Agricultural Phosphorus Management and Water Quality Protection in the Midwest

Phosphorus is an essential nutrient for growth of crops and aquatic vegetation and often needs to be applied to land for optimal crop growth. Land application of phosphorous as animal manure, biosolids (sewage sludge), and mineral fertilizer can increase the risk of phosphorus pollution of fresh water. The movement of phosphorus from agricultural land to surface and ground water is a complex process involving multiple pathways. Phosphorus moves into surface freshwaters dissolved in runoff water and attached to particulate matter eroded from the land. Recently applied P is particularly prone to losses and is affected by factors such as the form of P applied, the time since application, and the placement. The factors contributing to P loss from agricultural land to surface waters are commonly grouped as source (site and management)factors and transport factors. Topics covered by section include: phosphorus contamination of surface freshwaters; the role of phosphorus on agricultural land; forms of phosphorus in runoff, lakes and streams; manure as unfalanced fertilizer manure phosphorus; source factors contributing to phosphorus delivery to surface waters; phosphorus application; erosion; surface runoff; subsurface drainage; distance from the field to concentrated flow or to the water body; P indexes in U.S. EPA Region 7; interpretting P Loss Risk ratings; reducing the effect of P source and transport factors; cost and effectiveness of phosphorus management practices, and alternative manure application strategies.