WATER CHEMISTRY IN FORESTED CATCHMENTS AFTER TOPSOIL TREATMENT WITH LIMING AGENTS IN SOUTH SWEDEN

Critical loads of sulphur and nitrogen are exceeded in South Sweden, a nd nutritional imbalances are expected to appear with time in forests. During 1984 paired catchments were established in a northwestern sout heastern gradient in South Sweden. The aim was to study long-term limi ng effects on throughfall, soil water, groundwater and runoff. Dolomit ic limestone and wood ash were tested at one locality, Hagfors (59 deg rees N). Three adjacent catchments were used; one reference area, one treated with dolomitic lime (0.5 kg/m(2)) in 1985, and one with wood f ly ash (0.22 kg/m(2)) in 1988. The lime and the fly ash was granulated and applied by a helicopter in the end of May. Measurements concernin g chemistry of the precipitation, throughfall, soil water and runoff h as been conducted since spring 1984. The results showed that top-soil spreading of liming agents, besides the desired effects on soil chemis try, after some years also affected the quality of the recipient water . In the dolomitic lime treated catchment the positive effects were mo st obvious, with raised pH-, Cu-, and Mg-values and lowered Al-, Fe- a nd Mn-values. A positive trend regarding lower nitrogen (NO3-) leachin g could also be calculated Wood ash in the used amount affected only s lowly, but after six years the runoff water indicated increased pH-val ues as well as increased Ca- and K-values and Ca/Al-ratios. Dolomitic lime in the amounts of 0.5 kg/m(2) was concluded to be sufficient to a chieve positive effects in catchments of the present type. Wood ash in the amount of 0.22 kg/m(2) although enough for recycling purposes, wa s not sufficient enough in increasing pH in runoff to prevent acid lea ching from the forest soils.