#SoilMatters: Spring Rootflush always precedes Budswell

Photo credit: M. Suderman

Benton City, WA -
Soil temperatures have risen 4-6°F in the past week. This has signaled these Chelan cherry buds to swell. This is an early ripening variety. Which means the number of days a farmer has to grow and nurture the crop are limited. This means every day counts from bloom until harvest and are critical to develop the fruit in preparation of harvest. For instance, an early variety may have 70-80 days from Full Bloom (pollination) until harvest. A week of cooler than normal weather or delayed nutrient application, reduces the growing response window by 10%; a limiting factor, if you will. All early crops are vulnerable to the uncertain eastern Washington weather conditions; this can include cold temperatures, rain, hail, frost, etc. all of which can limit the amount AND quality of harvestable fruit to ship to stores.

Soil fertility applications can begin based on the plant development stage. Roots are foraging just like a grizzly bear awakening from hibernation...hungry, thirsty and ready the ‘grow’. A reminder that roots always grow two to three weeks ahead of budswell activity.

Last fall, many orchards were not fertilized as usual due to a late harvest (~3 weeks) and an early snow. All efforts were focused on getting fruit picked and into the packing house or C.A. storage. Basically, Postharvest fertility was cancelled and trees went into dormancy ‘hungry’. It’s like going to bed without supper. Dormant plants’ sole energy (food) source is stored carbohydrates. These are built via photosynthesis in the previous growing season. The photosynthates needed for the upcoming crop are above the energy requirements of the current crop and stored until needed. When trees are overly stressed during the growing season, it has a direct effect on the current crop quality AND next crop’s potential too.

If this happened in your orchard(s), you likely have a plant-energy deficit going into the bloom stage. An energy deficit at bloom can reduce the viability of blossoms, limit pollination activity, cause premature abortions, etc. Regardless of the cause, it costs on the bottom line of profitability. Trees are well aware of the “available energy” stored for use and self-regulate accordingly. This can be a major limiting factor in setting a crop versus a really good crop.

With a well planned fertility program in place, you can produce tonnage without sacrificing quality. In Neoteric Agriculture, utilizing “plant-ready” nutrients delivers a higher level of use efficiency for a more positive crop response.

Spring Root-flush

 

Spring Root-flush

Winter dormancy is an important development stage in the tree growth cycle. During this time period crops rest and recharge for the upcoming growing season. Both cold air and soil temperatures are required to supply much needed “chill hours” for resting trees. “Chill hours” are a lot like REM sleep to you and me. REM sleep is the nightly deep-sleep that is vital for keeping us healthy and well rested upon awakening. Simply put, trees need cold temperatures to slow (or stop) their growth activities. When temperatures are too mild, trees do not receive adequate “chill hours” and break dormancy in an energy-deficit condition. In other words, trees don’t sleep well and awaken stressed.

 

 

Spring root-flush:

In California, normally happens with prunus species like almond, early peach, plum, nectarine, apricot and cherry varieties, in the 3rd to 4th week of January. This activity begins when soil temperature (in top 2-4”) reaches 45°F and precedes bloom by approximately three weeks. Buds visibly swell with water and nutrients. The new hair-root growth is needed to support the upcoming crop with water and nutrients. Once root-flush is underway, growers should take advantage by beginning fertigation or soil fertility applications. Nutrient focus should be on root health and crop support.

 

Temperature:

Soil temperature is a major driving factor in the onset of spring rootflush. Currently, soil temperatures, in California are 50-52°F (well above 45°F) due to the high volume of rain (4-5”) that has fallen in the past four to five weeks and continues to saturate much of the state. California has another 4-6” of rain forecast in the next week. Due to this increase in soil temperature, rootflush is now underway.

 

Chill hours:

http://fruitsandnuts.ucdavis.edu/Weather_Services/chilling_accumulation_models/Chill_Calculators/?type=chill  [Check your current chill hours]

Another concern is that “chill hours” are below normal for early January and trees are not getting the rest they need. Rootflush is underway and therefore so is root respiration. Respiration is the plant process of “burning up” or releasing stored nutrient energy for plant use. This is a problem because new roots are using up nutrient energy that is meant for the upcoming bloom.  Due to these circumstances, an energy deficit is beginning that cannot be restored from dormant rest. If you enter the bloom stage in an energy deficit (stressed) condition, it will affect the plant’s ability to pollinate, set and “stick” crop. One symptom of bloom stress is “June drop”. Plants self-regulate by aborting excess crop to ensure they do not run short on nutrients. They are programmed to know how much crop load they can support based on their health and availability of nutrition.

 

Feed the Soil:

When short on “chill hours”, the next-best alternative is to supply energy to the plant via “plant-ready” nutrition. Treatment emphasis should be on the soil, since the roots are already at work. Using an orthophosphate source provides much needed “plant-ready” phosphorus for root growth and health. A unique root benefit is a fungicide-like response within the rootzone. This is especially important in waterlogged conditions. Unlike polyphosphate fertilizers, orthophosphate is not temperature dependent. This means it is readily absorbed by new roots in cold soil temperatures (<63-68°F). In addition to feeding the soil, this is also an ideal time to re-inoculate the rhizosphere with soil microbiology. The more diverse your soil microbiology, the better your soil-nutrient and water efficiency you will experience. Dr. William Albrecht said, “We must not forget that microbes are what make a living soil ‘alive’…microbes, eat at the first sitting…Plants eat second. Plants and microbes must be in symbiotic activity and not in competition for fertility if our productive soils are to be maintained.” So, how productive are your soils? As the farmer, it is good stewardship to know and make necessary adjustments to nurture the soil and ensure it is still productive for the next generation.

Here’s to your success!

 

 

 

 

 

 

 

Almond bloom: A very important stage in the life of the crop; one filled with anticipation and trepidation. At this stage, growers work to get pollen (from the Anther; male part) in contact with the Stigma (female part) by various means.

The Science: Almond bloom is beautiful sight to see, but don’t think it is just for our enjoyment.  Almond trees’ primary objective is to propagate the species into the next generation. Blossoms are the “lure” plants use to attract pollinators. At the same time, plants’ physiological activities run at a feverish pace with time, temperature and weather all contending against the plants pollination efforts. The process, while orderly, behaves a lot like a Rube Goldberg device, due to the many intricate, interdependent activities involved. For example: When a pollen grain connects with the stigma, it is considered “pollinated” and starts the Pollination process. Next begins the “fertilization” process: The pollen tube elongates (while the sperm travels along it simultaneously) down the length of the Style to the ovary where it attaches to the ovule allowing the sperm a chance to fertilize the egg and form a Zygote. This process requires a large amount of energy from within each pollen grain. Every pollen grain contains both sperm and tube cells and the health and viability of the pollen is directly related to the nutrition available to the plant. There are many factors which can affect the almond bloom period. These are called “stressors”. Stressors are a problem, because plants must manage them, in addition to normal activities, at each stage of development. Some examples are Environmental (Temperature, precipitation, etc.), Cultural (Nutrition, irrigation, etc.) Biological (fungal, pest pressure, etc.). Without a plan, these can all significantly ill affect your crop’s yield potential. 

 

Practical application: At the start of the bloom stage, there is an internal plant “tug-of-war” between a large volume of plant “dormancy” hormones and the introduction of “reproductive/bloom” hormones.  As the tree awakens, it is thirsty (dehydrated) and hungry (energy deficit) from the dormancy period. Think of it like a grizzly bear awakening from hibernation; the bear’s top priorities are water and food, because much of its reserves were depleted while sleeping. Almond trees are no different. As a grower, you can take an active role in these needs. This is where a fertility plan can benefit you by increasing not only your orchard’s health, but yield and profitability. Let’s take a look at each of the stages of bloom and where your nutrient focus should be and why.

 

Green bud: Flower buds are swollen and green plant tissue is exposed, but no blossoms are yet visible. This is due to hair-root activity which has already been underway for 2 to 3 weeks. Roots are actively foraging for food and water supplies in preparation for the upcoming bloom event. Start fertigation plans now, with nitrogen and “plant-ready” orthophosphate for strong root support.  Application rates should be based on soil texture, to avoid over-applying for the soil’s capacity and plants’ needs. Why orthophosphate? When soil temperatures are under 63-65°F (top 6” of soil), phosphate (P2O5) is still soil-bound (especially in calcareous soil types) and not yet available for feeder roots’ use.  “Plant-ready” orthophosphate (H2PO4- or HPO42-) is not temperature dependent and therefore immediately usable by the roots, in cold soils. After dormancy, the root system and crop set are limited to the amount of stored nutrient energy available. This critical development stage is much like the start of a race and stumbling is not an option. Why take the chance of running short on nutrient supply? It is a Good Management Practice (GMP) and a major benefit to fortify roots and restock the root-system with phosphate, for the high energy demands that bloom puts onto the entire plant system.

 

Pink bud: Without a bud, you can have no bloom. Without bloom, you can have no almonds. Plant energy is vital for a good bloom. At this point, buds have been swelling up, growing rapidly. Nutrient application focus should now shift from fertigation to foliar feeding. While there is not yet a leaf in the field, there are on average, 75,000 to 150,000 blossoms per tree and each is rapidly drawing on stored plant energy reserves, which cannot be supplied via the root system, in cold soil temperatures. Applying “plant-ready” foliar nutrients directly to these plant parts, requires low per acre rates and provides nutrients/energy to supplement the demands of the pollination process. Foliar applications supplement the developing crop while soil temperatures warm and then begin soil-nutrient release for root uptake.

 

Full bloom: This is one of the most effective times to directly increase crop yield potential. When blossom pollination happens it triggers the fertilization stage. This is a time of massive energy demand. When fertilization occurs, almond kernel cell division starts. Under normal conditions, this takes 23 to 27 days to complete. However, it is directly affected by temperature and nutrient availability; warmer than normal temperatures accelerate (shorten) the cell division “window” and cooler than normal temperatures extend this process. Applying “bio-available” nutrients delivers energy and food, at this critical stage of crop development. In simple terms, more cells per kernel equals more weight per kernel at harvest. Remember, this is also a period when the plant is susceptible to infection through the blossoms and steps should be taken to avoid disease flare ups. Applying foliar orthophosphate helps plants build their own defenses for better health and disease resistance.

 

Petal fall: At this point, almond kernel cell division continues to occur at a very rapid rate. Soil temperatures are still cold (<63-65°F) and foliar feeding is an efficient way to supplement plant and crop nutritional needs. Time is of the essence here as the plant will soon begin to shift the growth emphasis from crop-set into canopy-development. Feeding focus should now be on the developing nutlets and canopy. Crop retention is vital to profitability and photosynthesis from a healthy canopy plays a major part from now and until harvest time. Almond trees instinctively know how much crop they can support based upon current stored energy reserves. Remember, a plants primary objective is to perpetuate the species into the next generation and trees will not set more crop than can be matured. When trees run short of energy during bloom, they will begin to self-regulate at Petal-fall stage, by aborting nutlets. This is a time to be very aware of the orchards growth response and be ready to make rapid GMP fertility decisions, as needed. The crop won’t wait for you, so be readiness is crucial!

 

40-45 days Post-Full bloom: Soil temperatures are normally still below 65°F, so you won’t yet be benefitting much from soil-fixed nutrient release. Foliar applications will still be very useful and should focus on boosting canopy health and vigor. Photosynthetic production and efficiency are crucial to get the plant feeding itself as early as possible. If you notice a weakly growing canopy, just after Petal-fall, it can be an early indicator of a heavy crop set (See everything you are looking at!). The tree could be sending extra nutrition to developing nutlets due to positive fertilization activity. Tissue sampling should happen once mature leaves are visible. Use the tissue results as a treatment guide for making fertility decisions. Don’t guess at what your orchard or crop needs.  At this stage, fertility applications are building internal solids (oils) for more kernel weight. Total Soluble Solids (oils) are heavier than water and will not evaporate when you dry down the orchard before shaking. This stage lasts (April 15—June 15) approximately 60 days. Fertility plans should include fertigation and foliar feeding with emphasis on nitrogen, potassium, calcium and traces as needed.

               

Here’s to your crop’s success!

For more information contact me via direct message.

Chill Hours - The Importance of Rest and Nutrition

           

            Chill hours are important to tree and vine crops during dormancy. This is the timeframe when the plant rejuvenates. This time is critical. Trees and vines, just like you and me, have to take a “vacation” from the busyness of the growing and producing stages. These hours are the time or opportunity for the plant to rest up for the next crop. It’s a vacation period for trees and vines to get rested. In California’s San Joaquin valley, this usually occurs when kids get excited because its foggy day schedule weather and shortened school days. It’s wet and cold and there is not a lot of sunshine. But this is perfect weather for permanent crops like pistachio, almond, peach or grapevines.

            Without adequate rest or “chill”, the plant works from an “energy deficit” position. This is a problem. It is the monetary equivalent of drawing money from your savings account because the interest earned isn’t enough to live on. You can’t do this for very long without dire consequences and the same is true with your crops.

            When you get enough rest, you wake up ready to go better. The same goes for trees. When they get enough rest, they wake up ready to grow better. When trees do not get enough rest, they will have delayed canopy development. This is an important detail because without leaves the plant cannot feed itself effectively. The more efficiently a tree can start growing leaves and a healthy canopy the sooner it can begin taking in sunlight, water, and carbon dioxide so that through photosynthesis glucose production kicks into gear and provides food for the plant and developing crop to feed on.

            On a year with short chill hours, the problem becomes an issue of how to make the most of a bad situation. For instance, in January you find that you have 400 hours or less of chill accrued to date. Historically by this time, we have between 700-800 hours. This is a harbinger and we need to pay attention because it’s telling us to be prepared for “what” the outcome of this can potentially be. This is important because some crops use an awakening agent to help crops rouse themselves, in order to harvest earlier. The problem with this is, when you apply a product to awaken a plant that has not gotten enough chill hours you induce an extreme stress condition or worse actually damage the plant’s fruit buds. That can have a long-term adverse effect. Think of how trees grow fruit buds. It usually develops on 2^nd year wood. So, if you hurt your tree badly, it could take two to three years to recover, assuming there are no other major stressors that occur to limit recovery. Growers should consider the tradeoffs carefully before proceeding with a “dormancy-breaker” spray for their trees especially those that have not gotten the proper amount of chill hours. We cannot merely wish good seasonal weather on our crops. If our crops don’t get enough chill, the plants themselves will be underdeveloped and this ultimately affects profitability.

Keeping energy in mind as you go through dormancy is important. Dormant plant energy comes from carbohydrate reserves. This becomes a high demand on heavy crop load years. As fall passes, the plant behaves much like a bear before going into hibernation. It eats and stores up food to carry it through winter until awakening in the spring. The difference with a plant is that, while it does its best to make and store up food reserves with both photosynthesis and the fall root-flush, it often falls short due to outside influences such as drought, large crop load stress, heightened insect pressure, imbalanced nutrition, etc. The bottom line: If you go to bed hungry, you will awaken very hungry and nutrient deficient.

As a grower, you decide what nutrition your crops receive. Therefore, if you want to ensure your crops are well fed for dormancy, feed them well BEFORE dormancy with next bloom in mind, as the goal. Remember good intentions don’t equal good actions. More to the point don’t apply materials because your neighbor is or it was a “good deal”. You should be testing your soil and tissues in the fall or before harvest, in order to determine what “got in” and what “ran short”. These are an annual progress report of your field’s health. If your adviser doesn’t offer these services, look around for one that does. After all, it’s your asset and investment. This information will help guide you to make more accurate decisions on what should be applied and at what rates. If you aren’t sure what should be applied, ask your crop adviser for counsel. If they aren’t experienced with your crop or soil type, get a second opinion. But, don’t fall prey to “analysis-paralysis” or information overload. If you trust your adviser (and you need to), because of their experience, success or approach, go forth with confidence.

Photo by Marc Suderman from Traver, CA