Cameron Zuber0 commentsMarch 14, 2021Irrigation

Field Note: Irrigating and Deep Soil Moisture After Rainy Season

The rainy season this year in the San Joaquin Valley has been fairly dry and has probably got many growers thinking about how much water they should start applying. In orchards, one consideration to add to the list is the soil moisture at deeper depths. As an example, let us look at information from a wetter rainy season in 2018. In the beginning of that year, soil moisture measurements were collected every month at a research site in Parlier, CA. While not extensive, it does show something interesting. Overall, the soil moisture increased at all depth month to month (i.e., green line to orange then to grey). By March, the soil moisture above 1½ feet reached the maximum wetness the soil could hold, called the field capacity (e.g., red box in image). However, no matter how much it rained, the soil moisture at and below 2½ feet consistently stayed below the field capacity. The trees at this location were planted in 2009 with a rootzone well past a five-foot depth and were beginning to leaf-out by the middle of March. While trees typically transpire much of its water needs from the upper portion of the rootzone, a decent amount is still absorbed from the lower portion. At this site, the soil moisture at and below the 2½ feet may not be enough to supply the water needs of the trees even with appropriate moisture in the topsoil. When scheduling your first few irrigations realize that you may have different soil moisture at different depths. A few minutes with an auger and using the “feel” test or looking at sensor data can give an idea of the soil moisture profile across all depths. Think about the size of your tree’s rootzone, the soil types in your field, and how wet the

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David Doll0 commentsMarch 7, 2021Horticulture, Irrigation

Drought and Almonds: Spring Considerations

The current drought conditions faced by California will impact the agricultural industry. Annual precipitation, snowpack, and reservoir conditions are well below average for this time of the year. Although there is some rain in the forecast, future rain and snowfall amounts are hard to predict. Furthermore, spring storms tend to come in warmer temperatures, leading to more rain but less snow at lower elevations. Although we cannot control the weather, there are things we can do to improve the use of water resources. These practices will improve the use efficiency of on-farm water resources. They also include strategies to help capture more water from spring rain events. Lastly, implementing practices now will provide on-farm data for future mitigation strategies as the Sustainable Groundwater Management Act (SGMA) comes into full enforcement. Start timing. Most farm operations begin to irrigate too early. This occurs even in low rainfall years. Stem water potential (SWP) or other plant-based monitoring systems are strongly recommended to help determine start timings in the spring. With SWP, recommendations are to wait to at least 2 bars more negative than baseline (remember, SWP is read in negative numbers). This will most likely lead to an irrigation timing around early- to mid-April, depending on leaf-out date. A study demonstrating this method was established in a ‘Butte’/’Padre’ located near Delhi, CA in a very sandy soil. The trial was established in the drought year of 2014-2015 and continued through 2017. Within this study, the delayed start to the irrigation did not impact yield in comparison to the grower standard. The dates for the first irrigation were between April 22nd – 26th, for all three years. Since ‘Butte’ and ‘Padre’ are later leafing cultivars, I suspect that ‘Nonpareil’ and other earlier leafing cultivars will be 1-2 weeks earlier. This delay saved between

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David Doll0 commentsFebruary 25, 2021Technology

Technology Corner: Q&A with Semios

EDITOR’S NOTE: This entry is part of an ongoing 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. I would like to thank James Watson from Semios who took the time to answer my questions regarding their irrigation monitoring platform 1. Semios is a platform that links in a variety of sensors using IoT and on-farm networks. These sensors provide data for on-farm decision support. They include water monitoring tools, pest management tools for insects, and weather sensors. Would you be able to briefly describe the mission of Semios and how it works to integrate these various sensors? Semios subscribes to the philosophy that granular, in-canopy climate is the fundamental element of key crop decisions made by growers whether it’s the development of insect and disease pressure or water requirements of the plant. For this reason, the Semios solution always incorporates methods for monitoring climatic conditions at a granular level with the goal to optimize all resource inputs for the best possible crop result. Semios has developed a configurable platform approach in response to growers telling us how they want their agtech experience simplified. They don’t want to be buried in data or have to log into many different systems to get the information they need to make a decision. By bringing these important elements together into one streamlined system, Semios gives growers a holistic view of the information that informs their key crop management decisions. 2. Please describe the basic hardware and sensor systems utilized within the platform. The basic Semios offering includes at least one out-of-block weather station and, depending on acreage, one to many in-block weather stations tracking the core climatic conditions of the orchard. These stations

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David Doll0 commentsJanuary 31, 2021Technology

Technology Corner: Q&A w/ Phytech

EDITOR’S NOTE: This entry is part of an ongoing 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. I would like to thank Mark Sherfy from Phytech who took the time to answer my questions regarding their irrigation monitoring platform. Phytech is an irrigation technology that monitors the tree’s water stress. Please describe the basic hardware system and software analysis that is behind Phytech’s irrigation management technology. Phytech has several different sensors in the field and each sensor has an important role to play in the overall puzzle. We are about understanding exactly what the tree needs and what it is feeling. The ‘bread and butter’ of our organization is our dendrometers, but we also have several other sensors such as water pressure, soil moisture probes, fruit sensors, frost sensors and loggers. By using all these sensors, we can give the grower daily irrigation recommendations and we display an intuitive color scheme that helps the grower understand the current plant status of the orchard. On top of this, we have just launched an analytical section on our website that displays all the season’s data in one area. This displays such things a heat maps, bar and line graphs over different periods of time. Varieties, blocks, and ranches can also be compared to see where adjustments need to be made. It is a tool that gives growers instant recommendations daily, but it’s also an analytical tool that can change the grower’s overall strategy. What crops have been successful in utilizing Phytech’s products? Quite a long list of crops. We have been extremely successful in the almond industry as we have found out that the ETc is not only different per orchard,

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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 Doll1 CommentMarch 26, 2020Irrigation

Almond Irrigation Scheduling: Deciding on a Crop Coefficient

Crop coefficients for almond have been studied for nearly 50 years. These values indicate the ratio of water use of almonds in comparison to fully irrigated grass (ETo). Values less than one indicates that almonds are using less water than grass at that period while values greater than one indicate a higher water use. This ratio needs to be multiplied by the daily ETo, whether actual or estimated, to determine the water usage for almonds. The crop coefficients provided below are research derived. Differing techniques have been used to develop the coefficients. Some rely on a “water-balance” method in which soil moisture levels are monitored and maintained to match water use. This method has been utilized by many researchers across the world and has formed the foundation of most irrigation research. A more exact method of this technique involves the use of a weighing lysimeter, which is a giant scale that measures the amount of water used by the tree. Due to a minimal number of lysimeters in the world, studies have not been performed until recently and the results for mature almond water use has yet to be published. Outside of the “water-balance” method, there are newer technologies that have been used to develop crop coefficients. These techniques utilize fluctuations of canopy temperature that occur from transpiration loss.  These measurements, when taking into account solar radiation, wind, and ambient air temperature and humidity, can be used to back-calculate the water loss. This method is known as “eddy covariance.” When reviewing the differing crop coefficients, it will be clear that the general trend is greater water use. Some of the upward trend is due to a change in irrigation practices and orchard canopy densities – the switch from surface/flood irrigation methods to pressurized drip and microsprinkler orchards as well as

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David Doll0 commentsJune 15, 2018Irrigation

Summer Irrigation: Considerations for Deficit Irrigation

Summer irrigation is challenging. Water use of mature almond trees is the highest of the season, with an average evapotranspiration being around 2.00 acre inches of water use per week during June and July for most of the San Joaquin valley. This doesn’t consider distribution uniformity problems as well as any high heat events that may occur, which may require increased water applications. During this period, it is common to see stressed trees. This is frequently due to the lack of or improper calculation of evapotranspiration (ETc) leading to under-irrigation. It may also be due to an under-performing irrigation system leading to poor distribution uniformity, in which some areas are getting over-irrigated while others are under-irrigated. Lastly, and sometimes surprisingly, poorly designed systems are commonly observed which aren’t able to meet the tree’s demand for the water in the summer.  This is due to miscalculation or variable well/pump flows, too low of application which requires long pump times, or general poor design that limits water flows (i.e. reduced pipe sizes to save money). Some stress during this period is okay. Mild water stress that occurs at the onset of hull-split has been shown to increase the uniformity (or ‘evenness’) of hull-split. Sometimes, especially in fine textured soils with high water holding capacities, this application of deficit irrigation can be applied earlier in June to draw down levels of stored soil moisture. In these cases, careful monitoring of tree stress through the use of a pressure chamber should occur. Water reductions should start in range of a 10-20% reduction. When trees reach a mid-day stem water potential (SWP) of 2-3 bars more negative than baseline, near-to-full irrigation should resume to reduce tree stress. As hull-split begins (~1% hullsplit, or when blanks split) AND there is a desire to reduce hull-rot, water

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David Doll3 CommentsDecember 15, 2017Irrigation

Is Winter Irrigation Needed?

The reduced late fall rains have led to relatively dry conditions throughout the State. Within the San Joaquin Valley, limited amounts of rain have fallen, with recorded precipitation around one inch in Merced. The lack of rain has led to a series of questions about winter irrigation requirements in which answers are included. Question (Q). Do I need to irrigate now? Answer (A). Evapotranspiration rates are very low and almond water use is even lower. A table has been included that has utilized the real-time evapotranspiration data (ETo), the corresponding crop coefficients (Kc), almond evapotranspiration (ETc) and rainfall for the MERCED CIMIS station. The need to irrigate should be based on almond water use, the amount of water that has been applied in the Late October through early December period, and rainfall. Week Starting: ETo Kc ETc (in) Rain (in) Nov 5th 0.48 0.69 0.3312   Nov 12th 0.38 0.69 0.2622 0.71 Nov 19th 0.34 0.6 0.204   Nov 26th 0.32 0.6 0.192 0.27 Dec 3rd 0.3 0.4 0.12   Total: 1.82   1.1094 0.98 Based on this example, ETc for the month of November and first week of December has been 1.11” with roughly 0.98” of rainfall. This suggests that an irrigation may be needed. If, however, any irrigation was applied in late October or November, most likely the water needs have been met. Water demands and rainfall are site specific. Determining the situation for the orchard location will be needed to determine localized water needs. When in doubt, checking soil moisture status may assist with the decision making. Q. I didn’t irrigate in Late October – December and rainfall has been limited, how do I apply the water? A. Irrigation sets should be shorter than 24 hours to reduce saturated soil conditions and the risk of Phytophthora. If

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David Doll0 commentsSeptember 9, 2017Horticulture, Irrigation

Almond Postharvest Management: Water Demands

After the hustle of harvest, it is easy to think that the orchard work is nearly wrapped up for the year. With almonds, this isn’t the case. Research over the past 30 years has identified the postharvest period as the primary development period that impacts next year’s crop. Not surprisingly, much of this work has shown proper irrigation practices during this period being the major factor. For this article, the post-harvest period will be defined as mid-August through early November. During this period, the trees can demand an estimated 12-15″ of water based on location and weather. Roughly 70% this demand is from the six weeks immediately after harvest – when the days are hot and longer (see included table). Shorting trees of water during this period of high water use (mid-August through September) has been shown to significantly reduce next year’s yield. In fact, research by David Goldhamer and Elias Fereras have found that the first 8″ of water applied during the postharvest period is the MOST CRITICAL water applied to maintain orchard yields. Why is this?  Almond floral bud differentiation, unlike other Prunus spp.,  begins in mid- to late-August and continues through early September. Water shortages during this time reduces carbohydrate development, leading to less energy being able to be directed towards the creation of next year’s flowers, affecting both flower quality and quantity. This, in-turn, leads to an overall reduction in fruit load. Practices should be employed to keep leaves on the tree through the postharvest period (early November).  Reducing tree stress through the harvesting process is the first step in maintaining highly productive trees. This includes being timely with shaking so trees are stressed for a minimal amount of time and understanding the amount of soil moisture and the rate of use – which includes taking

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