|Alber, Nadia -|
|Jackson, Randall -|
Submitted to: Canadian Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 4, 2014
Publication Date: N/A
Interpretive Summary: Cool-season grass response to defoliation is rarely studied under actual grazing conditions due to the cost and added variability of using animals. We conducted a grazing study to determine how the extent of defoliation of mature and immature grasses influences above- and below-ground productivity. We found that in a dry year, removing all forage each time grasses were grazed at a mature or immature stage maximized total pasture productivity. In a wet year, however, removing only half the forage was as productive as removing all forage. Root growth of orchardgrass was not influenced by maturity stage or forage removal either year, but in a wet year, root growth of meadow fescue was increased by grazing at a mature stage. Grazing these grasses to a lower height increases annual productivity, but this practice increases the risk of reducing plant longevity. This information is useful to livestock producers who utilize pastures.
Technical Abstract: Considerable differences exist among cool-season grass species in their production potential and response to management variables. We examined the effects of grazing management on forage and root production of two temperate perennial grasses, meadow fescue [Schedonoruspratensis (Huds.) P. Beauv.] and orchardgrass (Dactylis glomerata L.). Grazing factors studied were extent of defoliation (50 or 100% biomass removal) and leaf developmental stage (vegetative or mature) at time of grazing. In both 2009 and 2010, orchardgrass produced more above-ground biomass than meadow fescue despite yearly precipitation differences. In the drier year (2009), both grasses produced greater above-ground biomass under 100% extent of defoliation at either leaf stage. In 2010, orchardgrass produced greater above-ground biomass when grazed at a mature leaf stage for either extent of defoliation while few differences existed among grazing treatments imposed on meadow fescue. Grazing treatments had no effect on below-ground growth of orchardgrass either year. Meadow fescue root production was affected in 2010 only; grazing at a mature leaf stage increased below-ground growth for either extent of defoliation. Results suggest that grazing at a mature leaf stage to remove 100% of biomass maximizes aboveground production of both meadow fescue and orchardgrass. Complete removal of biomass, however, lengthens the grazing interval and may have a deleterious effect on grass persistence and nutritive value.