How to Limit the Spread of Broad-Leaved Dock

Broad-leaved dock is a problematic weed in permanent meadows and pastures. A European study led by Agroscope highlights the risk factors and recommends preventive measures.

Broad-leaved dock (Rumex obtusifolius L.) is a widespread problematic weed in intensively managed meadows and pastures in Switzerland and other European countries. The species outcompetes the forage plants and reduces forage quality and quantity, making grassland management difficult.

To identify prevention measures, a European team led by Agroscope involved in the EU project IWMPRAISE (‘Integrated Weed Management: PRActical Implementation and Solutions for Europe‘) evaluated risk factors for the occurrence of broad-leaved dock. To this end, a case-control study performed on commercial farms in Switzerland, Slovenia, and the United Kingdom compared parcels of land with high densities of broad-leaved dock (at least one plant per square metre) with nearby parcels free of or with very low densities of the species (controls: maximum of four plants per 100 square metres). Researchers recorded data on the management and history of the parcels, vegetation cover and composition, soil nutrients and texture, and the seed bank of the uppermost soil layer. A total of 156 parcels of land were studied, of which 80 were in Jura, the Prealps and the Swiss Central Plateau.

Risk factors: open sward, high soil-nutrient content, soil compaction

All three countries showed similar results: an open sward, high soil phosphorus and potassium content as well as soil compaction increased the risk for the occurrence of broad-leaved dock. These risk factors were evident in all three countries, despite their very different soil and climate conditions. No further variables could explain the occurrence of broad-leaved dock.

The typical plant species in the parcels with and without broad-leaved dock supported these findings: frequent companion species on the parcels with high densities of broad-leaved dock were broadleaf plantain and annual bluegrass, which are indicators for disturbed areas and nutrient-rich soils. By contrast, red fescue, crested dog’s-tail and spring grass were common indicators on the control parcels, i.e., characteristic species in meadows of moderate-to-high management intensity.

The number of germinable broad-leaved-dock seeds per square metre was significantly higher in the case parcels: On average, the soil contained 750 germinable broad-leaved dock seeds per square metre, with the number varying widely between 0 and approx. 3000 seeds per square metre. By contrast, control plots had on average only 75 broad-leaved dock seeds per square metre.

Dense swards, site-adapted fertilisation

In summary, the study illustrates the high relevance of site-adapted management and fertilisation as well as the promotion of competitive forage species for the prevention of broad-leaved dock infestation in permanent meadows and pastures. Because a soil seed bank can result in continuous seedling recruitment, it is crucial for successful broad-leaved dock regulation to prevent the weeds’ seed formation.