In Wallonia, as part of the European ClieNFarms project, nine farmers from Hesbaye and Condroz, supported by the CRA-W, have chosen cover crops as a lever to increase the climate neutrality of their farms, by reducing nitrogen requirements and increasing carbon sequestration in soils. The aim is to gain a better understanding of how to increase biomass, return more nutrients to the soil and optimise fertilisation of the following crop.
A total of 31 cover crops were tested in 2023 and 28 in 2024, mostly after winter cereals and before beet, potato or chicory. The amount of biomass varied significantly: Median of 1.4 t DM/ha in 2023 (0.23-5.37) and 2.3 t DM/ha in 2024 (0.77-3.73). The MERCI method (Méthode d'Estimation des Restitutions par les Cultures Intermédiaires, method for estimating yields from intermediate crops) was used to estimate N, P, K and stable carbon yields in order to adjust spring nitrogen fertilisation and, where appropriate, reduce inputs.
The project raised several points to consider:
– Choose species according to the previous crop, the following crop and the objectives;
– Check seed quality and carry out a germination test if necessary;
– Monitor slug pressure before sowing;
– Manage residues and regrowth of previous crops;
– Sow early and adapt planting to soil and weather conditions;
– Destroy the canopy at maturity for a good C/N ratio.
High-performance mixes include phacelia, niger, Egyptian clover, avena strigosa and a phacelia-clover duo that can achieve up to 4 t DM/ha when planted before 20/08. The relay cover, combining frost-sensitive species and frost-resistant legumes (crimson clover, hairy vetch), also proved effective in keeping the soil covered until spring before late crops.
A catalogue of solutions for making farms more climate neutral is available on the project website: https://clienfarms.eu/solutions/
Funding: European Union, Horizon 2020 programme
