Sensitivity of the land surface temperatureand Normalized Difference Water Index tosoil moisture on wheat and barley

The synergy between spectral indices and land surface temperature (LST) has been used as an indicator of crop status and soil moisture (SM). However, studies of the response times of these to changes in SM in the soil profile arescarce. The aim of this study was to analyze the sensitivity and response times of LST and the Normalized Difference Water Index (NDWI) to changes in SM as a determining factor of barley and wheat water status in the southeasternArgentine Pampas. Daily SM and LST were provided by stations installed over the crops, and NDWI from Sentinel 2 (S2). Results showed instantaneous correlations between SM and LST (r > -0.65) for soil depths explored by croproots (20-50 cm). No consistent relationship between NDWI and SM was observed, suggesting NDWI limitation for short-time changes in SM in humid and sub-humid conditions. During the critical period of crops, the relationship between NDWI and SM showed high correlation (r > 0.92) only at 10 cmwhen considering 1-day time lag. This study contributes to the understanding of spectral behavior of crops in the optical and thermal spectrum in field conditions, which is key to evaluating the usefulness of these data for monitoring agricultural systems.