Liming and fertilization of acid forest soil: Short-term effects on runoff from small catchments

Increased atmospheric deposition of strong acids and deposition of potentially acidifying compounds (e.g. ammonium) has caused a decline in pH and exchangeable base cations in forest soils in Sweden. In recent years, attention has been paid to liming of forest soil as a method to counteract the effects of acid deposition. Experiments with liming, fertilization and woodash treatment of acid forest soils started in 1984. The aim of this study was to determine the effects of low doses of lime (500 to 1500 kg ha^?1) in combination with N fertilizers on tree growth, nutritional status of trees as well as soil, and runoff chemistry. This paper describes the short term effects of liming and fertilization on runoff from ten small catchments in two regions in south Sweden. The effects of liming were small in both areas. In the catchments fertilized with N (NH₄NO₃), a substantial leakage of various N species appeared in runoff after treatment. The increased N output was dominated by nitrate. The excess leakage of N during 2 yr after fertilization was 25 and 13% as an average of the applied N in the two study areas. The mobile nitrate increased the base cations output via runoff with 10 to 100% during 1 yr after N treatment. The runoff of Al increased with 60 to 100% the first year in the fertilized catchments. Mobilization of cations was also influenced by ammonium, especially K that was exchanged by ammonium on the surface of the soil particles. The effects of woodash-treatment were small, however, sulfate in the ash leaked out following application and about 100% of the added sulfate was found in runoff during the first year.