The aim of our experiments was to investigate whether nutrient deficiency or toxicity is the cause for growth inhibition of wheat and barley in waterlogged soils. Experiments using two soils (top and subsoil) differing largely in various characteristics revealed a growth inhibition of wheat and barley in the case of subsoil due to water logging, without Fe or Mn toxicity. Water culture experiments with anaerobic (N 2 ) and aerobic aeration confirmed that oxygen deficiency did not induce nutrient toxicity (Fe, Mn) but caused sub-optimum nutrient supply (N, P, K, Mn, Cu, Zn) of wheat and barley plants. In a split-root water culture experiment with barley, cultivating half of the root system in varying combinations of aerobic/anaerobic and with/without K supply, it was shown that sufficient K uptake occurred only when K and oxygen were applied in the same root compartment. We suggest that due to O 2 deficiency in the root medium, synthesis of ATP may be inhibited leading thus to a decrease in nutrient uptake. Nutrient deficiency rather than toxicity appears to be the major cause for the poor plant growth in waterlogged soils.

Selenium (Se) is an important element associated with the enhancement of antioxidant activity in organisms. Potato is very suitable for fertilisation with Se (biofortification). The experiment was performed to examine the effect of foliar application of Se as sodium selenite (200 or 400 g Se/ha) at the tuberisation stage on a spectrum of amino acids in tubers of varieties. The trends of amino acids were consistent in both years of the study. Application of Se increased the relative content of total essential (EAA) and non-essential (NEAA) amino acids relative to the controls (Karin: EAA 16.81-21.73% and NEAA 14.18-18.63%; Ditta: EAA 4.71-13.00% and NEAA 5.78-6.49%). The increase in the content of phenylalanine (Phe) was particularly significant (up to 48.9%) when also the contents of aspartic acid (Asp), glutamic acid (Glu), threonine (Thr), and tyrosine (Tyr) increased significantly compared with the controls. The results of changes in the content of isoleucine (Ile), leucine (Leu), lysine (Lys), methionine (Met), valine (Val), alanine (Ala), arginine (Arg), proline (Pro), cysteine (Cys), glycine (Gly), histidine (His), and serine (Ser) were also discussed. The highest dose of selenium is shown as a stress factor. Its toxic effects resulted in a change of amino acid contents.

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In a one-year vegetation pot experiment we compared the effect of the digestate from a biogas station and mineral fertilisers on yield and quality parameters of kohlrabi, variety Seguza. Four treatments were used in the trial: 1) untreated control, 2) urea, 3) digestate, 4) urea, triple super phosphate, KCl, MgSO4. The rate of N was the same in treatments 2–4, 1.5 g N/pot. In treatment 4 the rate of P, K and Mg corresponded with the rate of these nutrients in the digestate treatment (3). The weight of single bulbs of the control unfertilised treatment were significantly the lowest (22.9%), as well as the nitrate (6.0%) and ascorbic acid content (66.2%) compared to the urea treatment (100%) and the other fertilised treatments. After the application of the digestate (treatment 3) and mineral fertilisers (treatment 4) the weight of single bulbs significantly increased by 27.9 and 29.2%, respectively, compared to the urea treatment (2). The content of ascorbic acid in the fertilised treatments did not differ (772–789 mg/kg) but it increased significantly compared to the unfertilised treatment (511 mg/kg). There were no significant differences between the two treatments fertilised with mineral fertilisers in the bulb nitrate content (678 and 641 mg NO3−/kg fresh matter, respectively). After digestate application their contents decreased significantly to 228 mg NO3−/kg fresh matter. Digestate treatment resulted in comparable or better yield and qualitative parameters compared to treatment with mineral fertilisers.

SUMMARYIn a greenhouse pot experiment with kohlrabi, variety Luna, we explored the joint effect of N (0.6 g N per pot = 6 kg of soil) and S in the soil (25-35-45 mg kg -1 of S) on yields, on N, S and NO 3 -content in tubers and leaves, and on alterations in the amino acids concentration in the tubers. S fertilisation had no effect on tuber yields. The ranges of N content in tubers and leaves were narrow (between 1.42-1.48 % N and 1.21-1.35 % N, respectively) and the effect of S fertilisation was insignificant. S concentration in the tubers ranged between 0.59 and 0.64 % S. S fertilisation had a more pronounced effect on the S concentration in leaf tissues where it increased from 0.50 to 0.58 or to 0.76 % S under the applied dose. The NO 3 -content was higher in tubers than in leaves. Increasing the S level in the soil significantly reduced NO 3 -concentrations in the tubers by 42.2-53.6 % and in the leaves by 8.8-21.7 %. Increasing the S content in the soil reduced the concentration of cysteine + methionine by 16-28 %. The values of valine, tyrosine, aspartic acid and serine were constant. In the S 0 , S 1 , and S 2 treatments the levels of threonine, isoleucine, leucine, arginine, the sum of essential amino acids and alanine decreased from 37 to 9 %. The histidine concentration increased with increasing S fertilisation. S fertilisation of kohlrabi can be recommended to stabilize the yield and reduce the undesirable NO 3 -contained in the parts used for consumption.

Due to continuous single nitrogen fertilization, we hypothesized a built-up deficiency of micronutrients in crops that would limit plant growth and crop quality. In 2-year field experiments using urea-N fertilized grain maize (Zea mays L.), hybrid KWS 2376 at 0, 120 and 240 kg N ha (1 crop uptake of Zn, Mn, Cu and Fe was studied at DC 32, DC 61 and in the grain harvested. Micronutrient contents at DC 32 stage Á 1st node (aboveground phytomass) and DC 61 Á flowering (ear leaf) were all at levels indicative of adequate micronutrient supply to the crop. At both sampling occasions the Fe:Zn and Fe:Mn ratios were adequate implying that Fe did not inhibit the uptake of Zn and Mn. The application of nitrogen increased the Fe content at the 1st sampling in both years; in the second year the same was also the case for the Zn content. Nitrogen nutrition increased the contents of Mn and Fe at the 2nd sampling only in year 2; in the other treatments no changes were observed in the micronutrient contents. Micronutrient correlations in the grain were discovered between Zn and Mn contents and between Fe and Mn contents. In the second year the highest N-rate significantly increased the Fe and Zn content of the grain compared with the lower rates of nitrogen fertilization. Grain yields were not affected by the rate of nitrogen and ranged between 13.65 and 14.34 t ha (1 (1st year) and between 13.68 and 14.18 t ha (1 (2nd year). Nitrogen fertilization did not reduce the content of micronutrients in the plant or grain of maize. It is evident that the continuous single use of N fertilization so far has not resulted in a micronutrient deficiency of the plants limiting the nutrient density of the grain or reducing its quality.

Heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in soils and plants of four different ecosystems (forest, grassland, agro and urban ecosystem) at different distances from the source of the pollution were analyzed in order to assess and compare soil contamination in the various ecosystems and determine the potential accumulation of plants depending on the place they inhabit. Correlation relationships among heavy metals in soils differ depending on the ecosystem, and between soil and plant, the heavy metals showed significant correlation for Cu, Mn, Ni, Pb and Zn. Contamination factor (C), degree of contamination (C) and pollution load index (PLI) were used in order to determine the level of environmental contamination of the study area. All studied ecosystems were rated as moderately contaminated (except agroecosystem, which was found as low contamination ecosystem) according to C and extremely polluted according to PLI. The highest pollution in both cases was found in urban ecosystem, and Cd, Cu and Fe were determined as the biggest pollutants.

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