This work presents the results of the study on the effect of ridge shape (the height of ridge) and harvest time, defined by the soil temperature, on the yield structure of three table potato cultivars. Analysis was performed based on three-year results (2004-2006) obtained from the experiment established in the split-split-plot design at the Agricultural Experimental Station in Zawady of the University of Natural Sciences and Humanities in Siedlce. Irrespective of the cultivar, tubers with a diameter from 50 to 60 mm constituted the largest proportion in the total yield, while the smallest tubers of the fraction below 30 mm. Harvest time had a significant effect on the weight of small tubers fraction with a diameter to 30 mm and from 30 to 40 mm. ridge shape significantly modified the yield of tubers with a diameter from 50 to 60 mm. Significantly higher tuber yield was obtained from the typical ridge (with a height of 20 cm), than from the high ridge (24 cm). The yield of large tuber fraction, above 60 mm, depended only on the weather conditions prevailing in the growing season.

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