Makar Viktorovich Silaev

The article presents the results of an 18-month field experiment assessing the impact of 11 mulching substrates used in urban soils on a range of physical, chemical, and biological properties. The following substrates were studied: serpentine, marble, volcanic tuff, foam glass, coconut chips, painted and unpainted pine chips, large and small fractions of larch bark, and large and small fractions of pine bark. The substrates used were shown to have no negative impact on pH, total carbon (Corg) content, or its water-soluble forms (Cws), and no effect of the substrates on soil bulk density. The use of mulching substrates on urban soils contributed to an increase in the biological activity of the soil prokaryotic complex and a decrease in the number of sanitary-indicator and potentially pathogenic bacteria (Escherichia coli) in the soil, which reduces potential risks to the health of the urban population. The most favorable soil properties, based on the totality of the studied parameters, are formed under organic mulching substrates consisting of fine-sized particles, coconut chips and larch bark. An increase in the content of microscopic fungi in the upper horizon of urban soil under a 5-cm-thick mulch layer was detected. This may pose potential risks to human health due to the allergenic and potentially pathogenic properties of some soil micromycetes and requires further research. The obtained results allow us to recommend mulching urban soils with organic substrates not only for decorative purposes but also to enhance biological activity and, consequently, improve the biological condition of soils in anthropogenically transformed conditions.