Streamwater nitrate concentrations in six agricultural catchments in Scotland

The concentrations of nitrate-N (NO3N) in catchment inputs and outputs have been compared and contrasted between 6 farm catchments in Scotland, 3 in the West and 3 in the North-East. Forms of intensive animal farming ranging between beef and dairy cattle, sheep and poultry give different sources for potential NO3N leakage from the systems. While stream reaches bordered by intensive cereal production give rise to the largest inputs to surface waters, climatic influences result in the more-efficient use of fertilizer- and farm waste-N in the West, and an enhanced potential for N-loss to waters in the cooler North-East, regardless of the N-inputs being considerably lower in the latter region. Although the EC Nitrate Directive limit of 11.3 mg NO3N l−1 was not exceeded, peak values occurring during summer baseflows and autumn soil rewetting were commonly larger than the ‘target’ maximum concentration of 5.65 mg NO3N l−1.