This calculation comes from the EPA Region 5 load reduction model which is designed to calculate reduction of nonpoint source pollutants. This calculation assumes that you have a silt loam type soil – this is the most common type of soil in Indiana. Nutrient reductions (phosphorus and nitrogen) are assumed to come from the reduction of sediment transported nutrients. Attached phosphorus and nitrogen is calculated from USDA-ARS (US Department of Agriculture – Agriculture Research Service) research (Frere et al., 1980) and uses an overall phosphorus concentration of 0.0005 pounds of phosphorus per pound of soil. The nitrogen concentration is 0.001 pounds of nitrogen..
This calculation is also used to provide information about the amount of algae saved from our lakes and streams. Knowing that one pound of phosphorus can produce 500 pound of wet algae (University of MN Extension Service, 2003), by installing a 5 foot wide by 10 foot long native planting area, you can reduce 2.125 pounds of phosphorus from entering the water system which will in turn save 1063 pounds of algae from our lakes and streams.