Effects of nitrogen fertilization on the nutritional quality of mule deer winter forages
Date
1972-01
Authors
Williams, Gary L., author
Glover, Fred A., advisor
Wallmo, O. C., committee member
Swope, Harold M., committee member
Nagy, Julius G., committee member
Bailey, James A., committee member
Lehner, Philip, committee member
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Abstract
Winter mortality resulting from starvation has been a serious problem on mule deer (Odocoileus hemionus) ranges throughout much of the western United States. Such losses have occurred in Colorado during recent years after snow concentrated animals on areas having inadequate food supplies. Associated with their interest in reducing starvation losses, the Colorado Game, Fish and Parks Division began testing fertilizer and 2, 4-D treatments to improve forage conditions on winter feeding sites used by mule deer in Middle Park, Colorado. This study undertook to determine how nitrogen treatments affected the nutritional quality of two forage plants on winter range. Ammonium nitrate fertilizer (33% N) treatments supplying 30, 60, 90, and 120 pounds of elemental nitrogen per acre were applied to three study sites during early November, 1969. An untreated plot on each site served as a control. Bluebunch wheatgrass (Agropyron spicatum Pursh) and big sagebrush (Artemisia tridentata Nutt.) current annual growth collected from the fertilized plots during May, June, September, and December of 1970 and March, 1971 were analyzed for crude protein, cell-wall constituents, calcium, and phosphorus. Separate analyses were performed on leaf and twig portions of big sagebrush. The in vitro digestibilities of all forage samples were determined in duplicate and big sagebrush leaves were analyzed for volatile-oil content. Nitrogen fertilization failed to increase significantly (P >0.05) the concentration of crude protein in big sagebrush tissues during May and September but increased significantly (P <0.05) the concentration of crude protein in big sagebrush tissues during June, December, and March. Nitrogen fertilization increased significantly (P <0.05) the concentration of crude protein in bluebunch wheatgrass during June. This increase was retained throughout the non-growing season. Nitrogen treatments failed to influence significantly (P >0.05) the concentrations of cell-wall constituents, calcium, phosphorus, or volatile oils in the tissues or the in vitro digestibility of the forages. Concentrations of all measured nutrients in the forages and the digestibilities of the forages varied among study sites and among collection dates.
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Subject
Forage plants
Plants -- Effect of nitrogen on
Mule deer