Leaf development of eight grass species following grazing

Abstract

Grazing by herbivores affects grass species both morphologically and physiologically. A study was conducted on an irrigated pasture near Outlook, Saskatchewan, Canada during the summer of 1991 to determine leaf regrowth after grazing of reed canarygrass (Phalaris arundinacea L.), slender wheatgrass [Elymus trachycaulus (Link) Gould ex Shinners subsp. trachycaulus], intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey subsp. intermedium], orchardgrass (Dactylis glomerata L.), meadow bromegrass (Bromus beibersteinii Roem. & Schult.), smooth bromegrass (Bromus inermis Leyss.), tall fescue [Festuca arundinacea (Schreb.) Wimm.] and timothy (Phleum pratense L.) in order to evaluate the suitability of these species for grazing. All eight species were mob-grazed by sheep at a stocking density of 30 animals ha-1. Physiological stage of leaf development was determined at 7, 14 and 21 d following defoliation. Smooth bromegrass and timothy consistently produced the greatest number of leaves for all regrowth periods. Tall fescue produced the least number of leaves at all time periods. Fifty-five percent of slender wheatgrass tillers and 19% of intermediate wheatgrass tillers were reproductive 21 d after defoliation. Based on leaf regrowth after grazing measured by leaf appearance, the grasses were ranked into three groupings – meadow bromegrass, smooth bromegrass and reed canarygrass ranked highest; intermediate wheatgrass, slender wheatgrass and orchardgrass ranked intermediate; and timothy and tall fescue ranked lowest. Key words: Leaf, regrowth, grass, grazing