PHRED is a computer program written in C to run on the Radio Shack Tandy 6000 microcomputer. This program quantifies nonpoint source pollution in the form of sediment and phosphorus from cropland that is either in rotation or in continuous corn. It computes the production cost and net return to the farmer for existing conditions and for combinations of management practices. It also derives the corresponding dollar value benefit of pollutant reduction for each of the possible conservation practices and determines a benefit-to-cost ratio (B/C ratio). Conservation practices are incrementally applied to fields with excessive erosion rates in order of best B/C ratio until either an overall B/C ratio of 1 or an allowable erosion rate is achieved. Printouts of erosion rates, sediment delivery, phosphorus delivery, on and off site benefits, production costs, net returns, and conservation practices are available on a field by field basis and as aggregated totals for the farm and/or watershed.