The effectiveness of nitrate vulnerable zones for limiting surface water nitrate concentrations

This study considers the surface water concentrations of nitrate in areas designated as nitrate vulnerable zones (NVZs) for between 12 and 15 years. The study proposes a range of tests of the effectiveness of nitrate management within the NVZs and in particular the results from within NVZs were compared to a range of controls. The tests show that:

(i) Sixty-nine percent of NVZs showed no significant improvement in surface water concentrations even after 15 years.

(ii) In comparison to a control catchment 29% of NVZs showed a significant improvement but 31% showed a significant worsening.

(iii) The average improvement relative to a control due to NVZ designation was 0.02 ± 0.08 mg N/l/yr.

(iv) Differences between NVZs could not be significantly related to the size of the NVZ, uptake of the scheme, extent of uptake, land use change or geology of the local aquifer.

(v) Land use data suggest that NVZ designation buffered the designated areas against wider changes in arable farming in England and helped maintain a higher proportion of arable within the areas than would be expected.

The lack of objective success for NVZ designation suggests that nitrate pollution control strategies based on input management need to be rethought.