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The effect of organic, mineral and combined organic and mineral fertilization of soils on the winter wheat yields and nutrient contents in soils was evaluated in long-term field experiments. Two sites with different soil characteristics were evaluated - Lukavec u Pacova (cambisol) and Ivanovice na Hané (degraded chernozem). The type of fertilization influenced wheat yields. Nutrient uptake by winter wheat was higher under nitrogen (N) fertilization, which resulted in a negative balance of phosphorus (P) and potassium (K) and to a decrease of nutrient contents in the more fertile soils at Ivanovice na Hané. Two soil tests (Mehlich 3 method and NH4-acetate method) were used to determine P and K availability. The mineral nitrogen fertilization negatively and significantly affected NH4-acetate extractable concentrations of nutrients in the soils and these were lower in comparison with concentrations of P and K determined by Mehlich 3 method. Relative availability of P in alkaline soils from Ivanovice treated with mineral N increased while the soil pH decreased.

The 28-day incubation experiment was carried out to evaluate the impact of the application of digestate (Dig); digestate with straw (DigSt); pig slurry (Slu) and mineral fertilizer (NPK) on Cd, Cu, Mn and Zn availability, on K2SO4-extractable carbon content and on the soil pH value in long-term contaminated soil. At days three and seven of the experiment, the 0.01 mol/L CaCl2-extractable fractions of Cd, Zn and Mn significantly decreased under organic treatments (Dig, DigSt and Slu) with the most pronounced effect under Dig treatment. The NPK treatment caused the increase of risky element concentrations since day 21 of incubation which was accompanied with pH decrease. The contents of 0.5 mol/L K2SO4-extractable carbon were the highest at day 3 and 7 of incubation in organic treatments. The significant correlations between 0.5 mol/L K2SO4-extractable carbon and CaCl2-extractable metal concentrations showed a close relationship between fresh organic matter added in organic fertilizers and risky element availability, suggesting that newly added labile organic matter can form temporary ligands with risky elements and release them later following its decomposition.

The field experiment with different soil tillage treatments has been carried out in Prague-Ruzyně locality (Czech Republic) since 1995. Data of two growing cycles in the years 2007-2010 and 2011-2014 were evaluated. Tillage technique was decisive for changes in soil characteristics and crop yields. Bulk density, organic carbon (Corg) and microbial biomass C (Cmic) were more equilibrated throughout all tested soil layers (0-0.1; 0.1-0.2 and 0.2-0.3 m) in conventional tillage (CT). In reduced tillage (RT) and no-tillage (NT) treatments significant accumulation of Corg and increase of Cmic in the surface layer were found, compared to CT. No significant differences in Corg and Cmic between two growing cycles were determined; however, mostly higher values were obtained in the top layer of NT during the second growing period. Higher bulk density under conservation tillage techniques did not negatively affect soil characteristics and should be taken in consideration for data evaluation as it can alter interpretation of their changes in the soil profile. Crop yields were comparable in CT and RT. Yield decrease in NT was mostly observed for winter wheat and pea. Beneficial effects of RT and NT conserving soil moisture on crop yield were not observed in dry years.

A 38-day incubation experiment was carried out in order to evaluate the response of plant-available portions of heavy metals in long-term contaminated arable and grassland soils on addition of ethylenediaminetetraacetic acid (EDTA) and alfalfa (Medicago sativa L.) meal. Soils with different soil management (arable and grassland) from the vicinity of a lead smelter were used in the experiment. Readily available heavy metal fractions of Cd, Pb, Zn and Cu increased in the presence of EDTA at the beginning of experiment. The increase of heavy metal availability was higher in the arable soil with lower content of soil organic carbon than in the grassland soil. Addition of EDTA increased content of K2SO4-extractable carbon which remained higher throughout the overall time of experiment. During the first part of the experiment, the alfalfa meal addition decreased the available metal concentrations in the EDTA-treated grassland soil whereas no effect of alfalfa meal was observed in EDTA-treated arable soil.

An incubation experiment with addition of EDTA and alfalfa into soils contaminated with heavy metal over 200 years was carried out in order to evaluate the EDTA effects on microbial properties. Alfalfa was added to soils together with EDTA to examine its abilities to improve microbial activities affected by EDTA. The obtained results showed that the addition of EDTA led to a significant decrease of microbial biomass C during the first 24 days of incubation. At the end of the experiment the microbial biomass C significantly increased quite close to the original level. The EDTA amendment caused, probably due to the toxic effects, a significant increase in respiratory activities and of the metabolic quotient qCO2. An addition of alfalfa significantly improved the microbial biomass C contents in arable soils treated together with EDTA. Both, respiratory activities and qCO2 significantly increased after the soil treatment with EDTA together with alfalfa. EDTA alone decreased the microbial biomass, alfalfa alone as organic substrate was mineralised and utilised by soil microorganisms for their metabolism.

The effects of liming by CaO and CaCO3 on soil microbial characteristics were studied during laboratory incubation of long-term contaminated arable and grassland soils from the vicinity of lead smelter near Příbram (Czech Republic). The CaO treatment showed significant negative effects on soil microbial biomass C and its respiratory activity in both studied soils, despite the fact that microbial biomass C in the grassland soil increased sharply during the first day of incubation. The metabolic quotient (qCO2) in soils amended by CaO showed greater values than the control from the second day of incubation, indicating a possible stress of soil microbial pool. The vulnerability of organic matter to CaO could be indicated by the availability of K2SO4-extractable carbon that increased sharply, particularly at the beginning of the experiment. The amendment of soils by CaCO3 moderately increased the soil microbial biomass. The respiratory activity and qCO2 increased sharply during the first day of incubation, however it is not possible to ascribe them only to microbial activities, but also to CaCO3 decomposition in hydrogen carbonates, water and CO2. The pH values increased more sharply under CaO treatment in comparison to CaCO3 treatment. The improvement of soil pH by CaCO3 could be therefore more convenient for soil microbial communities.

The relationships among soil microbial biomass, pH and available of heavy metal fractions were evaluated in longterm contaminated soils during an incubation experiment with the amendment of zeolite (natural clinoptilolite) and the subsequent addition of glucose. The values of pH after the addition of glucose decreased during the first day of incubation approximately at about one unit and corresponded with the maximum increase of microbial biomass. The available heavy metal contents extracted by H2O, 1 mol/l NH4NO3 and 0.005 mol/l DTPA increased during the first two days of incubation. Only a few significant relationships were found between the available metal contents and pH or microbial biomass. This fact could be ascribed to the different dynamics of the microbial biomass, pH and metal availability after glucose addition, when the highest metal contents during the incubation were usually reached one day later in respect to the greatest changes of pH and microbial activity. In comparison to soils without zeolite addition, the variants with natural clinoptilolite showed lower heavy metal contents in all used extractants with the exception of Cd which in H2O extracts tended to increase.

A laboratory incubation experiment with zeolite and glucose was performed to evaluate the effects of zeolite amendment in heavy metal contaminated soils from two smelter areas on some microbial characteristics [Kremikovtzi (K1, K2) in Bulgariaand Příbram (P1, P2) in the CzechRepublic]. The content of microbial biomass showed a tendency to decrease in Kremikovtzi soils whereas in Příbram soils no significant effects were found after zeolite amendment. Respiratory activity and metabolic quotient (qCO2) decreased on the second and third day in Kremikovtzi soils amended with zeolite, no effects were observed in Příbram soils. Heavy metals decreased the content of microbial biomass in Kremikovtzi soils whereas the contaminated soil from Příbram area had the highest microbial biomass compared to non-contaminated soil during incubation, probably due to lower mineralization of carbon. The respiratory activity did not show any significant effects of zeolites on the evolution of CO2 and qCO2 in heavy metal contaminated Příbram soil. The respiratory activity in non-contaminated Příbram soil remained during the experiment lower in comparison to contaminated one, however the addition of zeolite increased qCO2.

The laboratory incubation with glucose treatment was carried out in order to estimate the possible effects of increased microbial activity on heavy metal availability. The soils from vicinity of a lead smelter operating for more than 200 years were used for the experiment. The DTPA-extractable heavy metal contents increased after glucose addition and mostly reached the highest values the second day of the incubation. The comparative study, where the chloroform fumigation was used prior to the incubation in order to decrease the microbial activities, showed especially from second day of incubation significantly lower DTPA-extractable metal contents compared to non-fumigated treatments. The interactions among the maximum possible availability of DTPA-extractable heavy metal fractions and native soil microbial characteristics were studied in differently contaminated arable and grassland soils. Irrespective of different heavy metal contents in soils, significant correlations were found among the maximum percentage increase of DTPA-extractable Pb and Cd and the ratio Bc/TOC and metabolic quotient (qCO2) which may be a result of the important role of organic matter and microbial characteristics in soils on the heavy metal availability.