The impact of fertilization with the compost prepared from treated sewage sludge with Scots pine bark additive and mulching with the fresh forest ectohumus on the soil conditions, chosen parameters of one-year old Scots pine seedlings growth as well as the occurrence of soil mites (Acari) with special emphasis of oribatid mites (Oribatida) was investigated in the paper. The trials were carried out in 2008 at forest nursery Białe Błota (Forest District Bydgoszcz) on the rusty soil. The whole area of the experiment was irrigated with the use of stationary sprinkling machine.
Analysis of the soil pH in particular variants of the experiment indicated that the use of organic fertilization and mulching decreased pH value. Content of available phosphorus ranged from 5,51 to 7,64 mg P2O5 100g-1 of soil, and the higher values were noted on plots fertilized with the compost and mulched. Similar dependence was noted in case of the available potassium content. Scots pine seed-lings on plots fertilized with the compost were significantly higher than those grown on plots with mineral fertilization. Organic fertilization increased also sig-nificantly the fresh mass of the above-ground parts seedlings - on average, by 79%. Impact of mulching - carried out in September - was insignificant on all the studied parameters of one-year old Scots pine seedlings growth. Investigated soils during the spring period were characterized by the low and uniform density of mites in case of particular variants - 1,08-1,99 individuals per m-2. In autumn on the non-mulched plots the density of those arthropods was slightly decreased, and in case of mulched plots - this density was ten times higher. In the two dates of the study Actinedida were predominant, and their percentage ranged from 30 to 93% of all the mites. After the measure of mulching on the adequate plots, the density and the species diversity of saprophage oribatid mites distinctly increased and among them - the eurybiont and cosmopolitan Tectocepheus velatus was the pre-dominant species.