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Title: SOIL C AND N DYNAMICS ON GRAZED NORTHERN MIXED-GRASS PRAIRIE AFTER SEVERAL YEARS OF SEVERE DROUGHT

Author
item Schuman, Gerald
item INGRAM, LACHLAN - UNIVERSITY OF WYOMING
item STAHL, PETER - UNIVERSITY OF WYOMING
item VANCE, GEORGE - UNIVERSITY OF WYOMING
item GANJEGUNTE, GRISHA - UNIVERSITY OF WYOMING
item WELKER, JEFF - COLORADO STATE UNIVERSITY

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/17/2004
Publication Date: 10/31/2004
Citation: Schuman, G.E., Ingram, L.J., Stahl, P.D., Vance, G.F., Ganjegunte, G.K., Welker, J.M. 2004. Soil c and n dynamics on grazed northern mixed-grass prairie after several years of severe drought. Agronomy Abstracts 4018.

Interpretive Summary:

Technical Abstract: Rangelands account for 161 million hectares in the U.S. Good grazing management has been shown to enhance soil C storage. Soil organic C (SOC) dynamics was assessed on grazed paddocks (i.e., lightly and heavily season-long) as well as ungrazed exclosures. SOC was assessed both 10 (1993) and 20 (2003) years after initiation of grazing of a northern mixed-grass prairie. Soil was collected at 10 m intervals along 50 m transects located in duplicate grazed paddocks and ungrazed exclosures to a depth of 60 cm. Grazing increased SOC in the 0-30 cm depth compared to the ungrazed exclosures after 10 years of grazing, resulting in a C sequestration rate of 0.30 MT C/ha/yr. However, after 20 years, including several years of severe drought, the ungrazed and lightly grazed treatments showed little differences in SOC contents and the heavily grazed treatment exhibited a 30% loss in the 60 cm profile. Season-long, heavy grazing has also resulted in a shift in plant community composition and a reduction in annual above-ground biomass. Good grazing management, however, did result in improved C sequestration potential in rangeland soils and appears to be important in ensuring long-term production and sustainability of these ecosystems.