Summary:

The study determined the influence of microirrigation (microjet sprinkling and drip irrigation) and organic fertilization (compost prepared on the base of sewage sludge) on growing vigour and degree of mycorrhiza of Scots pine (Pinus sylvestris L.) seedlings as well as occurrence of soil mites (Acari) after treatment of edafon inoculation. Two-year (2004–2005) field experiments were carried out in forest nursery at Białe Błota, Forest Inspectorate of Bydgoszcz. Investigations were conducted on a brown podzolic soil formed from loose sandy soil. The first order factor was irrigation used in three treatments: without irrigation (control), drip irrigation, microjet sprinkling. The second order factor was fertilization, used in two variants: mineral fertilization (standard applied in forest nurseries), organic fertilization (compost). The plot area was 4 m2 and contained 4 rows (4m length) of Scots pine (Pinus sylvestris L.) seedlings. Total number of plots in each experiment was 24 (3 x 2 x 4). Organic fertilizer was produced on the base of sewage sludge (80%) and highmoor peat (20%). This fertilizer was spread in spring (dose: 100 t · ha-1) and mixed with the topsoil (10 cm deep) before establishing of exact field experiments. Introduction of edaphon consisted in the mixing of topsoil (2 cm deep) with an organic matter obtained from the surface of partial cutting in habitat of fresh coniferous forest. Drip irrigation was done with the use of drip lines „T-Tape” (in-line emitters spaced 20 cm apart). Micro-jet irrigation was done with the use of micro-jets “Hadar”. Terms of irrigation and water rates were established according to “Directives for irrigation of forest nurseries on open areas”. In late autumn the growth of plants was evaluated. The height of seedlings (cm) and shoot diameter (mm) were measured. The soil samples for investigation on mites were taken twice a year (in May and October). The samples of 17 cm2 and 3 cm deep were taken from all plots in 3 replications. Mites were extracted from the material in high gradient Tullgren funnels. Oribatid mites (including the juvenile stages) were determined to species. Other mites were determined to order. The root systems of the seedlings were studied using a stereomicroscope (magnification 10–50x). To standardize the sample, lateral roots were taken from three different levels of the entire root system from each plant (top, middle and bottom), cut into small pieces (ca. 1cm), and mixed in a Petri dish containing water. The percentage of mycorrhizal short roots for each plant was assessed by counting at least 200 short roots from the mixture of segmented roots under the stereomicroscope. Morphotype data were recorded on overall morphology and colour. The experimental data has been statistically processed by variation analysis. Fisher-Snedecor test was used to determine a significance of influence of experimental factors and Tukey test was used to define significant differences between the combinations. Studied irrigation systems significantly increased the height of twoyears’old Scots pine seedlings. There were no significant differences in the seedling height between the two irrigation systems studied (drip irrigation and microjet sprinkling). Fertilization of the seedlings with compost significantly increased the height and diameter of seedlings. Significant interaction of irrigation and organic fertilization was observed. Drip-irrigated Scots pine seedlings grown on plots fertilized with compost were characterized by increased height and diameter. Experimental factors differentiated the mycorrhizal development of 2-years’old Scots pine seedlings. Dominant morphotype belonged to Thelephora terrestris. Studied irrigation systems advantageously affected the abundance of mites (Acari), including Oribatida. An influence of fertilization on these arthropods was not detected.