Summary:

The aim of the study was to determine the population density and group composition of soil mites (Acari), and especially species composition of oribatid mites (Oribatida), in rhizoboxes with apple trees, and to investigate the potential effect of biopreparations on the Acari fauna. The investigations were conducted in 2011-2012, on the basis of a glasshouse experiment established at the Institute of Horticulture in Skierniewice in 2009. The acarological examinations were carried out in rhizoboxes with apple cultivars ‘Topaz' and ‘Ariwa' grafted on M.26 rootstock and growing in the following combinations: C - control (without fertilization), N - mineral fertilization (standard NPK mineral fertilization, in doses of 70/60/120 kg of respective ingredient per hectare), O - fertilization with manure (at 30 t/ha), M - application of the biopreparation Mycosat (20 g/plant + ½ dose of manure, i.e. 2.5 g per rhizobox), H - application of the biopreparation Humus Active 2% + Aktywit PM 1%.
The average total number of soil mites in the different experimental combinations was in the range from 10.70 (combination C) to 12.97 thousand indiv. ∙ m-2 (combination N). Within the hierarchy of mites, the predominant group were oribatid mites, which constituted from 73.9 to 91.2% of all soil mites. The lowest number of them was found in the control rhizoboxes, and the highest in the combination with the biopreparations Humus Active + Aktywit PM (H). Altogether, 6 species of Oribatida were found in the experiment. The lowest number of Oribatida species (2) was found in the control rhizoboxes, and the highest in combination M (5). Among the Oribatida, the species that was always strongly dominant was Tectocepheus velatus (D = 89.4-99.1%). The population density of this species was high in all the rhizoboxes (7.50-11.62 thousand indiv. ∙ m-2), with the largest numbers found in combination H