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Rumex obtusifolius (broad‐leaved dock) is a problematic weed that reduces yield and nutritional value of forage in grasslands of temperate regions worldwide. We conducted an on‐farm study to identify management practices and environmental factors that influence the risk of the occurrence of R. obtusifolius in high densities in permanent, productive grasslands used for forage production. Following a common protocol, a paired case–control design was implemented in Switzerland (CH), Slovenia (SI), and United Kingdom (UK) to compare parcels with high densities of R. obtusifolius (cases, ≥1 plant m−2) with nearby parcels free of or with very low densities of the species (controls, ≤4 plants 100 m−2). A total of 40, 20, and 18 pairs were recorded in CH, SI, and UK respectively. Parameters measured included data about management practices and history, vegetation cover and composition, and soil nutrients and texture. Across countries, increased vegetation cover reduced the relative risk of R. obtusifolius occurrence. By contrast, increased soil phosphorus and potassium and high soil bulk density raised the relative risk. These effects were consistent across countries, as no interactions between country and any of the factors were observed. The two indicator species for case parcels, Plantago major and Poa annua, were typical species of disturbed areas and fertile soils, while indicators for control parcels were characteristic of grasslands under medium to high management intensity (e.g., Festuca rubra, Cynosorus cristatus, Anthoxantum odoratum). We conclude that the risk for grassland infestation with R. obtusifolius can be significantly affected by management practices. Prevention measures should target phosphorus and potassium fertilisation to the forage plants' requirements, minimise soil compaction, and maintain dense swards. [ABSTRACT FROM AUTHOR]

Rumex obtusifolius is a problematic weed in temperate grasslands worldwide as it decreases yield and nutritional value of forage. Because the species can recruit from the seed bank, we determined the effect of management and soil properties on the soil seed bank of R. obtusifolius in intensively managed, permanent grasslands in Switzerland (CH), Slovenia (SI), and United Kingdom (UK). Following a paired case-control design, soil cores were taken from the topsoil of grassland with a high density of R. obtusifolius plants (cases) and from nearby parcels with very low R. obtusifolius density (controls). Data on grassland management, soil nutrients, pH, soil texture, and density of R. obtusifolius plants were also collected. Seeds in the soil were germinated under optimal conditions in a glasshouse. The number of germinated seeds of R. obtusifolius in case parcels was 866 ±152 m-2 (CH, mean ±SE), 628 ±183 m-2 (SI), and 752 ±183 m-2 (UK), with no significant difference among countries. Densities in individual case parcels ranged from 0 up to approximately 3000 seeds m-2 (each country). Control parcels had significantly fewer seeds, with a mean of 51 ±18, 75 ±52, and 98 ±52 seeds m-2 in CH, SI, and UK, respectively, and a range between 0 and up to 1000 seeds m-2. Across countries, variables explaining variation in the soil seed bank of R. obtusifolius in case parcels were soil pH (negative relation), silt content (negative), land-use intensity (negative), and aboveground R. obtusifolius plant density (positive). Because a large soil seed bank can sustain grassland infestation with R. obtusifolius, management strategies to control the species should target the reduction in the density of mature plants, prevention of the species' seed production and dispersal, as well as the regulation of the soil pH to a range optimal for forage production. [ABSTRACT FROM AUTHOR]