AGRICULTURAL SOIL EROSION RATES FOR THE LINGANORE CREEK WATERSHED IN THE PIEDMONT PHYSIOGRAPHIC PROVINCE OF THE CHESAPEAKE BAY WATERSHED

The loss of soil from agricultural lands presents a substantial risk to the sustainability of arable fields and downstream water resources within the Chesapeake Bay. The 137 Cs (Cesium-137) technique was used to quantify soil loss for representative agricultural settings (pasture/hay and cultivated crop) of the upper Linganore Creek watershed (146 km 2 ) in the Piedmont Physiographic Province portion of the Chesapeake Bay watershed. The 137 Cs inventory for the reference site was 2,183 becquerels per square meter (Bq/m 2 ), and inventories for agricultural sampling points range from 467 to 2,623 Bq/m 2 with a median of 1,401 Bq/m 2 and mean of 1,399 Bq/m 2 . Redistribution rate estimates for the 68 sampling points from all the sites, ranged from 48.8 megagrams per hectare per year (Mg/ha/yr) of erosion to 9.7 Mg/ha/yr of deposition, with a median and mean erosion rate of 13.5 and 15.5 Mg/ha/yr, respectively. The net erosion rates computed for sites ranged from 2.7 to 25.3 Mg/ha/yr with a mean of 15.3 Mg/ha/yr. The sediment delivery ratio is 100 percent for all sites except two pasture/hay sites with values of 85 and 89 percent. The mean erosion rates for these agricultural sites are greater than the overall sediment yield for watersheds in the Piedmont Physiographic Province, indicating that agriculture is an important source of sediment to the Chesapeake Bay. These findings indicate a capacity for further soil loss in agricultural areas and the potential delivery of this sediment to the Chesapeake Bay. Limitations of these data include the need to account for local variability of soil redistribution rates due to slope and profile curvature of hillslopes. The 137 Cs approach provides useful estimates of onsite and offsite soil loss for better management of agriculture and water resources and has the potential to assess the effectiveness of future conservation practices within the Chesapeake Bay Watershed.