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Chemical water quality of runoff from grazing land in Nebraska: II. Contributing factors

Schepers, J.S., Hackes, B.L., Francis, D.D.
Journal of environmental quality 1982 v.11 no.3 pp. 355
water quality, agricultural runoff, grazing, grazing intensity, rangelands, pastures, precipitation, sediments, prediction, nitrogen, ammonium nitrogen, phosphorus, hydrochemistry, carbon, chemical oxygen demand, rain, plant litter, leachates, cattle manure, cows, calves, chlorides, environmental indicators, wildlife, nutrients, regression analysis, nonpoint source pollution, point source pollution, water pollution, pasture management, Nebraska
The chemical quality of runoff water from a 32.5-ha portion of a 40-ha cow-calf pasture area at the Roman L. Hruska U.S. Meat Animal Research Center near Clay Center, Nebr., was determined over a 3-year period. Precipitation and hydrologic characteristics, stocking rates, and sediment contents in the runoff were used to predict the average concentrations of eight chemical constituents in the water. Predicted concentrations of NH4-N, total Kjeldahl nitrogen, total phosphorus, total organic carbon, and chemical oxygen demand were directly related to the density of grazing livestock. A combination of one or more hydrologic or rainfall factors significantly improved the prediction. Leachates from the standing plant material, surface litter layer, surface soil, and manure deposits indicated manure and standing plant material were likely sources of most chemical constituents in runoff water. Chloride appeared to be a possible indicator of wildlife or livestock activity.