The heterogeneity of the properties of the coprolites Aporrectodea caliginosa and Lumbricus rubellus in model experiment with chernozem soil

The changes in the physical and microbiological properties of the coprolites of earthworms Aporrectodea caliginosa and Lumbricus rubellus were evaluated in laboratory experiments using the arable horizon of migratory-mycelial chernozem. In coprolites the following physical parameters were determined: particle size distribution, specific surface area, calculated by the effective particle diameter; microbiological parameters: the total number of cultured bacteria and the enzymatic kinetics of lipases according to the Michaelis –Menten model with the calculation of the maximum reaction rate ( V m ) and Michaelis constant ( K m ). The model experiment included two stages: the first stage – earthworms of two species were kept together, in the second – separately. The control was the source soil and the soil with litter. Coprolites and the soil in which earthworms lived were analyzed and compared with the control. Two types of earthworms give a non-additive effect on physical and microbiological properties. Depending on the species composition, the nature of the change is different. For the two species contained together a decrease in the specific surface area in coprolites was noted, as well as an increase in the fraction of the fine sand due to the reduction of the fractions of silt, fine and medium dust. For A. caliginosa kept separately it was found, that the specific surface of coprolites increases compared to the control, the silt and fine, medium, coarse dust, fractions rise due to a significant reduction of the fine sand fraction. For L. rubellus coprolites a decrease in the specific surface area, an increase in the fractions of medium, fine sand and coarse dust, due to the reduction of silt, fine and medium dust fractions, are shown. The number of cultured heterotrophic bacteria is higher in coprolites compared to the control. The greatest increase is observed in the variant where two species are kept together. The lipase activity ( V m ) of the soil also increases when two species are kept together compared with the control and with A. caliginosa kept separately. Under the influence of L. rubellus the lipase activity decreases. Coprolites differ in all the investigated properties from the control (soil and soil with litter), as well as from the soil where earthworms lived.