Franz Niederholzer8 CommentsSeptember 19, 2012Nutrient

Fall Foliar Fertilizers: Targeted v/s General Approach

A PCA asking me the other day what I thought of a general micronutrient (iron + molybdenum + zinc + copper + manganese + boron +?) compared to a standard zinc + boron spray program that is common in postharvest almonds in the areas where I work. This question got me thinking about a review of fall fertilizer programs in general, with a focus on foliar nutrients. There are more than a dozen mineral nutrients essential for plant growth. However, only a handful of those nutrients have been shown to be important – in general — to profitable almond production. These

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David Doll14 CommentsOctober 21, 2011Nutrient

Post Harvest Foliar Sprays

After harvest is a good time to apply a few different foliar nutrients to the trees before the leaves fall. Nutrient uptake occurs through wood and leaf tissues. Applying when leaves are still green and active increases the sprayed surface area, thus increasing the efficiency of the spray and uptake of the nutrients. Applications can be made when leaves are off the tree, but the reduced surface area leads to a reduced nutrient uptake.  Below are considerations to make in regards to a few commonly applied foliar nutrients. Boron. Studies have shown that a foliar spray of boron can increase crop set regardless of boron hull content. If the tree is deficient in boron, the resulting “yield bump” is greater than in sufficient trees, but the “yield bump” is still observed in sufficient orchards.  Two pounds of Solubor (20% Boron) applied with 100 gallons of water/acre is commonly used. This article detailing boron foliar sprays highlights the specifics. Urea/Nitrogen. Fall foliar applications of lo-biuret urea are thought to reduce the incidence of bacterial canker and bud drop within almond. It is thought that this reduction is due to an increase of tissue nitrogen content which may increase overall tissue health making it more resistant to bacterial infection. Fall Urea applied for bacterial canker prevention should be applied later in the season (i.e. first week of November) and at a rate of 100 lbs/acre. Studies have also shown that fall applied lo-biuret urea can increase yield. Although studies have not shown the yield increase to be significant, it has been observed in two trials. Both yield increases were observed with the lower end of urea use, between 10-25 lbs/acre. Higher applications of urea did not produce as much of an effect and in some cases led to foliage burn and leaf

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David Doll2 CommentsJanuary 27, 2011Horticulture, Nutrient

Bloom Spray Additives: Do they work?

Bloom is approaching. Several questions about whether or not bloom spray additives increase flower pollination and set have been asked. I will try and answer them the best I can using information from previous trials across the state. Much of this information is gleaned from Roger Duncan’s presentation delivered at the 2010 Stanislaus Almond Day. Should I include foliar nutrients in the bloom spray?Several trials from four different advisors from areas across the state (Duncan – Stanislaus, Holtz-Madera, and Edstrom – Colusa, and Viveros – Kern) have indicated that nutrients and other additives included with bloom sprays do not increase yield of almonds in properly maintained orchards. In most trials, yields of the untreated control were higher than the foliar nutrient applied treatment. These were multiple replicated trials held over several years. Materials used can be seen by viewing the presentation linked below. This trial data can be seen in Roger Duncan’s 2010 NSJV Almond Day presentation (click link). What about Pristine® Fungicide?Pristine® fungicides is a boscalid/strobilurin mixture that has been used successfully for several foliar fungi that commonly affect almond flowers and leaves (i.e. Brown Rot, Rust, Scab, etc.). There is evidence that suggests that Pristine® causes a yield bump when applied during the bloom or post bloom period. Research by Jim Adascaveg (UC Riverside) and Roger Duncan (UCCE Stanislaus) tested this hypothesis and have not found a significant increase in yield from a bloom or post bloom Pristine® application. It is important to state that in Duncan’s trials (Stanislaus Co.), the yields were higher in treatments containing Pristine®, although not statistically significant. Duncan found this same insignificant yield bump when applying Gem®, another strobilurin, in the post-petal fall period. Conversations with a local consultant indicated mixed success of the Pristine® yield bump across his multi-year trial. Although he

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