A condition for achieving a high potato tuber yield on an early harvest is to provide plants with good growth conditions. In modern horticulture, plant growth stimulants have been gaining increasing importance. This study examined the effect of dose (0.2 dm³ ha^–1 or 0.4 dm³ ha^–1) and date (leaf development stage – BBCH 14-16, tuber formation stage – BBCH 41-43, leaf development stage and tuber formation stage) of Tytanit^® application (8.5 g Ti in 1 dm³) on the growth of very early-maturing potato cultivars (‘Lord’, ‘Miłek’). Following the Tytanit^® application, the plants were higher and produced a greater aboveground biomass and tuber weight, however, the leaf weight ratio (LWR) and leaf area ratio (LAR) were lower than in the cultivation without the growth stimulant. Tytanit^® had a greater effect on the leaf weight ratio (LAR) and tuber weight for the ‘Lord’ cultivar. Tytanit^® dose had no effect on the plant growth. A double Tytanit^® application resulted in a reduction in the length and weight of stems and tuber weight. The date of Tytanit^® application had no effect on the weight of leaves. The leaf area ratio (LAR) was the highest when Tytanit^® was only applied in the tuber formation stage, and the leaf weight ratio (LWR) was the highest when Tytanit^® was applied twice. A positive correlation was found between the tuber weight and the LWR and LAR.

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