Preprints
https://doi.org/10.5194/egusphere-2025-3232
https://doi.org/10.5194/egusphere-2025-3232
28 Jul 2025
 | 28 Jul 2025
Status: this preprint is open for discussion and under review for Biogeosciences (BG).

Increased soil CO2 emissions after basalt amendment were partly offset by biochar addition in an urban field experiment

Arthur Vienne, Jennifer Newell, Jasper Roussard, Rory Doherty, Siobhan F. Cox, Gary Lyons, and Sara Vicca

Abstract. Enhanced weathering (EW) and biochar amendment are proposed carbon dioxide removal (CDR) techniques with potential co-benefits for soil health and plant productivity. However, knowledge gaps remain regarding their impacts on soil carbon dynamics and heavy metal mobility. This study investigates the effects of basalt and biochar amendments on soil CO2 efflux (SCE), soil base cation dynamics, biomass yield and heavy metal uptake in clover (Trifolium pratense) and mustard (Brassica juncea) field plots. Despite potential CO2 uptake through weathering, we found that basalt increased SCE in both crops, suggesting increases in soil organic matter (SOM) decomposition and/or rhizosphere respiration. Biochar enhanced plant biomass and reduced plant uptake of several trace metals in both mustard and clover plants, while basalt did not affect any of the 33 assessed elements in aboveground plant biomass. While basalt alone increased CO2 efflux, co-application with biochar tempered this response, potentially mitigating a basalt-induced priming of soil organic matter decomposition. Hence co-application of biochar with basalt countered the basalt-induced rise in soil CO2 emissions, while biochar also reduced plant trace metal uptake, highlighting biochar’s potential to mitigate both environmental and food safety risks.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Biogeosciences.

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 paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Arthur Vienne, Jennifer Newell, Jasper Roussard, Rory Doherty, Siobhan F. Cox, Gary Lyons, and Sara Vicca

Status: open (until 11 Sep 2025)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-3232', Anonymous Referee #1, 18 Aug 2025 reply
  • RC2: 'Comment on egusphere-2025-3232', Anonymous Referee #2, 29 Aug 2025 reply
Arthur Vienne, Jennifer Newell, Jasper Roussard, Rory Doherty, Siobhan F. Cox, Gary Lyons, and Sara Vicca

Data sets

datasets for the basalt-biochar experiment Arthur Vienne https://zenodo.org/records/15001309

Model code and software

R scripts for data analyses Arthur Vienne https://zenodo.org/records/15001309

Arthur Vienne, Jennifer Newell, Jasper Roussard, Rory Doherty, Siobhan F. Cox, Gary Lyons, and Sara Vicca

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Short summary
This study explored how adding crushed basalt and biochar to soil affects plant growth, soil carbon emissions, and plant trace metal uptake. While basalt alone increased carbon dioxide release from soil, combining it with biochar reduced this effect. Biochar also boosted plant growth and lowered the amount of trace metals taken up by crops. These findings suggest that using biochar with basalt may improve soil health and help manage environmental risks.
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