Abstract (from Science Direct): Agricultural drought is characterized by low soil moisture levels that negatively affect agricultural production, but in situ soil moisture measurements are largely absent from indices commonly used to describe agricultural drought. Instead, many indices incorporate weather-derived soil moisture estimates, which is necessary, in part, because the relationships between in situ soil moisture and agricultural-drought impacts are not well quantified. Our objective was to use in situ soil moisture data from monitoring networks in Oklahoma and West Texas to identify a soil moisture-based agricultural drought index that is (i) strongly related to crop-yield anomaly across networks, (ii) comparable across time [...]