For soybean producers, K fertilizer is the costliest input; while under-fertilization can decrease seed yields, over-fertilization may not result in a yield increase. Our recent work at Edisto REC showed that over-fertilization of K can reduce soybean seed yields. Hence, from a producer’s perspective, finding the optimum K fertilizer application rates is vital. Moreover, despite being an immobile nutrient in the soils, K still leaches out of the root zone in sandy, low organic matter soils. These factors together make K of greater concern for South Carolina soybean producers. Hence, this project aims to determine optimum K fertilizer rates to maximize soybean yields and farm profits.