David Doll2 CommentsSeptember 6, 2016Nutrient

Postharvest is a Good Time for Boron Foliar Sprays

Boron is a critical micronutrient for fruit set.  Work has shown that yield can be reduced when boron hull concentrations fall below 80 ppm. In order to determine deficiency, a hull analysis should be taken to determine tree boron status. Leaf tissue levels are not consistent in providing boron status. Applications of boron should occur to the ground if hull levels are below 80-100 ppm. Boron foliar applications, however, should be considered for nearly all orchards except ones approaching toxicity (hull boron greater than 200 ppm). Boron foliar applications have been shown in several studies to increase yields in orchards deemed boron sufficient. A study from 1999 compared the application of foliar boron at two locations – one in Fresno County and the other in Glenn County – for two years. The Fresno County location applied the foliar sprays either in September, December, or February at three rates (0 lbs/acre, 0.71 lbs/acre, and 1.5 lbs/acre of boron) using Solubor® (a 20.5% boron product). The Glenn County site applied the foliar spray either in August, September, or February at four rates (0 lbs/acre, 0.71 lbs/acre, 1.11 lbs/acre, 1.50 lbs/acre, and 1.91 lbs/acre of boron) using Borosol® (a 10% boron product). At the Fresno Location, the September application was the most effective in increasing tree boron levels, fruit set and yield. All rates out-performed the control. At the Glenn County location, the increasing rates increased tree boron tissue levels almost linearly for the August and February timings. February application timings at both sites increased initial fruit set, but the greatest increase in tissue concentration, nut set, and yield response came from the September timing. The increases observed are most likely is due to the increased efficiency in nutrient uptake from the active leaves. If a September application cannot be made, a February/early pink bud spray should be considered. Ground applied boron should

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David Doll5 CommentsJuly 12, 2014Nutrient

Importance of Hull Sampling for Boron

Boron is a micronutrient for almonds. It is required in the process of flower fertilization, being involved in directing the germinating pollen tube. Deficiencies lead to a reduced nut set, and in severe cases, an appearance of a “nonproductive symptom.” Within the tree, boron deficiency can lead to a dieback of small twigs and a “weeping branch” like look.  Boron is also toxic at too high of concentrations.  Often being found in areas with high soil boron or in blocks irrigated with water containing boron, toxicity symptoms appear as gummy nuts that may  form “stick tights” or presence of gum exuding from pruning wounds, bud and leaf scars, and spurs.

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Franz Niederholzer1 CommentSeptember 9, 2013Nutrient

Sustainable Nutrient Management: a Review.

Almond harvest looks to be progressing well (knock, knock).  Orchard fertility/nutrition planning for the 2014 is beginning.  Now is a good opportunity to review the basics of almond orchard nutrient management.  While some of what follows will be review for many readers, a quick review may be of value. Sustainable nutrient management comes down to the four R’s – the Right Rate, the Right Time, the Right Place, and the Right Material.  A sustainable approach to orchard nutrition is intended to optimize crop production and maximizing net profit while reducing the risk of environmental contamination.

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David Doll8 CommentsAugust 17, 2013Nutrient

Postharvest Fertilization – Q&A

Q. How much nitrogen should be applied in the postharvest period? A. This depends.  This should be based upon the current tissue N levels detected from mid-July sampling. If within the prescribed ranges of leaf N (2.2-2.5%), 20% of the budget should be planned for application. If richer (>2.5%), slightly less can be added. If really high N leaf levels are observed (>3.0% in mid-July), postharvest fertigation may not be needed. 

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David Doll3 CommentsOctober 17, 2012Nutrient

High Boron Hull and Leaf Values…

There have been a few questions regarding high boron levels in hull and leaf tissue sampled from this past year. The general consensus is that it is “just one of those odd things that occur every year.” Never-the-less, that prompted me to give Dr. Patrick Brown (UC Davis) a ring and inquirer about environmental influences on boron.

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Roger Duncan10 CommentsAugust 23, 2012Nutrient

Hull Analysis for Boron – Why?

Harvest is here. This is a good time to pull a a bag of almond hulls for a boron analysis. In making this recommendation, there are questions that are consistently asked. I already know my leaf tissue levels, so why do I need to perform a hull analysis for boron? Leaf sampling is not effective in determining the levels of boron as there are no obvious foliar symptoms of moderate boron deficiency. Furthermore, leaf levels may appear adequate while the actual levels within the tree are too low or high. Since the hull of the almond is a “sink” for boron, the analysis of mature almond hulls is a better indicator of boron status. When should I collect samples for a hull analysis? Boron will continue to accumulate in the hull until harvest. The best time to collect a hull sample is anytime after shaking the nuts. Varieties within the orchard may have differing boron levels due to different yields; it may be useful to pull a sample from the other varieties. How do I interpret the results? Trees with hull boron levels of less than 120 ppm may benefit from a postharvest boron spray (1-2 lb of a 21% B product in 100 gallons of water per acre). This will help with pollen germ tube growth in the flowers next spring but will not improve overall boron status of the tree. Boron applied earlier in the season as foliar spray is not a substitute for this timing because it is sequestered into the hull and is unavailable for the developing fruit bud. Hull boron of less than 80 ppm indicates the need for a ground application.  Fertilize with 2-4 pounds of actual boron per acre.  This is equivalent to 10-20 pounds of a 21% soluble boron product (i.e. Solubor). Boron can be applied through the irrigation system, broadcast or

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Roger Duncan2 CommentsAugust 2, 2010Nutrient

Hull Samples for Boron Analysis

What is the most common nutrient deficiency in Northern San Joaquin Valley almonds? If you said nitrogen or zinc you are wrong. While zinc and nitrogen are commonly applied to area orchards, boron is often neglected and therefore boron deficiency is far more common. If you haven’t applied boron TO THE GROUND recently and your orchard is east of the San Joaquin River, you are almost certainly deficient. Boron is essential for pollen tube growth. There are no obvious foliar symptoms of moderate boron deficiency, but less than optimum boron can reduce nut set. Analysis of mature almond hulls is a much better indicator of boron status than a leaf analysis. Wait until harvest to collect hulls because they will continue to accumulate boron while splitting. Trees with hull boron levels of less than 120 ppm may benefit from a postharvest boron spray (1-2 lb of a 21% B product in 100 gallons of water per acre). This will help with pollen germ tube growth in the flowers next spring but will not improve overall boron status of the tree. Hull boron of less than 80 ppm indicates the need for a ground application. Fertilize with the equivalent of 10 – 20 pounds of a 21% boron product per acre. Boron can be injected through micro-irrigation systems, broadcast or sprayed on the ground, or included in a herbicide spray. Herbicide sprays containing glyphosate may need to be buffered to prevent reduction of herbicidal activity. Hull levels over 200 ppm indicate excessive boron.

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