The effects of organic waste materials on Miscanthus × giganteus yield and Zn and Ni content

The aim of the experiment was to determine the yield of Miscanthus × giganteus M 19 in the first three years of cultivation and its bioaccumulation of Zn and Ni in aboveground and underground parts in response to different doses of sewage sludge and substrate left after the production of white mushrooms. Miscanthus × giganteus is a grass species that adapts to different environmental conditions and can be grown in various climatic zones of Europe and North America. In April 2018 the experiment was established in a randomized block design and with four replications in central-eastern Poland. Waste organic materials (municipal sewage sludge and mushroom substrate) were applied to the soil in 2018 in the spring before the rhizomes of giant miscanthus were planted. Each year (from 2018 to 2020) biomass was harvested in December. The yield of fresh and dry matter and the total content of Zn and Ni, after wet mineralization of plant samples, were determined by optical emission spectrometry (ICP-OES). After the third year of cultivation, the content of Zn and Ni in rhizomes and in the soil was determined again. In relation to control, an increase in the yield of miscanthus biomass in response to organic waste materials was noted. Plants responded to mushroom substrate (SMS) with the highest average yield (16.89 Mgha^-1DM), while on the control plot it was 13.86 Mg  ha^-1DM. After the third year of cultivation, rhizomes of Miscanthus x giganteus contained higher amounts of Zn (63.3 mg kg^-1) and Ni (7.54 mg kg^-1) than aboveground parts (40.52 and 2.07 mg kg^-1), which indicated that heavy metals were retained in underground parts.