A previous study used forty-two years of daily precipitation and evapotranspiration data (1959 - 2000) along with yearly crop yield data for the Kentucky locations of Louisville, Lexington and Paducah to determine time periods during the growing season when it is critical for the crop to have adequate moisture to make maximum yield. Averaging the results for the three locations found that the critical moisture interval (CMI) begins roughly 55 days (approximately 8 weeks) into the growing season and lasts for approximately 2 weeks. This study was conducted to quantify the amount of moisture necessary during the CMI to maximize crop yield. The amount of yield increase during the CMI was determined by establishing a base yield prior to the CMI of 1,200 lb/acre and this value was used as a measure of crop growth progress in the first eight weeks of the growing season for each location. The yield increase during the CMI for each season and location was determined as the difference between the base yield and the yearly average yield. Predicted yield increases during the CMI were subsequently predicted using a quadratic equation with CMI precipitation as the independent variable. For Lexington, Louisville and Paducah the resulting equations predicted maximum yield increases of 1,385, 1,658 and 1,002 lbs/ac for corresponding moisture amounts of 3.02, 5.46 and 2.45 inches of moisture respectively. On average the resulting equations showed that one to three inches of moisture during the CMI should provide a substantial yield increase during the CMI of 944 to 1,273 lbs/acre.