Nutrient leaching from fertilized forest watersheds in Scotland.
Leaching of fertilizers into streams was studied in several forested catchments. In Braes of Angus Forest, fertilized catchments were compared with unfertilized catchments; in Loch Ard Forest, leaching was compared before and after NPK fertilization. P continued to be lost to streams in Loch Ard Forest 3.5 years after fertilization, whereas losses of N and K returned to normal after 3 and 2 years respectively. P losses amounted to 15% of the amount applied, averaging 2 kg/ha per yr. N losses amounted to 4% of applied in a partially treated catchment. K losses amounted to 20% of applied. N run-off, in the first year, from two adjacent fertilized watersheds in Braes of Angus Forest amounted to 9% of applied, of which 63% was in the form of nitrate. This amount of leaching is unlikely to be detrimental to fish production in streams, and could increase stream productivity and so be beneficial. However, leaching into closed areas of water could be undesirable.