# Cover crops do not increase C sequestration in production crops: evidence from 12 years of continuous measurements

Pauline Buysse, Bernard Bodson, Alain Debacq, Anne de Ligne, Bernard Heinesch, T. Manise, Christine Moureaux, Marc Aubinet

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## ► To cite this version:

Pauline Buysse, Bernard Bodson, Alain Debacq, Anne de Ligne, Bernard Heinesch, et al.. Cover crops do not increase C sequestration in production crops: evidence from 12 years of continuous measurements. EGU 2017. European Geophysical Union General Assembly 2017, Apr 2017, Vienne, Austria., 2017. hal-02735435

HAL Id: hal-02735435

https://hal.inrae.fr/hal-02735435

Submitted on 2 Jun 2020

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# Cover crops do not increase C sequestration in production crops: evidence from 12 years of continuous measurements

Pauline Buysse (1,2), Bernard Bodson (3), Alain Debacq (2), Anne De Ligne (2), Bernard Heinesch (2), Tanguy Manise (3), Christine Moureaux (2), and Marc Aubinet (2)

(1) INRA-AgroParisTech, Université Paris Saclay, UMR ECOSYS, Thiverval-Grignon, France (pauline.buysse@inra.fr), (2) University of Liège - Gembloux Agro-Bio Tech, TERRA, Ecosystems-Atmosphere Exchanges, Gembloux, Belgium, (3) University of Liège - Gembloux Agro-Bio Tech, TERRA, Crop Science, Gembloux, Belgium

The numerous reports on carbon (C) loss from cropland soils have recently raised awareness on the climate change mitigation potential of these ecosystems, and on the necessity to improve C sequestration in these soils. Among the multiple solutions that are proposed, several field measurement and modelling studies reported that growing cover crops over fall and winter time could appear as an efficient solution. However, while the large majority of these studies are based on SOC stock inventories and very few information exists from the CO₂ flux dynamics perspective. In the present work, we use the results from long-term (12 years) eddy-covariance measurements performed at the Lonzée Terrestrial Observatory (LTO, candidate ICOS site, Belgium) and focus on six intercrop periods managed with (3) and without (3) cover crops after winter wheat main crops, in order to compare their response to environmental factors and to investigate the impact of cover crops on Net Ecosystem Exchange (NEE). Our results showed that cumulated NEE was not significantly affected by the presence of cover crops. Indeed, while larger CO₂ assimilation occurred during cover crop growth, this carbon gain was later lost by larger respiration rates due to larger crop residue amounts brought to the soil. As modelled by a Q10-like relationship, significantly larger R10 values were indeed observed during the three intercrop periods cultivated with cover crops.

These CO₂ flux-based results therefore tend to moderate the generally acknowledged positive impact of cover crops on net C sequestration by croplands. Our results indicate that the effect of growing cover crops on C sequestration could be less important than announced, at least at certain sites.