Six field experiments on the use of mineral soil for amelioration of pine-dominated peatland forests were established in the 1920’s and 1930’s on drained mires in southern and central Finland. The treatments consisted of varying amounts of different textured mineral soil added on top of peatland. Soil samples were taken 52–74 years after the mineral soil application in 10 cm layers, up to 40 or 50 cm depth. The samples were analysed for pH, ash content, bulk density and nutrient concentrations. In two of the experiments, foliar samples of Scots pine were analyzed 66 and 77 years after the mineral soil application, and in one experiment, tree growth was measured for the period of 31–60 years after the application. The mineral soil had a long term effect on the physical and chemical properties of the top peat layer. Ash content and bulk density of the peat increased along with increasing application amounts, as did soil total P, K, Ca, Mg, Zn, Fe and B. The changes caused by the mineral soil were mostly restricted to the top 30 cm layer. The higher the soil fine fraction was, so was the increase in peat total P, K, Ca and Mg amounts. The addition of mineral soil increased tree growth and improved nutrient deficiencies (P, K) of Scots pine on one experiment, but decreased the B concentrations near the deficiency level.