Question: What is the impact of the presence of Rhinanthus minor on forb abundance in newly established swards?
Location: Wetherby, West Yorkshire, UK (53°55′ N, 1°22′ W).
Method: A standard meadow mix containing six forbs and six grasses was sown on an ex-arable field and immediately over-sown using a randomised plot design with three densities of Rhinanthus minor (0, 600, and 1000 seeds per m2). Above-ground biomass was analysed over a period of three years, while detailed assessments of sward composition were performed during the first two years.
Results: Values of grass biomass were reduced in the presence of Rhinanthus, especially at the higher sowing density. The ratio of grass:forb biomass was also lower in association with Rhinanthus, but only at the higher sowing density. The presence of Rhinanthus had no effect on species number or diversity, which decreased between years regardless of treatment.
Conclusions: Although not tested in a multi-site experiment, the benefit of introducing Rhinanthus into newly established swards to promote forb abundance was determined. The efficacy of Rhinanthus presence is likely to depend on whether species not susceptible to the effects of parasitism are present.
Nomenclature: Stace (1997).