Järvis, J.*, Ivask, M., Nei L., Kuu, A. and Haiba, E. 2017. Preliminary Assessment of Afforestation of Cutover Peatland with Spot Application of Sewage Sludge Compost. Baltic Forestry 23 (3): 644-657.

   The aim of the study was to seek a method for the quick revegetation of depleted peat mining areas in a near-city landscape, where the natural recovery of vegetation was impeded by a lack of some nutrients.

   The test area was pure milled peat that remained mainly free of vegetation cover for ten years after the mining process ended. Seedlings of Alnus glutinosa (black alder) and Betula pendula (silver birch) were planted in sewage sludge compost-filled drill-holes with a diameter of 20 cm and depth of 50 cm. For comparison, spot-applied multicomponent fertiliser was used in drill-holes of the same size, which were back-filled with the same peat, for the test group. Seedlings with spot-applied fertiliser without drill-holes and control seedlings without treatment were also planted into cutover peatland. Significantly greater (p < 0.001) average annual growth of height (73 cm) was followed with one-year-old silver birches planted with sewage sludge compost at the end of the growing season compared to other seedlings treated with multicomponent fertiliser (56 cm with drill-holes and 55 cm without holes). Significantly longer (p < 0.05) root growth in the vertical direction (53 cm) was achieved for compost-treated birches compared to both fertiliser treatment groups (47 and 42 cm). The average values of the length of the largest leaves were determined in the case of the compost treatment group (83 mm) compared to fertiliser treatment groups (68 and 67 cm; p < 0.05). Similar growth trends of the same parameters were achieved with one-year-old black alder seedlings, but the differences were not statistically significant in most cases. Usage of sewage sludge compost with the current drill-hole planting method can be suggested for afforestation of cutover peatlands with silver birch for its remarkably high height growth-promoting efficiency compared to fertiliser treatments. With black alder, the height growth-promoting effect of the compost was weaker, being similar to the fertiliser treatments.

   Keywords: reforestation, afforestation, reconstruction, sewage sludge compost, biosolids, height growth