Issue link: https://www.e-digitaleditions.com/i/1463529
ALMOND ORCHARD 2025 GOAL One approach is to use a pressure chamber to sample several trees over time, and select whichever trees are closest to the average. If those trees are adequate representations of the block, then they should give you representative data. Another option for highly variable orchards might be to evaluate soil variability. Kisekka is working with a grower who has implemented zone irrigation management. The grower mapped his soil based on electrical conductivity so that he could irrigate soils with similar infiltration rates together. Even without the irrigation set up this way, installing sensors in each of these zones could be beneficial to understanding the varying levels of tree stress that could be occurring at any given time, rather than just irrigating to the average. The full picture for irrigation decisions Determining when to irrigate with these technologies is a critical question. But for the full picture to make irrigation decisions, growers need to know not only when to irrigate, but also where and how much. Dr. Kisekka's research is unique in that it's looking to answer all three of these questions, with particular emphasis on the "where." 2 "If you have an orchard, it's very unlikely that you're going to have uniform yield everywhere in the orchard," said Kisekka. "So we try to implement precision irrigation management where we try to raise the yields in poor producing areas, or if we can't raise the yields then we should reduce inputs." Through soil mapping, sampling and soil moisture probes, Kisekka is able to get a really good picture of the reservoir of available water for the crop and its capacity in various areas of the field to take on more moisture. As he is collecting this data, Kisekka is also experimenting with a new type of neutron probe that can measure soil moisture over an entire block, called a cosmic ray. This is not something growers are using but could be very useful for measuring soil moisture across a large area. Interestingly, Kisekka is observing a correlation between the data from this cosmic ray neutron probe and stem water potential. This may be another potential indirect measurement for stem water potential in the future over a large area. Shackel cautions against relying too heavily on soil-based measurements to determine tree water stress. "Measuring the soil moisture to tell if the plant is stressed is a little like feeling the hospital bed to determine if the patient has a fever," he said. Both researchers emphasize an approach that measures both the soil and the trees themselves. To complete the picture, Kisekka is also looking at evapotranspiration data from satellite remote sensing and validating that against an in-orchard flux tower, similar to the work that is happening with the T-Rex project. His research is finding that the remote sensing service IrriWatch agrees with the very precise measurements he is taking from the flux tower in the orchard. This satellite service offers daily evapotranspiration (actual ET) measurements via satellite down to ten meter by ten meter resolution, which answers the question of how much water the orchard is using. Bringing these three areas of data together is ultimately what growers will need to answer the fundamental irrigation questions of when, where and how much. "The soil, the plant, and the atmosphere each help us answer a different question," said Kisekka. "And that's why our research is unique: because we are looking at more of a complete picture of irrigation management." The next steps in water use efficiency Growers have achieved unprecedented efficiency gains in recent decades. To reach absolute peak performance, the next steps will require site-specific precision irrigation that is optimized to meet the needs of the trees themselves. The ongoing research to validate these commercially available sensors is an important step toward the Almond Orchard 2025 goal to reduce the amount of water used to grow a pound of almonds by an additional 20%. 3 2 Youtube "Next Generation of Almond Orchard Irrigation System Designs" https://www.youtube.com/ watch?v=taVjfbdpGms 3 https://www.AlmondBoard.com/Goals Efficient Okay Poor Identifying Orchard Pockets With Sensors Water stress levels in an orchard can vary, even down to the tree. Selecting the right tree to monitor as an average for an area is crucial. Almond Board of California 14