Response of potato tuber yield and uptake to potassium and nitrogen in sandy soils

Abstract Potassium (K) is essential for potato ( Solanum tuberosum L.) production, influencing physiological processes, nutrient uptake, and tuber quality. This study evaluated the interactive effects of K and nitrogen (N) on potato yield and quality in Florida's sandy soils to determine optimal K application rates for maximum yield and improved N use efficiency. A 2‐year experiment was conducted in a split‐plot design with three N rates (168, 224, and 280 kg N ha −1 ) in the main plot and six K rates (0, 112, 224, 336, 448, and 560 kg K 2 O ha −1 ) in subplots in four replications in Hastings, FL. Results revealed a significant effect of seasons on the soil K availability, uptake, tuber yield, and nutrient use efficiency. The soil K levels and uptake increased with higher K application rates across all potato growth stages. Regression analysis identified optimum K rate of 425 and 535 kg K₂O ha −1 for total and marketable tuber yield, respectively. In the first season, total tuber yield increased by 33% and 38% at K application rates of 336 and 560 kg K₂O ha −1 , respectively, compared to no K application. Tuber specific gravity was not affected by K rates, while the higher K application rates increased the N use efficiency and decreased benefit‐cost ratio. The study concludes that K application rates above 425 kg K₂O ha −1 maximize potato tuber yield and enhance N efficiency, supporting the revision of K recommendations in sandy soils based on low K status.