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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Franz Niederholzer7 CommentsApril 13, 2011Nutrient

Using Urea Efficiently

Summary: Soil applied fertilizer is intended for root absorption by plants. Manage fertilizer nitrogen (N) to keep as much of it as possible in the root zone to maximize crop N uptake, crop yield, and protect the environment. To keep urea fertilizer N in the root zone 1) incorporate urea into the soil with water or cultivation within a day or two of application and 2) don’t over irrigate when incorporating urea using water. Inject liquid fertilizers containing urea (for example, UAN32) into irrigation systems in the middle third of the irrigation set. This delivers urea N evenly through the root zone, avoiding leaching that can occur when urea is injected too early in the set and limited root zone distribution when injected too late in the set. Background: Urea is the most commonly used dry nitrogen (N) fertilizer in the U.S. It provides half of the nitrogen in UAN (Urea Ammonium Nitrate) 28 or 32 liquid fertilizers. Dry and liquid fertilizers that contain urea have several advantages — relatively high N content (28-46% N), ease of handling and reasonable price relative to other N sources. However, nitrogen from applied urea can be lost from the root zone when used improperly, wasting money, reducing plant available N, and risking reduced crop growth and yield. The lost N can also be an environmental contaminant. Growers and PCAs should be aware of how to avoid N losses and get the most from urea fertilizer dollar. Within days of application, urea N can be lost from the crop root zone in two ways – through ammonia volatilization or urea leaching. This article will briefly describe how these losses can occur and how to manage urea to avoid them. The uncharged urea molecule (H2N-CO-NH2) breaks down in or on the soil into two ammonium molecules

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David Doll0 commentsApril 29, 2010Nutrient

Tips for Maximizing Nitrogen Use Efficiency for Almond

Previously this week, I wrote an article discussing nitrogen needs within the almond orchard. Application of nitrogen, as briefly discussed, varies in efficiency based upon techniques of application and irrigation/fertigation systems. Below are some tips to maximize efficiency and reduce losses for many common fertilizer application strategies. Maximize Efficiency:1. Apply N only when leaves are present and the tree roots are active. Avoid dormant season applications.2. Efficiency can be increased by applying N in small doses more frequently than large doses less frequently.3. Apply a uniform irrigation that is adequate to carry the N into but not past the root zone.4. Because young fruit trees have a fairly constant N uptake, apply multiple applications of N throughout the growing season.5. Mature trees need most of the N in the spring, around 70-75% of the nitrogen budget.6. Late summer/postharvest applications, 25-30% of the budget,will help with flower bud differentiation and formation for next year’s crop.7. Fertigation has generally been very efficient in N applications.8. Analyze leaves in July each year to fine tune N level to the orchard. Maintain the level in the adequate range. Minimize Losses:1. If fertilizer is surface applied, disc or irrigate N into the root zone shortly after application.2. Fertilize the tree, not the covercrop. Evaluate how best to bypass the covercrop. This may be by applying the fertilizer to the herbicide sprayed strip, mowing, or cultivating the covercrop.3. Don’t over irrigate. Nitrogen is soluble and moves with water. Excessive runoff of tail water or leaching will remove N.

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David Doll4 CommentsMarch 26, 2010Nutrient

Nitrogen Content in a Gallon of UAN-32

I have been emailed a few questions in regards to calculating the amount of nitrogen in a gallon of Urea Ammonium Nitrate (UN-32 or UAN-32). Since UN-32 is widely used to fertilize/fertigate almonds, it is necessary to know how much is being applied per application. 1 gallon of UN-32 weighs 11.02 pounds. 32% of the weight is nitrogen – hence the “32.” This roughly equals 3.4 pounds of nitrogen per gallon, or 55 ounces. So, following the guidelines suggested by Brent Holtz (UCCE San Joaquin),when fertigating 2nd leaf trees with UN-32, at 110 trees/acre, no more than 4 gallons should be used in a single application. I hope this helps.

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