David Doll1 CommentMay 31, 2020Irrigation

Almond Irrigation Scheduling: Sourcing ETo

When determining plant water demand, the current environmental conditions must be taken into consideration. These factors, which include temperature, solar radiation, wind speed, humidity, and percentage of soil cover, influence both the rate of evaporation from the soil and the rate of transpiration from the plant (also known as evapotranspiration). By knowing these variables, we can calculate the evapotranspiration of the plant of interest. Research over the past 50+ years has refined the ways we estimate evapotranspiration. Initial estimates used to be performed using evaporation pans (Epan). Epan filled with water would be manually monitored for water evaporation on a daily basis. Water evaporation was then correlated with water use by fully irrigated grass (ETo) through the use of lysimeters. Fast forward a few years, with the development of more precise electronics, weather stations demonstrated the ability provide accurate measurements of the required variables. Using these data, a correlation between measured weather variables and ETo was developed. This equation, known as the Penman-Monteith equation, or some variation, is now used by nearly every weather station to estimate ETo. Having the ability to identify the rate of ETo is the foundation of irrigation scheduling. Although it is variable due to day-to-day environmental fluctuations, it is accessible through multiple sources. Within California, State funded weather stations placed throughout California measures the required water variables. These values are reported on the CIMIS web-site and are available free of charge. Within other almond growing areas, similar programs also exist, but are not as thorough. Thankfully, many weather stations can provide an estimation of ETo – as long as they have the ability to measure the required variables. Furthermore, ETo information is often made available in many publications, including trade newspapers, websites, and extension offices. Regardless of where the ETo information is sourced, it is

Read More
David Doll0 commentsMay 30, 2020General

Field Note: Simple Technique to Shave Down Tree Stakes

Written By Cameron Zuber, Staff Research Associate, UCCE Merced Have some tree stakes that do not fit into your post-pounder or lost the point making it hard to drive into the soil? Try using a shovel to shave down the stake first. Using a shovel is an easy and safer alternative to axes or knives as the cutting motion and blade edge is away from the user. It is also readily available and something people normally are willing to be a bit rough with when using. A proper technique when using a shovel to shave down a stake is: Place the stake on flat ground. Stand on the end you are not shaving down and place your back foot on the stake. Have your other foot planted firmly on the ground to help you balance when shaving the stake. Place your hands comfortably far apart along the handle. One hand should be towards the top of the handle to provide more force when shaving. The other should be place as close to the shovel’s blade to help direct the shovel tip to properly hit the stake. Angle the shovel’s blade at an approximate 20° to 30° angle from the stake. If the stake is rectangular, direct the shovel’s tip at the corners of the stake not the flat edges. Starting away from the cut end of the stake, push the shovel forward working with the grain of the wood. Continue shaving down, working towards the cut end of the stake. If trying to make into a point, angle the shovel’s blade at an approximate 45° angle as you get closer to the cut end of the stake. Otherwise keep the same 20° to 30° angle as you work towards the cut end. Repeat on all corners of rectangular stakes or

Read More
David Doll0 commentsMay 30, 2020Pistachio

Copper Deficiency in Pistachio

Copper is a micronutrient of plants. In certain situations, soil levels may be low enough or plant growth demand high enough that deficiency may occur. Within pistachio, this deficiency often occurs in the middle of the season (July-August) on young, fast growing trees. Symptoms include the die-back of new growth, forming a “shepherd’s crook.” Most, if not all, new growth will show this deficiency. In these cases, a foliar spray containing copper can help remediate the deficiency. Ideally, deficiency should be prevented to maximize growth. To prevent copper deficiency, plan to apply 0.1 lb/acre or 0.100 kg/ha of a chelated copper as a foliar spray when the new canopy is 50-90% expanded. This spring-time application will prevent the symptoms from occurring later in the summer. Soil applications should also be considered if soil values are low. Cooper sulfate can be fertigated in acidic soils, while a chelated product (EDDHA, or similar) should be used in alkaline soils. Soil applied rates of 1-2 lbs/acre or 1-2 kg/ha should be sufficient.

Read More
David Doll0 commentsApril 17, 2020Weeds

Herbicide Drift: PPO Herbicides

Protoporphyrinogen oxidase (PPO) enzyme inhibitors are a common class of herbicides used within almonds. They include the active ingredients oxyfluorfen and carfentrazone-ethyl. These compounds are reasonably effective in managing broadleaf weeds. Due to their limited translocation within the plant, they are often referred to as contact herbicides even though they can also provide residual control at higher rates. Off-target drift by these herbicides can damage almonds. Generally, however, the effects are more short-term due to the contact nature of these products on foliage. The reduced medium- to long-term effects of herbicide drift is useful when utilizing these chemistries on young trees. Even so, drift should be avoided as this can cause leaf spotting and loss, reducing photosynthetic area. More information on PPO herbicides and drift can be found here. PPO herbicides have a distinctive pattern when drifted onto almond leaves. At the location where the droplet lands, syptoms occur relatively rapidly. The lesion typically has a yellow outer-halo, a purple middle-halo, and a brown lesion in the center. These lesions fall out of the leaves in 2-3 weeks, giving the appearance of shot-hole fungus.

Read More
David Doll0 commentsApril 17, 2020Diseases

Shot Hole Fungus on Almond

Shot Hole is a fungal disease caused by Wilsonomyces carpophilus. The disease is able to infect leaves, fruits, and green wood. Leaf infections are characterized by a lesion that is between 1/8″-1/4″ (3-6 mm) in diameter, with a definitive yellow halo. Often, the lesion has a small black fruiting body in the center. As temperatures warm, the lesion drops from the leaf, leaving a hole. Fruit infections are generally smaller in diameter (~1/8″), appearing purplish-brown, slightly cork-like in appearance, and are raised. Severe fruit infections can kill the developing nut or cause deformities, impacting quality. Twig infections are similar to fruit infections. In severe cases, multiple lesions may girdle the green branch, causing dieback. This disease is very common in almond producing areas around the world. It survives/overwinters on infected twigs and as spores within leaf buds. Infection occurs when there is ample moisture and temperatures above 36F/2C. In warmer conditions, the fungus can produce spores and infect leaf tissues in less than 6 hours. Multiple infection cycles can occur within a season due to re-occurring rain events, which can cause severe defoliation. Due to the requirement for leaf wetness, this disease tends to be more prevalent in production areas that have significant rainfall after leaf-out. Frequent periods of leaf wetness that are greater than 6 hours will increase the risk of disease. In order to prevent infections, fungicides should be applied prior to rain events. These products kill the spores as they begin to germinate, reducing the number of infections. If rainy periods persist, multiple fungicide sprays will be needed. For more information on control, please see the Univ. of California Integrated Pest Management website. It highlights the life-cycle and fungicide chemistries to utilize for control. When diagnosing, be aware that there are a lot of problems that look

Read More
David Doll0 commentsApril 17, 2020Diseases, Weeds

Glyphosate Drift on Almond

Glyphosate is a very effective herbicide due to the stability of the chemical once it enters the plant. Off-target drift of this herbicide onto almond, however, can cause reduced, stunted growth, and if in high enough concentrations, tree death. Drift symptoms are usually very obvious and appear similar to severe zinc deficiency. In some cases, the only way to determine the possible cause is to make a foliar application of zinc – if the symptoms are alleviated, it was a deficiency. If not, the damage was from glyphosate. After the appearance of the symptoms, it could take 2-3 months for the tree to begin to grow normally. Applying glyphosate at any time of the year can injure the tree, including dormancy. Therefore, care must be taken to reduce drift and the subsequent effects by using properly calibrated spray equipment, drift reducing surfactants, and reduced winds at the timing of application. The pictures below show the effects of dormant applied glyphosate drift onto almond 2 months after the application. The second photo shows the recovery of the limb and was made 10 weeks after the herbicide application. Once drift damage occurs, there is nothing that can be done besides to wait for recovery. Applying foliar nutrients does not expedite recovery. This has been demonstrated in multiple field demonstrations and trials. Prevention is the best cure.

Read More
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

Read More
David Doll4 CommentsFebruary 9, 2020Diseases, Horticulture

2020 Bloom Considerations

As the 2020 almond bloom/crop year begins, there are several considerations to keep in mind. These points may be useful to help understand observations from the field as well as provide an understanding of any direction received. Nut set. Flower set percentages will vary from year-to-year. For mature trees, about 20-30% of the flowers will set while younger trees will be slightly higher. Even though this is low, crop loads are still high due to the number of flowers that are in each tree. A mature tree will have an estimated 35,000-50,000 flowers, depending on tree size. For more information on this, please see this article: https://thealmonddoctor.com/2016/03/07/almond-set-and-nut-drop/ which discusses the results of a tagging study which followed the development of almonds through the season. External factors greatly influence the set percentages. Crop load from the previous year impacts the amount of energy available for flower formation and bloom. High yields from the year before will reduce the number of flowers that will set nuts. Poor weather conditions can reduce bee flight hours, kill flowers in freezing temperatures, or promote disease. The period of weather risk extends into the fertilization period, which continues for several weeks. Keep in mind that the crop is susceptible to frost and diseases as long as there is a risk of frost and rainfall.   Several factors can be mediated by good farming practices. These include the presence and strength of pollinators (usually honeybees), post-harvest practices, and nutrient deficiencies. Honeybees are required for varieties needing cross pollination (most CA orchards – 2.0-2.5 hives/acre) and recommended for self-compatible varieties (0.5-1.0 hive/acre, although the exact number is unclear). Stronger hives (8+ filled frames) are essentially an insurance policy for poor weather conditions. Hive numbers and placements should take into account the weather. Post-harvest treatment of the trees is

Read More
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

Read More
David Doll0 commentsDecember 8, 2019Irrigation

Water Meters: Formatting the Data for Use

Water meters are a necessary tool to determine water applications to the orchard. Having access to this near-real-time data can provide insight into the irrigation practices by helping determine if the proper amount of water was applied to a block. Furthermore, a deeper analysis of this information can assist with managing field variability by improving distribution uniformity and even estimating yield. Before diving deeper into the data from water meters, it is important to format the data into a consistent value across the operation. Even though water meters are sold in all shapes and sizes, there are generally two types: totalized flow (reporting the total amount applied to the field) or current flow meters (reporting the current flow of volume). Knowing which type of meter is present within the orchard is required to understand the application of water to a particular block. Due to manufacturing differences and meter types, data may be reported differently. Common units used within the United States are gallons (gal), acre inches (a.i.), acre feet (a.f.), cubic feet per second (CFS), or gallons per minute (GPM). Within the rest of the world, the metric system is used and reporting is either in liters or cubic meters (cbm) with flows reported as liters or cubic meters by time (second, minute, hour). Totalized meters will report as a number of a particular unit applied. This value has to be subtracted from the previous measurement to determine how much water was applied over a period. Current flow meters report the flow of water and reports it as a measurement over time (e.g. gallons per minute). This data has to be multiplied by the irrigation set time to determine the amount of water applied. After the initial data is collected, it is then needed to format it into a common

Read More