Speakers
Description
Introduction
The development of anaerobic digestion plants associated to agricultural farming systems allow biogas production that benefits farmers and society but raises questions on impacts and ecosystem services provision generated by this development. In literature, many studies have focused on digestate application and fertilising value, in experimental trials; most of them are short-term studies and very few of them take account of the whole cropping system, including crop new sequences that can be associated to anaerobic digestion systems.
In the Metha3G research project, we considered anaerobic digestion as an opportunity to redesign cropping systems and contribute to agro-ecological transition, by reducing environmental impacts and maximizing some ecosystem services provision. Then, to this end, we studied carbon (C) and nitrogen (N) in innovative cropping systems associated to anaerobic digestion systems in commercial farms.
Materials, methods
We selected 10 plots in 3 commercial farms having individual or collective anaerobic digestion systems for 10 to 15 years. We consider these farmers as pioneers as they experiment with combinations of new practices as they go along: shallow or no tillage, anaerobic digestion, cover crop management and diversified cropping systems including legumes.
We measured over 2 years some variables considered as related to ecosystem services such as stocks of soil organic and mineral N, plant N at different dates (especially energy crops), potential mineralisation of soil C and N, enzymatic activity and soil stability. Beyond the assessment of ecosystem services, we acquired the variables related to N dynamics to calibrate and evaluate Syst’N® (Parnaudeau et al 2012, Bedu et al., 2023), a tool for estimating N losses in cropping systems.
Results and discussion
The first results show differences between farms, one of them having particularly high levels of soil C and N and then a high soil stability. The differences were difficult to assign only to practices related to the anaerobic digestion system (digestate management and energy crops), as soil and tillage differ from one farm to another. Nevertheless, we can describe real and consistent cropping systems and their results in terms of impacts and ecosystems services.
The quality of the first simulations with Syst’N® was variable but promising. Some plots were from the outset well simulated with Syst’N®, in terms of soil N mineral dynamics and plant N. Others need calibration especially when there are several species associated on the plot; this work is ongoing. The next step will consist to test different scenarios of cropping system management to identify the best ones.
Acknowledgements
We thank G. Vrignaud (ACE) and A. Haumont (Aile) who provided the contact of the farmers; we thank S. Busnot, F. Gaillard, C. Bouillis, J.M. Busnel for their technical help, and ADEME for its financial support.
References
Bedu M., Lefèvre L., Dupont A., Dubrulle P., Reau R., Debaeke P., Guinet M., Jeuffroy M.-H., Maury P., Schneider A. ... Parnaudeau V. (2023-11). Adding a diversity of legumes to a crop decision-support system: Maintaining satisfactory accuracy while keeping the model simple. European Journal of Agronomy, 151, art. 126999, https://dx.doi.org/10.1016/j.eja.2023.126999, https://hal.inrae.fr/hal-04288580
Parnaudeau V., Reau R., Dubrulle P., 2012. Un outil d'évaluation des fuites d'azote vers l'environnement à l'échelle du système de culture : le logiciel Syst'N. Innovations Agronomiques 21, 59-70.
| Keywords | Anaerobic digestion, innovative cropping systems, nitrogen dynamics, ecosystem services, modeling |
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