Relationships between the evaporative stress index and winter wheat and spring barley yield anomalies in the Czech Republic

Abstract

There is a growing demand for timely, spatially distributed information regarding crop condition and water use to inform agricultural decision making and yield forecasting efforts. Thermal infrared remote sensing of land-surface temperature has proven valuable for mapping evapotranspiration (ET) and crop stress from field to global scales using energy balance models. This is because canopy temperature is strongly regulated by the transpiration flux, which is reduced under stress conditions. This study investigates the utility of an evaporative stress index (ESI), computed using the thermal-based Atmosphere-Land Exchange Inverse (ALEXI) surface energy balance model, for explaining yield variability over the Czech Republic for the period 2002-2014. ESI timeseries, representing standardized anomalies in the actual-to-reference ET ratio and an indicator of vegetation health, are compared with yield data collected for winter wheat and spring barley crops in 32 agricultural districts, comprising a range of climatic conditions within the Czech Republic. Correlations between ESI and yield anomalies vary with climatic region, with strongest correlations identified in the more drought-prone South Moravian districts and weaker relationships in the wetter highlands regions. In most regions, correlations with spring barley yield anomalies exceeded performance for winter wheat. For both crops, correlations peaked during the 1 to 2 mo period prior to the nominal harvest date. These results provide guidance for effective integration of remotely sensed moisture stress indicators within operational yield forecasting systems.