March 2021, Issue 10

Shelling Out Useful, Real-World Almond Knowledge

As we continue to move into almond bloom, the time to start is now. Every month brings new needs and new possibilities to your orchard, so we’ve done our best to put together the following advice for your almonds.
Nutrient Uptake Curves and Their Role in Crop Protection
Nutrient Accumulation Rate vs. Total Nutrient Accumulation
As we continue to watch petals fall from our trees and leaves unfurl, our next thought (if it isn’t already) should be centered on the development of an early Spring fertilizer plan to begin addressing the crop’s nutrient demands. To generate full yield potential while mitigating disease pressure, almonds require large amounts of nutrients to be applied at various time periods that coincide with physiological stages. The first period that should be addressed by our fertigation practices is the early Spring period that begins roughly 30 days after full bloom when trees are beginning to expand their leaves and transpire. Once this occurs, trees will shift from utilizing stored reserves for energy to nutrition found in the soil solution. When diving deeper into specific periods during nutrient uptake we can exploit the relationship between Accumulation Rate and Total Accumulation.

Nutrient uptake curves for most crops hold the same general pattern, increasing over the growing season at varying rates. Once trees begin to transpire and steep nutrient uptake occurs, even fertile soils are not able to keep up with nutrient demand and can easily result in a deficit. Avoiding this nutrient deficit is key in maximizing bud set and mitigating against June drop. Because Nutrient Accumulation Rate peaks well before Total Nutrient Accumulation, nutrients must both be present in the right form as well as in the soil solution to take full advantage of uptake.  When accumulation rate is not considered when formulating our fertilizer plans, early fertilizer applications can be late which could negatively impact crop stages later in the season. In order to fully exploit nutrient uptake, early-season fertigations should begin immediately following petal fall/leaf expansion and prior to the beginning of the steep uptake period of 20-30 days post-bloom.
Nutrients' role in Crop Production 
Nitrogen, phosphorous, and potassium are categorized as primary macro-nutrients because they are needed in large amounts when compared to other nutrients. Nitrogen is a key constituent of both amino acids (building blocks of proteins) and chlorophyll, making it critical for optimal reproductive and vegetative growth. Almonds have a very high nutritional protein content and therefore require Nitrogen in very high quantities to reach 100% yield potential. Phosphorous is an essential component of nucleic acids (DNA/RNA) and is involved in both cell membrane function and energy transfer. Phosphate fertilizers are typically applied to promote healthy seedling and root development during key stages. Almonds require more Potassium than any other nutrient we apply in our fertilizers (1,000 lbs of meat can remove up to 100 lbs of K20). Potassium drives many functions within plants, such as the building of carbohydrates and proteins, sugar translocation/starch formation, and stomatal regulation. These nutrients are typically needed in the greatest quantities because they are central to these various processes and compounds.
Calcium, magnesium, and sulfur headline a similar category of nutrients termed, secondary macro-nutrients. These nutrients are needed in large amounts but typically represent a much smaller portion of a grower’s inputs when compared to the primary macro-nutrients. Calcium is critical for healthy soil structure but also plays a prominent role at the cellular level within plants, from its importance to cell wall structure, cellular membrane function, and new cell formation (meristematic portions). Magnesium is the central element of the chlorophyll molecule and is an enzyme activator, catalyzing various chemical reactions within the plant. Sulfur is a component of amino acids (synergistic with Nitrogen), important in protein synthesis, and critical for nodulation in legumes.

Micronutrients are the final classification of nutrients and are needed in very small amounts during specific stages of crop development. Boron and zinc play an important role during the bloom period and are commonly added to fungicide sprays during this period. Boron is vital in meristematic cellular differentiation and pollen tube elongation while Zinc is also important for proper flowering and pollination because of its role in cell division. Iron and manganese both play important roles in the development and formation of chlorophyll, while manganese also influences nitrogen metabolism, enzyme activation, and electron transport. While many of these nutrients have additional functions, it’s important to highlight the most common and best-understood roles in crop development.  
Matt Comrey, Wilbur-Ellis Technical Nutrition Agronomist
The 4Rs of Nutrient Stewardship
Whether it be almonds farmed in the Southern San Joaquin Valley or potatoes grown in the Columbia Basin in Washington state, producers and advisors should ALWAYS apply the 4 Rs of Nutrient Stewardship in their decision making process.
  1. RIGHT SOURCE: Match fertilizer type to actual crop need
  2. RIGHT RATE: Matches amount of fertilizer type to current crop needs
  3. RIGHT TIME: Makes nutrient available when crops need them
  4. RIGHT PLACE: Keeps nutrients where crops can use them
4R Nutrient Stewardship provides a framework to achieve cropping system goals such as increased production, in-creased grower profitability, enhanced protection of the environment, and improved sustainability. For example, applying high rates of nitrogen in the fall to almonds obviously makes no sense because it is the wrong time but applying high rates of potassium to almonds in the fall may make perfectly good sense, since winter rains may be able to move potassium into the root zone (the right place) to maximize availability the following season. Though not openly stated in all of the Wilbur-Ellis Almond Grower Newsletters, the 4 Rs of Nutrient Stewardship have been well thought out in each and every one of our nutritional articles and are certainly practiced by all Wilbur-Ellis agronomists when advising nutrient inputs on your acres. Wilbur-Ellis field agronomists use facts when making nutrient management recommendations; crop removal rates and uptake curves, yield expectations, soil and plant tissue analysis data, environmental conditions, and historic fertility practices on YOUR farm. 
To P or Not to P?
Well, let’s rephrase that. To apply phosphate fertilizers to almonds or not, that is the question? For 2021 phosphate supplies are going to be very tight, meaning phosphate fertilizer prices are going to be firm with projections of higher costs as Midwest planning places increased demand on a limited supply.
Almond growers and advisors need to practice due diligence in determining where supplemental phosphorus needs to be applied to almond orchards. Along with nitrogen and potassium, phosphorus is called a primary macronutrient because in most plants it is one of the nutrients required in the greatest amounts compared to the secondary macronutrients (sulfur, calcium, and magnesium) and the micronutrients (zinc, iron, manganese, copper, boron, molybdenum, chlorine and nickel). However, almonds, like most other nut crops, have a relatively low P requirement compared to N and K. For example, 1000 lbs. of almond meat removes about 70 lbs. of nitrogen and 100 lbs. of potassium fertilizer K2O. Contrast that to just 15-20 lbs. of phosphate fertilizer P2O5. Furthermore, almonds have a long growing season when soil temperatures are warm and soil P availability is at its highest. Putting these considerations together translates into P nutrition in the majority of almond orchards is adequately provided by Mother Nature.  

Soil analysis does a good job of accurately determining the P content in soils but we do not have a good critical value to base phosphate application decisions upon. Summer leaf sampling and analysis are preferred. According to current UC and CDFA guidelines, orchards having a July leaf content of 0.10% or higher indicate adequate P supply. Choose your inputs wisely and always rely on your Wilbur-Ellis agronomist to guide you through your fertility management decisions.
Carl Bruice, Wilbur-Ellis National Nutrition Technical Manager
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2021 Irrigation System Start-Up
With almond bloom in full swing throughout much of California and little rain in the forecast, the 2021 irrigation season is upon us. So, the question becomes, “are irrigation systems ready for the new season?” Unfortunately, that process should have begun directly following the 2020 almond harvest, as a fall flush just prior to leaf drop is ideal for system shut-down. If that fall flush did not take place, there is simply no time like the present, as it is imperative to get this done before the new season.      
Where to begin?  First off, evaluate the water supply. After a water analysis, inspect the entire irrigation delivery system, from filters to hose ends. What do we see? Are there signs of biologicals, sedimentation, mineral/bicarbonate contamination in the lines, filters, mains, submains laterals, and emitters? Are emitter devices showing signs of plugging? Inspect these devices closely…even pulling a few emitters apart to do so. Are spaghetti’s plugged? How about the hose ends themselves? Are they filled with debris and contaminants? Remove a figure-eight or two from the furthest laterals on the block to inspect the hose ends prior to turning on the water. Then, once water is flowing again, what does the effluent from these hose ends look like? Does it resemble chocolate milk?  Are floating chunks of algae present? Is the flush water initially dirty, then clean for a few minutes before turning cloudy once again? If possible, cut an inline emitter out of the hard hose and inspect for contamination. Is it biological or of a different source? 
The fact that the system has been stagnant over the winter months creates a larger challenge, as contaminants may have hardened and become encrusted over time. This may necessitate more than flushing the system with clean water, it will likely call for a chemical flush, based on the contaminants found in the system. Ag Water Chemical professionals will diagnose, prescribe and carry-out the proper flush protocols to clean the system. 
This may translate to a chemical injection, monitoring of ppm levels to assure contaminants are dislodged and mitigated through a quick flush or it could necessitate charging the system to the desired ppm and allowing the system to sit for 24-48 hours before purging the entire system clean. There may even be a need for secondary chemical injection and flush. This is a site-specific process, as one size does not fit all. Yet, it directly impacts system efficiency and distribution uniformity, both of which contribute greatly to total ROI.
Ultimately, water treatment and system maintenance are key to more efficient water delivery, which begins now.  Producers can and should start with a clean irrigation system and maintain optimum performance throughout the year with the Wilbur-Elis / Ag Water Chemical solution of site-specific diagnosis, treatment, and service.

Some key in-season flush protocols:
  • Regularly flush laterals (monthly, bi-weekly if needed)
  • Flush complete system after fertilizer injections (critical with organic applications)
  • Flush from larger to smaller lines – mains and submains, then laterals
    • This procedure should be completed at system start-up each spring as well
  • When flushing lateral lines, assure proper velocity and volume to purge contaminants   
    • Good rules of thumb include:
  • A minimum of one-gallon flow/minute for 5/ 8” line and smaller or 1.5 ft/second.
    • A white one-gallon bucket for flush water helps to identify impurities and calculate flow. 
    • Never open more than 5 – 8 laterals at a time, as additional open lines will reduce the velocity of flow, which reduces the effectiveness of the flush (dependent upon the total number of laterals per block).
  • Always note pressures and flows at the initial system start-up
    • Changes in these parameters are key indicators of in-season issues
Doug Larson, Ag Water Chemical


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