In contrast, no significant relationshipswere found between vf and concentration for the dissolved inorganic nitrogen forms. The point-source effect on U wasmarginally significant for NO3−–N (pb0.10), but no significant effect was observed for PO4 3−–P or NH4+–N (Fig. 2c). However, the relative change between the two reaches in U for
NH4+–N (i.e., Udown−Uup/Uup) increased as the contribution of the point-source to streamNH4+–N load (loaddown−loadup/loadup) increased (U NH4+–N relative change=3.41+0.35[NH4+–N relative load],r2=0.912, p=0.003, n=6). This relationship was not observed for U of NO3−–N and PO4 3−–P or for the rest of the nutrient uptake metrics. In the agricultural stream, Sw of NH4+–N, NO3−–N and PO43−–P averaged N1 km at both the upstream and the downstream reaches (Table 4). The point-source input caused a marginally significant (pb0.10) increase in Sw of NO3−–N and PO4 3−–P, but did not affect Sw of NH4+–N (Fig. 2d). Values of vf for NH4+–N, NO3−–N and PO4 3−–P were within the range of 10−5 m/s, and did not differ between reaches (Table 4; Fig. 2e).