Forage biomass, soil cover, stability and competition in perennial grass–legume pastures with different Paspalum species

The short life span, irregular forage production and susceptibility to weed colonization of cool-season grass–legume pastures are serious problems in grazing dairy systems in warm-temperate regions. The inclusion of warm-season species has the potential to mitigate these problems. In this study, we evaluated the effect of the inclusion of two warm-season grasses with different growth habits on seasonal forage biomass, soil cover and weed colonization. Three different pasture mixtures were evaluated under grazing: conventional pasture (CP) [tall fescue (Festuca arundinacea), white clover (Trifolium repens) and birdsfoot trefoil (Lotus corniculatus)], CP with Paspalum dilatatum and CP with Paspalum notatum (CP + Pn). Forage biomass and soil cover were sampled thirteen times during a 3-year trial, and sampling times were grouped by season for the analyses. The mixtures with Paspalum showed higher soil cover in the autumn, while in the winter CP had higher soil cover than CP + Pn. Competition with tall fescue was similar between mixtures with Paspalum, when considering biomass, but it was higher in CP + Pn when considering soil cover. The inclusion of P. notatum increased biomass during the autumn but decreased the mixture performance during winter by reducing tall fescue soil cover. The addition of a warm-season grass species with a moderate competing ability like P. dilatatum is likely to avoid a negative impact on the cool-season component of the pasture.