Muriate of potash (KCl) is the most commonly used source of potassium (K) fertilizer for potato (Solanum tuberosum L) production in the San Luis Valley of Colorado. This study was designed to investigate the effect of a new source of potassium fertilizer-potassium acetate (Bio-k) as supplemental application to KCl in Mesa Russet potato production. This study was conducted at Colorado State Universitys San Luis Valley Research Center in 2016 and 2017. Treatments included (1) Preplant application of Bio-K (Bio-K Pre), (2) Bio-K pre + one time application of foliar Bio-K (Bio-K Pre + foliar), (3) Foliar application of Bio-K twice (Bio-K foliar twice), (4) Preplant application of KCl (KCl pre), (5) One time application of foliar Bio-K (Bio-K foliar once), and (6) a control treatment where no K fertilizer was applied. 44.8 kg KCl/ha was banded in all treatments except the control treatment before any supplemental application of Bio-K. Bio-k pre increased total tuber yield in both years compared to all other treatments except the one-time application of foliar Bio-K treatment. In this study, the application of Bio-K pre-plant increased marketable tuber size (> 114g), large marketable tuber size (> 170 g), and premium tuber size (> 284 g) yields in both years compared to the control treatment. For tuber bulking, Bio-k foliar twice, Bio-k pre, and Bio-k pre followed by one-time foliar application of Bio-k increased tuber bulking than the control at 105 days after planting (DAP), and one-time foliar application of Bio-K increased tuber bulking than the control at 118 DAP. No difference was observed in tuber bulking among treatments in 2016. It can be concluded that supplemental application of Bio-k in Russet potato production improves tuber yield and tuber quality.