Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 13, issue 19
Biogeosciences, 13, 5609–5617, 2016
https://doi.org/10.5194/bg-13-5609-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 5609–5617, 2016
https://doi.org/10.5194/bg-13-5609-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 07 Oct 2016

Research article | 07 Oct 2016

Effect of iron oxide on nitrification in two agricultural soils with different pH

Xueru Huang1, Xia Zhu-Barker2, William R. Horwath2, Sarwee J. Faeflen1, Hongyan Luo1, Xiaoping Xin1, and Xianjun Jiang1 Xueru Huang et al.
  • 1College of Resources and Environment, Southwest University, 2 Tiansheng Road, Beibei, 400715 Chongqing, China
  • 2Biogeochemistry and Nutrient Cycling Laboratory, Department of Land, Air and Water Resources, University of California Davis, CA 95616, USA

Abstract. Iron (Fe) affects soil nitrogen (N) cycling processes both in anoxic and oxic environments. The role of Fe in soil N transformations including nitrification, mineralization, and immobilization, is influenced by redox activity, which is regulated by soil pH. The effect of Fe minerals, particularly oxides, on soil N transformation processes depends on soil pH, with Fe oxide often stimulating nitrification activity in the soil with low pH. We conducted lab incubations to investigate the effect of Fe oxide on N transformation rates in two subtropical agricultural soils with low pH (pH 5.1) and high pH (pH 7.8). 15N-labeled ammonium and nitrate were used separately to determine N transformation rates combined with Fe oxide (ferrihydrite) addition. Iron oxide stimulated net nitrification in low-pH soil (pH 5.1), while the opposite occurred in high-pH soil (pH 7.8). Compared to the control, Fe oxide decreased microbial immobilization of inorganic N by 50 % in low-pH soil but increased it by 45 % in high-pH soil. A likely explanation for the effects at low pH is that Fe oxide increased NH3-N availability by stimulating N mineralization and inhibiting N immobilization. These results indicate that Fe oxide plays an important role in soil N transformation processes and the magnitude of the effect of Fe oxide is dependent significantly on soil pH.

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The effect of Fe oxide on N transformation processes were different in soils as a function of pH. 15N-labelled ammonium and nitrate were used separately to determine N transformation rates combined with Fe oxide (ferrihydrite) addition. Iron oxide addition stimulated net nitrification in the low-pH soil (pH 5.1), while the opposite occurred in the high-pH soil (pH 7.8). Fe oxide increased NH3-N availability by stimulating N mineralization and inhibiting N immobilization at low pH.
The effect of Fe oxide on N transformation processes were different in soils as a function of...
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