EVALUATING ALFALFA CULTIVARS AND GERMPLASMS FOR PASTURES USING THE MOB-GRAZING TECHNIQUE

There is growing evidence that alfalfa (Medicago sativa L. sensu lato) germplasms that perform well in trials that are mechanically clipped may not persist well under grazing. This trial assessed the persistenc e of nine alfalfa germplasms under grazing over a period of 4 yr in no rtheast Saskatchewan. The germplasms included registered cultivars and experimental strains of M. sativa ssp. media Pers. and M. sativa ssp. falcata (L.) Arcang. with a range of growth habits and winterhardines s. Each paddock was seeded with all entries in mixture with smooth bro megrass (Bromus inermis Leyss.) and grazed repeatedly for 1- to 2-d pe riods, using high stocking rates, to ensure that all entries were graz ed uniformly. Three grazing intensities - light, moderate and intense - were set by varying the rest period between gratings. Ground cover o f all the currently recommended alfalfa cultivars of the media ssp. de clined during the trial; the germplasms of falcata ssp. increased; and two media ssp. strains from northern Alberta maintained fairly consta nt ground cover. Grazing intensity affected rate of stand decline but not final ranking of germplasms, so there was no grazing x germplasm i nteraction. Seeded and volunteer smooth bromegrass maintained better s tands under light than intense grazing, whereas volunteer bluegrass (P ea spp.) performed better under intense grazing. Ground cover of alfal fa germplasms was generally correlated with their annual yield and pro portion of total dry matter yield. The results suggest that falcata ge rmplasms should be included in seed mixes for long-term pastures and t hat mob grazing be used to assess the persistence of alfalfa germplasm s before they are recommended for use in pastures.