David Doll3 CommentsSeptember 14, 2011Irrigation

The Importance of Post-Harvest Irrigation in Almond

Multiple entries have covered the aspects of ensuring irrigation during the post-harvest period. This practice has been based off of previously conducted research and is recommended due to the detrimental effect that post-harvest water stress has on the following year’s crop. Never-the-less, many growers do not recognize the importance of this practice. An irrigation stress or deficit during the post-harvest period has been shown to reduce bloom, fruit set, fruit load, and individual fruit weight. For example, a University of California study conducted between 1989-1990 that deprived trees of post-harvest irrigation resulted in a 10% reduction in fruit set, a 33% reduction in fruit load, and a 43.3% decrease in kernel yields for the nonpareil variety*. It is thought that the sensitivity of the almond to the lack of post-harvest irrigation is most likely due to the late fruit bud differentiation which occurs from late August to early September. As the first “round” of harvesting is completed, keep in mind the need to irrigate the trees. It is easily forgotten with the hustle and bustle of harvest, but the potential consequences of forgetting should turn the practice into a priority. *Research paper cited: Goldhamer, D.A., Viveros, M. 2000. “Effects of preharvest irrigation cutoff durations and postharvest water deprivation on almond tree performance.” Irrigation Science. Vol 19: 125-131.

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Joe Connell7 CommentsNovember 1, 2010Nutrient

Late Fall, A Time for Potassium Soil Applications

Maintaining adequate potassium (K) nutrition is especially critical for almond trees and fall is an excellent time to address K deficiency through soil potassium applications.    Potassium is found in one of three forms in the soil:  fixed K, exchangeable K, and K in solution.  Fixed K is tightly held within soil particles or is part of potassium-bearing minerals and may only be very slowly released through weathering.  Exchangeable K is attached by electrostatic charges to soil particles and is in flux with potassium ions in the soil solution.  Soluble K consists of ions moving freely within the soil solution constituting a readily available form of K.  At any given time, a soil will contain a unique balance of fixed, exchangeable, and soluble potassium characteristic of that soil type. Potassium is thus in equilibrium and moves back and forth between these states as the supply of K+ and other cations varies. Potassium ions (K+) have a one plus charge and are readily adsorbed by negatively charged soil clay particles becoming unavailable to the tree.  Avoid any type of application that broadcasts potassium over a large soil area because more of the K becomes fixed. UC research showed that four years of broadcast applications only moved K 6 inches down into the soil while banded treatments penetrated 2 feet.  Banded treatments have worked well under non-tillage but if you cultivate, shank the band in to get the material closer to the root zone.  Applying a gypsum (calcium sulfate) band overtop of previous potassium bands can help free up more potassium.  The calcium ions (Ca ++) in gypsum have a plus two charge and will displace potassium ions on the clay particles thus freeing up more potassium to remain in the soil solution while moving it deeper into the root zone.  Gypsum

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David Doll0 commentsAugust 31, 2010Irrigation

The Importance of Post-Harvest Irrigation in Almond

Multiple entries have covered the aspects of ensuring irrigation during the post-harvest period. This practice has been based off of previously conducted research and is recommended due to the detrimental effect that post-harvest water stress has on the following year’s crop. Never-the-less, many growers do not recognize the importance of this practice. An irrigation stress or deficit during the post-harvest period has been shown to reduce bloom, fruit set, fruit load, and individual fruit weight. For example, a University of California study conducted between 1989-1990 that deprived trees of post-harvest irrigation resulted in a 10% reduction in fruit set, a 33% reduction in fruit load, and a 43.3% decrease in kernel yields for the nonpareil variety*. It is thought that the sensitivity of the almond to the lack of post-harvest irrigation is most likely due to the late fruit bud differentiation which occurs from late August to early September. As the first “round” of harvesting is completed, keep in mind the need to irrigate the trees. It is easily forgotten with the hustle and bustle of harvest, but the potential consequences of forgetting should turn the practice into a priority. *Research paper cited: Goldhamer, D.A., Viveros, M. 2000. “Effects of preharvest irrigation cutoff durations and postharvest water deprivation on almond tree performance.” Irrigation Science. Vol 19: 125-131.

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David Doll7 CommentsDecember 21, 2009Nutrient

Making a Zinc Dormant Spray

Question came in this week regarding the decision on the timing of a zinc spray. When should I make a Zinc Spray?Research by UC Specialist Dr. Scott Johnson at the Kearney Agricultural Center has shown that a zinc foliar spray is the most effective when made during the post harvest period. Applications of zinc should be made to the tree around late October – early November. The idea is to have a leaves still on the tree when the application is made. Dr. Johnson has shown that a roughly 3% of the zinc applied is taken into the tree from a fall foliar spray, but this is dependant upon the source of zinc. Defoliation may occur after the application, but do not worry as sufficient zinc should have made its way into the plant tissues. Is making a dormant zinc application a bad idea?If a fall application of zinc was not made and the orchard is suspected to be deficient in zinc, making a dormant application of zinc will increase zinc tissue levels. The percentage of uptake is slightly less, around 2.0-2.8%, and it is harder to get a large amount of zinc into the tree. This is due to the fact that the shoots, buds, and bud scars only account for roughly 3% of the surface area of a peach/almond branch. Therefore the amount of spray landing on the tree surface is significantly less than when the leaves are still attached (Leaves make up the other 97% of the surface area). To counter this, higher rates should be used during the dormant period. What type of material should be used in a zinc spray?Dr. Scott Johnson’s (UC Specialist) work has shown that the “biggest bang” for your buck comes from Zinc Sulfate (high uptake, moderate phytotoxicity). There are other

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David Doll0 commentsNovember 2, 2009Weeds

Fall survey for problematic weeds

Written by David Doll, UCCE Merced CountyMonitoring weeds in the fall provides the ability to evaluate the current year’s weed control program. By surveying the orchard for areas of weed species that escaped control, control practices can be adjusted to control these weeds in the following year. Fall monitoring also provides the ability to identify emerging winter species and allow for the selection of a pre-emergent herbicide to control spring weeds. (Note: Pre-emergent herbicides are usually applied at a later date – December-February). Surveying for weeds is relatively simple. After the first rains look for annual weeds in the tree rows to check the effectiveness of any previous pre-emergence herbicide applications. Check the ground cover in the row middles for any perennial seedlings. Record weed infestations and use a map to show areas of escaped weeds. With the emergence of herbicide resistant weeds in almond orchards (Hairy Fleabane, Pigweed, Horseweed, etc.) control of escaped weeds is critical to an affordable weed management program. For example, controlling glyphosate resistant fleabane with spot treatments of Rely/Gromoxone tank mix that has been found on 3 acres of the orchard block is more affordable than trying to control it over the entire 40 acre block. Only by monitoring can the areas infested by escaped weeds can be identified. It is important to use a different chemistry and address these escaped weeds BEFORE they become to big or go to seed. Below are some pictures of common weeds to help in identification:Figure 1: Bermudagrass (Cynodon dactylon). Vigorous spring- and winter-growing perennial. Frequently becomes a problem in mowed orchards. Very competitive for moisture and nutrients. Spot treat with postemergents. Figure 2: Dallisgrass (Paspalum dilatatum). Perennial commonly found in orchards. Seedlings in spring and summer. Tends to become dominant in mowed areas and standing water. Figure 3:

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Roger Duncan5 CommentsOctober 6, 2009Nutrient

Post-harvest Boron Applications Can Increase Almond Yields

Written by Roger Duncan, UC Farm Advisor, Stanislaus Boron deficiency is very common in orchards and vineyards planted on the eastern side of our county. This nutrient is essential in pollen tube growth and fertilization of the flowers. Moderate boron deficiency does not produce recognizable foliar symptoms but trees do not set their full potential of fruit. Boron tends to accumulate in almond hulls and thus hull samples provide a better indication of boron status than do leaf samples. Harvest is an easy time to sample hulls. If samples are collected much earlier than harvest, a false reading may be obtained because boron may continue to accumulate in the hulls as long as they remain green on the tree. The current boron guidelines for hulls are as follows: 80 ppm or lower = deficient 80-150 ppm = adequate Over 200 ppm = may be toxic Soil applications are the best way to correct a deficiency. Be very careful when applying boron—a little boron fertilizer goes a long way and will last for a few years. Soil applied boron fertilizers should be broadcast, not banded. Research has shown that even orchards with up to 120 ppm benefit from a post-harvest foliar application of boron. In University of California trials in Stanislaus and other counties, postharvest boron sprays often increased nut set and yield 20-30% the following year compared to non-treated trees. Timing: The goal of the foliar application is to get the boron into the flower buds (actually pollen tube mother cells) that are developing for the next year. Therefore, timing of application is very important. During the growing season (March through July), large quantities of boron go into the developing hulls. If foliar boron is applied at this time, most of the boron will go into the hulls and is

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David Doll4 CommentsSeptember 21, 2009Horticulture

Post Harvest Pruning of Mature Orchards

Pruning is one of the subjects that can have ten people explain it in ten different ways. This has to do a lot with the traditional thoughts on how an almond tree should look, the believed benefits of pruning, and personal experiences. It is one of the most important practices of orchard maintenance due to the expense and its effect on orchard yield and longevity. Therefore pruning should be considered more of a science than an art. Pruning can be broken down into two phases: The tree training phase and the maintenance period phase. During the tree training phase, we work to establish and shape the permanent framework of the tree through primary and secondary scaffold selection. This occurs through the first three years of the orchard life. The maintenance pruning phase occurs from the 4th leaf on and is done to maintain the shape of the tree. This post will focus on pruning during the maintenance period of the orchard life. In order to understand the principles of pruning, we need to understand the underlying principle of orchard management: We are farming sunlight. The more sunlight that is intercepted by tree leaves, the more production we can achieve within our orchard. Therefore, trees need to fill the available space as quickly as possible to achieve maximum yields. Along with this, we want to ensure orchard viability by having sufficient fruitwood to produce a sizable crop for the life of the orchard. So, to do this, do we need to prune? The short answer is “no.” Studies by by farm advisors Roger Duncan (Stanislaus Co.), John Edstrom (Colusa Co.), Bill Krueger (Glenn Co.), and Mario Viveros (Emeritus, Kern Co.) have demonstrated that pruning does not increase yield over minimally, or “unpruned” trees (Table 1). As we can see, conventional, annually

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David Doll0 commentsSeptember 14, 2009Horticulture

Inspecting the Orchard During the Post-Harvest Period for Damage

Shaking has almost been completed throughout many almond orchards. Through this process, a lot of stress has been placed on orchard trees. Trees may have also been damaged throughout the duration of the growing season or during the harvesting process. After harvest is completed, it is helpful to walk the orchard and observe for problematic areas. Things to look for:Shaker or other mechanical damage that may lead to infection by Ceratocystis,Mite damage or webbing in trees,Areas containing a large amount of stick-tights,Excessive leaf defoliation due to either mite infestation or lack of water,Gumming of the trunks or scaffolds,Areas affected by hull-rot,and/or areas of poor nut pick-up. To find out how to prevent this problems, look for patterns. Does the damage appear in any specific locations, such as at the end of irrigation runs, near irrigation valves, areas of different soil textures, or near orchard borders? Were shaker damaged trees shook at the beginning or end of the day? Is only one variety affected? Identifying these patterns will provide valuable clues about what went wrong and allow corrective practices for the coming year.

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David Doll6 CommentsSeptember 1, 2009Horticulture, Nutrient

Postharvest Care for Almonds

We are mid way through almond harvest. As we finish up shaking our Nonpareils, we need to keep in mind the list of orchard tasks to help maintain crop production for the next year. For almonds, flower bud differentiation takes place during the month of September. This means that next year’s bloom and subsequent crop is being formed in the middle of this year’s harvest. During this time period, there are three important cultural practices that need to be considered by almond growers.They include irrigation, nitrogen fertilization and pruning. 1. Post-harvest irrigation is very important to keep the leaves active and functioning until normal leaf drop, which typically takes place at the end of October, early November. By preventing premature defoliation, we let the tree transition its nutrients from the leaves back to the fruiting spurs. The nutrients that are known to migrate from the leaves to the spurs at the onset of leaf fall are nitrogen, potassium and phosphorous. These nutrients play major roles in bloom development and fruit set. If the orchard does prematurely defoliate due to lack of water, irrigate to encourage re-growth. This may reduce yields in the following year, but yield loss will not be as significant as not watering at all. If watering does not occur, not only will fruit bud differentiation be poor, the orchard will suffer from premature flower drop in late winter. The best advice is to avoid this situation all together by properly managing your water during the harvest period. 2. After irrigation, nitrogen fertilization is the most important cultural practice in an almond orchard. For most of our orchards, split nitrogen applications provide the most efficient use of nitrogen. A post-harvest nitrogen application can be of 20 to 40 pounds per application – dependent upon tree age- totaling no

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