Animals require well-balanced nutrition. The elemental content of the vegetation of meadows is influenced by as many factors such as heat, rainfall, irrigation, soil type and nutrients, meadow types, species, aspects of the vegetation period and cultivation.
Natural meadows used extensively are common sights on river floodplains. Since chemi
Weeds, in a wider sense, are plants not directly involved in growing, although their nutritional values make them important costituents of feed. Meadows are enriched by their relatively high microelement content.
On the sampling sites, the ratio deviated from the ideal 2/3 parts monocotyledon and 1/3 part dicotyledon, but this did not mean a Mn deficiency as it would have been assumed.
At the beginning of the year 2000 subsequently to a mine accident high heavy metal content mud entered the catchment area of the Tisza and was transported through the whole Hungarian section of the river. The majority of the heavy metals had been bounded to the floating sediment that was deposited on the flood-plain soil during flood forming a...new, 5-10 cm thick layer. In the mud samples collected after the flood there was a clearly visible dark grey layer with significantly higher heavy metal content that was formed by the pollution wave and it was sorruonded by a light layer. The upper layer of flood-plain soils are formed from this mud layer during the soil development process, so the amount of Lakanen-Erviö soluble heavy metals that correlate with bioavailable heavy metal content was examined as well. In this case only the lead content was significantly higher in the dark layer.
New mud samples were collected after the 2001 flood. Separate layers could not have been identified, their colour was similar to those of the previous year’s light layers’. Comparing to this light layer the total Zn and Lakanen-Erivö soluble metal content was significantly lower in the mud samples of the year 2001. While the proportions of total and Lakanen-Erviö soluble metal concentrations were equal in both of the layers regarding the elements, these ratios have significantly changed next year regarding Pb and Zn: the amount of Lakanen-Erviö soluble metals considerably decreased.
As a result of sequential extraction the heavy metal content was rather low in the water soluble and exchangeable and NaOH-soluble fractions, so heavy metals found in the mud could be released in greater amount only in case of a heavy acidification.