Impact of control of dock (Rumex obtusifolius ) on potential production from N-fertilised swards

The effects of dock control using the herbicide Pastor [clopyralid + fluroxypyr + triclopyr] on the production and quality of perennial ryegrass-based swards were investigated over four years (1999 to 2002) in south-west England ; UK. Experiments used treatment plots containing docks at different levels of infestation ; under a high nitrogen (320 kg N ha-1) fertilizer and silage-stage cutting regime. On the herbicide-treated plots ; there was near-complete elimination of docks in year 1; some docks emerged in year 2 ; and received a second herbicide application. On the unsprayed plots ; docks increased in vigour under the management of high N and mowing ; and by year 3 contributed an unacceptable proportion (38-50%) of the herbage dry matter (DM) yield. The yield of additional non-dock herbage was typically 3-4 t DM ha-1 year-1 (30% of the total) ; which was similar to ; or slightly less than ; the dock herbage it replaced. Digestibility of the dock herbage was lower than that of the grass ; especially at the mid- and late-season harvests. Results are discussed in terms of the agronomic appraisal of dock control measures.