Bernardita Sallato described the basics of nutrient demand and their impact on fruit quality, tools to determine rate, and a review of monitoring strategies at NCW Stone Fruit Day 2025. Part of North Central Washington Tree Fruit Days sponsored by WSU Extension, NW Cherry Growers, Pear Bureau NW, and North Central Washington Fieldmen’s Association.
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| So thank you Bernardita, I see your slides. Can you just talk for a second so I can make sure we can hear you? | Title slide. Presentation title: Optimizing tree fruit nutrition for fruit quality. Author information: Bernardita Sallato, Tree Fruit Extension Specialist, Washington State University. |
| Hello everybody. Can you hear me okay? | |
| We can hear you great. Okay thank you Bernardita, take it away. | |
| Perfect. Thank you Tianna for the invitation. I’m sorry for not being there with you all. And, I’m gonna try to keep track of my time. Tianna cannot stop me this time, so wish me luck to stay on time. So, I have a lot of things to share with you. Great panel, by the way, and I agree with most of the things that were shared. | |
| So what I want to cover in this talk today is to go very briefly into the basics, revisit some of the basics, but not go too deep into those. Share some summaries of research findings that we’ve been evaluating in the last 5 years here in Washington and end up with providing nutrient management guidelines. | Slide titled “Overview” appears with three bullet points: revisist nutrient basics, summary of research findings, and optimizing nutrient management. |
| So first of all, and I’m not going to go into the details of why the nutrients are important. I think we all understand that nutrients are essential for the life of the trees and fruit quality and just development. That’s why they are called nutrients, because they are essential. And the limitation of any of these elements listed here might end up causing either the death of the trees or bad quality, or not maximizing the fruit production and quality that you might have in your orchards. So how we monitor these elements in the trees is via testing. So there’s good luck for us that we have a standard test. It’s and old test, and it’s not bad because it’s old. Actually it remains the most important and reliable test to understand the nutrient levels in the tree. And those elements, we have here a table where I’m sharing the range or the critical values that you would like to have with this testing. Now, its also important to understand the limitations of this testing. So we don’t overvalue or estimate things that are not really provided by this test. So first of all, we need to collect the right tissue, and for that, there’s a lot of guidelines. But basically you want to collect a young mature leaf from your orchard, from the site. So earlier in the season normally this is the leaves that are below in the branch, and later in the season it becomes the leaves that are in the upper section of the shoot. And actually, even if you collect tissues later, like in August or September, you can collect the upper leaf as long as it is a recently mature leaf. Now, again, what this tissue test tells you is only that your tree is within an adequate range. That means it does not tell you what is the cause of the problem. So it will only tell you: Are you in the adequate range, deficient, or toxic? It doesn’t translate into the amount, And this is sometimes the mistake that we have. When we want to interpret these results, they do not always correlate with the amount that you are applying or the amounts that you have in the soil. It only tells you that the tree is within an adequate nutrient level. It is similar to going to have a blood test, for example, and just having a range that is standardized for this specific species, in this case, cherries. | Slide titled “Nutrient concentration”. A bullet list explains that standard tests indicate adequate uptake or deficiency, but do not reflect issues or total nutrient needs. A table lists recommended concentration ranges for macro and micronutrients in cherries. |
| So you have that resource. And where these nutrient tests come from or standards come from very long studies, that they have provided all other factors in adequate levels. So everything that was talked about before in the panel. For example, there’s no limitation her to provide these ranges in terms of water, light, or any other limitations in the soil, nematodes, insects, or others. So think about this curve only for a specific element, and what it shows here is that every organism, in this case, cherry trees, will respond as the concentration of this element starts to increase. So we have a very, like a bell-shaped curve. And initially we have a severe symptom. So no growth, a lot of symptoms in the trees, even death if we have a deficient concentration or low concentration of these elements in the tree. But then we get to this range where we call the lower critical concentration, and that is where you would like to sit on, because that is when you get the maximum return of this application of nutrients. This is no longer an additional application of nutrient will have an impact, as you can see in this curve. | Slide titled “Response to nutrient concentration” appears which contains a graph of organism health versus nutrient concentration, with lower and upper critical thresholds defining an optimal range between deficiency and toxicity. The graph forms a bell curve with both high and low concentrations of the nutrient causing symptoms. |
| So this is exactly where you want to sit, right? Adding more nutrients when you are sitting in this upper side of the curve will only cost you more money. | The section of the curve from the lower critical concentration point and the exact middle of the curve is highlighted in green. |
| And for some elements, we have a shape that is narrower, like this red shape here. So that means that the range of adequate levels is small. These elements are, for example, nitrogen, where you can go from deficiency to toxicity very quickly, boron, and manganese. | A red line is drawn on the graph, it is also a bell curve, but is much narrower in comparison to the original graph. |
| And for other elements, on the other hand, you will have a plateau that lasts for a long period of time. For example, calcium, phosphorus, and potassium. This is not really a symptom that you can identify in the orchard when you continue to apply these elements, even if you have reach the maximum benefit of this concentration. This is where I’m putting more emphasis in this curve which is very simple. But I put this emphasis because, In Washington, we tend to be in this upper range. We tend to be sitting beyond this green range, and I will show you some results. And what happens there is that you don’t see that there’s toxicity or a negative impact, it only costs you more money. So these elements, we need to keep an eye on those too. | A blue line is drawn on the graph, it is also a bell curve, but is much wider in comparison to the original graph. |
| And again, this curve also shows us that only under deficiency, adding nutrients will have a measurable benefit. Which is in this first stage of the curve, as you can see. And that’s why, sometimes, when we read reports or previous research, we see that adding some elements have an improvement in fruit quality or fruit size or yield. That’s because you are sitting in a deficiency level at the start. So understanding, where are you? Where is your block in this curve? Is very relevant. | Text appears on screen reading “Only under deficiency, adding nutrients will have a measurable benefit”. |
| Now, just as a background, what I mentioned before regarding that we see normally in this upper range in Washington. We’ve been doing a lot of research in my lab with my colleagues, and in 2019, for example, we evaluated over 100 sites, and, as you can see here, these are the macronutrients. Everything in green is orchards that were sitting in the adequate range. But you can also see that there’s a lot of sites, a large proportion of sites that are sitting in that excessive level, especially when we think about calcium and magnesium, also for phosphorus, potassium… We all have many sites that are in that excessive level, and we also have a few that are in deficiency, mostly calcium and potassium. And those are related to sandy soil. | Slide titled “Nutrient levels in WA orchards” which contains 5 pie charts showing the concentration levels of nitrogen, phosphorus, potassium, calcium, and magnesium for 100 Washington orchard sites in 2019. The green sections indicate an adequate range of the nutrient, with yellow representing low concentration, and red representing excess of the nutrients. The charts indicate that excess nutrient levels are common, especially for calcium and magnesium, with some excess also present for nitrogen, phosphorus, and potassium. |
| This other is a different study. We evaluated over 500 samples, in this case, 3 different cultivars, Chelan, Coral, and Skeena, the three different colors. And here also we found that the nutrient levels in the fruit, where, in all the elements is above what is referenced in the literature. So, you can see, these green boxes are the references that we have found in other countries and literature science in Washington. Not only do we have a huge variability, but all our means, or the averages, are sitting above that range. So keep that in mind. This is not new. There’s many research that we’ve been conducting, showing exactly that. | A slide titled “Fruit Nutrient levels vs reference” appears which contains multiple plots comparing fruit nutrient concentrations reference ranges across three cherry cultivars. The reference ranges are indicated visually, and most measurements and averages fall above those ranges, showing widespread nutrient excess. |
| Now, what are the growing conditions in Washington that might be limiting? Again, Washington has excellent growing conditions for tree fruit. And that’s why we tend to sit in that upper range. But also we apply a lot of nutrients too. It used to be a marginal cost, the fertilization programs. Probably no longer, so we have to pay attention to that. But we do have some areas that we have challenges, especially with micronutrients, because we have these caliche calcium carbonates in the soil, or we have high pH. We tend to lead again with the examples that I gave you will excessive application of elements, or excessive content of these elements in the soil. This is not only for the application, but naturally our soils are very rich in potassium and calcium. And also, of course, we have other factors related to, for example, drainage in out soils, compaction, and irrigation plays a very important role in that fruit quality. | A slide titled “WA growing conditions” appears which contains a photo of a white calcium carbonate deposit layer in the soil, as well as a photo of a fruit tree with wilting and browning of the leaves. Bullet points on the page state that the growing conditions in Washington are excellent but we can have issues with deficiency in micronutrients and excess of macronutrients. |
| Okay so now, moving into how to then optimize having this information. How do we optimize nutrient management? | A slide titled “Optimize Nutrient management” appears with a photo of cherries in large bins in the orchard during harvest. |
| We’re gonna use a very simple equation. We calculate the rate based on the demand of the trees, minus the supply. And I will go through these different steps, and we apply an efficiency, especially for nitrogen. When we think about the demand, there’s a lot of demand throughout the season, fruit leaves, roots, and new shoots. But if we use the fruit as the only produce that we are taking out of the orchard, it gives us a very good idea of what we need to be replacing, because the rest of the components tend to be recycled in the orchard. | A slide appears with the formula for rate, “Rate = (Demand – Supply)/Efficiency” as well as a pictographic formula for demand which shows that the demand is the sum of the needs of the fruit, leaves, roots, and shoots. |
| So we have developed, and there’s other resources from other parts of the world. But in our studies we have developed these tables of demand for different cultivars. The good news is that, as you can see here, there were no statistical difference between the cultivars, so in general, the amount needed for each of these varieties are not different. So you can confidently rely on these values to calculate your demand. And here is an example we have, to make it easy 10 tons of production. You just multiply the range that is below in in bold, and you can have an idea of what is the amount that you need. Of course you can say there’s a big range between 19 and 49 pounds. Sorry, but that will depend in most cases in the vigor of your orchard. So if you have a lot of vigor in your orchard, you will try to move towards the lower side of this demand, and if you see that your orchard is in the weaker side, you would like to move your values to the higher amount. Again, just keep an eye on these values. These tables are available for you in our tree fruit extension webpage. And we update those very recently. So you can use those. | Slide appears showing demand tables for Washington cherry production. A table lists recommended nutrient demand ranges by cultivar, and bullet points below give an example calculation converting those ranges to total nutrient needs based on yield |
| Now we have the demand. Now, how we estimate the supply, this becomes a little bit challenging, because it depends on the element. For the most part we will have to consider the soil, the water supply, and everything that you put in there, for example, compost, manures, or even if you incorporate your pruning material, everything can be incorporated into the supply. | Slide appears showing the formula for rate as previously shown, a red circle is drawn around the word supply. Three boxes appear below this equation containing the words: soil, water, and amendments/cover. |
| I’m going to start with the last one, the amendments or manure or compost. Normally, the values change a lot. So my only recommendation is that you test those products. If you are applying manure or compost, ask for the test, and you can estimate or calculate how much you’re adding into the orchard. And there’s also several resources that I found online in fact sheets. I would recommend that if you look online, you search for university resources or scientifically validated extension resources. This is from Ohio State University, and it provides a very good idea of how much nitrogen you are applying using these different amendments. | Slide titled “Amendments” appears with a table of measured nitrogen content in organic inputs, including manure and composts. The table demonstrates how laboratory testing is used to estimate nitrogen application rates per acre. |
| The irrigation is another one that is very important to consider, because in some cases (not all) you can be adding quite a lot of nutrients through the irrigation alone. I’m using a reference here of 24 inches of irrigation throughout the season, which is quite standard. Actually, I saw a reference from Tim Ward maybe 10 years ago which was double this amount. But now that we’ve been a bit more efficient in the use of water, I’m using a number that is more conservative. | Slide titled “Water” appears with two bullet points stating that irrigation of 24 inches is 652,000 gal/acre, and that irrigation can provide a high amount of calcium, chloring, sodium, boron, and nitrate. |
| And here you can see the amount of nutrients apply in this irrigation strategy. This is a water analysis from Mattawa. This is a real water analysis from a grower that shared that with me, and we calculated, then, how much you are adding of these elements, which are the most common that might be in your water just by irrigation. So if we think about that in this case we are adding 68 pounds of nitrogen only with the irrigation. So just keep that in mind. This is very easy to evaluate. The water quality does change throughout the season, but if you consider the spring water quality and midsummer water quality, you can get an idea of how much you are adding with the irrigation. | A table appears summarizing estimated nutrient inputs from water, demonstrating that irrigation can supply large amounts of nitrogen, potassium, calcium, and magnesium. |
| Now, moving into the soil, how we estimate the soil supply? Again, nitrogen is very particular, because it’s very mobile in the soil, and it differentiates from the other elements quite a bit in terms of how we calculate that. I’m not going to go in detail on these different forms, and how the nitrogen from the fertilizers or manures become available, or in forms that are available for the plant which are ammonium and nitrate. | A slide titled “Soil N Supply” appears containing a diagram illustrating the soil nitrogen supply, demonstrating how nitrogen from the soil and added inputs is transformed into available forms and taken up by the plant. |
| But I do want to highlight that nitrogen has many forms that might be lost throughout the season. So, for example, volatilization, denitrification, and leaching, leaching being the most important, especially in soils that are very sandy, like in the Mattawa area. Sandy soil can lead to the leaching. Because there’s so many losses of nitrogen in the soil is very hard to use the soil analysis as a good estimator of the supply. | Red text appears on the diagram highlighting the ways that nitrogen can be lost from the soil. |
| So to replace that, because it’s not a very stable value by doing the soil tests of nitrogen, we use the organic matter a much more stable source of nitrogen. And again, I’m not going to go into how these numbers came from, or where these numbers came from, but we have a very good idea that around seven to 14 pounds of nitrogen are provided for every percent of organic matter in your soil. Generally our soils are very low, having 1% of organic matter will be very average for Washington soil. So think about a supply of seven to 14 pounds of nitrogen just with the organic matter that is present in your soil. Of course, if you have more organic matter, there’s even more that you can multiply that factor. | Slide titled “Soil – Nitrogen” appears with a photo of dark, rich looking soil, and text highlighting the level of nitrogen provided by organic matter per acre. |
| So again, going back to the example, if we have 10 tons of cherries. Let’s go very conservative. Let’s go to the higher value that we have in the demand table. So there we have the extraction. A 49 pounds of nitrogen, and then we subtract the supply from the organic matter. We estimate seven in this case, and 12 pounds of nitrogen from the water. We only need to apply 30 pounds in total in your whole production for a 10 tons of production. Another important thing specifically for nitrogen. Again, because nitrogen is very mobile, and we can lose a lot of this nitrogen that we are applying because it’s too hot, or we have a very sandy soil, we have to account for an efficiency. And the efficiencies that the ranges of efficiencies that I’m giving here are very standard, and of course, are very broad. And I’m going to go into how we can increase the efficiency in our orchard. And of course it will give you if we have a 40% efficiency very low. We will have more than double the amount of nitrogen that we need to be applying. And of course, we want to go into this 35, sorry 37.5 pounds. If we have this 80% efficiency. | Slide appears illustrating nutrient management for a ten ton per acre yield. It show a nitrogen budget that subtracts soil and nitrate contributions from crop removal to estimate the remaining nitrogen needs, then show how different efficiency assumptions change the recommended application rate. |
| Okay, that’s for nitrate. Now for the other elements, we use a slightly different strategy. For the other elements, because they are less mobile in the soil, so values are much more stable, we use this soil test. I caution you that not all the soil tests are created equal. So it’s important to use the methods that are recommended by the Soil Science Society of America. I wrote that wrong there. It’s not Social, it’s Soil Science Society of America. And what they do is that they mimic what is available for the root uptake. What we want to do for the rest of the elements is to do the soil test and maintain these ranges that are provided here. So as long as we keep our nutrient levels within this range, we only need to estimate the demand minus the supply again. This is for all the elements, except for nitrogen. And don’t attempt to translate these values into supply or amount, because it doesn’t work that way, and you will end up with a lot of nutrients being supplied, and it doesn’t really correlate or work in that sense. | Slide titled “Soil levels” appears with a table of optimal soil nutrient ranges. The table lists target ranges for macro- and micronutrients and emphasizes maintaining adequate levels rather than translating soil test values directly into fertilizer amounts. |
| This is just to highlight that there are differences with nitrogen. The cations have different forms of mineralization, precipitation, or weathering, or absorption, or desorption, so many components in the soil that they would get the cations attached sometimes are not available or not readily available, but they are not really lost. The only loss that we have with cations are the leaching again in very sandy, coarse soil. | Slide titled “Soil – Cations” appears containing a diagram illustrating how soil cations such as potassium, calcium, and magnesium move through the soil system, temporary binding to soil particles, losses through leaching or precipitation, and uptake of the nutrients by the plant. |
| When we interpret this soil analysis, one factor that is very relevant is the texture. And just to as a reminder. Again, we talked about nitrate. It leaches in all type of soils. So it moves very easily because it doesn’t have a positive charge. And so this element tends to be lost throughout the season, especially when we are irrigating, and more important in very sandy soils. But the cations, because they have a charge, tends to stay longer in the soils, but they can be very mobile in very sandy soil or sandy soil. So understanding the texture of your soils is very relevant to interpreting the results of your soil analysis, how long or how much they represent the amount or the supply throughout the season. |
Slide appears with two photos of soil layers. One of the soil photos is very sandy and the other is not. Colorful bubbles containing the chemical formulas for various nutrients are placed at the top of the soil photos. The nitrate molecule is moved downwards in both photos to represent how easily it moves through the soil via leaching. The molecules with a positive charge are then moved downwards through the sandy soil, representing that cations tend to stay in the soil, but can be mobile in sandy soils. |
| Also. These are the micronutrients. In general they have low mobility, so we don’t really think about those too much. I will talk about those later in in a bit. | Two bullet points appear on screen stating that boron, chlorine, and sodium are mobile in soil, and that iron, manganese, zinc, copper, and molybdenum have low mobility. |
| Another point that I want to make is that in many cases we think about our soil as that upper layer of our soils. In these are pictures the first two are from the Yakima Valley, and the last one is from the Mattawa area. And while we do have very sandy soils, in the upper layer we can have a sandy loam soil. So the thing about that soil that is the nutrients will leach and move away. In many cases we have stratified soils. That means that we have different textures in the profile of their soils. Of course, if we have rocks, or we have caliche, or a compacted layer like in the in the middle picture, here a clay compacted layer, the elements tend to remain in that upper section of the soil. But also, even if we have very sandy soil like in the third one, just having that different stratification, different physics in the in the soil, the water and nutrients will remain in that upper section of the soil. | Slide titled “Washington soils” appears containing three example photos of stratified soil, different types of soil layers are visible in each. Colorful bubbles containing chemical formulas of 6 nutrients sit at the top layer of the soil and do not move into the other layers of soil. |
| That is why, in many of our soils we see excessive nutrient levels. This is another study that we conduct in 2018. And what I’m showing here I have shown this in the past is that we tend to be in that very high supply. This is potassium. These are about 197 sites and 67% are in that range of excessive or very high supply of potassium and the sites that are in yellow, the 11% that are in deficiency. Those are generally sites that are in the Mattawa area, Ringgold area, very sandy soil. | A bar graph titled “Available K in WA” appears, showing that for many of the soil test sites, potassium was in excessive supply. The x-axis of this graph is potassium in parts per million and ranges from 0 to 900. A red line at 200 parts per million indicated an ideal level of potassium. A pie chart above this graph show the listed percentages of sites that were excessive, adequate, and deficient in potassium. |
| The same for calcium we tend to have very high supply of calcium in our soils. Only 4% were in that deficiency range. Again, this were in very sandy soil. So we do have sites with deficiencies. In most cases we are in high levels, even excessive level of this cation, so keep that in mind. | A bar graph titled “Available Ca in WA” appears, showing that for many of the soil test sites, calcium was in high supply. The x-axis of the graph is Calcium in meq/100g and ranges from 0 to 30. Percentages are written in colorful bubbles on the screen showing that 56% of tested soils had a caliche layer and therefore very high calcium, 41% had high calcium, and 4% of tested sites were deficient in calcium. |
| Now moving onto the micronutrients, which I have not talked too much up to this point. These are one of the issues that we face in cherries in Washington, because these elements have low mobility in the plant, but also they become not available when we have high pH in our soil. These are symptoms very typical symptoms of blindwood with zinc, and the broomwish, or something like that with a zinc deficiency. But the chlorosis is a very classical symptomatology for iron deficiency. Zinc deficiency, too. | Slide titled “Micronutrients” appears with 4 photos of typical deficiency symptoms of micronutrients. Bullet points state that micronutrients are required in low amounts, have low mobility, and are not available if the pH is too high. |
| And, as you can see in this chart, or you’ve probably seen this multiple times, iron is the one that becomes very unavailable for the plant in pH around 7 to above, and this is the general Ph that we have in Washington. So in most cases we see this chlorosis is related to iron. But because iron is very easy to distinguish, sometimes it masks the deficiency of these other elements, which are manganese, boron, copper, and zinc. All of them can become deficient in these levels of pH. | A chart appears showing the availability of iron, manganese, boron, copper, and zinc at different pH levels. The pH scale from 4 to 10 is denoted along the top of the chart and the nutrients are represented as horizontal bars with gradients that get darker with more availability at a certain pH level. All these elements are shown to be most available in acidic environments, with iron being most available in pH 4 to 5 and in short supply in alkaline environments. |
| This is just a picture to show you that in our growing region, Eastern Washington, our pH are generally in that high range above 7. | A map of the state of Washington appears with an overlay of the soil pH in different parts of the state. Darker colors on the map denote higher pH and, most of Eastern Washington is shown to have a pH in the high range. |
| And I don’t want to miss the opportunity to mention that Boron is very important. Again, this is a micronutrient that can become unavailable in high pH, but also it’s an element that has very limited mobility, and it depends on the tissue and the time of the year or the developmental stage. So in most cases we rely in the reserves of Boron in the plant, for this stage that is crucial for our production, right, which is the pollination. And boron is important for pollen tube growth, root tips, and shoot tip growth. So all the new cell growth relies on the having boron. And that’s why we need to apply boron in this stage prior to bloom time to secure that it is available at the stage that we need it. | Slide titled “Boron” appears with a photo of a blooming fruit tree with bees pollinating the flowers. Bullet points state that boron is important for meristematic growth and that it has restricted mobility. |
| And finally, I have a about 2 min to go through this, and I will try to go fast and leave some time for questions. | Slide appears showing the formula for rate as previously shown, a red circle is drawn around the word efficiency. |
| So for all these elements again, in particular for nitrogen, because the inefficiencies that we tend to have in the soil, we want to reduce these inefficiencies as much as possible. So one guideline will be that if we manage everything as if we were in a sandy soil, we will be good in all situations, but if you know that your soils are heavy or not sandy, then you have much more flexibility in terms of the timing of application, because those other nutrients will not move much. So when we think about efficiency, we think about timing of application that needs to be the right timing. We think about keeping our root health in good condition. So this includes thinking about nematodes, thinking about pests and diseases, and or excessive or lack of water, everything that can affect that growth. The source of fertilizers that we are using, and of course, the placement to put them in the right place for root uptake. | Slide titled “Efficiency” appears which contains a photo of cherry trees and a bullet point list which states that the timing of nutrient applications, root health, source of fertilizers, and fertilizer placement are all important for efficiency. |
| For the timing, and this aligns with what Lee shared in the panel before. For nitrogen in particular, in cherries, we know that root growth, I highlighted that in red, that’s the curve of root growth. This work was done in Chile, but we’ve been doing the same type of work, and we have found that we have very similar response in our trees and in our newer rootstocks, too. So we’ve been working in Gisela 5, 12, 6, and also in Maxima 14. And we see that this this same pattern which we have a root growth. The first one, the first flush or peak that you see here relies entirely, almost entirely in the reserves from the previous season, and that is in this period of pit hardening. That’s where we have the starting of that root growth. But we are not taking too much in that time of the year, because we are relying in the previous season. After that period of first root growth, the roots stop to grow when we have the enlargement of the fruit. So when fruits start becoming strong in size, the root growth is not very active, so there’s not much uptake in that time of the year. And then we have the second root flush, which we always see that every year, and in all varieties, which happens right after harvest. So we harvest the fruit. We stop the shoot growth, and this is where we have most of our root growth. This is the timing where it’s most efficient if you need to apply nutrients, if you are in a deficiency level, this will be a good timing for providing those nutrients to the plant so it can replenish and have the reserves for the following year. I highlight here the last peak of root flush, because we not always see that in Washington, especially in dwarfing rootstocks, we might not have that fall root flush. And in that case full application of nutrients will be better if we do it because we need it. But also we can do it via foliar application. | Slide titled “Timing” appears with a line graph plotting the length of white roots in cm, the length of shoots in cm, and the fruit diameter in mm versus the date, which ranges from September to May. A red line highlights the line for the length of white roots and an the second peak of root growth is circled to show the second root flush. We can see the initial peak of root growth as well as the, slightly smaller, second peak of root growth as described. A bullet point list highlights that nutrients should be applied at the end of shoot growth in the fall. |
| Root uptake again, making sure that we have healthy roots. The roots tends to grow at 49 Fahrenheit, 15 degrees Celsius, and the moisture content is essential for root growth, but also for moving these elements into the root zone. | Slide titled “Root Uptake” appears with a photo of roots in the soil as well as a diagram of a root tip. Various nutrients are shown entering the root tip. A bullet point list highlights that soil temperature, moisture content, and oxygen level are important for root uptake. |
| And finally, the Foliar application in most cases is less efficient. In in the physiology of the trees, foliar application should be used only in very specific cases, because the plant has the system to take up nutrients through the root. Which are these situations? When we have root problems, or problems with the uptake of nutrients. Again, in Washington, this will be the case for micronutrients, because we have high pH, they become not available for the plant to take up, and that that is why we have very efficient response to micronutrients with a foliar application. We also want to apply foliar, when we know that we are coming from a very cold winter, or we have cold condition in the spring and we need those elements. For example, boron, as I mentioned before. Correct transient nutrients, micronutrients, because we need them in very low quantities, they can be efficiently supplied foliarly – like boron zinc and molybdenum. And fall application of nitrogen and zinc sometimes might have double purpose, such as defoliate earlier or more homogeneously, and build reserves, so that is the recommendation for foliar fall application. | Slide titled “Foliar application” appears with a photo of leaves changing color in an orchard. A bullet point list highlights the situations in which foliar application should be used, including restrictions in root uptake, transient nutrient deficiencies, and in the fall. |
| So last, just remember that the rate to be calculated based on the demand of the trees minus the supply. We need to improve our efficiencies, and we have tools such as monitoring leaf and soil levels with a testing, validated testing. So with that, I’m done. And I’m happy to answer any question. If there is time for that. | Slide titled “Remember…” appears with bullet points showing the formula for rate, and a reminder to improve efficiencies and monitor leaf and soil levels. The author’s contact information is stated at the bottom of the slide. |
| Okay, Bernie, we have just a couple of questions for you. And if you guys have other questions, please put them into the Q and A. Or send me a text. So with these high amounts of fertilizers in our soils, are there some cases where we should just skip fertilization altogether? Are these nutrients already available in forms in our plants? | Camera view switches from Bernardita to audience. |
| Absolutely. So I had more examples, but I didn’t have time to go through that. But in some cases as I show you with the water application of nitrogen, we don’t need to apply anything, and that’s why we call them macronutrients. So nitrogen, potassium, calcium and magnesium are required in large quantities. Phosphorus too, but not as much, maybe 10 times less than potassium and calcium and potassium. And phosphorus doesn’t move in the soil, so it’s something that we tend to apply, maybe every three years if you have deficiency in the soil. For the other elements, nitrogen is the one that we tend to apply every year, because there’s low efficiency in retaining that nitrogen in the soil. But again, because we have nitrogen in our system, if you use this calculation, you don’t need to apply any nitrogen in your soil. And I’m not going to talk about calcium, because I show you that chart. We have plenty of calcium in our soils, and in most cases we don’t need it. I’m not saying that we never need it, but in most cases we don’t need it. So just keep an eye on what levels you have in the soil and calculating these demands, and you will come up with a number that might be a lot lower than what you are actually applying. | Camera view switches back to Bernardita. |
| Thank you, Bernardita. I think we’re out of time for questions today. But this is a really important topic. This might be one place where we can be really efficient next year. So thank you very much, Bernardita, for sharing that with us today. | Camera view switches back to audience. |
