Articles | Volume 13, issue 19
https://doi.org/10.5194/bg-13-5609-2016
https://doi.org/10.5194/bg-13-5609-2016
Research article
 | 
07 Oct 2016
Research article |  | 07 Oct 2016

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

Xueru Huang, Xia Zhu-Barker, William R. Horwath, Sarwee J. Faeflen, Hongyan Luo, Xiaoping Xin, and Xianjun Jiang

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.

Download
Short summary
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.
Altmetrics
Final-revised paper
Preprint