David Doll0 commentsAugust 6, 2020Technology

Technology Corner: Q&A w/Tule Technologies

EDITOR’S NOTE: This entry is part of a series to highlight a new technology related to almond and tree nut production. The question/answer format is set to focus more on the technical aspects and application of the technology. In many articles, I discuss the importance of irrigation. With that in mind, I though I would reach out to a company that assists with irrigation scheduling based on site-specific data: Tule Technologies. Thanks to Valerie Bednarski for taking the time to answer my questions. Tule is an irrigation technology that determines site specific water use for a specific crop. How does this technology work? Tule measures the actual evapotranspiration (ET) of your orchard. We are able to do this using the Surface Renewal Method that was developed at the University of California at Davis (Paw U et al. 1995; Snyder et al. 1996; Shapland et al. 2012a and 2012b; Shapland et al. 2014). ET is the process of evaporation from plant and soil surfaces and from within plant tissues (i.e., water movement through stomata). In most modern agricultural systems, ET is the dominant process of water loss from a field. (Editor’s note: more info on ET here) What equipment is installed, and resources are used to determine water use? The Tule Sensor is installed in the orchard and is positioned above the canopy. The sensor is able to measure the amount of evapotranspiration from the orchard based on air movement.  As the wind moves over your orchard, it picks up the water that transpires from the trees and carries it to our sensor. This is how we are able to measure the crop water use over a broad area. An installed pressure switch is fitted to the irrigation system. This provides a direct measurement of irrigation durations. Using site specific irrigation specifications,

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David Doll0 commentsJanuary 29, 2020Horticulture, Irrigation

Influence of water availability on orchard spacing and development

Orchard canopy coverage has been shown to correlate with yield. As canopy size increases, more sunlight is intercepted by the leaves. This leads to the production of more energy that can be directed to the tree, leading to more growth, and therefore more crop. Correlation of intercepted light at mid-day (PAR) and kernel yield per acre. Research conducted by Lampinen, et al. What is often forgotten is the most critical to canopy development: water. Without access to water, tree canopy growth will slow or stop due to the reduction of gas exchange and photosynthesis, leading to smaller canopy size. Water is generally limited within an orchard system by either supply (e.g. reduced access to irrigation water) or delivery issues (e.g. irrigation engineering or water infiltration issues). To complicate this even further, water availability is not necessarily simply the amount of irrigation water available per area of orchard. It also takes into account rainfall that has been stored within the soil, general water availability, system engineering and distribution uniformity, and water infiltration rates. Limitations in any of these will lead to a reduction of the tree’s available water. Work by researchers in California has shown the correlations of canopy coverage with yield. This research was performed by gathering the amount of light intercepted at mid-day and comparing it to measured yields within orchards in California. This work has identified that high-producing orchards tend to alternate around 50 kernel lbs for every 1% of light intercepted, giving a theoretical maximum yield of 5000 lbs/acre.  Since it takes water to develop the canopy, this correlation can be also be extrapolated to water use: every percent of the tree’s water needs met will provide roughly 50 kernel lbs of crop in California’s growing conditions. An orchard with >80% light interception requires full irrigation to

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David Doll3 CommentsApril 10, 2017Irrigation

Yellow Trees from Being Too Wet

It is very common to see yellow trees in the spring. The lack of color is often due to saturated soils which reduces the movement of oxygen into the soil, killing fine feeder roots. This impacts the ability for the tree to take in water and nutrients, leading to micro-nutrient deficiencies, impacting nut set and tree growth. In severe cases, especially with younger trees, the symptoms are similar to glyphosate drift or zinc deficiency. Later-season carry-over effects are also observed and include a limited rootzone, which leads to severe water stress during hull-split and harvest. Most of the time, this problem is caused by the orchard being irrigated too soon. Many operations apply water because it is perceived as needed or they are wanting to apply fertilizer. The need to apply water, however, is usually very low in the spring due to the cooler conditions and crop stage. Based on the 30-year average almond evapotranspirational values across California, water use from Mid-February (bloom) through the first week of April for almonds across the State ranges from 3.6″ to about 4.25.” This demand is often met by rain and the tree accessing stored moisture within the soil. To determine when to start applying water, plant stress or soil moisture levels should be monitored. The soil profile should be starting to dry at the two to three feet zone and can be checked with with the use of a shovel, auger, or soil moisture sensors. If using the pressure chamber to monitor plant stress, irrigation should be considered when trees are 1.5-2 bars more negative than baseline. For more information on the use of a pressure chamber in perennial crops, please see this document. If wanting to apply nitrogen, applications should occur by ground application or the shortest fertigation set as possible. These practices will help to properly time the first

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David Doll0 commentsMay 24, 2016Irrigation

Water Use Efficiency: Irrigating for the Highest Crop per Drop

Written by David Doll (UCCE Merced County) and Allan Fulton (UCCE Tehama County) This past week I presented on our preliminary findings of the water production function trials underway across the state. Highlights included the release of some newer crop coefficients that were determined using eddy-covariance stations placed in the North and South, discussion on water needs, and the impact of water stress on crop growth. Of most interest was the crop coefficients, which were higher than what most operations use, and led to the questions of the need for that much water. Crop coefficients (Kc) are derived to estimate ET for various crops as they develop over the course of a season.  Kc’s are developed under conditions where soil moisture is not limited and the crop is not stressed at all.    So, they represent maximum ET or water use.  . In the case of almonds, there have been several recent efforts to determine these values (see below). Various methods have been used ranging from simpler soil-water balance to more advanced biometeorologic eddy-covariance measurements. All of these have led to significantly higher calculated Kc’s and crop ET, with one set suggesting that around 60″ of water was needed in Bakersfield conditions. It is important to keep in mind that ET does not equal irrigation need.  The two will be more similar in almond growing areas with lower rainfall and more different in higher rainfall areas.  Water holding capacity of orchard soils and root depth will also influence the relationship between ET and irrigation need.   Even increases in production do not necessarily correspond with higher ET and more irrigation. There is increasing evidence that when given the conditions, “luxury consumption” of water will occur. In other words, the water demand is present, but crop load does not increase. This highlights the value of

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David Doll4 CommentsAugust 22, 2014Irrigation

Water Stress and Varietal Differences

A few visits and emails have highlighted differences in leaf drop patterns observed across varieties within an orchard. Full rows of trees will have yellow leaves that drop in time, characteristic of water stress while other varieties appear unaffected. These “in-field” observations suggest that almond varieties respond differently to the amount of water applied. For example, the variety ‘Monterey’ and ‘Aldrich’ have been observed to show signs of stress before ‘Nonpareil’ trees even though crop load is similar. In these cases, these trees may undergo severe leaf drop while ‘Nonpareil’ appears unaffected.

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David Doll5 CommentsFebruary 14, 2014Irrigation

Determining Orchard Water Needs With Yields

In delivering workshops on irrigation (and drought) management, there are always a few questions on how to estimate canopy coverage without the use of special equipment. Not being content with the typical answer of “Use your best guess,” I began to review the research, and found that an estimate of photosynthetically active radiation (PAR) (also known as mid-day light interception) can be calculated from orchard yields. This question was asked because in a water short year, the available water needs to be spread out evenly as the respective % of evapotranspiration. This following will help determine how much water your trees are using.

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David Doll8 CommentsJanuary 16, 2014Irrigation

Severe Drought Management Recommendations for Almond

UC researchers have urged growers not to take aggressive actions in reducing tree size or crop load in response to the West side water shortages this year. Severe pruning will increase new growth which would increase the leaf surface and evapo-transpiration rates (ETc) of the tree. Crop thinning has a similar effect and is also not recommended. By reducing crop load, the source/sink ratio of the tree is disturbed, causing the tree to put nutrients into vegetative growth instead of the nuts.

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David Doll1 CommentJune 15, 2010Irrigation

Irrigation Scheduling Part 3 – Taking in account irrigation efficiency

When water is applied to an orchard, loss of some amount of water should be expected. Growers must consider this loss of water when calculating the actual amount of water being applied. This amount will vary on the irrigation system used, soil and climatic conditions, and water management conditions. Water applied to a field can be lost by run-off, percolation below the root zone, sprinkler spray evaporation and off-target drift. Efforts to minimize these inefficiencies should be employed, and could include longer irrigation sets at lower rates, the construction of tailwater return systems, and/or sub-surface installed systems. Irrigation efficiency (Ea) is defined as the percentage of applied water that is held in the root zone. Mathematically, it would look as follows:Ea = water stored/water applied. Irrigation methods commonly used within the almond orchard include surface irrigation systems such as flood and furrow and pressurized systems that include sprinkler, drip, and micro-sprinkler. As we can see in table 1, irrigation efficiency differs with each system. With surface systems, fast movement of the water from the head end to the tail of the field end usually results in higher irrigation efficiency. Within pressurized systems, distribution depends on design parameters including spacing, nozzle type and size, riser height and operating presure.  Keep in mind that maintenance and filtration affect pressurized systems more than surface based systems. Pressurized systems, however, are usually more efficient due to the reduction of run-off and water loss through deep percolation. Table 1: Application efficiency typical of various irrigation systems. System Ea (%) Basin/Flood 65 – 80 Furrow 65 – 75 Solid Set Sprinkler 75-85 Microsprinkler 85-90 Drip 90-95 When calculation orchard water use, irrigation efficiency must be accounted or under-irrigation will occur. Below are some examples that show the different water application needs due to difference in irrigation efficiency. General

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