|Karl, Michael - USDI-BLM|
Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2001
Publication Date: November 1, 2001
Citation: HAFERKAMP, M.R., HEITSCHMIDT, R.K., GRINGS, E.E., MACNEIL, M.D., KARL, M.G. SUPPRESSION OF ANNUAL BROMES IMPACTS RANGELAND: VEGETATION RESPONSES. JOURNAL OF RANGE MANAGEMENT. v. 54. p. 656-662. 2001. Interpretive Summary: Annual bromes have invaded thousands of acres in the Northern Great Plains. Many studies have shown a decline in weight gains of stocker cattle as the grazing season progresses from spring to fall in the Northern Great Plains. One might question how much of this decline is simply due to maturation of plants, and how much of the decline may be due to presence of large amounts of early maturing annual bromes in the forage standing crop. We studied the biological impacts of the presence of brome by comparing brome infested rangeland to similar sites on which brome had been suppressed with fall applications of atrazine. Forage yields collected during the growing season reflected not only brome suppression, but also influence of precipitation, temperature, and grazing. This forage base varied over time, but generally was not less than 700 pounds per acre. Significant increases in crude protein concentration for western wheatgrass in July (7.1 vs. 9.1%) and August (6.0 vs. 7.1%) with brome suppression suggest steer performance may be improved with brome suppression.
Technical Abstract: Japanese and downy brome, introduced annual weedy grasses, have invaded thousands of hectares of Northern Great Plains rangelands. Presence of annual bromes can alter seasonal patterns of forage production and quality and require management changes for efficient use of infested rangelands. We compared biological impacts of the presence of brome by comparing brome infested rangeland to similar clay pan sites in which brome had been suppressed with fall applications of atrazine at 0.56 kg ha**-1 in 1992 and 1993. Each pasture replicate (12 ha) was stocked with 8 crossbred steers from mid-May to mid-September 1993 and 1995 and to mid-August 1994. Standing crop samples collected during the growing season reflected not only brome suppression, but also influence of precipitation, temperature, and grazing. This forage base varied temporally from date to date and year to year, but generally was not less than 800 kg ha**-1. Brome suppression significantly increased crude protein concentration for western wheatgrass (Pascopyrum smithii Rydb. [Love]) in July (7.1 vs. 9.1%) and August (6.0 vs. 7.1%). This increase in forage quality of one of the dominant perennial grasses suggest steer gains may be improved with brome suppression.