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Research article - Peer-reviewed, 2021

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

Bruni, Elisa; Guenet, Bertrand; Huang, Yuanyuan; Clivot, Hugues; Virto, Inigo; Farina, Roberta; Katterer, Thomas; Ciais, Philippe; Martin, Manuel; Chenu, Claire


The 4 per 1000 initiative aims to maintain and increase soil organic carbon (SOC) stocks for soil fertility, food security, and climate change adaptation and mitigation. One way to enhance SOC stocks is to increase carbon (C) inputs to the soil.In this study, we assessed the amount of organic C inputs that are necessary to reach a target of SOC stocks increase by 4 parts per thousand yr(-1) on average, for 30 years, at 14 long-term agricultural sites in Europe. We used the Century model to simulate SOC stocks and assessed the required level of additional C inputs to reach the 4 per 1000 target at these sites. Then, we analyzed how this would change under future scenarios of temperature increase. Initial stocks were simulated assuming steady state. We compared modeled C inputs to different treatments of additional C used on the experimental sites (exogenous organic matter addition and one treatment with different crop rotations). The model was calibrated to fit the control plots, i.e. conventional management without additional C inputs from exogenous organic matter or changes in crop rotations, and was able to reproduce the SOC stock dynamics.We found that, on average among the selected experimental sites, annual C inputs will have to increase by 43.15 +/- 5.05 %, which is 0.66 +/- 0.23 Mg C ha(-1) yr(-1) (mean +/- standard error), with respect to the initial C inputs in the control treatment. The simulated amount of C input required to reach the 4 %0 SOC increase was lower than or similar to the amount of C input actually used in the majority of the additional C input treatments of the long-term experiments. However, Century might be overestimating the effect of additional C inputs on SOC stocks. At the experimental sites, we found that treatments with additional C inputs were increasing by 0.25 % on average. This means that the C inputs required to reach the 4 per 1000 target might actually be much higher. Furthermore, we estimated that annual C inputs will have to increase even more due to climate warming, that is 54 % more and 120 % more for a 1 and 5 degrees C warming, respectively. We showed that modeled C inputs required to reach the target depended linearly on the initial SOC stocks, raising concern on the feasibility of the 4 per 1000 objective in soils with a higher potential contribution to C sequestration, that is soils with high SOC stocks. Our work highlights the challenge of increasing SOC stocks at a large scale and in a future with a warmer climate.

Published in

2021, volume: 18, number: 13, pages: 3981-4004

Authors' information

Bruni, Elisa
Universite Paris Saclay
Guenet, Bertrand
Ecole Normale Superieure (ENS)
Huang, Yuanyuan
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Clivot, Hugues
Universite de Lorraine
Virto, Inigo
Universidad Publica de Navarra
Farina, Roberta
Consiglio per la Ricerca in Agricoltura e L'analisi Dell'economia Agraria (CREA)
Swedish University of Agricultural Sciences, Department of Ecology
Ciais, Philippe
Universite Paris Saclay
Martin, Manuel
Chenu, Claire
Universite Paris Saclay

Sustainable Development Goals

SDG13 Take urgent action to combat climate change and its impacts

UKÄ Subject classification

Soil Science
Environmental Sciences

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