David Doll8 CommentsMarch 29, 2015Nutrient

Young Tree Nitrogen Fertilization

In attempts to incorporate varying media within the website, here is my first go at using Google Hangouts to LiveCast a presentation. The recorded presentation below provides nitrogen fertilization considerations for  newly planted and developing orchards. Total length is around 15 minutes. A quick overview of the presentation: Nitrogen is nitrogen. Several studies within CA have indicated that there is no benefit in using different types of nitrogen for fertilizing young almond trees. Some fertilizers, however, may influence soil pH as well as be more prone to leaching; Studies within Merced and Colusa COunty have indicated that newly planted trees will maximally grow with actual nitrogen applications between 3-4 ounces. This has to be adjusted for tree density and application efficiency; Developing trees have developing rootzones which leads to inefficient applications. If fertigating, the best irrigation system would deliver nitrogen directly to the rootzone of the tree (e.g. single line drip with punched emitters). If not possible, controlled release fertilizer has been shown to grow as well as conventional fertilizer and have a lower labor cost (one application and done for the season). The 120 day controlled release blend in this trial was supplied by Agrium Technologies; Do not apply more than one ounce of actual nitrogen per application per year of growth. This helps reduce lanky growth and nitrate uptake toxicity; Take into account residual soil nitrogen and nitrogen within the irrigation water if using a well. In some cases, these may provide sufficient nitrogen; Finally, don’t start too early. Give the trees time to grow and draw down some of the moisture within the rootzone. Around 6″ of growth should be visible prior to the first fertilization. Here is a link for a pdf copy of the presentation.

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David Doll6 CommentsMarch 7, 2014Nutrient

Almond Nitrogen Uptake: Seasonal Perspective

There has been a lot of workshops and seminars discussing nitrogen management in almond. The data and conclusions discussed from these trials has been thought provoking, and has provided information to help better manage almond orchard nitrogen.  One particular slide has caught my attention – and provides the basis of nitrogen timings for almond orchards.

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Franz Niederholzer14 CommentsMarch 14, 2013Nutrient

Nitrogen Management in Mature Almonds, Part 1

Nitrogen is the most important mineral nutrient in almond production.  It is absorbed as nitrate or ammonium by active roots.  Mature almond trees use 80% of their total annual N requirement between March (full leaf out) and mid-May – June (kernel fill).    If the N isn’t available in this key application window, yield can be lost. To maximize yield (income) while minimizing N losses from the root zone ($ losses) that hurt growers wallets and may harm the environment attention to the four R’s – Right Rate, Right Time, Right Place, and Right Material — is needed in all orchard fertility programs.  Different nutrients are needed at different times and amounts by almond trees.  Spring is a key time for almond orchard nutrient management and the key time for nitrogen inputs.

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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 Doll0 commentsSeptember 6, 2012Nutrient

Post Harvest Nitrogen: How Much?

Generally, we recommend 20-25% of the season’s nitrogen budget to be applied in the post harvest period. This is based upon having a Mid-July leaf nitrogen value within the range of 2.2-2.5%.  This nitrogen is used for the post-harvest growth processes, which includes both vegetative and fruit bud development and some vegetative growth. When making this application, the sooner, the better, as it will help reduce tree stress.  Studies have shown that ‘Nonpareil’s’ fruit bud differentiates about 7-14 days after harvest, while other varieties, such as ‘Carmel’, the majority of fruit buds differentiate prior to ‘Carmel’ harvest. This timing will be delayed in cool, mild years. Tree stressed imposed during this period will reduce fruit bud set, and the buds will remain vegetative (leaf buds). In the cases of above recommended mid-July leaf nitrogen levels, nitrogen should still be applied, but the amount should be reduced. For example, if leaf nitrogen values are around 2.8%, apply 15-20% of the total seasonal nitrogen budget. If over 3%, reduce that application further to 10-15% of the total nitrogen budget. Nitrogen should be applied with caution in the post-harvest period as early rains may leach nitrate in sandier soils. Late fall (Late September, early October) nitrogen applications should also be reduced; the trees ability to pick up nitrogen is decreased due to lower levels of transpiration.

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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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David Doll0 commentsMay 19, 2012Nutrient

Estimating Nitrogen Needs = Estimating Your Crop

Research by Dr. Patrick Brown’s group at UC Davis has been reviewing nitrogen use efficiency of almonds. In their studies they have shown that almonds, when properly fertilized (i.e. not over/under-fertilized),  export between 60-65 pounds of N from the orchard for every 1000 kernel pounds harvested. This number includes all green weight removed to achieve the 1000 kernel pound yield – roughly 4000 pounds of hulls, shells, leaves, debris, and kernels. Interestingly enough, they also have found that orchards that are under-fertilized will export less N (65 lbs). Knowing this, is it possible to determine the nitrogen needs of the trees for the season? Simply stated, “Yes,” but only if an accurate estimate of crop can be made. The ability to accurately estimate a crop is gained through experience and the taking of careful notes from the early season to allow comparison with the sheets provided at harvest. Once a crop estimate is determined, the estimated kernel yield/acre can be multiplied by 60 pounds to determine the total amount of N required/acre for that year. Since almond goes through a period of several drops and weather events (i.e. frost, hail, etc), this adjustment can be modified in season to account for the change. Never-the-less, applying only 60 pounds of N for every 1000 kernel pounds will not meet the trees need because the application efficiency of nitrogen is not 100%. Further work within the study demonstrated that almonds are much more efficient than previously thought, with roughly 70-75% of the nitrogen applied through a micro-irrigation system making its way into the tree. Taking this use efficiency into account, we need to multiply the pounds required by crop demand by 1.4, giving a number of 84 pounds of N for every 1000 kernel pounds. So how does all of this relate to nitrogen leaf sampling?

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