Accuracy of remote soil moisture sensing using Sentinel‐1A satellite

Abstract Several studies have demonstrated the water conservation potential of soil moisture sensor‐based irrigation scheduling on turfgrass areas; however, research is lacking on the accuracy of satellite‐based moisture measurements. A field study was conducted in 2023 to investigate the accuracy of moisture values based on electromagnetic pulses emitted from the synthetic aperture radar mounted on Sentinel‐1A. The estimates based on satellite remote sensing were compared to measurements collected on fairways 2 and 7 of Sunset Golf Course (Las Campanas, NM) by a ground‐penetrating capacitance sensor (Toro Precision Sense 6000 [PS 6000]) during June and July 2023. The relationship between values estimated using Sentinel‐1A and readings from PS 6000 was significant but weak ( R 2 ranging from 0.01 to 0.045) on fairway 2 on all sampling dates. On fairway 7, the association was significant only on two of four sampling dates, reaching R 2 values of 0.015 and 0.021. The relationship was significantly negative (slope −0.37; R 2 = 0.037) for fairway 2 on one sampling date. Generally, the satellite‐derived soil moisture data underestimated soil moisture variability when compared to PS 6000 measurements and indicated a greater moisture uniformity than actually present. Results of our study indicate that Sentinel‐1A satellite data appear to be impractical for the purpose of determining soil moisture in turfgrass areas. More studies are needed to improve the accuracy of measurements and to determine if different mathematical models should be used to estimate soil moisture based on reflectance values on turf areas.