The role of cattle in the volatile loss of nitrogen from a shortgrass steppe

1573-515X

NH 0 3 volatilization ; denitrification ; grazing ; spatial heterogeneity ; translocation ; nitrification ; leaching ; urine ; feces ; 15N

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Geosciences

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 NH 0 3 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 NH 0 3 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 NH 0 3 from senescing vegetation of 0.26 g N · m-2 · y-1, an order of magnitude larger than all other losses combined.

Electronic Resource