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
<p>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.</p> <p>In this study, we asse...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-07-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/18/3981/2021/bg-18-3981-2021.pdf |
| Summary: | <p>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.</p>
<p>In this study, we assessed the amount of organic C inputs that are necessary to reach a target of SOC stocks increase by
4 <span class="inline-formula">‰ yr<sup>−1</sup></span> 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.</p>
<p>We found that, on average among the selected experimental sites, annual C inputs will have to increase by 43.15 <span class="inline-formula">±</span> 5.05 %, which is
0.66 <span class="inline-formula">±</span> 0.23 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">Mg</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">C</mi><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">ha</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">yr</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="71pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="bdd63efbfb3454e80aa8f8ea29d9d672"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-18-3981-2021-ie00001.svg" width="71pt" height="15pt" src="bg-18-3981-2021-ie00001.png"/></svg:svg></span></span> (mean <span class="inline-formula">±</span> standard error), with respect to the initial C inputs in the control treatment. The
simulated amount of C input required to reach the 4 ‰ 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 <span class="inline-formula"><sup>∘</sup>C</span><span id="page3982"/> 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.</p> |
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| ISSN: | 1726-4170 1726-4189 |