Undersowing rare arable plants in cereals as a new instrument in weed management—Restoration ecology meets weed science

Abstract Weed control is necessary in agriculture, but it is also known to be one of the main drivers of plant biodiversity loss in agricultural landscapes. Since biodiversity is essential for ecosystem service provision, new approaches in weed management are needed to simultaneously increase biodiversity and prevent yield losses due to weed competition. In this study, we investigated the establishment of undersowing cereals with rare arable plant (RAP) species, their weed suppression ability and influence on spring barley yield. We collected data at the species level for RAP and weed coverage and their fluctuations during a 3‐year on‐farm trial, supplemented by a second 1‐year on‐farm trial to confirm the results, both located in Southwestern Germany. The experiments were set up as randomized complete block designs with four treatments consisting of a control, a topsoil translocation and two treatments with seeded RAP species mixtures at two levels (low vs. high number of seeds). Our results indicate a successful reintroduction of 55% (6 of 11 species) by seeded RAP mixtures and 15% (3 of 20 species) of species translocated via topsoil. Seeded RAP mixtures achieved RAP coverages up to 17%, while topsoil translocation reached a maximum of 11%. Over the 3 years, we recognized a fluctuation in RAP coverage in the topsoil translocation of −4.5%, while we noted a fluctuation in RAP coverage in the seeded treatments of more than −50%. We found a maximum reduction in common weed coverage by 77% in plots containing high numbers of RAP seeds. Spring barley yield achieved 2.5–3.5 t ha −1 and was neither significantly affected by RAP mixtures, common weeds or both. Synthesis and Applications . The establishment of RAP in spring barley suppressed common weeds and reduced their coverage. This led us to the assumption of a natural weed suppression that can be considered for biodiversity‐enhancing approaches in weed management. For weed management, we recommend seeding mixtures of RAP, whereas topsoil translocation requires further investigation to ensure optimal application.