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Analysis of spatial distribution of sewage-sludge born cadmium on the experimental plot revealed positive correlation of total cadmium and organic matter. Soil pH fluctuated randomly on the field. 'Bioavailable' concentrations, as determined by NH4-acetate extraction, were closely correlated to the total cadmium levels, and only negligible effects of pH and/or organic matter fluctuations were recorded. Desorption model using modified Freundlich isotherm was applied to predict risks of cadmium solubilization at different conditions. Simulations revealed that the organic matter content within the ranges found at the experimental field cannot support a proper immobilization of cadmium at pH-range observed at the field. The phenomenon was explained by ineffective care for the soil in the past. [ABSTRACT FROM AUTHOR]

Large-scale vermicomposting under outdoor conditions may differ from small-scale procedures in the laboratory. The present study evaluated changes in selected properties of a large-scale vertical-flow windrow vermicomposting system with continuous feeding with household biowaste. The windrow profile was divided into five layers of differing thickness and age after more than 12 months of vermicomposting. The top layer (0-30 cm, age <3 months) was characterised by partially decomposed organic matter with a high pH value and an elevated carbon/nitrogen (C/N) ratio. The earthworm biomass was 15 g kg -1 with a population density of 125 earthworms per kilogram predominantly found in clusters. The greatest amount of fungi (3.5 µg g -1 dw) and bacteria (62 µg g -1 dw) (expressed as phospholipid fatty acid analysis) was found in this layer. Thus, the top layer could be used for an additional cycle of windrow vermicomposting and for the preparation of aqueous extracts to protect plants against diseases. The lower layers (graduated by 30 cm and by 3 months of age) were mature as reflected by the low content of ammonia nitrogen, ratio of ammonia to nitrate nitrogen and dissolved organic carbon, and high ion-exchange capacity and its ratio to carbon. These layers were characterised by elevated values for electrical conductivity, total content of nutrients, available magnesium content, and a relatively large bacterial/fungal ratio. On the basis of the observed properties, the bottom layers were predetermined as effective fertilisers.

One of the elements showing strong beneficial effect on plants at low concentrations and toxic effects at higher concentrations is titanium (Ti). We investigated the interconnection between the Fe uptake and the Ti intoxication in model experiment on Fe-deficient spinach (Spinacia oleracea) plants to help to elucidate the mechanism of the biological activity of titanium in plants. The two different Ti (0 and 20 mg L⁻¹) and two different Fe (0 and 1.35 mg L⁻¹) concentrations in hydroponic medium were used in all four possible combinations. We compared chemical analysis of Ti and Fe in roots and shoots with the changes of the in vivo chlorophyll fluorescence. Although Fe and Ti concentration found in shoots of Ti-non-treated Fe-deficient plants was comparable with that in Ti-treated Fe-deficient plants, the soluble form of Ti present in the growth media had a negative effect on photosynthetic activity monitored by chlorophyll fluorescence measurements. The presence of Fe in growth medium significantly decreased the Ti concentration in shoots and increased the photosynthetic activity. Here, we propose that Ti affect components of electron transport chain containing Fe in their structure (particularly photosystem I) and decrease the photosystem II efficiency., (Copyright © 2010 Elsevier GmbH. All rights reserved.)

The quality of medical plants used for the production of galenics or pharmacologically useful compounds is usually assessed by the content of biologically active compounds. Because most of these plants are grown in fields, this study focused on stimulation of active compounds by in vivo elicitation. Foliar application of elicitors on the immunostimulating medical plant purple coneflower ( Echinacea purpurea L. Moench.) grown on soil was used to increase the content of biologically active phenolics. Natural plant stress mediators and their derivatives (acetylsalicylic acid, salicylic acid, and methyl salicylate) as well as newly introduced biocompatible metal elicitor [titanium(IV) ascorbate] were chosen as active components of foliar sprays. A tremendous increase of phenolics (up to 10 times compared to control) and stimulation of the biomass yield were achieved. Tuning of organ specificity by modulation of the concentration of elicitor was also observed. This methodology represents a convenient alternative to cell suspension or hydroponic cultures being applicable in wide agricultural practice.

Titanium (Ti) has significant biological effects on plants, being beneficial at low and toxic at higher concentrations. From results of our hydroponical experiment with oats, we have recently proposed that the effect called hormesis is the mechanism of Ti action in plants. Here, we present the experiment with oats (Avena sativa L. cv. Zlat'ák) grown on soil where Ti was applied using leaf sprays. Two different soils, three different concentrations of Ti(IV) citrate spray solution (0, 20, and 50 mg Ti/kg), and three different Mg concentrations in each soil were tested. Some physiological parameters (dry and raw weights, top heights, chlorophyll content) and element contents (Mg, Fe, Zn, Mn) were determined. Ti showed considerable effects on all physiological parameters and the element's contents were determined. Differences between the two different soil types used was only in the strength of the effect of Ti; the trends remained unchanged. Generally, the effect of Ti is considerably weaker if Ti is applied on leaves than if being added to the nutrient solution. Thus, we confirm here that the action of Ti on plants could be explained by the hormesis effect.