Reed Canarygrass Binary Mixtures with Alfalfa and Birdsfoot Trefoil in Comparison to Monocultures
- T. A. Jones ,
- I. T. Carlson and
- D. R. Buxton
Maintenance of both components in a grass-legume mixture is an important objective of temperate perennial grassland management, yet one species is often lost from the stand within a few growing seasons. Our objective was to study factors that influence the persistence of reed canarygrass (Phalaris arundinucea L.) in binary mixture with alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.). Two divergent cycle-2 specific leaf weight (SLW) populations of reed canarygrass were grown in binary alternate-row mixture under a three-cut-per-year management with each of four legume cultivars: Olympic and Baker alfalfa and Norcen and Dawn birdsfoot trefoil. By the eighth harvest, alfalfa had competitively excluded reed canarygrass. Calculations of relative yield total indicated that competition between alfalfa and reed canarygrass was for de Wit's different space (the two species limited by different factors to at least some extent and therefore at least somewhat complementary in their exploitation of environmental resources) at early harvests. Birdsfoot trefoil mixtures reached equilibrium by the spring after establishment, with botanical composition thereafter varying from 67 to 81% legume. In contrast to alfalfa-reed canarygrass mixtures, competition between birdsfoot trefoil and reed canarygrass was for the same space (the two species strictly limited by and competing for the same factors) at early harvests and for different space at late harvests. No yield differences between SLW populations were found in mixture, although high SLW yielded 19% more than low SLW in monoculture over eight harvests. Reed canarygrass had higher in vitro digestible dry matter concentration in mixture than in monoculture as long as reed canarygrass yields in mixture did not exceed yields in monoculture. Legumes were taller and more mature in mixture than in monoculture at early harvests. Increased height and advanced maturity may be mechanisms responsible for the legume's dominance. Performance of forage species for agronomic and quality traits in monoculture, however, did not predict their performance in mixture.
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