A watershed-scale impact assessment on a second-generation transgenic soybean yield due to climate change

Global estimates suggest that climate change will lead to significant crop yield losses, mainly caused by drought and heat stress. Second-generation transgenic crops are expected to alleviate these constraints. HaHB4-soybean is a second-generation transgenic crop tolerant to high temperatures and dry growing conditions created in Argentina carrying the sunflower HaHB4 gene. In this study, the Soil andWater Assessment Tool (SWAT) was used to estimate the potential impacts of climate change on the HaHB4-soybean yield in the Carcarañá River Lower Basin (CRLB) by considering two greenhouse emission scenarios (Representative Concentration Pathway 4.5 and 8.5) projected by four Global Circulation Models for two future 18-year periods (near future, 2022-2039, and far future, 2082-2099). Synthetic HaHB4-soybean yield data were generated for the baseline period (1998-2015) using the calibrated CROPGRO-soybean model. This dataset was considered for calibration and validation of HaHB4-soybean yield in SWAT. The results indicate that average annual runoff, soil water content, and percolation increased by 90%-214%, 0.7%-24%, and 69%-270%, respectively, under the climate change scenarios compared to the baseline period. Thus, a higher frequency of severe flooding and an increase in the amount of water that recharges the aquifer should be expected in the CRLB for the rest of the 21st century. Our findings suggest that climate change will positively impact HaHB4-soybean yields under both RCP scenarios. The percentage change of the average annual HaHB4-soybean yield at the basin scale ranged from 2.8%-28% relative to the baseline period. These increments could be associated with a combined effect of increased rainfall and CO2 concentration plus the tolerance of HaHB4-soybean to higher temperatures. In terms of spatial distribution, the positive impact of climate change on HaHB4-soybean yield was found to be more significant in the upper (southwest) than in the middle-lower (northeast) region of the CRLB.