Indiana Soybean System Model (ISSM): I. Crop model evaluation

Abstract A soybean crop model, SOYGRO version 5.41, satisfactorily simulates soybean growth, development and yield under Indiana conditions, following the calibration of varietal coefficients and the use of water retention values to approximate soil water limits. Century 84 (MG II) and Williams 82 (MG III) soybeans were grown at two locations during 1985–1989 to provide crop growth and yield data for model calibration and validation. Model predictions tracked the observed trends in soybean yield over the years, and the patterns of crop growth and development through the season. Predicted values of yields, leaf area index and other crop growth indicators were mostly within one standard error (SE) of observed means in 1988 (severe drought) and 1989. Simulation experiments showed that yield potential at Bedford (southern Indiana) was higher than at Throckmorton (central Indiana) for all planting dates (10 and 25 May and 5 June). Century 84 has a slight yield advantage over Williams 82 for 10 May planting. If 1988 drought is excluded, this yield advantages is stochastically dominant. For late planting (5 June), the reverse is true (Williams 82 yielded more). There was no difference for 25 May planting. Using Duncan's multiple range test groupings, a set of typical weather years were obtained. This grouping, based on crop yield potential, will be useful in simulation analysis for pest management strategy evaluation.