Forage yield of simple and complex grass–legume mixtures under two management strategies

Foster, A., Vera, C. L., Malhi, S. S. and Clarke, F. R. 2014. Forage yield of simple and complex grass–legume mixtures under two management strategies. Can. J. Plant Sci. 94: 41–50. Limited information is available on the dry matter production, protein content and species composition of complex mixtures of introduced perennial forage crop species for hay and pasture in the moister regions of Saskatchewan. A field experiment was sown on 2008 May 27 at Melfort, Saskatchewan, Canada, on a thick Black Chernozem (Udic Boroll) silty clay soil, to compare the effects on dry matter yield (DMY), protein content and species composition of perennial forage crop monocultures and mixtures, under a two-cut and a three-cut management system, in 2009, 2010, 2011 and 2012. Eleven treatments consisted of monocultures of hybrid bromegrass (Bromus riparius Rehm.×Bromus inermis Leyss.), smooth bromegrass (Bromus inermis Leyss.), crested wheatgrass [Agropyron cristatum (L.) Gaertn], intermediate wheatgrass [Agropyron intermedium (Host.) Beauv.] and alfalfa (Medicago sativa L.); simple mixtures of each of these individual grass species with alfalfa; a more complex mixture of all these grass species and alfalfa, and a very complex mixture consisting of the complex mixture plus meadow bromegrass (Bromus riparius Rehm.), orchardgrass (Dactylis glomerata L.), tall fescue [Festuca arundinacea (Schreb.) Wimm.], timothy (Phleum pratense L.) and slender wheatgrass [Elymus trachycaulus (Link) Gould ex Shinners]. The alfalfa was inoculated with rhizobium, and no fertilizer was added to any treatment during the course of the study. The two-cut system yielded higher than the three-cut system in all years. In 2009, the first cutting year, all treatments, especially under the two-cut system, produced similar forage DMY, with monoculture grasses yielding as much as that of their mixture with alfalfa. In 2010, 2011 and 2012, however, monoculture alfalfa and grass–alfalfa treatments had higher DMY than the monoculture grasses. Monoculture alfalfa also showed superior DMY than most grass–alfalfa mixtures, especially during the last 2 yr of the study. In conclusion, the inclusion of alfalfa in forage mixtures, grown in unfertilized soil, significantly increased forage yield, especially after the first production year, and these grass–alfalfa mixtures yielded almost as much as monoculture alfalfa. Also, the inclusion of alfalfa significantly increased the forage protein content over the grass alone treatments. Hybrid bromegrass, grown alone or in mixture with alfalfa, yielded similar to the other grasses tested, while crested wheatgrass did not compete as well as other main grasses, grown alone or in mixture with alfalfa. In this study, the use of complex or very complex mixtures of introduced grasses with alfalfa did not increase DMY over the simple grass–alfalfa mixtures.