This study examined the effect of fertilisation with compost prepared from hygienised sludge with an addition of pine-tree bark and mulching with fresh forest ectohumus on selected growth parameters for two- and three-year-old Scots pine trees and on the incidence of mites (Acari) in the soil. The experiment was carried out in 2009-2010 in the Białe Błota forest nursery (Bydgoszcz Forest District) on proper rusty soil. The entire area of the experiment was irrigated with a stationary sprinkler.
Organic fertilisation with compost prepared from hygienised sludge with an addition of pine-tree bark resulted in a significant increase in the plant height and the diameter of the root neck in two-year-old pine trees. The effect of mulching on these parameters was not significant. The synergistic effect of the factors on the plant height and the diameter of the root neck was not significant. Organic fertilisation significantly increased the height of 3-year-old pine trees, whereas it did not have a significant effect on the root neck diameter. Mulching increased the plant height significantly, but no statistical effect on the diameter of the root neck was demonstrated. Although no significant interaction of either experimental factors in their effect on the plant height and the diameter in the root neck was observed, the parameters tended to increase in the experimental option, which included organic fertilisation and mulching. Mulching had a significant effect on the presence of soil mites, especially oribatid mites (Oribatida). Their density increased greatly after the procedure. This growth, as well as an increase in the ratio of Oribatida to Actinedida could be a sign of improvement of the biological balance of the soils under study and their biological activity.