Research and environmental assessment of complex yard compost
The problem of environmentally safe disposal of a large amount of leaf litter generated every year in urban parks and squares is relevant. In this regard, the toxicity of complex yard compost on the basis of leaf litter, as well as ground with addition of yard compost, is assessed. In this paper, three types of substrates were studied: complex yard compost, soil-ground and native soil. Yard compost by 50% consisted of leaf litter. The soil-ground consisted of 40% of composting products of yard compost, 25% of soil-forming rock (sandy loam), 20% of greenhouse recoil including peat, 15% of building sand. The native soil (urban soil) was studied as a control. Soil toxicity control was carried out by chemical and biological methods (a bioindication, and a bioassay). The species diversity and abundance of the mesofauna in the studied substrates was studied. An increase in the number of representatives of Julida sp. and Geophilomorpha in complex compost, compared with native soil was found. The abundance of Eisenia fetida in the compost was 40 pieces per m2; in native soil this species was not found. The number of Eiseniella tetraedra is not large and amounted to 7-12 pieces per m2 in compost, but exceeded their number in native soil by 3-4 times. Cucumis sativus, Solanum lycopersicum, Raphanus sativus, Lepidium sativum were selected as test objects. A phytotest was performed on seed germination of Raphanus sativus and Lepidium sativum. The species diversity of pathogenic fungi has been analyzed. The inhibition of seed germination in the studied substrates was noted. Chemical analysis showed that the concentration of Cd in the studied substrates exceeds the permissible concentration approximately by 7-10 times, Cu and Pb by 2-4 times. Hg was not found in these substrates. The studied complex compost is not recommended to grow vegetables without taking measures to reduce the overall toxicity. Compost and soil-ground on its basis can be used as a substrate for lawn and cultivation of ornamental crops.