The investigation, carried out in the years 2008-2009, aimed an assessment of effects of four factors: place of growing, irrigation, presprouting of seed potatoes and use of effective microorganisms on marketable quality of potatoes grown under organic farming system. Eight cultivars, representing different earliness groups, were tested. Genotype had the largest influence on occurrence of external and internal tuber disorders. The place of growing (soil type) affected occurrence of common scab, black scurf, deformations and rust spot. Drip irrigation reduced incidence of common scab, tuber deformations and rust spot. Presprouting of seed potatoes and effective microorganisms exerted the smallest influence on the marketable tuber quality.
