David Bečka

Thallium uptake by white mustard (Sinapis alba L.) grown on moderately contaminated soils—Agro-environmental implications

The work focused on Tl uptake by white mustard (Sinapis alba L.) grown on moderately contaminated soils with different characteristics. The data presented here clearly demonstrate the ability of white mustard to (hyper)accumulate Tl. Substantially higher Tl levels were was found in mustard grown on the Arenosol as compared to the carbonate-rich Leptosol; a relationship between the content of labile Tl (adsorbed, bound to carbonates etc.) in soil and its uptake by the plant is suggested. Approximately 3-fold lower concentrations of Tl in roots and stems of the mature mustard (compared to the young plant) indicate a decreasing trend of Tl uptake with the age of the plant. The exchangeable/acid-extractable and reducible Tl fractions were evaluated as the dominant fractions controlling Tl transfer from both contrasting soils. Thallium associated with the residual fraction (e.g., incorporated into silicates) was rather stable in the rhizosphere, proving a negligible influence of root exudates on Tl release from such an operationally defined fraction, despite the anthropogenic origin of Tl. Regarding our results, when mustard is cultivated for nutrition purposes and/or as green manure, it may pose an important source of Tl introduction into the food chain.

Effects of Conventional and Stabilized Urea Fertilizers on Soil Biological Status

Effects of stabilized urea fertilizers [Alzon 46 (A) and UREAstabil (US)] on soil microbiological and chemical parameters and also on grain yield, 1000-grain weight, and oil content were tested in a precise field study on Luvisol in 2010–2012. Winter rapeseed (Brassica napus L. cv. Californium) was fertilized both in autumn [45 kg nitrogen (N) ha−1] and in spring (155 kg N ha−1) with A [urea with DCD (dicyandiamide) plus pyrrodiazole (1,2,4-1H-triazole)], US {urea with NBPT [N-(n-butyl)-thiophosphoric acid triamide]}, and conventional N fertilizers (pure urea, calcium ammonium nitrate). Eleven parameters were used to evaluate the soil status: microbial biomass carbon (C; microwave method [MW]), dehydrogenase activity, arylsulfatase activity, available organic carbon, electroconductivity, Corg (MW method), and pH (in water, H2O). None of the 11 parameters demonstrated significant difference between control, conventional N fertilizers, and stabilized urea fertilizers. The greatest yield significantly different from the control (zero kg N ha−1; 2598 ± 881 kg ha−1) was found for both stabilized urea fertilizers: A (200 kg N ha−1; 3772 ± 759 kg ha−1) and US (200 kg N ha−1; 3764 ± 625 kg ha−1). The control achieved the greatest oil content (46.0 ± 1.2%), which was significantly different from all N-fertilized variants, and also the greatest 1000-grain weight (5.62 ± 0.62 g).

Technologies and Varieties of Fodder Beet in Organic Farming

In the organic farming system where the concentrate feeds are purchased a crop rotation for producing none only forage has been found to be expensive in relation to forage production costs, fossil energy inputs and the loss of production while crops are being established. The aim of organic farming is to create coexistence of multilateral, biologically and ecologically balanced weeds with low biomass production and strong culture crop. In weeds regulation we use preventive measures (seed rotation, late sowing, parallel growing of covering under sowings etc.), but also direct regulation methods, i.e. harrowing and line weeding (Petr et al., 1992). Fodder beet is a crop for which cultivation areas are reduced, since in 2000 the sown area of 7597 hectares, but in 2007 decreased to 807 ha in the Czech Republic. A slight increase can be recorded in the year 2008 845 ha. Even though the area of fodder beet reduced this crop has an irreplaceable role in maintaining biodiversity in agro ecosystems. Therefore, at present there is a new application in organic farming, which is among the good fore crop. Fodder beet areas in all over the world are not great. But it is a pity, because this crop has very high feed quality. Nowadays fodder beet could find new use in organic farming, especially as excellent feed for dairy cattle and energy crops. In ecological production of fodder beet we have some unsolved questions concerning i.e. weeds reduction, beet competitiveness improvement and optimal stand density. Fodder beet is a wide-row crop with slow initial development, which decreases its competitiveness in relation to weeds. This crop has very high feed quality. Fodder beet could find new use in ecological farming, especially as excellent feed for dairy cattle (Kodes et al., 2001). Energy crops with wide ratio of nutrients – fodder beet, semi-sugar beet and sugar beet – provide more energy in comparison with cereals or forage crops. Fodder beet provides maximum amount of energy per one hectare and presents easily digestible feed (Kosaį, 1985). The most important factor determining nutritional quality of feeds is digestibility. Its value significantly influences amount of nutrients and of energy available for animal (Mudįik et al., 2006).