The prices of potassium (K) fertilizer and other fertilizers have increased significantly during the last two years. Profitable crop production requires appropriate soil K levels so careful fertilization planning is required. Iowa State University soil-test interpretations and fertilizer recommendations were updated in November 2002. Two important changes were to recommend higher soil-test K (STK) levels for optimum yield of Iowa crops and to suggest efficient K fertilizer application methods for some conservation tillage systems. These recommendations are explained in Iowa State University Extension publication PM 1688, A General Guide for Crop Nutrient and Limestone Recommendations in Iowa, which is available at your county extension office or at www.extension.iastate.edu/pubs.