Relating Water Stress to Yield Estimates Using Thermal Remote Sensing: An Application across the U.S. Corn Belt

Water deficits are the single most important factor limiting crop yield. Evapotranspiration (ET) includes crop water use through transpiration as well as water lost through evaporation from the soil. ET is, therefore, an indicator of soil moisture availability and vegetation health. The Evaporative Stress Index (ESI) is an ET-based crop stress index that represents the temporal anomalies in the ratio of actual to potential ET. ESI has demonstrated capacity to explain regional yield variability in water limited regions. However, its performance in some regions where the vegetation cycle is intensively managed appears to be degraded. In this study, we extend the field-scale mapping of ESI and the analysis of ESI-yield correlations to three sites across the US Corn Belt: Ames, IA, Bondville, IL, and Mead, NE. We have demonstrated field-scale ESI has the advantage of being able to resolve different crop types with varying phenology. Moreover, incorporating phenological information can improve yield-correlations by accounting for effects of phenology such as variable planting date and emergence date. However, this improvement is predicated on the availability of accurate yield data for model development. This approach prototypes a methodology that benefits operational yield monitoring using remote sensing based ET estimates.