ECOSYS contributes to the optimization of recycling practices of organic waste products (OWPs) applied to valorize the nutrients they contain, stimulate soil biological activity and increase carbon storage in soils, while addressing the reduced negative impacts related to their use (contaminants, pathogens). The approaches developed range from controlled process studies to observations and experiments in open-field conditions. The SOERE-PRO constitutes a key device that is widely shared in the unit and over as experimental support for long-term observations. The return of OWPs to soil is an agronomic practice that influences several other service axes: (1) the biological activity of soils and their structural and functional biodiversity; (2) the environmental quality of agroecosystems and the soil filtering function, since OWPs can be sources of contaminants (organic and mineral contaminants, GHGs, VOCs, dust and particles) or modify the fate of contaminants present in the soil; and (3) the substitution of fertilizers as alternative sources of nitrogen and phosphorus. Finally, optimizing the distribution of OWPs within a regional territory is an excellent example of a problem requiring an integrated territorial assessment.
The objectives of this axis were as follows:
- Take into account the interconnection of biogeochemical cycles involving OWPs to assess their use as alternative sources of nutrients for crops, their capacity to promote the carbon storage in soils and to reduce GHG (N2O) and other contaminant gasses (NH3, VOC).
- Identify the factors that explain the variability of behavior for different OWPs in terms of recycling practices and pedoclimatic conditions.
- Measure and predict effects on soil properties (structural stability, water balance, biological activity, resistance to telluric plant diseases) and on the transfer and potential impacts of associated contaminants.
- Conduct global assessments of recycling practices at local (parcel, exploitation) and territorial scales (small agricultural peri-urban regions).
The highlights achievements were as follows:
➢ Actions carried out within contractual projects, such as the insertion of OWPs in cropping systems, taking into account their fertilization effects (ISARD and PROLEG projects); characterization of new OWP such as digestates (DIVA, DIVAGRO); and determination of the potential effects of OWP applications on soil carbon stocks, N2O emissions and nitrate leaching at spatial scale (PROSTOCK project). Some projects have considered the ecosystem service provided by recycling practices (ECOSOM and PROLEG projects) and the dys-services linked to OWP pollutant emissions (CEMABS, Pharma-PRO, Pharma-BOUE projects) as well as the monetarization of externalities (PRO-EXTERN project).
➢ Consolidation and renewal of collaborations within LabEx BASC (SADAPT, Agronomy, Public Economy units), with the implementation of several projects addressing peri-urban agriculture and waste recycling, including other units specialized in waste treatment processes (LBE, IRSTEA-OPAALE in Rennes) and ecological approaches (Metis, LEESU, both FIRE units). In addition, UMT Alter'N and partnerships with technical institutes ensure operational transfer of the results to technical users.
➢ Development of "territorial" approaches integrating the distribution of the sources of OWPs and needs of crop successions according to the types of soils and uses involved. An engineer profile was designed in this context, resulting in the recruitment of an IR (Florent Levavasseur) in 2015.
➢ Assessment of spatial distribution of topsoil organic carbon (SOC) content, cultural operations and crop successions from varied approaches and especially remote sensing (GESSOL PROSTOCK, BASC SOCSENSIT, TOSCA PLEIADES-CO, TOSCA “Théia Cartographie Numérique des Sols” projects).
This axis is managed by Sabine Houot and is mainly driven by the Soil team (46 publications are related to this axis, representing approximately 20% of the articles produced by the team) with implication of all the teams and connections with all other transversal axes. Ten peer-reviewed articles were co-signed by at least two of the unit's teams.