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Various soil extraction methods were developed for the determination of total and/or plant-available concentrations of potentially toxic elements. In this experiment, four single extraction procedures ( aqua regia, HNO3, acetic acid, DTPA) were tested for the determination of extractable contents of As, Cd and Zn. 35 soils differing in their physicochemical properties an d in total element contents were used in this experiment. Extractability of elements from soil samples varied following the indi- vidual elements and/or extraction agents used. The strong acids were not able to release the elements tightly bound into the si l- icate sample matrix. However, such techniques remain utilizable for the approximate determination of "pseudototal" element con- tents in soil, especially if soil samples are affected by anthropogenic contamination. The concentrations of As, Cd, and Zn determined in soil extracts by both mineral and organic acids covered in most cases the element portion representing more than one soil element fraction determined using SM&T sequential extraction procedure. Solutions of acetic acid and DTPA were able to release a part of the element fraction bound in Fe/Mn oxides and organic matter of soil sample. Arsenic represents an excep- tion because it is not released by DTPA.

High biomass production Salix smithiana was proved as the plant able to accumulate substantial amount of Cd and Zn in aboveground biomass. Nevertheless, in heavily contaminated soils (mainly by Zn) willows can suffer from chlorosis because of Fe deficiency induced by excess of Zn amount. Method such as chemophytostabilization seems like very good measure for planting willows in such heavily contaminated soil. In our experiments we evaluated effect of rock phosphate on changes in Zn and Fe bioavailability and accumulation of these elements by willows together with the willows growth on heavily contaminated soil. Addition of rock phosphate reduced plant-available Zn concentrations in soils resulting in significant decrease of Zn content in leaves. In the case of Fe, however, its contents in the leaves significantly decreased as well, although the mobile portion of Fe in soil remained unchanged. Yield of aboveground biomass in rock phosphate treatment was not significantly different in comparison to the control. After the first vegetation period, we can conclude that reduction of Zn contents in willows after rock phosphate application did not lead to suppress of Fe deficiency and improvement of willow growth in heavily contaminated soil.

The reutilization of residues derived from the bio-energy processes in agriculture is important for more effective nutrient cycle in ecosystem. This study evaluated wood fly ash (WFA) as an agricultural soil supplement. Spring wheat was grown on two different soils amended with different ash rates. The aim of our study was to investigate long-term effects of Cd contained in WFA on spring wheat vitality and yield during 3 years of cumulative ash application. Cd concentration in samples was analysed by inductively coupled plasma optical emission spectrometer (ICP-OES). WFA addition significantly decreased (p < 0.05) total Cd content in spring wheat, especially in the second experimental year and with increased WFA rate, probably because of increased soil pH and ash sorption ability caused by the ash addition. Grain yield was affected by the addition of ash at lower doses where we observed almost 100 % yield increase compared to untreated control and wheat straw showed the highest yields at the most ash enriched treatments growing in the last year. The risk of Cd contamination appears to be low, even from the long-term view and hence there are justifiable grounds for applying wood ash to the soil.