ASHS 2025 Conference

Salinas Valley is a major U.S. production region for cool-season vegetables. As regional producers work to achieve groundwater sustainability, there is a growing need to improve irrigation efficiency while sustaining crop yields. Recent advancements and availability in satellite-derived evapotranspiration (ET) data provide opportunities to inform on-farm water management. Quantifying the accuracy and limitations of these methods, however, remains important to build trust for increased operational adoption. This is especially the case for short-season vegetable crops, where performance evaluations of satellite-derived ET have been limited to-date. OpenET is a free, publicly-available platform that uses an ensemble of six satellite-based models to monitor and archive daily-to-monthly ET throughout the western U.S. at 0.25 acre resolution. In this study, daily OpenET values were compared with in-situ ET data from an eddy covariance system deployed in commercial broccoli fields during 2023 (66 days) and 2024 (76 days). Applied water was measured by an on-site digital flow meter, and precipitation was recorded by a nearby weather station. Cumulative totals from the OpenET ensemble mean were within 8.2% and 0.7% of in-situ data during the 2023 and 2024 deployment periods, respectively. Summary performance metrics were within previously published ranges for cropland sites during 2023 (mean bias error: 0.27 mm/day, mean absolute error: 0.65 mm/day) and 2024 (mean bias error: 0.02 mm/day, mean absolute error: 0.61 mm/day). Ensemble ET totals represented 88% of the 344 mm of total water received from irrigation and rainfall for the full crop cycle in 2023 (92 days), and 67% of 518 mm water received during 2024 (101 days). Results indicate OpenET quantified crop water consumption at these two sites with reasonable accuracy, while revealing differences in irrigation application efficiency. Additional discussion will address potential sources of satellite model uncertainty, challenges of collecting eddy covariance data in commercial plantings of short-season horticultural crops, and future verification efforts planned for regional high value specialty crops.