Frost Seeding into Aging Alfalfa Stands

Little is known about the potential to frost‐seed cool‐season pasture species into mature alfalfa (Medicago sativa L.). Experiments were conducted in 1995 and 1996 near Arlington, WI (four sites), and Lancaster, WI (three sites), to evaluate the establishment and response to seeding rates of five cool‐season grasses and red clover (Trifolium pratense L.) frost‐seeded into mature alfalfa (2‐ to 5‐yr‐old stands with 30 to 50 plants m−2). Smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), reed canarygrass (Phalaris arundinacea L.), timothy (Phleum pratense L.), and red clover were frost‐seeded into mature alfalfa stands at six seeding rates. Orchardgrass, perennial ryegrass, and red clover had higher densities and responses to seeding rate than smooth bromegrass, timothy, and reed canarygrass in the seeding year, but these differences were less pronounced in the postseeding year. Orchardgrass contributed more grass dry matter in the seeding year but was similar to smooth bromegrass and timothy and greater than perennial ryegrass and reed canarygrass in the second year. Alfalfa and weed suppression were highest with orchardgrass due to its aggressive growth habit, high occurrence, and winterhardiness. Postseeding–year mixture yields were high for smooth bromegrass, orchardgrass, timothy, and reed canarygrass, but low for perennial ryegrass and red clover. Forage yield increased with seeding rate at sites with the greatest initial establishment. The results of this study suggest frost seeding temperate pasture species into mature alfalfa can increase plant diversity and forage yield while suppressing weeds.