Potassium (K) fertilizer for corn and soybean has been studied widely across the northcentral US, but research has been limited in Indiana recently. This study evaluates the effects of potassium fertilizer in a corn and soybean rotation on soils that are low in soil test K in Indiana. Many plant and soil measurements were studied including, visible atmospheric resistant index, leaf K, grain yield, grain K concentration, and soil K and is presented in the text.