Summary:

The purpose of the study was to determine the influence of organic fertiliza-tion and mulching on the growth of one-year old Scots pine seedlings (Pinus syl-vestris L.) and biological properties of soils in forest nursery under conditions of micro-sprinkler irrigation. The experiments were carried out in forest nursery Bi-ałe Błota (Forest Inspectorate Bydgoszcz) the rusty soil. Two experiments were conducted: the first one – in 2005, and the second one – in 2006. Both these trials were established as two factorial experiments in split-plot system, in four replica-tions. The first factor was fertilization applied in the two variants: N₁ – treated sewage sludge (⅔) + bark (⅓) and N₂ – treated sewage sludge (⅔) + sawdust (⅓). The second factor was mulching with fresh cap-humus from the fresh coniferous forest, used in the two variants: S – mulching with litter and C – without mulch-ing (control). The single plot area was m². Total number of plots in the experiment was 16 (2 investigated factors x 2 variants for a factor x 4 replications). Organic fertilizer was produced on the base of treated sewage sludge (⅔) and Scots pine bark (⅓) or sawdust (⅓). This fertilizer was applied with the dose of 100 t . ha^-1 in spring and mixed with the topsoil (10 cm deep) before Scot pine seed time. Mulch-ing with litter obtained from fresh coniferous forest was done – after emergence of Scots pine seedlings – with the dose of 100 m³ . ha^-1. Irrigation was done with the use of micro-sprinklers “Nelson”. Terms of irrigation and water rates were estab-lished according to directives for irrigation in forest nurseries on bare areas. The use of organic fertilization with sewage sludge with the bark additive, increased significantly the height of seedlings, as compared to those which were fertilized with sewage sludge with the sawdust additive. Seedlings cultivated under condi-tions of mulching with the cap-humus from the fresh coniferous forest were sig-nificantly higher than those grown under control conditions (without this mulch-ing). Ectomycorrhizas – noted on Scots pine seedlings – were created mainly by Thelephora terrestris. Mycorrhizas of T. terrestris were predominant on Scots pine roots independently from the experimental variant (treatment). Mulching was the factor which influenced on the total number of mites, including the number of oribatid mites and their species diversity. Influence of organic fertilization with different additives on these indices was not detected.