Soil fertilisation with Cs-contaminated and uncontaminated wood ash as a countermeasure to reduce Cs uptake by forest plants.

The purpose of present study was to find out whether wood ash with a high pH value and neutralizing capacity reduces Cs uptake by forest plants many years after the radionuclide fallout. The effects of one-time point fertilisation with Cs-contaminated and uncontaminated wood ash alone or in combination with KCl on Cs transfer from soil to young leaves and green shoots of various dwarf shrubs and tree species were examined in a long-term fertilisation experiment (2012-2021) conducted in Bazar mixed forest, around 70 km from Chernobyl nuclear power plant. The results indicated minor effects of soil fertilisation, although there were differences between Cs uptake by species and years. Soil amendment with Cs-contaminated wood ash generally did not affect Cs uptake by young shoots and leaves of plants over the growing season in the first year and only slightly decreased T for Cs in the following years. The effect of a single application of Cs-uncontaminated wood ash on reducing Cs uptake by plants was generally negligible. Application of Cs-contaminated wood ash in combination with KCl reduced plant Cs uptake by about 45%, however, such reduction was only significant in some years for bilberry berries, young leaves and green shoots of lingonberry and alder buckthorn. Thus application of wood ash to Cs-contaminated forest soil many years after radionuclide fallout generally does not reduce Cs uptake by forest vegetation in a mixed forest ecosystem and this countermeasure should be applied with caution.