High-temperature indicators for capturing the impacts of heat stress on yield: lessons learned from irrigated wheat in the hot and dry environment of Sudan

Abstract

High temperatures occurring during flowering and early grain filling substantially decrease cereal yields. Drawing on accumulated evidence showing that, compared to air temperature (Ta), crop canopy temperature (Tc) better explains observed yield reductions caused by heat stress, we evaluated the usefulness of Tc versus Ta in designing high-temperature indicators for agrometeorological services, including crop monitoring and forecasting. The hot and dry environment of Sudan provides an ideal testbed. Tc was derived from the combined simulation of a crop model and a land surface model. Based on regressions linking the high-temperature indicators with irrigated wheat yield variations in 3 regions of Sudan over the last half-century, we found that using phenological periods rather than months for the wheat season (November to February), and using Tc rather than Ta, more effectively tracks the adverse effects of high temperature on yield during the key periods. The Tc-based indicators calculated for the key phenological periods have more robust multi-region applicability than the Ta-based indicators calculated for months and season, although they do not necessarily outperform the region-specific indicators in terms of explanatory power. We determined that the key periods were the vegetative growth period for the relatively cool region, and the reproductive growth period for the relatively hot regions. These findings suggest that agrometeorological services at the national and global levels should adopt Tc-based indicators, which will ultimately help players in global food systems adapt to climate change by preparing for wheat supply disruptions due to high-temperature extremes.