21 Sep 2022
 | 21 Sep 2022
Status: a revised version of this preprint is currently under review for the journal BG.

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

Imane Slimani, Xia-Zhu Barker, Patricia Lazicki, and William Horwath

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: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-194', Anonymous Referee #1, 26 Oct 2022
  • RC2: 'Comment on bg-2022-194', Anonymous Referee #2, 23 Jan 2023

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.