| Summary: | As some trace elements can enhance plant nutrient uptake and assimilation, it was hypothesized that foliar silicon application could enhance nutrient content in early-crop potato tubers. The effect of dosage (23.25 g Si∙ha<sup>−1</sup> or 46.50 g Si∙ha<sup>−1</sup>) and time (the leaf development stage—BBCH 14–16, tuber initiation stage—BBCH 40–41, at both the leaf development stage and tuber initiation stage) of the silicon application on the nutrient contents in early crop potato tubers was investigated. Silicon had no effect on the potassium (K), phosphorus (P), calcium (Ca), or magnesium (Mg) contents in potato tubers, but it reduced sodium (Na) accumulation, especially under water deficit conditions during tuber bulking. This resulted in a reduction in the mass ratios of Na<sup>+</sup>/Ca<sup>2+</sup> and Na<sup>+</sup>/Mg<sup>2+</sup> in tubers. Silicon dosage significantly affected the Na accumulation by potato tubers only in the warm and very dry growing season. Under drought stress, silicon at 46.50 g Si∙ha<sup>–1</sup> reduced the Na content in potato tubers more than at 23.25 g Si∙ha<sup>−</sup><sup>1</sup>. Under periodic water deficits, the time of silicon application affected the Na accumulation by potato tubers more than the silicon dosage. The Na content in tubers was the highest with two silicon applications. Although silicon reduced the Na accumulation, the ratio of the sum of univalent cations to the sum of bivalent cations (K<sup>+</sup> + Na<sup>+</sup>)/(Ca<sup>2+</sup> + Mg<sup>2+</sup>) in tubers was at the same level, both in cultivations with and without silicon.
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