Comparison of two soya bean simulation models under climate change : II Application of climate change scenarios

The effects of climate change (for 2050 compared to ambient climate) and change in climatic variability on soya bean growth and production at 3 sites in the EU have been calculated. These calculations have been done with both a simple growth model, SOYBEANW, and a comprehensive model, CROPGRO. Comparison of the results from the 2 models indicated the sort of climate change conditions in which model results differed and may become less reliable. The effectiveness of possible management responses to climate change and the uncertainty in the model results were also evaluated with both models. Both models calculated for the climate change scenarios at Oxford a strong increase in irrigated seed yield. For Montpellier and Seville, however, CROPGRO calculated a considerable increase in irrigated yield for these scenarios, whereas SOYBEANW calculated only a slight increase. Without irrigation, the seed yield increase for the climate change scenarios was almost identical for the 2 models, i.e. considerable, slight and nil for Oxford, Montpellier and Seville, respectively. Changes in climatic variability did not result in a yield change at any site, both with and without irrigation and both for CROPGRO and SOYBEANW. With irrigation, the change in the coefficient of variation (CV) of seed yields by climate change was nil (except for decrease at Oxford) for both models and without irrigation, this change in CV was variable depending on site, climate change scenario and model. The management response analyses showed that the crop variety did not need to be changed in response to climate change, that the yield increase due to climate change was stronger for an advanced sowing date (but only without irrigation), and that irrigation requirements decreased with climate change only in the case of an early sowing date. This pointed to the need for advancing the sowing date with climate change. The uncertainty analyses showed that the yield change due to climate change was practically not affected by the used crop variety and soil type, but that this yield change may become different when a different growth model was applied or a different sowing date was chosen