Considerations for March 2022

March is a month full of surprises. Weather can be highly variable, with rain, risk of frost, and heat waves all being possible. Below are some points to consider as the season progresses. Ongoing frost concerns. Frost conditions can occur through the end of March. Maintain a watchful eye on the weather conditions to reduce the risk of any frost event. Critical temperatures after petal fall are around 28F (-2.2C), and temperatures at or below 28F for an extended period will cause crop loss. Micro-irrigation can increase orchard temperature by a few degrees, with higher flows of water providing a greater warming effect. More on frost mitigation can be found here. With irrigation occurring during multiple frost events, it is common to see trees push slow and with pale green growth. This is due to saturated rootzones that lead to loss of fine feeder roots and low micronutrient uptake. Soil irrigation levels should be monitored, and irrigation withheld until stored soil moisture begins to drop. Furthermore, nitrogen applications should not occur during the period of frost risk as running water for extended periods of time will leach nitrogen out of the rootzone. Crop losses from frost are hard to define in early March. Frost affected flowers will have blackened tissue inside the ovary, or flowers may appear blighted and remain on the tree. Trees will slightly compensate for loss of flowers with a slight increase in fruit set percentage of the remaining flowers as well as greater nut size. Therefore, in areas of minimal damage, the impacts might not be observed. In areas with losses greater than 10%, yield reductions should be expected. If frost damage is suspected, it is important to contact any insurance company as soon as possible and trim the early season fertilizer applications until a better

March 6, 2022

Major Nutrient Fertilizers: Thoughts to Reduce Operational Costs without Impacting Productivity

Increasing input prices are being observed across the farming sector. Fertilizer prices have increased due to demand, government regulations, weather, trade issues, and energy prices. Prices are some of the highest in a decade, with nitrogen and phosphate fertilizer prices nearly double what they were in 2020. Within almonds, maintaining the proper fertilizer status within the tree is important to maintain yields. Research projects have determined how much of each major nutrient is needed for the tree to maximally produce. These studies first occurred in the early 1990’s and were re-done between 2008-2013. In summary, the projects concluded that for every 1000 lbs of almond kernels harvested, 68 lbs of nitrogen, 92 lbs of K2O, and ~12 lbs of P2O5 are removed from the orchard. These nutrients need to be re-applied to maintain yields. Leaf tissue, soil samples and other in-season assays and monitoring can be used to determine if optimal levels have been achieved. If optimal levels are present, input levels should only match crop demand, while if excess amounts are present, applications can be reduced. These adjustments will help reduce waste, run-off, and leaching.   More on this here and here. Nitrogen (N) usage and uptake occurs when there are leaves on the tree. As such, N applications should only occur in-season. When applying N, more than 68 lbs/1000 kernel pounds of production is applied – typically around 85 lbs/1000 kernel pounds of production. This inefficiency of about 20-30% considers the N lost to NOx conversion, run-off, and leaching. Fortunately, I have observed many orchards much more efficient than this. These orchards have been able to reduce N amounts applied based on the observation of high N within leaf samples.  They have found that maintaining N levels at 2.5% in mid-July allow for the maintenance of high yields (>3000

October 30, 2021

Phosphorus and Almonds

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March 17, 2021

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,

August 6, 2020

Regulated Deficit Irrigation: Is it appropriate for your operation?

Regulated deficit irrigation is the practice of reducing irrigation to obtain some type of desired stress level. This practice is often used during the initiation of the hull-split period to reduce hull-rot strikes. It also has been utilized during periods of water shortages to save 5-15% of the seasonal water use of almond. Due to the limited effect on yield, as well as the benefits, it has been advocated for application within orchards by the University and industry (including myself!). This practice, however, can have negative impacts when applied incorrectly and should only be used if deemed appropriate. In theory, this practice is easy to apply. Water application rates should be cut to achieve -15 bars stem water potential for two weeks preceding the onset of hullsplit (e.g. Blank split). This stress should be maintained at this level for this period. At the end of the two weeks, regular irrigation resumes and the orchard prepares for harvest. The difficulty in application has everything to do with accurately monitoring plant stress. Every orchard and orchard practice creates a different approach in application. For example, assuming similar irrigation levels, stress levels achieved in a mature orchard planted on sandy soil will occur in a shorter time frame than an orchard on a heavier clay loam. Every orchard site requires careful monitoring to determine when to cut and resume full irrigation. I have observed numerous orchardists apply tree stress only to see a reduction in kernel yield. This is due to ongoing gains in nut weight that occur between the onset of hull-split and harvest. If the tree is significantly stressed during this period, the conversion of carbon to fats is reduced, impacting the final crack out percentage. One closely monitored orchard in which I worked, demonstrated a 10-15% reduction in kernel weights

July 19, 2020

Almond Shaker Damage

Shaker damage is commonly observed across orchard operations. This damage occurs when the force of the shaker is greater than the strength of the bark, causing it to tear away from the tree. The obvious damage not only impacts tree vigor, but also provides an opportunity for infection by wood canker fungi which can kill the tree. If the shake is properly timed and executed, shaker damage can be greatly reduced (and even eliminated) within an orchard. A common misconception is that trees that are kept too wet during the harvest period will be damaged by the harvesting process. Interestingly, this has never been supported in research nor found to be consistently true across operations. Research in the mid 90’s by Gurusinghe and Shackel found that withholding irrigation during July through harvest did not reduce bark damage of the trees. To further elaborate, they found no difference in bark strength with respect to shaker damage for almond trees grown under various irrigation treatments. Irrigation treatments included a wet treatment and dry treatment, in which mid-day stem water potential (SWP) was maintained at -9 bar and -20 bar, respectively, through the month of July/August. Despite this range in tree water status, both treatments exhibited the same gradual increase in bark strength through July and August. Based on this, the researchers concluded that water stress did not influence the timing or rate of tree bark strengthening. Based on the lack of direct effect of moisture status on tree bark strength, it is thought that the damage observed in wet areas of the orchards is most likely due to the delays in ripening. Research has found that decreased water stress (Goldhamer and colleagues, 2006) and high nitrogen status (Saa and colleagues, 2016) both  delay ripening. These trees, when shaken at the same time

August 20, 2019

Cover crop research review: How can it help almonds?

Cynthia Crézé (1), Jeffrey Mitchell (1), Andreas Westphal (2), Danielle Lightle (3), David Doll (3), Mohammad Yaghmour (3), Neal Williams (4), Amanda Hodson(4), Houston Wilson (5), Kent Daane (6), Brad Hanson (1), Steven Haring (1), Cameron Zuber (3) & Amélie Gaudin (1) Department of Plant Sciences, University of California – Davis Department of Nematology, University of California – Riverside University of California Agriculture and Natural Resources – Cooperative Extension Department of Entomology and Nematology, University of California – Davis Department of Entomology, University of California – Riverside Department of Environmental Science, Policy and Management, University of California – Berkeley Although cover cropping is compatible with almond production and is often implemented in other orchard systems, this practice has never been widely implemented in California. The potential benefits are recognized by growers, especially their value for pollinator forage and soil health but operational concerns, lack of cost-benefit analyses and unclear best management practices have hampered wide adoption. As cover cropping can provide significant sustainability benefits, there is an urgent need to assess and develop feasible and beneficial cover crop systems for California almond production. Here is some insight gathered by a research team assessing the impacts of multiple cover crop management strategies on: 1) soil health, 2) water use and dynamics, 3) bee visitation and pollination, 4) weed and pest pressure (NOW) and 5) almond yields in four orchards across the Central Valley precipitation gradient. Cover crop research trial in almond: Project website: https://almondcovercrop.faculty.ucdavis.edu Design: Three commercial orchards in Corning (Tehama county, 2nd leaf), Merced (Merced county, 16th leaf) and Arvin (Kern county, 16th leaf). One experimental station: Kearney (Fresno county). Two cover crops: Soil Mix (2 legumes, 2 brassicas & 1 grass), Pollinator Mix (5 brassicas, Project Apis M – https://www.projectapism.org/pam-mustard-mix.html) Compared to resident vegetation & to bare soil. Cover

June 30, 2019