Tuesday, 11:00 AM in BR D (RICC)
(subject to change)
The Susquehanna River is the single largest source of nutrients to the main stem of the Chesapeake Bay. We estimated four categories of net anthropogenic inputs: (1) atmospheric deposition, (2) fertilizer, (3) nitrogen fixation by vegetation, and (4) food and feed imports. Deposition was estimated based on data from CASTNet and NADP monitoring stations and modeled estimates for regions and species that are not monitored. Fertilizer application rates within counties were obtained from the literature. Nitrogen fixation was derived from crop area data from the Census of Agriculture multiplied by N fixation rates from the literature. Net N import in food and feed were derived from crop and animal data from the Census of Agriculture and data from the literature on crop and feed N contents and animal and human N requirements.Total net anthropogenic N inputs were 4707 kg N km-2 y-1, partitioned as follows: atmospheric deposition 28%, fertilizer 14%, N-fixation 17%, and food and feed import 41%. Only about 21% of N inputs are exported in rivers, with the remainder stored in vegetation, soils, and groundwater, or denitrified. Trend analysis indicates that there was a slight decrease in N export from 1980 to 2005.
