How We Grow

2021 July/Aug How We Grow

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ALMOND ORCHARD 2025 GOAL Saa is confident that the projects in the portfolio are asking the right questions on behalf of almond growers, and these interesting questions have attracted the very best researchers in this field of study. The result is a comprehensive irrigation portfolio, where each individual project is tackling grower priorities in a coordinated and collaborative manner. The synergy achieved by the projects within the irrigation portfolio has Saa understandably excited. This research is not only designed to bring data and validation to optimal irrigation but to produce models that growers can use to improve water use efficiency in their daily operations. The strategy hinges on visualizing how much an almond tree is transpiring, predicting how much the tree is going to be able to produce, and adjusting irrigation applications accordingly in real time. There are numerous variables that need to be analyzed, validated, and modeled to take this strategy from the research stage to the orchard. Visualizing actual tree evapotranspiration To optimize irrigation timing and amount, it is imperative to know exactly how water is being used in that orchard. No grower wants to undersupply water to their crop, thus, if left to estimation, it is likely that more water will be used than is necessary. A valid model that paints a picture of actual water use in an orchard, instead of using referential coefficients (i.e. Kc) to define how much to irrigate, will improve a grower's water use efficiency in the long term. This is especially critical in the current environment with emerging regulations such as the Sustainable Groundwater Management Act (SGMA). Drs. Bill Kustas, Andrew McElrone, Martha Anderson and Kyle Knipper of the USDA's Agricultural Research Service (ARS), Professor Alfonso Torres-Rua, of Utah State University, among others, have collaborated to build a model for determining actual tree evapotranspiration (ETa) in winegrapes through a project called GRAPEX. 4 The team is now carrying over that same expertise and multidisciplinary collaboration from grapes to almonds in the Tree Crop Remote Sensing of Evapotranspiration EXperiment (T-REX). Applying a similar approach to their success in winegrapes, the team will validate their model specifically for almonds and make it available on OpenET, 5 a public-private partnership that makes satellite-based data on evapotranspiration widely accessible. This means that in the future growers will be armed with actual ET data for each of their orchards down to the individual tree level, which can be far more precise than using traditional approaches of expected evapotranspiration and crop coefficients. Most growers do not yet have variable rate irrigation down to the tree level, but Kustas – who was recently named to the USDA-ARS Science Hall of Fame for his work in remote sensing for improved irrigation water scheduling – believes this is coming in the long-term. This data will inform growers on which trees are stressed and need extra water, and where the orchard can still thrive with less. The ability to use satellite information in this area will also allow growers to observe actual tree transpiration variability in an affordable and practical manner at multiple resolutions (i.e. tree level, block level, orchard level, etc.). 6 5 OpenET 6 "Two Scientists Named to ARS Science Hall of Fame" DATA INPUT Advancements in water use efficiency begin with understanding exactly what's happening at the individual tree level. Researchers will use data from satellites, drones, and ground sensors as well as tree-level yield data to evaluate water use of each individual tree in the orchard. Tree Sensors ETa Imagery Data Yield Spatial Variability Smart Controllers Individual Tree Irrigation Density Tracking Technologies Continue on page 11 "Growers don't want just another website to visit or scientific paper to read. They want answers." — Sebastian Saa Almond Board of California 10

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