Evaluation of Nitrogen Runoff and Leaching Potential in the High Plains (An)

Nitrogen losses in runoff and leaching from crop production for the 110 counties over the Ogallala aquifer in the High Plains region are estimated. Cropland distribution by crop, soil, irrigation system, and rotation practice is estimated using the 1992 National Resources Inventory database. Nitrogen runoff and leaching are simulated using the EPIC-PST model for each production system. Average nitrogen runoff per acre in the 110 counties ranges from 0.11 to 11.76 kg/ha (0.1 to 10.5 pounds/acre), with an average of 4.71/kg/ha (4.2 pounds/acre). Average nitrogen leaching per acre ranges from 0 to 12.10 kg/ha (0 to 10.8 pounds/acre), with an average of 3.14 kg/ha (2.8 pounds/acre). Counties with great nitrogen losses tend to be those that are heavily furrow irrigated and/or have large acreage of corn. The results are compared with those provided by two previous national assessments of groundwater contamination potential. Became this study takes into account the differences in cropping systems and physical characteristics across counties, differences in groundwater contamination potential are more fully revealed.