Comparative study of potassium rates and sources on potato yield and quality in Florida

Abstract Sandy soils are prone to potassium (K) leaching; therefore, developing guidelines for the optimum K application rate and fertilizer source is necessary. This research aimed to evaluate the optimum K fertilizer rates and identify the best K fertilizer sources for potato ( Solanum tuberosum L.) production, considering the impacts of insufficient or excessive fertilization on potato yield and tuber quality. The experiment was carried out on Florida sandy soil in a randomized complete block design with four replications and nine treatments, a combination of three K sources (potassium sulfate [K 2 SO 4 ], potassium chloride [KCl], and potassium magnesium sulfate [K 2 Mg 2 (SO 4 ) 3 ]) and three rates (224, 280, and 336 kg K 2 O ha −1 ). Potato tuber yield was affected by different K fertilizer sources. Applying KCl resulted in a 10.3% and 9.0% increase in marketable and total tuber yield, respectively, compared to K 2 SO 4 . However, KCl application resulted in significant tuber quality deterioration regarding lower tuber‐specific gravity. Yield and quality of potatoes were improved with the application of K₂Mg₂(SO₄)₃. No significant increase in tuber yield with increasing K rates from 224 to 336 kg K 2 O ha −1 . The highest K rate (336 kg K 2 O ha −1 ) resulted in a 10‐fold and threefold drop in tuber‐specific gravity values in 2022 and 2023, respectively, compared to 224 kg K 2 O ha −1 . These results suggest that K application rate and fertilizer source must be optimized to balance potato yield and tuber quality.