Fig. 3. Relation between concentration enrichment and the fraction of applied water lost to evapotranspiration (ET) (from values in Table 1) for the agricultural profiles at California (CA), Indiana (IN), Maryland (MD), Nebraska (NE), and Washington (WA) and for the NE riparian zone site. Concentration enrichment is defined as C_obs/C_app, where C_obs is the observed unsaturated zone concentration based on the average of median NO₃^––N values from all lysimeters at each site and C_app is the applied concentration based on the total applied N divided by the total water inputs. Applied N rates were taken from local estimates (filled circles) and county estimates (empty circles) as indicated in Table 1. The curves show the expected increase of C_obs/C_app with increasing ET for various leached fractions of N (N leached below the root zone/N applied).