A field trial was performed in the years 2004-2006 in the Plant Breeding and Acclimatization Institute, Jadwisin Branch, in light and acid soil. The aim of this investigation was to determine the influence of Soil Fertilizer on the level of available forms of macroelements in the soil, content of humus, yield of potatoes and chemical composition of tubers. The Soil Fertilizer applied on the straw caused increase of humus in the soil by 17%. After applied straw with Soil Fertilizer the yield was higher about 7,1%. The tubers yield obtained after application of straw with Soil Fertilizer but without phosphorus and potassium fertilization was comparable to the yield after application of straw with mineral fertilization (phosphorus - 43,6 kg.ha-1 P and potassium - 83,0 kg.ha-1 K). Differences in chemical composition of potato tubers between object with straw + Soil Fertilizer in comparison to object with straw only were not significant.