S. Bittman et Dh. Mccartney, EVALUATING ALFALFA CULTIVARS AND GERMPLASMS FOR PASTURES USING THE MOB-GRAZING TECHNIQUE, Canadian Journal of Plant Science, 74(1), 1994, pp. 109-114
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.