Plant-available water (PAW) capacity is one of the fundamental soil properties affecting crop yield. For claypan soils in Central Missouri, the topsoil thickness above the claypan layer is highly related to profile PAW, and in turn greatly influences crop yield. Quantitative determination of PAW capacity at a field scale has been challenging. A Simple Inverse Yield Model (SIYM) was devised and applied to estimate PAW capacity at high resolution for well-drained Wisconsin soils. The SIYM first simulates corn yield with using a daily water budget model for a range of PAW levels, and then PAW is inversely estimated by matching measured yield data with simulated yield. The objectives of this study were to investigate on claypan-soil landscapes (1) corn (Zea mays L.) grain yield variability and the relationships between PAW and corn grain yield, and (2) SIYM performance for estimating PAW capacity. Corn yield obtained from two claypan-soil fields for a total of nine site-years were used with the model to estimate PAW capacity. The correlations between corn yield and the measured profile PAW were only significant for water-stressed years. The regression r2 values between SIYM-estimated PAW capacity and the measured profile PAW¬ capacity were 0.43 for Field 1 and 0.31 for Field 2 with respective errors of 18 mm and 50 mm. The large error for Field 2 was primarily contributed from estimates at highly-eroded backslope areas. The SIYM did not perform for claypan soil as well as for well-drained soils probably because claypan hydrological characteristics complicate the dependency of corn yield on PAW and introduce additional variability in yield. This additional variability weakened the working assumption of the SIYM of profile PAW being the primary yield-limiting factor. These limitations need to be addressed when apply SIYM for claypan-soil fields.