Agricultural limestone is commonly used in Iowa to maintain optimum soil pH for crops. However, there is insufficient information concerning the reaction time of lime sources in the soil and short-term effects on crop yield for different sources and application rates. This information is needed to improve soil pH management and lime recommendations. The objective of this study was to study the soil pH and crop response to the application of pure calcium carbonate (CaCO3), and calcitic or dolomitic limestone in a typical acid soil of northeast Iowa.