PERSISTENCE OF COOL-SEASON GRASSES UNDER GRAZING USING THE MOB-GRAZING TECHNIQUE

Evaluation of grass germplasms for pasture is usually done in trials w hich are harvested mechanically. This study evaluated the persistence of 13 cool-season grass species and germplasms under 4 yr of grazing i n northeast Saskatchewan, using the mob-grazing technique. Thirteen gr ass germplasms were contained within each paddock, and the paddocks we re grazed by large groups of cattle so that all the herbage was consum ed evenly in 1-2 d. Three grazing intensities (light, moderate and int ense) were established by varying the rest period between gratings. Gr ound cover declined more rapidly under intense than under light grazin g, but no interaction was found between grazing intensity and grass ge rmplasm. The ground cover of the seeded grasses generally declined but at different rates during the trial, giving a significant grass x yea r interaction. Parkway crested wheatgrass [Agropyron cristatum (L.) Be auv. ssp. pectinatum (Bieb.) Tzvel.] declined less than Carlton smooth bromegrass (Bromus inermis Leyss.) and the meadow bromegrass (Bromus biebersteinii Roem and Schult.) cultivars. The most rapid stand declin e was observed in intermediate wheatgrass [Elytrigia intermedia (Host) Nevski], northern wheatgrass (Elymus lanceolatus Scribn. gr Smith), a nd hybrid wheatgrass [Elytrigia repens (L.) Nevski x E. spicata (Pursh ) D. R. Dewey]. Seeded grasses were replaced mainly by bluegrass (Pea spp.). The results suggest that mob grazing is a useful technique for evaluating new species and germplasms intended for long-term pastures.