Preprints
https://doi.org/10.5194/egusphere-2023-2221
https://doi.org/10.5194/egusphere-2023-2221
07 Nov 2023
 | 07 Nov 2023

The six rights of how and when to test for soil C saturation

Johan Six, Sebastian Doetterl, Moritz Laub, Claude Raoul Müller, and Marijn Van de Broek

Abstract. The concept of soil organic carbon (SOC) saturation emerged a bit more than 2 decades ago as our mechanistic understanding of SOC stabilization increased. Recently, the further testing of the concept across a wide range of soil types and environments has led some people to challenge the fundamentals of soil C saturation. Here, we argue that to test the concept, one should pay attention to 6 fundamental principles or rights (R’s): the right measures, the right units, the right fractionation method, the right soil type, the right mineralogy, the right saturation level. Once we take care of those 6 rights across studies, we find a maximum of C stabilized by minerals and estimate based on current data available that this maximum stabilization is around 82 ± 4 g C kg-1 silt+clay for 2:1 clay dominated soils while most likely only around 46 ± 4 g C kg-1 silt+clay for 1:1 clay dominated soils. These estimates can be further improved using more data, especially for different mineralogies across varying environmental conditions. However, the bigger challenge is on how and which C sequestration strategies to implement in order to effectively reach this 82/46 g C kg-1 silt+clay in soils across the globe.

In recent years, several studies (e.g., Begill et al. 2023; Salonen et al. 2023) have questioned the concept of soil carbon (C) saturation, i.e., organic C stabilized by soil minerals (Hassink, 1997; Six et al. 2002). Here, we want to draw attention to six fundamentals that we think one should be cognizant about when “testing” and “questioning” soil C saturation.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.

Journal article(s) based on this preprint

15 Apr 2024
| SOIL Letters
| Highlight paper
The six rights of how and when to test for soil C saturation
Johan Six, Sebastian Doetterl, Moritz Laub, Claude R. Müller, and Marijn Van de Broek
SOIL, 10, 275–279, https://doi.org/10.5194/soil-10-275-2024,https://doi.org/10.5194/soil-10-275-2024, 2024
Short summary Executive editor
Johan Six, Sebastian Doetterl, Moritz Laub, Claude Raoul Müller, and Marijn Van de Broek

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2023-2221', Peter Fiener, 07 Nov 2023
    • CC2: 'Reply on CC1', Johan Six, 08 Nov 2023
  • RC1: 'Comment on egusphere-2023-2221', Anonymous Referee #1, 01 Dec 2023
    • AC1: 'Reply on RC1', Johan Six, 02 Feb 2024
  • RC2: 'Comment on egusphere-2023-2221', Anonymous Referee #2, 22 Dec 2023
    • AC2: 'Reply on RC2', Johan Six, 02 Feb 2024

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2023-2221', Peter Fiener, 07 Nov 2023
    • CC2: 'Reply on CC1', Johan Six, 08 Nov 2023
  • RC1: 'Comment on egusphere-2023-2221', Anonymous Referee #1, 01 Dec 2023
    • AC1: 'Reply on RC1', Johan Six, 02 Feb 2024
  • RC2: 'Comment on egusphere-2023-2221', Anonymous Referee #2, 22 Dec 2023
    • AC2: 'Reply on RC2', Johan Six, 02 Feb 2024

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Publish subject to minor revisions (review by editor) (02 Feb 2024) by Bas van Wesemael
AR by Johan Six on behalf of the Authors (12 Feb 2024)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (22 Feb 2024) by Bas van Wesemael
ED: Publish subject to technical corrections (28 Feb 2024) by Jeanette Whitaker (Executive editor)
AR by Johan Six on behalf of the Authors (05 Mar 2024)  Author's response   Manuscript 

Journal article(s) based on this preprint

15 Apr 2024
| SOIL Letters
| Highlight paper
The six rights of how and when to test for soil C saturation
Johan Six, Sebastian Doetterl, Moritz Laub, Claude R. Müller, and Marijn Van de Broek
SOIL, 10, 275–279, https://doi.org/10.5194/soil-10-275-2024,https://doi.org/10.5194/soil-10-275-2024, 2024
Short summary Executive editor
Johan Six, Sebastian Doetterl, Moritz Laub, Claude Raoul Müller, and Marijn Van de Broek
Johan Six, Sebastian Doetterl, Moritz Laub, Claude Raoul Müller, and Marijn Van de Broek

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Latest update: 29 Aug 2024
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

This manuscript is published as SOIL Letters publication as it provides a timely and important contribution, formulating six fundamental principles for the robust study of soil carbon saturation. This is an important topic in research on soil carbon and its role in climate change mitigation which should be of interest to the wider geoscience community.
Short summary
The sequestration of carbon (C) in soils is seen as a potential mitigation strategy. However, more than 2 decades ago the concept of soil C saturation, which puts a limit to how much C can be stabilized in a soil, emerged. Recently, this concept has been challenged in some studies. Here, we argue that if one pays attention to six fundamental principles when testing for soil C saturation, that the concept is robust and there is effectively a maximum to how much C soil minerals can stabilize.