Biomass yields of shoots and roots of plants cultivated in soil amended by vermicomposts based on tannery sludge and content of heavy metals in plant tissues

Sewage sludge application in agriculture is the simplest method of its management. Its content of organic and inorganic toxic components is a barrier to such management. Particular attention should be paid to the content of heavy metals whose presence in sewage sludge and later in soil poses hazard for plants, animals and people. The investigations aimed to determine the effect of vermicomposts obtained from tannery sludge on development of the root system and biomass of shoots as well as heavy metal concentrations in these organs. In the first year after the vermicomposts application their effect on the maize biomass increase was equal to the farmyard manure treatment but significantly worse than the mineral fertilization. The consecutive fertilizer effect of vermicomposts of tannery sludge ted on the increase in biomass of the shoots and roots of winter rape, sunflower and oats was comparable with the farmyard manure effect but notably better than the mineral fertilization. Heavy metal concentrations in individual plants were diversified; in the plants from vermicompost treatment they were as a rule lower than in the plants from mineral or farmyard manure treatment. Absorbed heavy metals accumulated primarily in the root systems, whereas the extremely high chromium content in vermicomposts did not cause its excessive accumulation in the cultivated plants.