The role of cattle in the volatile loss of nitrogen from a shortgrass steppe |
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Authors: | D. S. Schimel W. J. Parton F. J. Adamsen R. G. Woodmansee R. L. Senft M. A. Stillwell |
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Affiliation: | (1) Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA;(2) Present address: USDA-ARS Tidewater Research Center, Suffolk, VA, 23437;(3) Present address: Department of Animal, Dairy and Veterinary Medical Science, Utah State University, Logan, UT, 8422-4815;(4) Present address: Jefferson County Extension Office, 530 D Street, Madras, OR, 97741 |
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Abstract: | The cycling and volatile loss of N derived from cattle urine at upland and lowland sites within the shortgrass steppe of eastern Colorado was studied, using15N-labelled urea as an N source. Losses of NH03 were determined by direct measurement and by difference. Losses were higher from coarse (27% summer, 12% winter) than from fine textured (0–2%) soils. Immobilization and plant uptake of N accounted for significant amounts of added N. Extrapolating our plot measurements to a typical pasture, using spatially and temporally stratified urine deposition data, losses from upland sites were calculated to be 0.016 g N · m-2 · y-1, while losses from lowland sites were negligible. This resulted in an average loss of 0.011 g N · m-2 · y-1 for a pasture divided 70:30 between uplands and lowlands. The loss of urine N calculated assuming no spatial stratification would be sevenfold higher (0.076 g N · m-2 · y-1). Losses of NH03 from urine, animal biomass removal, and NH2O loss totaled only 0.07 g N · m-2 · y-1 , or about 25% of wet deposition input. We calculated a potential loss of NH03 from senescing vegetation of 0.26 g N · m-2 · y-1, an order of magnitude larger than all other losses combined. |
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Keywords: | NH03 volatilization denitrification grazing spatial heterogeneity translocation nitrification leaching urine feces 15N |
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