The impact of using humic substance for growing potato on quality indicators of tubers. Humic preparations are concentrated and economical form of organic matter which can relieve humus depletion caused by conventional fertilization methods. The trials were carried out in 2012 and 2013 at the Estonian University of Life Sciences in Estonia. The yield of tubers and starch, and commercial yield of potato, number of tubers per plant, tuber weight was studied in cultivar 'Ants' and 'Laura'. In the experiments humic preparation (HP) "Ruponics" was used in two different treatment variants. "Ruponics" 50 l ha-1 (HP50), "Ruponics" 25 l ha-1 (HP25) and control (HP0) 0 l ha-1 variant. The experiments showed that potato cultivars 'Ants' and 'Laura', HP did not have any significant positive effect on the tuber yield, commercial tuber yield or starch yield in 2012. Yields were higher in 2013 reaching up to 52.4 t ha-1 and year 2013 'Laura' HP50 had yield 35.9 t ha-1. The main role of the addition of HP is improving nutrient mobility in the soil and higher uptake of nutrients to plants. Positive effect of HP should appear when plant is growing under unfavourable conditions
