Impacts of Grazing On Four Pasture Forbs In Mixtures with Grasses or Legumes.

Ten species of forbs with significant forage value were seeded with 12 species of forages, including eight grasses and four legumes, in binary forb-forage mixtures. The forage species were alfalfa [Medicago sativa L. ssp. falcata (L.) Arcang.], creeping foxtail (Alopecurus arundinaceus Poir.), intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey]), kura clover (Trifolium ambiguum Bieb.), meadow brome (Bromus riparius Rehm.), orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), reed canarygrass (Phalaris arundinacea L.), sainfoin (Onobrychis viciifolia Scop.), smooth brome (Bromus inermis Leyss.), tall fescue (Schedonorus phoenix (Scop.) Holub.), and white clover (Trifolium repens L.). Six of the 10 forbs failed to become established. These included blueleaf aster (Aster glaucodes) [Eurybia glaauca (Nutt.) Nesom], boreal (Utah) sweetvetch (Hedysarum boreale Nutt.), Maximilian sunflower (Helianthus maximiliani Schrad.), Munro's globemallow [Sphaeralcea munroana (Dougl. ex Lindl.) Spach ex Gray], Palmer's penstemon (Penstemon palmeri Gray), prairie bundleflower [Desmanthus illinoensis (Michx.) MacM. ex B.L. Robins. & Fern.], sweet anise [Osmorhiza occidentalis (Nutt. ex Torr. & Gray) Torr.], and violet prairie clover (Dalea purpurea Vent.). In the 2nd and 3rd year of the study, following one establishment year, four forbs contributed significantly to the canopy area of some or all pasture mixtures. These were chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.), prairie flax (Linum lewisii Pursh), and small burnet (Sanguisorba minor Scop.). Four blocks of forb-forage mixtures were grazed and four were clipped four times per year, approximately every six weeks from mid-May through mid-September. Our hypothesis was that forbs would displace weeds, which averaged about 15% of pre-harvest canopy area. While in general weed and forb content were positively correlated, in cases where mixtures of a particular forage differed by harvest method, weeds were lower in grazed than in clipped plots, and forbs were higher in grazed than clipped plots.