is one of the important prerequisites for the pronounced ammonium fixation in flooded soils. However, the relation between ΔFe2+ and Δfix‐N was not stoichiometric. |
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| Keywords: | ammonium fixation clay minerals paddy soils octahedral Fe reducing conditions |
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