TECHNICAL ARTICLES IMPACT OF SHEEP BEDDING ON SOIL NUTRIENT DYNAMICS IN THE CENTENNIAL MOUNTAINS OF MONTANA AND IDAHO April B. Leytem 1 and Steven S. Seefeldt 2 Sheep and lamb production is an important industry in Idaho, with summer sheep grazing in the mountains a common practice. Sheep are concentrated in bedding areas at night leading to concentrated grazing and manure and urine accumulation in these areas. To address the effects of bedding on soil nutrient status, we monitored 16 bedding areas in the Centennial Mountains, with a general survey performed in 2004 followed by more intense monitoring of six sites from 2005 to 2006. In 2004, soils were analyzed for total carbon (C) and nitrogen (N), organic C, total P, Olsen P, water-soluble phosphorus (WSP), soluble nitrate, and soluble ammonium. Over the period 2005–2006, soils were analyzed for soluble nutrients including Olsen P, WSP, soluble nitrate, and soluble ammo- nium. The 16 sites evaluated in 2004 had significantly greater total N, C, and organic C concentrations in the nonbedded areas, whereas Olsen P, WSP, and ammonium concentrations were greater in the bedding areas. When six sites were monitored over time, there was no significant effect of bedding on soluble P concentrations over time or between bedding and control areas, whereas there was a significant effect of time on soluble N concentrations but no significant differences between bedding and control areas. Although these results are preliminary, it seems as if sheep bedding can alter the nutrient content of soils increasing some measures of soil nutrients, while decreasing others, which ultimately can affect the productivity and plant species diversity in these areas. (Soil Science 2008;173:503–510) Key words: Grazing impacts, soil nutrients, bed down areas. S HEEP and lamb production is an important industry in the state of Idaho, as well as in other states and provinces in North America. During summer months in western North America, many bands of sheep are grazed in the mountains. Sheep bands generally have 1000 ewes with more than 1000 lambs, and they are accompanied by a shepherd with a horse and dogs to move and protect them. At night, the sheep are concentrated in an area typically less than 0.5 ha to guard them from theft and predation. These sheep bedding areas are typi- cally on sites that are in open areas with few, if any, trees or shrubs and shallower soils and have reduced snow packs (Knight, 1994). Many of these sites are considered historic, in that they have been bedded on for up to a century. Consequently, large quantities of urine and manure may have been deposited on the sites, and heavy utilization and trampling of the vegetation, with mixing and possible compac- tion of the soil, may have occurred. There have been no published data in the United States determining the impact of bedding areas on vegetation diversity, biomass produc- tion, and soil nutrient cycling. In East Africa, the 503 0038-075X/08/17308-503–510 August 2008 Soil Science Vol. 173, No. 8 Copyright * 2008 by Lippincott Williams & Wilkins, Inc. Printed in U.S.A. 1 USDA, Agricultural Research Service, Northwest Irrigation and Soils Research Laboratory, Kimberly, ID. Dr. Leytem is corresponding author. E-mail: April.Leytem@ars.usda.gov 2 USDA, Agricultural Research Service, U.S. Sheep Experiment Station, Dubois, ID. Received March 7, 2008; accepted April 21, 2008. DOI: 10.1097/SS.0b013e31817d9d2f Copyright @ 2008 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.