The effects of perennial ryegrass overseeding on weed suppression and sward composition
Field studies were implemented to evaluate overseeding establishment of perennial ryegrass ('Lolium perenne' L.) and its ability to suppress weeds in established Kentucky bluegrass ('Poa pratensis ' L.). One irrigated and one non-irrigated trial were implemented at the Guelph Turfgrass Institute (GTI) and four non-irrigated and one irrigated in-use sites were situated on soccer fields in the Town of Oakville and at the University of Guelph campus. Three application rates of 2, 4, and 8 kg/100m 2 and seven application timings of May, July, September, May+July, May+September, July+September, and May+July+September were examined. Weed cover was not suppressed in 2005 but significant reduction due to overseeding treatments at 4 and 8 kg/l00m2 May+July+September existed in both trials at the GTI in August of 2006. No differences in weed cover were observed on the in-use fields in Oakville or at the University of Guelph campus. Perennial ryegrass populations increased in both GTI trials at all overseeding rates by the completion of the experiment in October 2006 and cover, upwards of 70%, was found in plots that had multiple overseedings at the 8 kg/l00m 2 rate. In-use fields did not exhibit an increase in perennial ryegrass when compared to the control plots.