Monday, November 5, 2007
99-8

The Influence of Soil Temperature and Moisture on the Fate of Urine-N in Grazed Pasture.

Curtis Dell, USDA-ARS Pasture Systems & Watershed Mgmt Research Unit, Bldg 3702, Curtin Road, University Park, PA 16802

While far fewer environmental concerns are generally associated with livestock grazing compared to crop and confined livestock production, the environmental impacts of grazing have not been fully assessed. The deposition of livestock urine creates small patches within pastures that receive large inputs of N leading to “hotspots” where disproportionately large leaching or gaseous N losses can occur. To correctly assess overall N losses from pasture, a better understanding of the fate of urine-N in these patches is needed. Soil temperature and moisture are known to impact the range of chemical and microbiologically-mediated transformations that urine-N undergoes, but the interaction of these factors within urine patch has not been studied. Laboratory and field data will be presented to clarify soil moisture/temperature interactions on ammonia and nitrous oxide emissions, N retention in soil, and plant N uptake in urine-amended soils.