Simulated Effect of Dry Spells at Critical Growth Stages on the Performance of kharif Sorghum Hybrids

Potential impacts of climate change on grain sorghum (Sorghum bicolar) productivity were investigated using the CERES-sorghum model in Decision Support System for Agrotechnology Transfer (DSSAT) v4.7. The model was first calibrated for two sorghum hybrids for two consecutive years, 2011years, and 2012years, , by Manjangouda et al. (2019) ) under the Northern Transitional Zone of Karnataka. In this study validated and calibrated DSSAT CERES model for both the hybrids was used to simulate the effect of dry spells -2 weeks and 4 weeks before panicle initiation and end of grain filling stages across 3 dates of sowing (1 st fortnight of June, 2 nd fortnight of June and 1 st fortnight of July) and model was run for the two consecutive years 2011 and 2012. Pooled data of two years, simulated outputs showed that irrespective of hybrids, date of sowing, and phase of the crop, withdrawal of rainfall for 4W resulted in a higher grain yield reduction (48.27 %) as compared to withdrawal of rainfall for only 2W (23.96 %). Among the two crop phases tested the crop phase before PI was found to be more sensitive to dry spells as the model simulated 38.90 and 71.46 Percent reduction in grain yield with 2W and 4W skipping of rainfall, respectively. At the same time, only 9.02 and 25.09 percent reduction in yield was observed with skipping of rainfall for 2 W and 4W prior to EGF. Similar trend was observed for top weight and root weight. We conclude that crop simulation models are applicable to assessing possible impacts of climate change on Kharif sorghum. This study concludes that exposure of crop to low moisture stress at peak vegetative phase, i.e., 2W to 4W before PI, results in a higher reduction of the grain yield. Hence, if a dry spell occurs at this phase, supplemental irrigation should be provided to realize a higher grain yield.