Chemical and bacteriological quality of pasture runoff

J. W. Doran; J. S. Schepers; N. P. Swanson

ABSTRACT:

Natural background characteristics and grazing cattle both influence the chemical and bacteriological quality of pasture runoff in south central Nebraska. The chemical quality of runoff from unstocked grassland was poorer than that from grazed pasture. The chemical quality of pasture runoff, which was better than runoff from cultivated cropland and urban areas, was within recommended water quality criteria. Cattle grazing increased fecal coliform (FC) counts 5- to 10-fold; however, FC counts in rainfall runoff from both grazed and ungrazed pasture, which were comparable to FC counts in runoff from cropland and urban areas, exceeded the water quality criterion of 200 organisms per 100 milliliters more than 90 percent of the time. The FC/fecal streptococci (FS) ratio of runoff from both grassland and ungrazed pasture was characteristic of wildlife feces, suggesting that the natural background level for bacteriological inputs may be large. Recommended bacteriological water quality criteria may be inappropriate for characterizing pasture runoff and other nonpoint sources of potential pollution.

Footnotes

J. W. Doran is a soil scientist with the Science and Education Administration-Agricultural Research, U.S. Department of Agriculture, 116 Keim Hall, East Campus, University of Nebraska, Lincoln 68583. J. S. Schepers is a soil scientist with SEA-AR, USDA, Lincoln, N. P. Swanson, now retired, was formerly an agricultural engineer with SEA-AR, USDA, Lincoln. This article is a contribution from SEA-AR in cooperation with the Nebraska Agricultural Experiment Station, Journal Series 6135. The research was supported in part by funds from the Environmental Protection Agency, Interagency Agreement EPA-IAG-78-D-X0088. Thanks are due LaMoine Brownlee, Larry Beerwinkle, Andrew G. Hashimoto and staff at the Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska, without whose assistance this project would not have been possible. Thanks also to Roland Knox for his cooperation in this project, to Dan Linn and Judith Lutgen for bacteriological analyses, and to Dennis Francis, Bonnie Hackes, and Joe Vavricka for chemical analyses. We acknowledge T. M. McCalla's personal support of the project as well.
Copyright 1981 by the Soil and Water Conservation Society

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