David Doll0 commentsApril 25, 2021Nutrient

Iron Deficiency of Almond

It is common to observe iron deficiency within new growth of almonds. Iron is an essential micronutrient that is used to build chloroplasts. Without iron, the leaves fail to turn green. More obviously, iron deficiency causes interveinal chlorosis – or yellowing between the veins – on new growth. Severe deficiency will reduce growth and lead to increased susceptibility to minor leaf pathogens. Iron deficiency is not observed on older tissues due to lack of mobility within the plant. Iron deficiency is commonly observed in the spring as yellowish looking trees. This is due to wet and saturated soil conditions that limit fine feeder root development. These roots serve as the primary point for iron absorption. Secondly, too wet of soils increases the amount of carbon dioxide (CO2), which forms carbonate (HCO3-) leading to a temporary increase in soil pH, which reduces iron’s availability. The solution for this cause is simple – withhold irrigation until soil moisture levels drop and good aeration can occur. It is very common to see recovery within 7-10 days after the soils have dried to field capacity. The second primary cause of iron deficiency is “lime induced iron chlorosis.” Since higher pH restricts iron uptake, it can create deficiencies. This is very common in poor quality soils in which the pH is greater than 7.5. A soil test or soil pH meter can help determine if high pH is the cause of the observed deficiency. Soil acidification or modification is recommended to resolve the symptoms. When dealing with “lime induced iron chlorosis,” there are a few strategies to manage. These include the use of acids or acid forming fertilizer to lower soil pH. Injecting acids into the fertilization system can be complicated, but tend to direct the acid to the area which contains the most roots

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David Doll7 CommentsApril 3, 2021Irrigation

Almond Drought Management: 2021 Update

Drought conditions are forecasted to persist into 2021 for California. Although almonds are relatively tolerant to drought from a survival standpoint, yields are impacted when water applications are reduced. To minimize this impact, the water use strategy that accounts for available water resources must be developed and applied to the orchard operation. These resources include contributions from stored soil moisture, rainfall, wells, and surface water resources.  Impact of water stress on almonds. Reduced water applications affect both in-season and future yields. In-season water stress reduces gas exchange, affecting the amount of energy that can be directed into kernel development. This often leads to reduced kernel size and weight, an increase in shriveled kernels, and minimal growth. Typically, nut set is unaffected. Although not exactly clear, the relationship between in-season crop loss and water stress is around 1 to 0.7-1.0, meaning that for every percent of reduced water application leads to the same percentage of crop loss (i.e. a 10% water deficit leads to 7-10% crop loss). Please note that this relationship isn’t exactly defined, and these numbers are estimates. Moderate to severe deficits will also affect next season’s crop. This crop loss is due to the reduced spur positions from the lack of growth and the reduced carbohydrate reserves going into floral bud development. This leads to reduced nut set. Nut weight and size will only be affected if in-season curtailments continue. . Field observations suggest that water shortage in a given year will have a greater impact on crop yields the following year, where the relationship of water stress (from the previous season) and crop loss approaches 1:2. This means that for every percent of reduced water application in year one, year two’s crop will be reduced by about 2% (i.e. a 10% water deficit leads to 20% crop

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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 Doll1 CommentFebruary 6, 2021Diseases

What is a FRAC group?

 A frequently asked question is “What is a FRAC group?” FRAC is short for “Fungicide Resistance Action Committee”. Simply put, it is a grouping of fungicides based on the mode of action. This numbering system helps users easily identify which type of fungicide chemistry they are using without having to worry about various trade names. It is an excellent tool to help with fungicide rotations to manage and prevent resistance. Fungicide resistance is a numbers game. Fungal pathogens have broad genetic diversity. This means that there is a chance that populations within the same pathogen species may be resistant to the applied fungicide. If this fungicide is applied in successive treatments, this population will continue to infect and spread amongst the host plant. Rotating to different chemistries reduces the risk of these “escapees.” It is important to note that resistance is not due to repeated applications of the same fungicide to the fungal pathogen, but rather that there already exists a resistant population of the pathogen. This resistant population is unaffected by the fungicide because of differences in its genetic code, and will continue to grow unless an alternate fungicide is used. More information on fungicide resistance, which includes some illustrated examples, can be found in this previous article on the Almond Doctor. FRAC groups were established in the early 1980’s. Each fungicide mode of action has a unique code. These codes are updated regularly to consider the changing availability of fungicide chemistries. They include both synthetic, microbial derived, and plant-based fungicides. FRAC numbers are easy to use and the rules are simple. If wanting to reduce fungicide resistance, do not apply the same FRAC group in successive fungicide sprays. By developing fungicide rotation programs, the odds of resistance formation are significantly reduced. This helps keep the fungicide chemistry effective

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