Productivity, and composition of smooth and meadow bromegrass mixtures with alfalfa under frequent cutting management

The value of smooth bromegrass (Bromus inermis Leyss.)–alfalfa (Medicago sativa L.) mixtures for pastures in central Alberta is limited by poor seasonal distribution of yield and low alfalfa persistence. Regrowth of meadow bromegrass (Bromus riparius Rehm.) exceeds that of smooth bromegrass. The effect of these grasses on yield, seasonal distribution and sward composition when grown in mixtures with alfalfa was evaluated. The DM yield of binary mixtures of Carlton or Manchar smooth bromegrass, or Regar meadow bromegrass with Peace or Beaver alfalfa was examined under a four-cut system at three sites in central Alberta for 3 yr. Annual yield was similar at all sites. Alfalfa cultivar did not consistently affect yield, but annual yield of meadow bromegrass-mixtures was 9 to 19% higher than mixture containing smooth bromegrass at Lacombe. Summer and fall production of meadow bromegrass mixtures was 18 to 53% and 40 to 69% greater (P ≤ 0.0001) than smooth bromegrass mixtures. Tiller weight of smooth bromegrass equalled or exceeded that of meadow bromegrass, so superior regrowth of meadow bromegrass mixtures was due to higher tiller density. Over 3 yr, annual yield of the alfalfa component was similar in smooth bromegrass- and meadow bromegrass mixtures, but alfalfa yield decreased (P ≤ 0.0001) 43 to 70% due to dramatic declines in alfalfa stem density. Competition from the associated grass and frequent defoliation reduced alfalfa longevity. Key words: Smooth bromegrass, Bromus inermis Leyss., alfalfa, Medicago sativa L., mixtures, pasture, sward structure