STRESS DAY INDEX MODELS TO PREDICT CORN AND SOYBEAN RELATIVE YIELD UNDER HIGH WATER-TABLE CONDITIONS

High water table conditions reduce crop yields. This study developed corn and soybean relative yield models for high water table conditions. The relative yield models were based on Stress-Day-Index (SDI) relationships using SEW30 (0.3-m water table depth) to describe the high water table stress criteria and normalized SDI crop susceptibility (CS) factors. The normalized crop susceptibility (NCS) factors were determined from previous studies conducted in North Carolina. The models were developed using existing field data for SDI and crop yield from Ohio. The resulting corn model was tested against data from India and North Carolina and explained 69% of the relative yield variance for the pooled data. The soybean model explained 66% of the variance in relative yield for six years of soybean data from Ohio. The models developed should improve relative yield estimates using DRAINMOD, a water table management simulation model.