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Increasing Irrigation Efficiency

Timing and system maintenance improve application accuracy, save water I. Scheduling Irrigation Using ET In this time of drought, irrigation experts recommend almond growers facing reduced levels of available water spread out irrigations over the season as much as possible in proportion to almond evapotranspiration (ETc). Understanding how to schedule irrigations using ET, therefore, is important for efficient water use. A first step toward optimum irrigation scheduling is to understand the changing demand of almond trees based on water use by evapotranspiration, or ET. Particularly in a water-short year, growers can use ET scheduling to apply limited resources throughout the season with an eye on minimizing damage to trees or crop losses. ET scheduling accounts for the loss of water through soil surface evaporation and transpiration through openings in the leaves. In almonds, ET will change throughout the year according to weather (heat and humidity impact evaporation) and time of year or crop stage (smaller leaf surface equals lower rate of transpiration). The amount of almond water demand (ETc) can be calculated using this equation: ETc = ETo x Kc. ETo represents water use by a reference crop, which is grass pasture. Evapotranspiration rates for reference crops can be found through a number of sources, including the free state-operated CIMIS system or through various free or fee-based services. Note that (ETo) is multiplied by a scientifically based crop coefficient (Kc). The Kc is a simplified way of representing the ratio of water use by the crop in question (ETc), such as almonds, to the reference ETo, which is water use by grass pasture. Almond crop coefficients have been updated by UC Cooperative Extension based on recent research and are available at AlmondBoard.com/AlmondCoefficient. Keep in mind that the crop coefficient will change throughout the year to account for differences in leaf surface area and other factors. It is especially important in a short water year to fully understand ETc to schedule irrigations based on refilling the soil profile according to the amount of water used for a particular period. In a drought scenario, researchers suggest holding off on early irrigations until trees are stressed, about a week after pressure chamber readings reach –12 bars. Even in non-drought years, some early stress benefits trees by avoiding root saturation early in the season. Once the irrigation season begins, growers should irrigate based on ETc on a prorated basis according to the amount of water they expect to have for the season. So if water deliveries are expected to be at 15%, not accounting for other sources, it is best not to skip irrigations, but to irrigate at a corresponding rate, according to schedule, at 15% of ETc. More information on scheduling irrigations using ET can be found on the UC Drought Management website. Another valuable resource is “Irrigation Scheduling 101,” pages 16–25 of the Irrigation Module of the California Almond Sustainability Program. An overview of the irrigation scheduling resources available to growers was covered in a recent Almond Update on AgNet/West radio. II. Testing for Distribution Uniformity In this time of drought, assuring high irrigation system efficiency and distribution uniformity (DU) through system maintenance is critically important. Systems should operate in the range of 90 to 95% DU, as it takes 22% more water to adequately irrigate with a 70% DU than with a 90% DU. Ensuring distribution uniformity of the irrigation system allows growers to improve site-specific applications of irrigation water and reduce variability in irrigation water delivery within the orchard. An annual distribution uniformity test can help reveal areas in need of maintenance or irrigation system modifications that could reduce high and low water distribution points that develop over time, as well as reduce variability in the delivery of water to the orchard. “After five years of operation, the ability of these micro-irrigation systems to apply water in the way growers think they are applying water has decreased,” said Merced County pomology farm advisor David Doll. “The pressure of most of these systems will degrade over time, especially if growers are using well water to irrigate. If your pressure drops, your ability to apply water efficiently drops, and even at a half-gallon per hour over the course of the season, that can be pretty dramatic.” Regular maintenance should go beyond walking the orchard to check for leaks, he added, and include flushing lines, inspecting nozzles or emitters, and cleaning screens. From there, look at how pressure drops across the field. Keep in mind that “goof plugs” and other line repairs can reduce pressure at the tail end of runs. A basic “catch-can” test can measure how much irrigation water is being delivered to individual areas to help identify if variability is being caused by the irrigation system and not other factors, such as soil variability. Improving uniformity not only prevents over-irrigating areas at the front end of the system, but also stressing trees at the other end, which can invite pests and other problems into the orchard. And research shows improving uniformity will also save water. UC Davis guidelines for DU testing can be found online. Of course, the first step toward ensuring distribution uniformity is a good system design, Doll said. Investing in a well-designed system that can deliver adequate pressure throughout the orchard will ultimately pay for itself. "Most of the distribution uniformity problems come from pumps, over time, not being able to deliver enough water,” Doll said. It’s a good idea, he added, when designing a system not to assume the pump will be able to deliver at the optimal rate, especially as the system ages. Frequent pump testing will reveal if growers need to install a booster or otherwise modify an existing system. And don’t skimp on mainlines. “The farther you are from the pump, the more loss of pressure you have, compounded by long runs of drip tape or microsprinkler hose,” Doll explains. As a result, trees at the end of these long runs are getting only 60% of what the rest of the orchard is getting.” For more information on the importance of testing for distribution uniformity, listen to a recent interview with Kern county farm advisor, Blake Sanden.  
Newsletter
Nov 07, 2017 // Orchard Management

Coping With Drought

During this time of unprecedented drought, the Almond Board has been providing information and tools to help growers cope with tight water supplies. This effort was kicked off at The Almond Conference last December with a workshop on irrigation strategies for drought management. Since then, we’ve published a series of articles in past issues of this newsletter to provide the most current research results from irrigation experts whose research is funded by the Almond Board through the Production Research Committee. You can review these articles at AlmondBoard.com/Outlook for more information on these key points: With severe restrictions, available water should be spread out over the season in proportion to almond evapotranspiration. With modest cutbacks, managed deficit irrigation for a 10 to 15% water savings just prior to and during hullsplit will not reduce yields. In scheduling irrigations, the pressure chamber is a valuable tool. Save some water for the end of the season. Studies in the late ’80s and early ’90s showed that postharvest irrigations drastically improved the following year’s crop. The lack of postharvest irrigation reduced yield the next season by more than 50%. When water supplies are significantly restricted, yields are reduced in the drought year as well as the subsequent year, but production can recover by the second to third season with sufficient water supplies. Two additional key topics are covered in this issue. I encourage you to read these articles and the others in the series if you have not already done so. Sincerely, Joe MacIlvaine, Chair Production Research Committee
Newsletter
Nov 07, 2017 // Environmental Sustainability

Irrigation Scheduling with Tight Water Supplies

California is in its third year of drought with no relief in sight, and not enough time left in the rainy season to make up for shortages. Under these conditions, growers with reduced levels of water should use all the technology available to optimize irrigations. In scheduling irrigation, the pressure chamber should be used to determine the stem water potential of the trees. Orchard irrigations should not be initiated until the trees reach -8 bars off their baseline, or about -12 to -13 bars, say Ken Shackel (UC Davis Plant Sciences) and Merced County farm advisor David Doll. Irrigations should be at the percentage of ET that can be afforded — for example, if 15% of water is available for the season, water at 15% ET at each irrigation. Growers interested in obtaining a pressure chamber can contact their UC farm advisor for options. Information on how to use the chamber is provided on the UC Fruit and Nut Research and Information Center website here and here. Almond Board–funded research by Shackel demonstrates that almond trees can survive through the year on as little as 6–8 inches of water (5–10% ET). This includes the 2-4 inches of water available within the soil profile. Other important actions under these conditions are to control weeds that compete for water, and to be sure your irrigation system is performing optimally. According to Jim Anschutz with Ag/H2O, a member of the Water, Energy and Technology Center at Fresno State University, it takes 1.8 acre-feet of water to compensate for a distribution uniformity (DU) of 75%. Speaking at the annual conference of the California Irrigation Institute in Sacramento in January, Anschutz added that a 10–15-year-old system may have a DU as low as 45–65%, and at a DU of 75% in almonds, the potential loss of revenue at $3 per pound would be $570 per acre. UC Davis has developed guidelines for DU testing. At a Jan. 28 almond drought management meeting, David Doll and Ken Shackel also noted the following very important issues: Under deficit irrigation, expect to see differences in tree water status and stress according to soils. Use the pressure chamber to identify areas of severe stress and adjust your irrigation approach before these areas become a problem. There is no evidence that heavy pruning, kaolin/whitewash sprays or reducing bud/crop load do any economic good to mitigate drought conditions. Fertility programs need to be throttled back, but not lacking. For instance, in-season adjustments for nitrogen should be based on early-season leaf sampling coupled with crop estimation.
Newsletter
Nov 07, 2017 // Orchard Management

Starting Out Right: Managing Irrigation in a Water-Short Year

How to best manage irrigation in a potentially short water year is a complex question for almond growers. A workshop at The Almond Conference in early December looked at irrigation strategies for drought management to help provide almond growers with some answers for season-long water management under different availability scenarios. These recommendations will be covered in this newsletter in more detail as the season progresses. Almond growers anticipating reduced levels of available water should spread out applications over the season, typically mid-March to mid-November, as much as possible in proportion to almond evapotranspiration (ETc). For initial season-long planning, historical values can be found on the UC’s drought management website. Current Almond Board-funded research is updating these ETc values; therefore, the values for the date periods given in the table should be used as the relative proportional ETc over the course of the season, and should be converted to the percent of total season-long ETc, which is the sum of the inches in each column (location). An important consideration in planning is addressing the period of bud differentiation for next year’s crop, which starts about mid-August and continues through the month of September. Moderate stress during this period will have little effect on subsequent years’ nut numbers, but severe stress during bud differentiation has dramatically reduced fruit set the following season, according to research. Once the season commences, starting at bloom, real-time estimates of ETc (=Kc*ETo) are available using the CIMIS (California Irrigation Management Information System). Starting at bloom, keep a running total, and also account for any meaningful rain and irrigation/fertigation. More information on what to do with these totals will be provided later. Ideally, for salt management, growers should aim to fill the soil profile prior to bloom. If excess salinity is a concern for your field, fill the soil profile before bloom to at least 4 to 5 feet. However, if salt is not an issue, it is better to save limited water for the growing season, and therefore, it is sufficient for only the top 2 feet of soil to be recharged just prior to bloom. So wait to irrigate as long as possible before bloom to see what winter rains will bring. This strategy will allow for a non-stressed spring push. Another important first step is to control weeds that compete for water. When water supplies are severely restricted, impacts to almond trees and crops are unavoidable. Recently completed Almond Board–funded research on drought survival of almond trees led by Ken Shackel (UC Davis), confirms almond trees can survive on very low levels of water — 7.6 inches total from rain plus soil-stored, in his trial. Yields are reduced in the drought year as well as the subsequent year, with reduction proportional to the degree of stress. Fortunately, production recovers by the second season after drought with sufficient water supplies. Severe pruning aimed at compensating for drought stress and other treatments, like kaolin sprays to reduce heat, had no benefit for yield or tree health.
Newsletter
Nov 07, 2017 // Environmental Sustainability

Drought Management "What Ifs"

With some rainfall (and snow in the mountains) in November and December, the water availability picture may brighten somewhat, but as Dr. Ken Shackel, UC Davis, said at an Almond Conference workshop on Irrigation Strategies for Drought Management, “No one has to be told we’re having a drought — it’s serious.” Dr. Shackel had some general advice for growers with limited water availability: Almond growers anticipating reduced levels of available water should spread out that reduction over the season, typically mid-March to mid-November, as much as possible in proportion to almond evapotranspiration (ETc). Control weeds! There is no benefit from heavy pruning, using so-called antistress or anti-transpiration products, or whitewash. Mild to moderate water stress at hullsplit, which may happen unintentionally if trees are on a deficit irrigation program, means less hull rot and speeds up hullsplit. Be aware that different soils within an orchard may result in different levels of stress among the trees. Be careful, and use a pressure chamber to determine which trees may become too stressed. Bruce Lampinen, also with UC Davis, made the point that tree density has increased, along with yields, since the last drought. “Drought will have a bigger impact this year because yields are higher, there is more canopy, and that needs more water,” he said. “The best growers are getting 4,000 pounds per acre in orchards with 80% light interception, which takes 56 inches of water,” he added, whereas a yield of 2,560 pounds per acre takes only 36 inches of water. Farm advisors Blake Sanden, Kern County; Allan Fulton, Tehama County; and David Doll, Merced County, underscored the critical importance of system tune-up and maintenance to optimize distribution uniformity. This is done through such actions as adjusting pressure regulators and keeping emitters free from plugging, which can boost irrigation system efficiency and save water. Sanden talks further about system maintenance in this video. The entire presentation, shared at The Almond Conference, can be viewed here.  
Newsletter
Nov 07, 2017 // Environmental Sustainability

Coping with Drought — Late Season Irrigation Is Vital for Next Year's Crop

In this series on coping with drought, the Almond Board has been providing information and tools largely resulting from Almond Board–funded research to help growers cope with tight water supplies. An important principle to follow if water supplies are severely restricted is to spread out available water over the season in proportion to almond crop evapotranspiration (ETc). The April and May issues of California Almonds Outlook provided instructions for calculating and using ETc as a guide. A key objective is to supply water for the entire season, saving some for late season. Water is needed during the period of fruiting-bud differentiation, which in normal years starts in July and continues to mid-September, or even into October for later varieties and cooler years. Moderate stress during this period will have little effect on the subsequent year’s yield; however, severe stress can dramatically reduce bloom, fruit set and yield the subsequent season. Studies done by David Goldhamer, emeritus UC irrigation specialist, and Mario Viveros, emeritus farm advisor, Kern County, on the Nonpareil variety demonstrated that lack of any irrigation after Aug. 28 on a shallow, 3-foot sandy loam soil in Kern County drastically reduced nut set by 74% and yields by 62% the following season. Subsequent studies on timing of almond fruiting bud and flower development by Bridget Lamp (formerly UC Davis, Plant Sciences), Dr. Vito Polito (emeritus UC Davis, Plant Sciences) and UC farm advisors Joe Connell, Roger Duncan and Mario Viveros provide insights into this yield reduction. Stress that occurred during the period of bud differentiation and flower development adversely affected flower quality to the extent that the next season’s crop was reduced. These studies tracked flower bud development of the Nonpareil, Carmel and Butte varieties. Bud development is a gradual process, with beginning and endpoints that range over windows of time, depending on individual buds. For Nonpareil and Carmel, the initiation of flowers spanned the period of July through mid-August. Flower bud differentiation is completed with pistil development; for the Nonpareil and Carmel varieties this occurred from August to mid-September. Bud development for the Butte variety was somewhat later and in a colder year (1998), and was not completed until the first part of October.
Newsletter
Nov 07, 2017 // Orchard Management

More Research Supports Almonds as Smart Snacking Choice

An Almond Board–funded study published in the October issue of the European Journal of Clinical Nutritioni found that study participants eating 1.5 ounces of dry-roasted, lightly salted almonds every day experienced reduced hunger and improved dietary vitamin E and monounsaturated (“good”) fat intake without increasing body weight.ii The newly published four-week randomized, controlled clinical study, led by Dr. Richard Mattes at Purdue University, investigated the effects of almond snacking on weight and appetite. The study included 137 adult participants at increased risk for type 2 diabetes. Participants were divided into five groups: a control group that avoided all nuts and seeds, a breakfast meal group and lunch meal group that ate 1.5 ounces of almonds each with their daily breakfast or lunch, and a morning snack group and afternoon snack group that each consumed 1.5 ounces of almonds between their customary meals. Despite consuming approximately 250 calories per day from almonds, participants did not consume more calories over the course of the day or gain weight over the course of the four-week study. Snacking has become nearly universal behavior in the United States, with an estimated 97% of Americans consuming at least one snack per day (data from 2003–2006; up from 71% in 1977).iii In light of increasing snacking frequency and snack sizeiv among U.S. adults, it is more important than ever to identify snacks that pose little risk for weight gain and provide nutrition and health benefits. According to Dr. Mattes, “This research suggests that almonds may be a good snack option, especially for those concerned about weight. In this study, participants compensated for the additional calories provided by the almonds so daily energy intake did not rise and reported reduced hunger levels and desire to eat at subsequent meals, particularly when almonds were consumed as a snack.” Press releases were distributed in the U.S., Canada, EU, India, China and South Korea, garnering over 200 million impressions through fall of 2013. iTan YT, Mattes RD. Appetitive, dietary and health effects of almonds consumed with meals or as snacks: a randomised, controlled trial. European Journal of Clinical Nutrition 2013; 67:1205-1214. October 2, 2013, doi:10.1038/ejcn.2013.184  iiU.S. Dietary Guidelines recommend that the majority of your fat intake be unsaturated. One serving of almonds (28g) has 13g of unsaturated fat and only 1g of saturated fat. iiiPiernas C, Popkin BM. Snacking increased among U.S. adults between 1977 and 2006. J Nutr 2010; 140:325-332. ivUS Department of Agriculture. What we eat in America, 2011.  
Newsletter
Nov 07, 2017 // About the Almond Board
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