21 Sep 2022
21 Sep 2022
Status: this preprint is currently under review for the journal BG.

Reviews and syntheses: Iron: A driver of nitrogen bioavailability in soils?

Imane Slimani1,2, Xia-Zhu Barker3, Patricia Lazicki4, and William Horwath1 Imane Slimani et al.
  • 1Department of Land, Air and Water Resources, University of California Davis, Davis, CA 95618, USA
  • 2AgroBioSciences Program, Mohammed VI Polytechnic University (UM6P), Hay Moulay Rachid, Ben Guerir 43150, Morocco
  • 3Department of Soil Science, University of Wisconsin-Madison. 1525 Observatory Drive. Madison, WI 53706-1299, USA
  • 4Department of Biosystems Engineering and Soil science. University of Tennessee Knoxville, Tennessee 37996, USA

Abstract. An adequate supply of bioavailable nitrogen (N) is critical to soil microbial communities and plants. Over the last decades, research efforts have rarely considered the importance of reactive iron (Fe) minerals in the processes that produce or consume bioavailable N in soils, compared to other factors such as soil texture, pH, and organic matter (OM). However, Fe is involved in both enzymatic and non-enzymatic reactions that influence the N cycle. More broadly, reactive Fe minerals restrict soil organic matter (SOM) cycling through sorption processes, but also promote SOM decomposition and denitrification in anoxic conditions. By synthesizing available research, we show that Fe plays diverse roles in N bioavailability. Fe affects N bioavailability directly by acting as a sorbent, catalyst, and electron transfer agent, or indirectly by promoting certain soil features, such as aggregate formation and stability, which affect N turnover processes. These roles can lead to different outcomes on N bioavailability, depending on environmental conditions such as soil redox shifts during wet-dry cycles. We provide examples of Fe-N interactions and discuss the possible underlying mechanisms, which can be abiotic or microbially meditated. We also discuss methodological constraints that hinder the development of mechanistic understanding of Fe in controlling N bioavailability and highlight the areas of needed research.

Imane Slimani et al.

Status: open (until 02 Nov 2022)

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Imane Slimani et al.

Imane Slimani et al.


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Short summary
In soils, there is a strong link between nitrogen availability and iron minerals. Indeed, these minerals are an important piece of puzzle of how nitrogen is produced and lost from soil. However, they have multiple outcomes on nitrogen availability depending on soil conditions and properties. For example, iron can limit microbial degradation of nitrogen in aerated soils but has opposing outcomes in non-aerated soils. This paper focuses on the multiple ways iron can affect nitrogen in soils.