The effect of climate change on water requirement of soybean in Gorgan

Climate change affects precipitation and temperature patterns and hence, may alter the crop water requirements. This research was conducted to evaluate the effects of climate change on evapotranspiration of soybean in Gorgan province. LARS-WG model was used to generate temperature and rainfall data for future period (2013-2042) under emission scenarios of B1, A2 and A1B. The generated and observed weather data for baseline period of (1985-2012) were considered as inputs for a crop-weather model namely, SSM. Soil evaporation, crop transpiration and water requirement of irrigated and rainfed soybean crop were simulated for eight different dates of sowing ranging from the May 11th to 24th July with 10 days interval. Test of significance of means showed an increasing trend in daily maximum and minimum temperature for most of the months, and for mean monthly values of rainfall in fewer months. The outputs of SSM model showed that during future period, soil evaporation would slightly decrease, but plant transpiration would increase. This increase is more significant in case of rained crop for about 15 percent. Evapotranspiration showed not significant change for irrigated crop in future period, but in rainfed conditions a 10 percent increase has been revealed. Finally, rainfed cropping of soybean is not common in the region it can be concluded that climate change will not significantly affect water requirement of soybean in Gorgan region.