Fertilizing First Year Almond Trees: Major Nutrients

Determining fertilizer needs for newly planted orchards is challenging. This is due to the desire to grow the trees as rapid as possible while considering the risk of uptake burn and irrigation system inefficiencies. To determine the optimal fertilizer plan, the amount and type of nitrogen and other nutrients need to be considered. Nitrogen: Rate studies conducted in California have found that tree growth seems to peak with 3-4 ounces of nitrogen application per tree. This is based on three different studies – one located near Arbuckle, CA and the other two in Merced County. Within the most recent studies in Merced County, applications were made every three weeks from April through July for a total of six applications. A total of 0, 1, 2, 4, and 6 ounces of actual nitrogen was applied during this period to replicated plots using a NPK blended fertilizer. The source of nitrogen did not create a difference in trunk caliper in the multiple studies within Merced County. Very simply stated, “nitrogen is nitrogen.” There are benefits, however, to the various nutrients that are within fertilizers. If soil levels of phosphorous or potassium are low, utilizing an NPK blend would provide an addition of these major nutrients. The same could be said about calcium-containing fertilizers. If these nutrients are at sufficient levels for plant growth, however, there is minimal benefit from adding additional amounts. Potassium and Phosphorous: Within California conditions, phosphorous (P) and potassium (K) do not appear to be the limiting factor with most soils. The two trial locations within Merced County were located on sandy soil and found no increase in growth from the inclusion of P and K within the fertilizer programs. This does not mean that these major nutrients are not important, rather that many soils contain adequate levels of

April 25, 2019

Frost Damage Effects: Points to Consider for 2018

The frost event from the week of the February 19th impacted almond production Statewide. Temperatures dropped in many areas below the critical temperatures. This was compounded with a low dew point which made frost mitigation strategies difficult. Damage has been reported from just about all production areas across the State. Damage reports at this time are challenging to make. Flowers and young nutlets should be checked to see if they have been killed. This is indicated by browning tissue on the inside of the tissues/ovary. This article from 2011 covers a variety of symptoms that may be observed. Damaged flowers and nuts will drop from the tree as the crop begins to set. This may take several weeks and may not be evident until the nuts begin to increase in size. Many will most likely fall off with this upcoming rain storm. It is a common misconception that the tree will compensate for crop loss with an increase in set percentage of the surviving flowers. This is not exactly true. There is some mild compensation due to a slightly higher set percentage of undamaged buds (~2% or so increase) as well as a gain from increased kernel size due to more energy directed to the embryo during the period of cell division. These two factors, however, are not enough to compensate for flower loss that may have occurred during bloom. Although many often hope, it is unlikely that the late blooming flowers will set as they often lack the energy within localized tissues to form a viable nut. Once a damage estimate can be made, the season plan should be adjusted. Nitrogen rates should be reduced if losses occurred. Depending on the severity of crop loss, certain pest management practices may also be omitted. These include late season bloom/petal fall

March 9, 2018

What influences hull-split timing?

Hull-split often occurs around the end of June though the first week of July within the San Joaquin Valley. The start and duration of hull-split is influenced by the variety, weather, and tree stress. As many are aware, the variety has the strongest influence on hull split initiation and progression, but this article will focus on the influence of weather and tree stress. Most people believe the weather experienced in mid-June strongly influences the start of hull-split. Research has indicated, however, that this is not true. Work by Ted DeJong (UC Davis Plant Sciences), has found that the beginning of hull-split (which is indicated as 1% hull split) can be predicted by weather conditions experienced during the first 90 days after bloom. Cooler conditions experienced during this time will lead to a later hull-split, while warmer conditions result in an earlier split. Temperatures in the latter half of the spring and early summer have a minimal influence on nut progression, regardless of being warmer or cooler than normal. The model can be found at http://fruitsandnuts.ucdavis.edu/Weather_Services/almond_hullsplit_prediction/ and can be applied using localized CIMIS data. There is some evidence to support that tree stress and nutrient status influences the duration of hull-split. Stress in June decreases water content within the hulls, which means a faster drying time when they begin to split (think of hull-split progression like a bell-shape curve – stress in June shortens the x axis).  This is often related to high heat experienced in June, which leads to tree stress due to inability to properly manage the irrigation or the application of regulated deficit irrigation (RDI). Nitrogen status of the tree also influences the rate of split, in which trees having a higher nitrogen content have a longer duration of hull split. Often vigorous orchards are grown with minimal

June 23, 2017

Yellow Trees from Being Too Wet

It is very common to see yellow trees in the spring. The lack of color is often due to saturated soils which reduces the movement of oxygen into the soil, killing fine feeder roots. This impacts the ability for the tree to take in water and nutrients, leading to micro-nutrient deficiencies, impacting nut set and tree growth. In severe cases, especially with younger trees, the symptoms are similar to glyphosate drift or zinc deficiency. Later-season carry-over effects are also observed and include a limited rootzone, which leads to severe water stress during hull-split and harvest. Most of the time, this problem is caused by the orchard being irrigated too soon. Many operations apply water because it is perceived as needed or they are wanting to apply fertilizer. The need to apply water, however, is usually very low in the spring due to the cooler conditions and crop stage. Based on the 30-year average almond evapotranspirational values across California, water use from Mid-February (bloom) through the first week of April for almonds across the State ranges from 3.6″ to about 4.25.” This demand is often met by rain and the tree accessing stored moisture within the soil. To determine when to start applying water, plant stress or soil moisture levels should be monitored. The soil profile should be starting to dry at the two to three feet zone and can be checked with with the use of a shovel, auger, or soil moisture sensors. If using the pressure chamber to monitor plant stress, irrigation should be considered when trees are 1.5-2 bars more negative than baseline. For more information on the use of a pressure chamber in perennial crops, please see this document. If wanting to apply nitrogen, applications should occur by ground application or the shortest fertigation set as possible. These practices will help to properly time the first

April 10, 2017

2016 Top Ten Articles

With 2016 coming to a close, here is a quick review of the top ten articles read this past year from “The Almond Doctor.” 10. Verticillium wilt of almond (and pistachio). An overview of the disease, symptoms, and management for almond trees. This disease has become more common with increased plantings on land previously cropped to tomatoes and cotton. 9. Bacterial spot vs anthracnose vs plant bug. A series of pictures and a table to help identify the symptoms of these diseases or insect damage. 8. Postharvest is a good time for boron foliar sprays. A review of some research and considerations when making fall boron applications.  7. Independence almond – some observations. A 2010 article that highlighted some early observations of Independence. This variety is becoming more widely planted with an estimated 200,000 acres in the ground.  6. Almond set and nut drop. Summarizing recent research as well as field observations, this article discusses spur dynamics and the various “drops” of almond fruit. 5. 2016 almond bloom considerations. An annual contribution highlighting considerations for the upcoming bloom. 4. Proper almond tree planting. An article written by Brent Holtz back in 2010.  3. Fertilizing young almond trees – a few tips. With all of the newer orchards planted the past few years, this article has been read with increased frequency. 2. The seasonal patterns of almond production. An article about tree physiology and almond production. One of the first articles written for “The Almond Doctor” back in 2009. 1. Nitrogen content in a gallon of UN-32. A short article written in 2010 that provided an answer to a question commonly received. This one was number one last year as well! I would like to thank you all for your support through 2016. We develop many of the ideas for these articles through your requests for visits, phone calls, emails, and

December 31, 2016

Managing Water Infiltration Problems

Over the past few weeks, there have been several farm visits discussing water infiltration issues. In many of these cases, chemical sealing of the surface soil has occurred. This creates a crust that reduces the movement of the water into the soil. In subsequent irrigation, when water is applied faster than the rate of infiltration, puddling occurs, leading to an increase in evaporation as well as saturated soil conditions. This impacts water use efficiency and tree health. A season of irrigation can require between 36 and 52 inches of applied water per acre. This is often applied to a limited area of an orchard, which is defined as the wetting pattern. Each irrigation system has a different wetting pattern, with micro-sprinklers somewhere around 30-60% of the orchard area, and drip around 20%. This means that, dependent on the system, the wetted area may receive 2-5 times more water than the targeted season’s application per acre. In other words, if  four acre feet/acre were applied using a drip system that wets around 20% of the orchard floor, the soil in that wetting profile has nearly 20 acre feet of water that must pass through in order to infiltrate the soil. This is a tremendous volume of water to pass through the soil, and it can leach away beneficial elements which leads to chemical sealing and infiltration problems. When infiltration rates slow, it is important to know the causes as not all infiltration issues are the same. Taking an analysis of the water and soil is a good place to start. Unlike soil sampling conducted in the fall, soil sampling of the top 2-3″ of soil should occur to identify the chemical imbalance.  Analyzing the soil and water will give an idea of salt load, SAR, pH, as well as other elements. This will help identify

June 16, 2016

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

May 5, 2016

2016 Almond Bloom Considerations

Adequate chill and recent warm temperatures have accelerated almond bloom. Timing is close to “normal” in southern and southwestern areas of the State, but are 1-3 weeks ahead further north. Below are some thoughts to keep in mind with the anticipation of rain this week. Authors note (2-16-2015): There has been some concern about the wording around the time of nutrient/boron sprays and bloom. Research has shown that boron applied postharvest to 10% bloom can increase yield, while applied later than 10% bloom will not have an impact. Nutrient sprays-with the exception of boron as described in the previous sentence- have not been found by researchers to increase yield when applied at bloom. Sorry for the confusion. Fungicides are usually effective for about 14 days after an application. This period of protection is decreased with rain events. Furthermore, as surface areas expands – whether it is the flowers or leaves – newly exposed tissues are unprotected from infection. This means that spraying too early may not provide the wanted protection. If planning to make a fungicide application, apply the material as close to the rain event as possible. Remember that it needs between 30-60 minutes to dry. Depending on the pre- and post-rain conditions, and the periods of leaf wetness, a fungicide spray may not be needed. Keep in mind that fungal diseases require several hour periods of leaf wetness – which comes from fog, dew, and rain. Be cautious with adding additional surfactants. Most fungicides have surfactants mixed with the active ingredient. Adding additional surfactants may impact the efficacy of the fungicide, damage the flower’s tender tissues, or impact bees. The label should indicate if a surfactant is needed. Avoid tank mixing in boric acid with sprays made during bloom when bees are active(1). Researchers at the University of California as well as around

February 15, 2016

Wet or Dry, Get Ready for Bloom

Franz Niederholzer, UCCE Farm Advisor, Colusa/Sutter/Yuba Counties Spring isn’t here yet, but it will be before we know it. What happens then, weather-wise, and how you react to those conditions could change the season for your operation. But, no one can be certain of the weather this spring. Will it be wet? The forecasters think there is a good chance for that. If that’s the case, more bees and bloom sprays, and less irrigation will be needed. But, they could be wrong and 2016 could be another dry year. Better plan for a wet or a dry spring. Here are some things to consider: Topic Wet Dry Bees Higher hive stocking rates (3 hives per acre, minimum of 6-8 frames, with one frame of brood) are recommended in wet years. Spray carefully. No difference from the last few years. Make sure bees have water sources and fungicides are applied with bee health in mind. Click HERE1 for link to Almond Board BMPs for bees. Bloom sprays With rain at bloom, UC recommends 2 bloom sprays – pink (5% bloom) and full bloom. If it is warm at bloom, use material(s) with anthracnose activity. If it continues to rain, more fungicides will be needed. The more fungicides used, the greater the need to rotate chemistries. Click HERE2 to see info on fungicide efficacy/timing/resistance management. One bloom spray, timed before or at full bloom will provide good disease control under dry (no rain) bloom conditions. Weed management Properly selected and applied preemergent herbicides, sprayed before rain saturates orchard soils, provides weed control when you can’t get into too-wet orchards. Pre or post emergent sprays will control weeds. Don’t fall behind. Controlling weeds saves water. Nitrogen management 20% of annual N budget should go on by mid-March. If it’s still raining after petal

January 25, 2016

2015 Top Ten Articles

In maintaining the tradition of counting down the end of the year, below are the top ten articles read in 2015 from the readers of “The Almond Doctor.” 10: It’s the Nut Price, Dummy. A great article by Franz Niederholzer that discusses the rationale behind the increased plantings. It was the number one read article in 2013, number 3 in 2014. 9: Leaffooted Bug Advisory for Almonds: Two of our IPM advisors, Kris Tollerup and David Haviland, provided an advisory for Leaffooted Plant Bug after the mild conditions of the 2014-2015 winter reduced insect mortality. 8: Almond Bloom 2015: General considerations for various concerns at bloom. An annual topic during a time of year with highly variable conditions. 7: Understanding and Applying Information from a Soil Test, Part 2: A part of a series of articles discussing soil nutrients as determined through a soil analysis written by Allan Fulton. 6: Proper Almond Tree Planting: An excellent article written by Brent Holtz discussing proper tree planting methods. Considering the number of new plantings in 2015, the article finding its way into the top 10 isn’t too surprising. 5: Drought Management for Almond: Drought was a major challenge for many operations in 2015. This article discusses strategies to help reduce the impacts of water stress and drought. 4: The Seasonal Patterns of Almond Development: Back from the dead, this 2009 article picked up over 1700 reads which may be due to the increase of almonds in the media. It covers the general biology of the tree and stages through the year. 3: More Leaves than Flowers: Why? : This past year, in many orchards, flower density was lower than normal, and trees pushed more leaves earlier than in the season. Issues from 2014 had a carry-over effect into 2015, and this article explains a few

December 31, 2015