Evaluation and improvement of CROPGRO-soybean model for a cool environmentin Galicia, northwest Spain

This paper describes the evaluation and improvement of the CROPGRO-soybean model for a cool environment in northwest Spain. The model was evaluated wi th a soybean (Glycine,max L.) 1994 field data set with three cultivars and three planting dates, The original model proved to underestimate biomass an d seed yield, so modifications were made to the temperature functions affec ting N-2 fixation and photosynthesis, in order to fit better to the experim ental data. The modified model was then tested, i.e., validated, with indep endent experimental data collected in 1995 at the same site with the same c ultivars and four planting dares. Comparing observed with simulated data in 1994, the modified model decreased the root mean square error (RMSE) for b iomass at harvest and seed yield from 1714 to 466 and from 940 to 333, resp ectively. For 1995, the validation year, RMSE for biomass decreased from 13 66 to 352, although the yield was now overestimated with no significant cha nge in RMSE. The average simulated harvest index (HI) for 1995 was greater than for 1994, the reverse of the measured values, Nevertheless, the modifi ed model was more reliable in predicting crop performances under these cool conditions than the original model. Moreover, the predictions of the modif ied model for a warm climate (Gainesville, FL) were quite acceptable. We co nclude that the modified model can be used successfully over a wider range of climates than the original version. (C) 1999 Elsevier Science B.V. All r ights reserved.