The investigations were conducted in the frame of EU Research project Wood for Energy – a Contribution to the Development of Sustainable Forest Management (2001–2005). The integrated wood ash experiment was set up in a 38-year-old Scots pine (Pinus sylvestris L.) stand on Arenosols in SW part of Lithuania. Raw (not hardened) wood ash and nitrogen fertilizers were applied in 6 variants: 1.25 t ash/ha; 2.5 t ash/ha; 5.0 t ash/ha; 180 kg N/ha; 2.5 t ash + 180 kg N/ha and control (no treatment). The changes of soil pH, the content of some nutrients, heavy metals in Arenosols and soil solution, the abundance of ammonifiers, nitrifiers and denitrifiers in forest floor and mineral topsoil after the application of wood ash are presented and discussed in this paper.