Phytotoxicity of composts based on Surgut sewage sludge in closed ground conditions

The paper is devoted to the study of the toxicity of composts based on sewage sludge in relation to radish seeds and seedlings, as well as earthworms. The most phytotoxic are the substrates of variant «b» – with the microbiological preparation «Tamir» and worms, the substrates of variant «b» – with «Tamir» (without worms) were less toxic, a weak toxic and even stimulating effect on the growth of radish roots was detected in the substrates of variant «a» – control, without worms and «Tamir». Due to the high phytotoxicity, compost № 1, № 3, № 5 and № 6 are not recommended for use in crop production, and substrates № 2(a) and № 4(a) in connection with the identified stimulating effect can be recommended. Phytotoxicity of substrates may be related to their composition: food waste is present in the composition of «toxic» composts, and this component is not present in «non-toxic» composts. The decrease and increase in the biomass of worms in composts does not correlate with the revealed phytotoxicity and the composition of their mycobiota. Due to the low species diversity and abundance of cosmopolitan, toxin-forming and conditionally pathogenic fungal species in the structure of mycocoenoses of bioconversion substrates, it can be assumed that their maturation time is insufficient. With an increase in the incubation time of composts of a similar composition for more than 30 days, we predict a change in the structure of their mycocoenoses towards an increase in the species diversity of non-toxic saprotrophs, as well as cellulolytics of the genera Trichoderma and Chaetomium. The prospect of further research in this direction is the compilation of a collection of micromycetes of composts.