Weed ingress in perennial ryegrass (Lolium perenne) and tall fescue (Schedonorus arundinaceus)-based swards under dairy grazing

Weed ingress was assessed monthly over four years in a total of six swards of perennial ryegrass (Lolium perenne) or tall fescue (Schedonorus arundinaceus) to which were added a legume (2 species mix), legume and forage herbs (4 species mix), or legumes + herbs + other grasses (8 species mix). Unsown species (weeds) present were from 13 families, of which Asteraceae was the most abundant. Asteraceae species increased from <1% to 18% of total basal cover in ryegrass-based swards and from <1% to 14% in tall fescue-based swards over the study period. Asteraceae reached 81% of total weed basal cover in perennial ryegrass- and 82% in tall fescue-based swards in the final year. While the basal cover of total unsown species was lower in perennial ryegrass- than tall fescue-based swards in the first three years of the study, increasing the number of sown species (from a 2-species to an 8-species mix) had little effect on the ingress of Asteraceae or other weed species.