12 Jan 2021

12 Jan 2021

Review status: a revised version of this preprint is currently under review for the journal BG.

Additional carbon inputs to reach a 4 per 1000 objective in Europe: feasibility and projected impacts of climate change based on Century simulations of long-term arable experiments

Elisa Bruni1, Bertrand Guenet1,2, Yuanyuan Huang3, Hugues Clivot4,5, Iñigo Virto6, Roberta Farina7, Thomas Kätterer8, Philippe Ciais1, Manuel Martin9, and Claire Chenu10 Elisa Bruni et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
  • 2LG-ENS (Laboratoire de géologie) - CNRS UMR 8538 - École normale supérieure, PSL University - IPSL, 2 75005 Paris France
  • 3CSIRO Oceans and Atmosphere, Aspendale 3195, Australia
  • 4Université de Lorraine, INRAE, LAE, 68000, Colmar, France
  • 5Université de Reims Champagne Ardenne, INRAE, FARE, UMR A 614, 51097 Reims, France
  • 6Departamento de Ciencias. IS-FOOD, Universidad Pública de Navarra, 31009 Pamplona, Spain
  • 7CREA - Council for Agricultural Research and Economics, Research Centre for Agriculture and Environment, 00198 Rome, Italy
  • 8Swedish University of Agricultural Sciences, Department of Ecology, Box 7044, 75007 Uppsala, Sweden
  • 9INRA Orléans, InfoSolUnit, Orléans, France
  • 10Ecosys, INRA-AgroParisTech, Université Paris-Saclay, Campus AgroParisTech, 78850 Thiverval-Grignon, France

Abstract. The 4 per 1000 initiative aims to promote better agricultural practices to maintain and increase soil organic carbon stocks for soil fertility, food security and climate change adaptation and mitigation. The most straightforward way to enhance soil organic carbon stocks is to increase carbon inputs to the soil.

In this study, we assessed the amount of organic carbon inputs that are necessary to reach a target of soil organic carbon stocks increase by 4 ‰ per year on average, for 30 years. We used the Century model to simulate soil organic carbon stocks in 14 European long-term agricultural experiments and assessed the required level of carbon inputs increase to reach the 4 per 1000 target. Initial simulated stocks were computed analytically assuming steady state. We compared modelled carbon inputs to different treatments of additional carbon used on the experimental sites (exogenous organic matter addition and one treatment with different crop rotations). We then analyzed how this would change under future scenarios of temperature increase. The model was calibrated to fit the control plot, i.e. conventional management without additional carbon inputs, and was able to reproduce the SOC stocks dynamics.

We found that, on average among the selected experimental sites, annual carbon inputs will have to increase by 43.15 ± 5.05 %, which is 0.66 ± 0.23 MgC ha−1 per year (mean ± standard error), with respect to the control situation. The simulated amount of carbon inputs required to reach the 4 ‰ SOC increase was lower or similar to the amount of carbon inputs actually used in the majority of the additional carbon input treatments of the long-term experiments. However, Century might be overestimating the effect of additional C inputs on the variation of SOC stocks in some sites, since we found that treatments with additional carbon inputs were increasing by 0.25 % on average among the experimental sites.

We showed that the modeled carbon inputs required to reach the target depended linearly on the initial SOC stocks. We estimated that annual carbon inputs would have to increase further due to temperature increase effect on decomposition rates, that is 54 % for a 1 °C warming and 120 % for a 5 °C warming.

Elisa Bruni 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-2020-489', Anonymous Referee #1, 10 Mar 2021
    • AC1: 'Reply on RC1', Elisa Bruni, 14 Apr 2021
  • RC2: 'Comment on bg-2020-489', Anonymous Referee #2, 16 Mar 2021
    • AC2: 'Reply on RC2', Elisa Bruni, 14 Apr 2021
  • RC3: 'Comment on bg-2020-489', Anonymous Referee #3, 20 Mar 2021
    • AC3: 'Reply on RC3', Elisa Bruni, 14 Apr 2021
  • RC4: 'Comment on bg-2020-489', Anonymous Referee #4, 24 Mar 2021
    • AC4: 'Reply on RC4', Elisa Bruni, 14 Apr 2021

Elisa Bruni et al.

Elisa Bruni et al.


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Short summary
Increasing soil organic carbon (SOC) stocks is beneficial for climate change mitigation and food security. One way to enhance SOC stocks is to increase carbon inputs to the soil. We estimated the amount of carbon inputs required to reach a 4 ‰ annual increase of SOC stocks in 14 long-term agricultural experiments around Europe. We found that annual carbon inputs should increase by 43 % under current temperature conditions, by 54 % for a 1 °C warming scenario and by 120 % for a 5 °C warming scenario.