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 Since they found that most reported values are at the lower end of the 1-4 range, they assumed that the
concentration of nutrients in sediment reaching a stream is approximately twice that in the in situ soil.
1.1.2.2 Feedlot Pollutant Runoff
Young et al. (1982) developed a pollutant runoff model for estimating total phosphorus,
chemical oxygen demand (COD) and biological oxygen demand (BOD) loads from animal feedlots for
single events. A submodel of the AGNPS model for estimating total nitrogen runoff is also
incorporated in to the feedlot model given below (Young et al., 1987). As with the dissolved nutrient
loading function for cropland and forest (Section 1.1.9) pollutant loads in the feedlot model are
determined by combining site-specific or default pollutant concentrations with runoff volume estimates
from the SCS Curve Number Equation. Animal waste pollutant load attenuation from the feedlot edge
to receiving watercourse is estimated by regression models available for several buffer area cover
types.
The feedlot model (Young et al., 1982; Young et al., 1987) was developed for estimating
pollutant runoff for Minnesota feedlots, but the model is applicable to other locations. The BOD
assessment is based on a COD/BOD ration conversions. Of the nutrient runoff models, the primary
author has more confidence in the phosphorus runoff estimates than the nitrogen runoff estimates due to
the complexities of nitrogen adsorption and desorption (Robert A. Young, personal communication).
Planners should therefore consider the increased uncertainty associated with the nitrogen runoff estimate
compared to the phosphorus runoff estimate. A computerized version of the feedlot model for
estimating phosphorus and COD runoff is available.3
To begin estimating feedlot pollutant runoff, name receiving water body and uniquely identify the
feedlot. Then prepare a feedlot site plan and calculate the acreage of feedlot watershed subareas
described below and shown in Figure 1.1.6.
3
Dr. Robert A. Young
USDA-ARS
North Central Soil Conservation Research Laboratory
Morris, MN 56267
612-589-3411
1.1-20
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