WATER-QUALITY IMPACTS OF CONSERVATION AND NUTRIENT MANAGEMENT-PRACTICES IN PENNSYLVANIA

A field-scale microcomputer model, CREAMS, was used to assess the impa cts of selected best management practices (BMPs) and nutrient manageme nt programs (NMPs) on sediment and nutrient losses from three location s with three soil and field configurations common to the Chesapeake Ba y drainage area in Pennsylvania. Several BMPs were evaluated, with CRE AMS simulations conducted for runoff, erosion, sediment and nutrient d elivery to the field boundary, and percolation and nitrate leaching th rough the crop root zone. Two separate NMPs were evaluated in combinat ion with the BMPs. The baseline NMP followed traditional manure and fe rtilizer application practices and the improved NMP used an improved, high management system that incorporated best timing, placement, and t ypes of nutrient additions. BMPs increased percolation and decreased r unoff compared to moldboard plowing with no conservation practices. Se diment exported from the fields was also reduced by the use of BMPS. R eductions in total nitrogen (N) and phosphorus (P) losses varied great ly for different BMPs and sites. Although BMPs reduced sediment-associ ated N and P losses, the improved NMPs, as compared with the tradition al baseline NMP, bad little effect on these losses. BMPs tended to inc rease, whereas the improved NMPs substantially reduced, nitrate leachi ng. The improved NMPs also greatly reduced P losses from those sites w here P loss was predominantly in soluble form rather than sediment ass ociated. The use of BMPs and improved NMPs together effectively reduce d sediment and total nutrient losses.