How We Grow

2022 Spring How We Grow

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WATER USE ALMOND ORCHARD 2025 GOAL Precision Irrigation Research: Sorting through the Sensors The number of new technologies for irrigation can be both exciting and overwhelming. Sorting through marketing and product information for various products can make it difficult to answer the question that most growers want to know: what is needed to get peak performance from an orchard with as little water as possible? UC Davis professor Ken Shackel believes the optimal answer to this question will come directly from the trees themselves. This represents an important paradigm shift for many almond growers. "I think where we've gotten off track is to think about irrigation as an engineering decision rather than a biology decision," Shackel said. He has spent much of his career researching viable ways for growers to irrigate based on early detection signals from the trees themselves. There are a variety of sensors that are marketed to provide this type of plant- based information for irrigation decisions. Shackel says most are theoretically sound, but he wants to confirm if they perform reliably in orchard environments. Measuring up to the pressure chamber This all started in the 1990s when researchers from the University of California demonstrated that stem water potential readings as a measurement of plant water status were a useful indicator to define irrigation decisions. This led to the promotion of the use of the pressure chamber as a basis for irrigation management in almonds for more than two decades. "Although the pressure chamber provides fundamental assistance to define when to irrigate, the adoption of the pressure chamber across the industry remains fairly low," said Sebastian Saa, associate director at the Almond Board of California (ABC). "This is mostly due to constraints with labor, technical training and the limited time within a day to assess midday stem water potential." Despite these challenges with the pressure chamber, there have been few other validated tools or approaches that have matched its accuracy and reliability when determining when to irrigate. But this may be changing, based on recent research that evaluates the validity of some of the sensors currently available to growers. Making sense of all the sensors The pressure chamber remains the standard for plant-based water potential measurements. But given the logistical challenges keeping the pressure chamber from achieving wider adoption, the industry is evaluating more automated alternatives that can be fixed on trees in the orchard to provide continuous data to growers. In separate research experiments, Shackel and associate professor Isaya Kisekka have been comparing results Micro-tensiometers Continue on page 13 Almond Board of California 12

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