EJSSEurasian Journal of Soil ScienceEurasian J Soil Sci2147 - 4249Federation of Eurasian Soil Science Societieshttp://ejss.fesss.org/10.18393/ejss.189467310.18393/ejss.1894673Dose- and source-dependent effects of foliar potassium on growth, tuber yield, and leaf nutrient status of potato (Solanum tuberosum L.) cv. ÇanlıbelZarbayim Babacanov Nazrin Rahmanova Sanubar Alakbarova Müjgan Masimli Ulkar Qanbarzade Shaban Maxsudov Rahila İslamzade rehile.islamzade@asoiu.edu.az152279-2902025-10-142026-02-142026-02-232026-04-01 Copyright © 2016 The authors and Federation of Eurasian Soil Science Societies Potassium (K) plays a central role in potato physiology and tuber bulking, yet foliar K programs may differ markedly depending on application rate and fertilizer source. This study evaluated the effects of foliar K source and dose on vegetative growth, tuber yield, and leaf nutrient status of potato (Solanum tuberosum L.) under controlled conditions. The experiment was conducted in a growth chamber from 2 February to 2 May 2025 using certified seed tubers of cv. Çanlıbel (Azerbaijan), obtained via the apical meristem technique and pre-sprouted for 20 days at 25 ± 2°C. A clay soil was used as the growing medium, and pots were maintained at 100% plant-available water throughout the experiment. Treatments were arranged in a completely randomized design with three replications (n = 3) and included a control (no foliar K) and foliar applications supplying 500, 1000, or 2000 mg kg⁻¹ K₂O from four K sources: KCl, K₂SO₄, KNO₃, and potassium silicate (K₂O₃Si). Foliar sprays were applied twice during the tuber bulking period using Tween-20 (0.1%) as a wetting agent. Foliar K significantly improved canopy development, increasing stem number, stem diameter, plant length, and total leaf number relative to the control, with responses generally strengthening as K₂O dose increased. Tuber yield per plant increased from 531 ± 25 g in the control to 663 ± 41 g under 2000 mg kg⁻¹ K₂O as KNO₃, while tuber number varied within a comparatively narrow range, indicating that yield gains were driven primarily by improved tuber bulking rather than tuber set. Leaf macronutrient concentrations (especially N and K) and micronutrients (Fe, Cu, Zn, and Mn) were enhanced by foliar K, with the greatest and most consistent improvements observed for KNO₃, followed by potassium silicate and K₂SO₄. Overall, foliar K application during tuber bulking-particularly KNO₃ at ≥1000 mg kg⁻¹ K₂O—was effective for improving potato growth, yield, and nutritional status under non-limiting water conditions.Potato, foliar fertilization, potassium sources, tuber bulking, nutrient status, yield components.