David Doll3 CommentsMay 5, 2016Nutrient

Potassium and Almonds: Rates, Timings, Other Tips

I received a few questions on potassium applications in almonds. These include points on rate determination, application timing, and other considerations. Q. How much potassium is needed? Almonds remove about 72 lbs of elemental potassium (K) for every 1000 kernel pounds. This is equivalent to 92 lbs of potassium oxide (K2O), the unit which potassium fertilizers are measured. This means that for every 1000 pounds of kernels removed, 92 lbs of K2O must be available or applied to prevent future deficiency. This is equivalent to 184 lbs of potassium sulfate (50% K2O) or 368 lbs of potassium thiosulfate (25% K2O). The amount of potassium applied should take into account leaf tissue levels as well as soil analysis. If the soil analysis reveals K values greater than 150 ppm, the trees are less likely to respond to K applications. In these cases, applications should match removal. If high amounts of K are available in the soil (>250 ppm), K rates could be reduced to help reduce costs (applications should match ~80-85% of demand) until soil analysis begins to show a decrease in K values. If lower than 150 ppm, rates should be increased to help build reserves. please note that some soils-such as sands- can not hold this much potassium. Leaf tissue levels of K are variable. “Critical values” established at other times of the year have not been verified to production levels of trees through research. Therefore, mid-July leaf sampling is still recommended for determining K status of the tree. If trees have a leaf K percentage greater than 1.7%, minimal gains will be observed with increasing applications. Leaf tissue concentrations below 1.4% require increased applications. Q. How should potassium be applied? K fertilizers can be applied by granular applications or through the irrigation system. Ground applications are often made

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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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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 Doll5 CommentsDecember 7, 2009Nutrient

Potassium Applications in Almonds

Having a major role in many plant processes, potassium promotes root growth, increases kernel/fruit size, and provides key metabolic features that include the formation of starch, translocation of sugars, stomata regulation, and the formation of xylem vessels. In general, plants deficient in potassium tend to have slow growth, with small, pale leaves. Trees that are severely deficient may have necrotic tips and margins. In many cases, the leaf tip curls upwards in a common symptom that is named the “Vikings Prow” (Figure 1). Since Potassium plays a large role in tree health, it is important to maintain proper levels of the nutrient within the tree. A critical leaf value of 1.4% has been established by the University of California and current research has suggested that levels above this value do not increase yields. Recent field studies by Roger Duncan (UCCE Stanislaus) have demonstrated that leaf potassium levels in excess of the 1.4-1.6% range did not increase yield. Through the study, leaf levels between 1.4-1.6% gave the best yield results, with yield decreasing when potassium levels were below this level. Leaf potassium levels higher than this range did not increase yield, and may actually reduce yields if applied in excess. Potassium usage by the almond crop is high. Upon harvesting the hulls and kernals, potassium is removed from the orchard. Studies by Dr. Patrick Brown (UC Davis), have shown that 76 pounds of potassium (92 lbs of K2O) are removed from the orchard for every 1000 pounds of kernals harvested. From nutrient analysis of the fruit parts, 70-80% of the potassium removed by the harvest is within the hull, while the rest is within the shell and kernel. Even though a large amount of potassium is used by the almond crop, it doesn’t always mean that large applications of potassium are needed

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