Abstract Improved irrigation water management requires accurate scheduling of irrigations which in turn requires an accurate calculation of daily crop evapotranspiration ( E t). Previous work by Neale et al. (1989) and Bausch (1993) have indicated that the reflectance-based crop coefficient ( K cr) for corn responded to crop growth anomalies and should improve irrigation scheduling. Thus, the purpose of this study was to develop a new procedure for using the K cr in irrigation scheduling and present results of simulations comparing different basal crop coefficient ( K cb) curves for corn to evaluate their effects on estimated crop E t. Irrigation scheduling simulations were performed using SCHED, the USDA-ARS Irrigation Scheduling Program, and three K cb curves (the one in SCHED, Wright's (1982) tabular data, and the K cr-based K cb). Simulated crop water use using the K cb curve in SCHED was considerably greater during vegetative growth (60 to 100 mm) than simulated crop water use using Wright's K cb or the K cr derived K cb curves for three growing seasons. Crop water use between the K cr-based K cb and Wright's K cb were different by approximately 20 mm each growing season. Crop water use was less in 1990 and 1992 for the K cr derived curve and greater for 1991; crop development was directly responsible for the differences. Although the differences between the Wright and Kcr basal crop curves were minimal, irrigations with the K cr-based K cb were more appropriately timed. Irrigations that are correctly timed minimize overirrigation as well as underirrigation.