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The aim of this work was to estimate the changes in contents of different sulfur (S) fractions in soils under conditions of lowering inputs of S from emissions together with the influence of application of manure and mineral fertilizers. Soil samples from long-term field experiments were used for this purpose. The samples were taken from 10 sites from precise long-term field experiments with different soil-climatic conditions in the Czech republic. The samples were analyzed using the following fractionation: (i) water soluble S (H 2 o extracts), (ii) sorbed S (0.032M naH 2 Po 4 extracts) and (iii) S occluded with carbonates (1M HCl extract). Furthermore, the concentration of total S (S tot ) and organic S (S org ) was determined. Soil samples were taken in the years 1981 and 2007. During 26 years a decrease of S tot by about 3-8%, water soluble S by 65-68% and sorbed S by 39-44% were observed in the topsoil of the evaluated soils. Furthermore, a low increase in the content of organic S was observed. The estimated ratio of S org reached 78.7-80.9% from S tot in the year 1981 and 87.7-89.8% in 2007. Farmyard manure (40 t/ha) applied every 4 years did not have a significant influence on S fractions and S tot contents in soils; intensive S fertilizing increased S tot and mobile S forms contents in soils. very close correlations were obtained especially between S tot and water soluble S and organic S.

For characterization of the ability of crops to reflect changing soil properties after the addition of ameliorative materials into the soil both pot and rhizobox experiments were provided. In the pot experiment, the influence of the addition of lime and limestone into contaminated Cambisol containing 7.14 mg Cd/kg, 2174 mg Pb/kg, and 270 mg Zn/kg on element availability for spring wheat was tested. The ameliorative materials were added into the pots containing 5 kg of soil in amount of 3 g CaO, and 5.36 g CaCO 3 per kg of the soil. Soil pH reached up to 7.3 in lime treatments compared to 5.7 in control soil. Mobile portion of soil elements (0.01 mol/l CaCl 2 extractable) dropped by 80% for Zn, 50% for Cd, and 20% for Pb, respectively. In both straw and grains of wheat reduced content of elements was observed in limed pots compared to the control ones. For a detailed characterization of the influence of root exudates on the strength of developed complexes in comparison with the bulk soil, short-term rhizobox experiment was set up under identical soil and lime treatments. Generally, the results of rhizobox experiment confirmed the findings from the pot experiment discussed above. Content of elements in shoots and roots of wheat dropped mainly in the case of Cd and Pb. Soil mobile portion of all three tested elements introduced clear depletion curve in control treatment, both limed treatments showed high stability of element complexes almost unaffected by wheat roots.

Mixture of plants (Festulolium: Trifolium pretense L.) was grown in the pot experiment with different forms of nitrogen nutrition. The fertilizers (ammonium sulphate or calcium nitrate or ammonium nitrate) were applied conventionally or according to the CULTAN method (Controlled Uptake Long Term Ammonium Nutrition). The absolute growth rate (AGR) and contents of free asparagine and proline in the aboveground biomass were determined. Additional nitrogen increased the dry weight of biomass and AGR of the plants treated with sidedress application in comparison with plants treated with the CULTAN method. The results suggest increased levels of free proline in CULTAN-treated plants while those of asparagine did not increase. The significance of these observations to the loss of potential yield and the relationship between methods of application is considered.

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The effect of arsenite [arsenic(III)], arsenate [arsenic(V)] and dimethylarsinic acid (DMA) on the growth of radish and the concentration of arsenic compounds in the roots and leaves of radish were investigated. Radish was grown in pots on Luvisols individually amended with arsenic concentrations of 20 mg kg À1 in the form of arsenic(III), arsenic(V), and DMA. In untreated soil, arsenate was the dominant arsenic compound; arsenite and DMA were also present. Arsenic(III) added to the soil was oxidized to arsenic(V), so that no differences between arsenic(III) and arsenic(V) soil treatments were observed. On DMA treatment, this compound remained in soil in high concentration in soluble and plant-available states, and the sum of arsenic(III), arsenic(V) and methylarsonic acid (MA) reached only 30% of water-extractable arsenic content. A low portion of soil arsenic added as DMA was immobilized, via adsorption, compared with inorganic compounds. Arsenic(III) was the dominant compound in radish roots planted in the untreated soil, whereas in leaves most of the arsenic present was arsenic(V). DMA was also detected in both plant tissues. A similar distribution of arsenic compounds was also found on arsenic(III) and arsenic(V) treatments. On DMA treatment, this compound showed high stability and the DMA concentration exceeded the sum of the remaining arsenic compounds [arsenic(III), arsenic(V) and MA] in both roots and leaves of radish.

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