Samenvatting

A large-scale field experiment was established in the Dubbele Dijk polder (Groningen, The Netherlands) to compare regenerative and conventional farming systems under identical crop rotations. The site presents a rare experimental condition: the upper 80 cm of topsoil was removed during construction of a secondary 'sleeper dike' for flood protection, leaving a near-zero organic matter baseline. This creates an exceptional opportunity to track soil restoration trajectories under contrasting management regimes from a defined, impoverished starting point, with a pre-experiment soil survey conducted in spring 2024 providing genuine time-zero data against which subsequent measurements can be referenced. The experiment covers 2 hectares and is embedded within three interconnected farmer study groups: an international group with farmers from the Netherlands, Germany and Switzerland (guided by Dietmar Näser); a national group of arable farmers from northern and southern Netherlands; and a regional group collaborating with the farmer-organisation 'Eiwitboeren van Nederland' (Protein Farmers from the Netherlands). Soil outcomes are benchmarked against the international 4 per 1000 Initiative (launched at COP21 in Paris, 2015), which targets an annual increase in global soil organic carbon stocks of 0.4% per year as a climate mitigation contribution (Minasny et al., 2017). The regenerative management system was initiated in June 2024 and is based on the principles of Friedrich Wenz and Dietmar Näser, adapted to the specific agroecological conditions of the Groningen polder landscape. Conventional management follows standard farm practice with synthetic nitrogen fertiliser and pure-stand cropping without companion plants.