21 Aug, 2022
David Doll2 CommentsAugust 21, 2022Nutrient

Using Mid-summer Leaf Samples to Guide Fertilizer Decisions: Part 2- Potassium

Potassium fertilizers have seen major increases in price over the past year. This is due to multiple factors, including increased demand, trade embargos with Belarus, and shipping constraints from Russian suppliers. Due to this price increase, many operations are trying to determine the appropriate amount of potassium needed for a specific orchard. Potassium fertility management is different than nitrogen. Potassium moves into the root through diffusion and mass flow. This means that it must be within the active rootzone to be utilized by the tree. Additionally, potassium is a cation (K+) and will respond differently based on the type of soil. High cation exchange capacity (CEC) soils have many charge sites, which can prevent potassium from being available to the plant. This can be further complicated by the presence of micas and other clay minerals. In low CEC soils, the opposite is true, the reduced number of charge sites in the soil mean higher potassium uptake for the plant. However, keep in mind that this higher availability in the soil can also lead to more potassium leaching below the rootzone, increasing costs, or reducing tree productivity. Potassium programs vary. Almonds use a significant amount of potassium, with 92 lbs of K2O needed for every 1000 lbs of kernels produced (92 kg of K2O/metric ton). Potassium is often applied as one of several products, including potassium sulfate, potassium chloride, potassium thiosulfate, and potassium nitrate. These materials may be applied blended with other fertilizers. For example, potassium chloride is commonly used within blends as it is easy to dissolve and stays in solution.  Other sources are available, but are often more expensive and, regardless of the sales pitch, equal in performance. The only exception is compost, which can be cheaper per unit depending on the source and the analysis. Due to the soil

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Franz Niederholzer0 commentsApril 11, 2014Nutrient

Potassium Webinar Q&A

At the end of February, David Doll and I presented a webinar on potassium nutrition of almond orchards hosted by Western Farm Press with support from Compass Minerals.  During the webinar, listeners asked questions and we tried to answer them at the end of the webinar.  We could only get through a few.  In this post, we try to answer at least a few of those questions asked (another link to the webinar…click here!).

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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 Doll7 CommentsJanuary 24, 2013Nutrient

Nutrient Removal for Almond

I have received a few inquiries about the nutrients removed for almond. Based on Dr. Patrick Brown’s group’s work (Sebastian Saa Silva and others), the amount of NPK removed with every 1000 kernel pounds of almond is: Nitrogen – 65 lbs, Phosphorous – 8 lbs, and Potassium – 76 lbs. This includes the nutrients removed will all of the materials exported out of the orchard in a typical pick-up operation – hulls, sticks, leaves, shells, and kernels. Keep in mind that more than the above amounts may be needed to compensate for the inefficiencies of application and uptake (i.e. nitrogen uptake efficiency is somewhere between 75-85%, condition dependent — so to have 65 lbs of uptake, 76-85 lbs of N must be applied). As noted in the comments below, potassium and phosphorous must be converted to oxides. This can be done as follows: Almond removal 8lbs of P = 18.4lb of P2O5 76 lbs of K = 91.2 lbs of K2O For Phosphorus o Lbs. P x 2.3 = lbs. P2O5 o Lbs. P2O5 x 0.43 = lbs. P   For Potash o Lbs. K x 1.2 = lbs. K20 o Lbs. K20 x 0.83 = lbs. K

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David Doll3 CommentsJuly 28, 2012Horticulture, Nutrient

Nitrogen and Potassium Leaf Content: Is There Such Thing as Too Much?

I have received a few questions regarding results of mid-July leaf tissue analysis. In many cases, when reviewing the leaf samples, I have noticed that levels of nitrogen and potassium are often much higher than the recommended mid-July levels. Having leaf nutrient contents well above adequate levels does not necessarily increase yield, but can increase fertilizer costs and hull rot incidence. Rationale for “pumping” up the trees above the adequate value is to address the “silent hunger” that may be taking place within the field. In other words, by overfeeding some trees, we are assuring that we are maintaining trees that may be borderline above the level of sufficiency. Performing this action may increase yields as some trees that are deficient will perform better; however, too much fertilizer will lead to waste. Assuming that the leaf samples were collected properly, the UC-established mid-July leaf values should be used for comparison.With nitrogen, leaves with 2.2-2.5% leaf nitrogen content indicate that the sampled trees are receiving enough nitrogen. Being a few tenths of a percent over this value (3.0%) is a good indication of over-fertilization, increasing the risk for hull rot. Regarding potassium, the sample is considered sufficient if it is above 1.4%. Most growers attempt to maintain their potassium leaf levels around 1.8-1.9% within their samples, buffering for the tree use and compensating for the spatial variability of potassium within the tree. I have seen several leaf analysis with potassium levels greater than 2% and have heard from growers that trees need to be above 2% to maintain production. This is not true. Research by Roger Duncan (Farm Advisor, Stanislaus County) found that orchards with potassium leaf levels greater than 2% did not have greater yields than orchards with leaf levels above 1.4%. If leaf samples are well above the sufficient levels, plan to reduce,

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