Persistence of Urea in a Coastal Plain Soil: An Incubation Study

Urea-based nitrogen sources can possibly lead to nutrient pollution of various water bodies due to leaching and runoff, and also trigger the diatom Pseudo-nitzschia spp. to produce shellfish poisoning. This causes economic and human health concerns in the Chesapeake Bay and other coastal regions. Urea-based fertilizer use has increased in recent years because ammonium nitrate was banned after the Oklahoma bombing incident. Thus, farmers switched to commercial urea-based fertilizers as an economical alternative. When manures are used as a nitrogen source, studies have shown urea to exist in runoff several days after application. To prevent these occurrences, researchers need to learn more about how urea behaves and pathway movement through soils to water bodies. The objective of this study was to determine how urea in urea-based fertilizers and manures persists in soil after application. Four treatments were used: poultry litter, broiler manure, urea prill, and a control. Our hypothesis was that soils amended with poultry litter and broiler manure will have slower mineralization (hydrolysis) rates of urea, and a longer release of inorganic nitrogen than soils amended with commercial urea fertilizers. The latter process is thought to provide a more rapid mineralization rate of urea, but shorter release of inorganic nitrogen over time. This study will inform those concerned about the health of the Bay as to what agricultural practices may harm the Bay. It will also aid farmers in choosing which urea-based fertilizers pose the least risk of polluting the environment through runoff and leaching.