Bernardita Sallato, WSU Tree Fruit Extension provide a review on recent findings regarding fruit quality and fruit nutrient levels. This presentation was part of the webinar series “Ensuring Premium Blueberry and Sweet Cherry Quality”, a two-day webinar focused on promoting blueberry and sweet cherry fruit quality, November 3, 2023. An event organized by Lisa Wasko DeVetter and Carolina Torres.
Text Transcript with Description of Visuals
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| Yeah, okay good. So thank you again for the invitation to Lisa de Verdura and Carolina Torres. I’m originally from Chile so I’m very happy to see some of the familiar names in the participants. I am a tree fruit extension specialist with Washington State University and I’ve been working on nutrient management for sweet cherries and also for apples here in Washington. | Title slide. Presentation title: “Nutrient management for high quality sweet cherries”. Author information: “Bernardita Sallato, Tree Fruit Extension Specialist, Washington State University”. |
| What I would like to cover, here is an overview, what is the importance of nutrition? Which many of you already know, just a brief overview. And then the nutrient versus fruit quality information that we’ve been gathering in the last four years here in Washington with a project with Carolina Torres and Matthew Whiting, and then some management strategies and suggestions for growers. | Slide titled “Overview” which contains a photo of cherries growing on a tree and a bullet point list outlining the three key topics of the presentation. |
| So first of all and one of the most important nutrients that we have to deal with in the plant nutrition is nitrogen. You can see here, very clearly, a section of trees that are deficient in nitrogen. The symptoms can be very evident in terms of growth, given that nitrogen is a fundamental element for a structure but also for functioning. | Slide containing a photo of a cherry orchard. One section of the trees is smaller in size than the others as well lighter green in color, indicative of nitrogen deficiency. |
| So whenever we see nitrogen deficiency, we normally see a reduced vigor. We also could see reduced yield and small fruit size and firmness. I’m going to share a little bit about that later. But also we can see more susceptibility to some diseases, the viruses, or any other type of a stress like drought or heat stress. | A bullet point list is added to the slide which contains potential outcomes of nitrogen deficiency including, reduced vigor and yield, small fruit size and firmness, and disease susceptibility. |
| On the other hand nitrogen excess can lead to many other problems some of them are similar so hard to distinguish. For example, we will have the opposite of low vigor: high vigor with excessive nitrogen. We have reduced yields due to that competition with vigor, reduced fruit quality, mostly due to that shading effect of the high vigor. But also, high levels of nitrogen delay maturity and that also means delay in color development. And we can also see that there’s some relationship with high disease susceptibility especially when we think about mildew which is an important disease here in Washington. | Slide titled “N-Excess” contains a photo of an apple tree with a great deal of vegetative growth, suggestive of high vigor. A bullet point list outlines the potential outcomes of nitrogen excess including excessive vigor, reduced yield and fruit quality, delayed maturity, and disease susceptibility. |
| Other important examples, not always available and sufficient in the soil for our cherry crop is potassium. This element is involved and fundamental in photosynthesis and for water relations. | Slide titled “Potassium K” contains a photo of a small fruit tree where the borders of the leaves show significant browning. Two bullet points highlight potassium’s importance in photosynthesis and water relations. |
| So normally when we are in deficiency, we see reduced fruit size, which is the thing that we see more commonly. But also we see some symptoms in the leaves like the picture that I’m showing there. | The mouse moves to point out the browning around the borders of the leaves in the photo. |
| But another important problem that we have seen here in Washington because of the high level of potassium in the soil is the limiting uptake of calcium and magnesium which are also two cations of importance. | Two additional bullet points appear highlighting that potassium deficiency reduces fruit size while excess potassium limits calcium and magnesium uptake. |
| Calcium, of course, in many fruit species is very important for fruit quality, and for cherry has been correlated with the susceptibility to cracking, with a reduced storability especially related to the stem greenness, and also there has been some reports relating the calcium content with pitting or firmness in the fruit. | Slide titled “Calcium – Ca” contains 3 photos of symptoms of calcium deficiency in cherries. The first shows cracking of the fruit on the tree, with holes on the bottom of the fruit. The second and third photos show pitting on the surface of the cherries with small indentations on the skin. |
| And another one that becomes very relevant, especially for Washington growers and I will imagine for southern cherry growers in Chile because of a reduced boron levels in the soil. We might have issues with this element especially because it’s needed earlier in the season for the fertilization of the ovule in the flower, so pollen tube growth. And so it’s normally something that we manage by foliar application during the late dormant application. | Slide titled “Boron – B” contains a photo of bees pollinating a flowering fruit tree. One bullet point stresses boron’s importance in fertilization. |
| So I’m not going to go through all the nutrients of relevance. All of them are called nutrients because they are essential for growth and for development. And the deficiency of one of them can lead to either reduced yield, death of trees, or bad quality. So this chart that I’m showing you here, you’ve probably seen it before, is a simplification of the response of the plant to a concentration of nutrient. | A bell curve-shaped graph titled “Response to a nutrient” shows organism health increasing with nutrient concentration to an optimal range, then declining at toxic levels, with labeled lower and upper critical concentration thresholds. |
| What is showing here is how, for example, what is important here is that we have a critical upper level and a critical lower level. When we are in low concentration of the nutrient in the plant, we might have this severe deficiency, but then leads to a hidden or mild deficiency that we cannot always identify by symptomatology. When we reach to the top of that productivity level, or the health of the organism, that is what we would call the critical concentration. And normally that’s where we would like to be sitting at, because further along if we continue increasing the concentration of the nutrients, it doesn’t have an impact in terms of yield or fruit quality, and it only could cost you more money just for adding more application of those nutrients. But then for some elements, not for all, we see that excessive levels of nutrients can also lead to hidden toxicity or antagonisms and also some severe symptomatology like a deficient calcium-related disorders. I’m going to talk about that later, but also other toxicity levels. | The labels for “Lower critical concentration” and “Upper critical concentration” are circled to highlight their importance. |
| So the problem with that? Simplification is very useful to understand that the plants do respond this way to nutrients, but it does not account for when we think about other limiting factors. So pretty much its telling us that, that is the response, for example for nitrogen, only if every other element is within adequate levels and with no other limitation. It doesn’t account very well for when we have interaction or antagonisms between elements. And of course, when we think about the practice of this information for growers, it doesn’t tell us what happened with the variability not only throughout the orchard, but also throughout the tree. And then it’s mostly focused on the health of the tree and not necessarily to the fruit quality. So many of you are creating or producing fruit that is not for the fresh market and so it needs to store for a long period of time. And so this curve might not be thinking about the impact of the nutrients in storage, so there are some limitations to this concept or the simplification of the plant response to nutrients. | Slide containing a photo of a cherry orchard. A bullet point list outlines the shortfalls of the simplification of plant nutrient response. |
| And I will give you a couple of examples of some trials that we’ve been doing here in Washington that can reflect on the usefulness, but also the limitation of that response. This is a trial that we did in two blocks. One block was considered a very good block with firm fruit and also bigger fruit size and another block that was managed pretty much the same, in the same area that had a small and soft fruit. And the grower then was very curious: what was the problem with both of them? | Slide titled “Fruit by Fruit” which contains a bar graph showing the fresh weight in grams the cherries in the block that had big and firm cherries versus the block which had small and soft cherries in 2020. The fresh weight of the big and firm cherries is shown to be significantly higher than the fresh weight of the small and soft cherries. A single bullet point states that this study was done with the ‘Chelan’ variety of cherry. |
| So what we did was a fruit by fruit analysis, meaning that we evaluated every single fruit for the fruit quality indicators and every single fruit was then evaluated for nutrition. So it was a very complete and detailed analysis. What we found here is that firm and big fruit was higher in phosphorus, potassium, magnesium, and boron concentration. Also pretty much all the elements were higher in terms of content because it’s a bigger fruit. Also we had higher soluble solid contents and higher dry matter in this better site. | A bullet point list appears next to the graph, detailing higher % of nutrients and increase in soluble solid content and dry matter. The detailed results of the bullet points correspond to the findings described in the audio. |
| And when we did the correlation between each single fruit with nitrogen content and fruit weight, we see that actually there was significant correlation, meaning the probability of having this data was very consistent. However, the relationship was not very strong. | A slide titled “Fruit Weight vs Nutrients” contains a scatter plot showing individual data points comparing fruit fresh weight by nitrogen content. The x-axis represents nitrogen content in milligrams and the y-axis represents fresh weight of fruit in grams. A diagonal trend line slopes upwards on the graph, indicating a positive relationship. And r value of 0.56 and an R squared value of 0.32 are shown |
| We observed that there was a much stronger correlation between fresh weight of the fruit and the potassium content which is consistent with some research that shows that relationship and what I explained at the beginning about the impact of potassium in water relations and also in the photosynthesis process. So here we were happy to see that there was a correlation that was consistent and actually very strong of 0.7. | An additional scatter plot appears showing individual data points comparing fruit fresh weight by potassium content. The x-axis represents potassium content in milligrams and the y-axis remains the fresh weight of the fruit in grams. A diagonal trend line slopes upwards on the graph at a steeper slope than the nitrogen graph, indicating a stronger positive relationship. An r value of 0.71 and an R squared value of 0.5 are shown. |
| Then we did this. We got enthusiastic, we said okay let’s evaluate this in different cultivars, different sites, and different regions in Washington. And so we did the same with three sites for ‘Chelan’, three sites for (indistinct), and five sites for Skeena. And we did a similar type of work, and what we observed after the three years of evaluation is that there was a significant correlation, but the correlations were very weak. For in this case for firmness and nitrogen and firmness and sulfur were the two that were significant, but they were very weak. | Slide titled “Skeena Firmness” contains two scatter plots, one plotting the relationship between nitrogen content and fruit firmness, and the other plotting the relationship between sulfur content and fruit firmness. Slight positive correlations are seen for both plots. |
| Another way when we separate this by size, this is where we start to see some differences. This is with diameter and nitrogen, and what you are looking at here is, site number one is in blue where we have a positive correlation between the size and nitrogen concentration. But then in site four, we had a negative correlation between nitrogen and diameter. The other small dots that you see are the other sites, which they show no correlation at all with diameter and nitrogen concentration. | Slide titled “Skeena Size” shows a scatterplot of cherry fruit diameter versus nitrogen concentration. Each point represents an individual sample and is color coded by site. Two trend lines are shown, one with a positive slope for site 1, and one with a negative slope for site 4, each of them with an R squared value beside it. The points from the other 3 sites show no trend. |
| So what we learned here is that the relationship was very site specific. For example, in site number one, we not only see positive relation with the size and nitrogen but also with boron and copper. In site four on the other hand, we saw a lot of negative correlation with pretty much all the elements except for boron, but there were no correlations at all with the any of the nutrients and size in the other three sites. | A bullet point list appears which outlines the 3 findings as stated in the audio |
| So then what we think about is, we are talking about the response of the fruit or the tree to one nutrient. But what happened? What are the other limiting factors? What are the situations in this site one and site four, for example, that lead to such a different response in fruit quality and the relationship with nutrients? | Slide titled “Limiting factors?” which contains a photo of cherries growing in an orchard. |
| So in the first example that I showed you, there was a very strong correlation with many elements and between size and nitrogen and also especially with potassium. What we observe here is that the main difference between the two sites was the crop load. Inside the first site, the one with high quality, firm and bigger fruit, we had four tons per acre and the other one had 10 tons per acre. You can make it simple, we can multiply by two to get the conversion to metric tons per hectare. | Text appears outlining the difference in the crop load of 4 versus 10 tons per acre in the first and second site of the ‘Chelan’ variety. |
| In the second experiment, the three-year trial where we didn’t see much correlation but we did see, on one site on ‘Skeena’, we see a positive correlation with a fruit size and nitrogen. What we observe is, that site is in an area here in Washington where normally the soils are very sandy. This is the Quincy area where the nitrogen levels are generally low. So in this case, we might have improved the size of the fruit, the relationship with when we increase the nitrogen level, because it was deficient. On the other hand, the other site where we didn’t have, and we actually had a negative response to nitrogen and fruit size, the levels of nutrients across all the elements were excessive in the soil and also in the tissue samples. | Text appears highlighting the presence of sandy soil and low nitrogen in site one of the ‘Skeena’ trial, and the excessive nutrients in site four of the trial. |
| So that also made us think about the relationship and the response that we have for nutrients. It’s not only a response when we are in which side of that curve that I show initially, if we are in a level of deficiency or in a level of excessiveness. But also to consider these as the most important nutrients that we need to be caring about which are carbon, oxygen, and hydrogen. These elements, we normally don’t consider as nutrients because we don’t apply them as fertilizers. But these are, in relative of importance, much higher of importance than the other elements. They are 95% of the dry matter of the plant. So if we have a limitation in light, in water, or in the health of the roots that are taking up the water especially, then we will have a much greater impact on fruit quality and then nutrients become a secondary problem. | A text box appears highlighting the importance of carbon, oxygen, and hydrogen in plant health. |
| The other thing I wanted to share, and this relates to the results that we obtain here in Washington, is the nutrient levels that we obtain in this fruit. And what we learned is that the fruit quality, one was very different between the year 2021 to 2023 so we have a wide range of uh fruit quality in terms of firmness and in size. 2022 we had the best quality fruit and that was, in most cases, because we had a lower crop load. We had some frost damage early in the spring so we have low crop load and that led to very good fruit quality. Then when we evaluated the nutritional content, in this case this is the concentration of the nutrients in the fruit. We also observed that nitrogen was higher in year 2022 but the other elements were not necessarily in relation to that better fruit quality. So they vary between years but not necessarily in relation to that fruit quality. | Slide titled “Nutrient levels in WA Cherries” shows a table comparing average nutrient concentrations for nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and boron in Washington sweet cherries across three years: 2021, 2022, and 2023. These values are compared to a reference range for ideal nutritional content from literature. |
| Another important thing that I wanted to point out, especially for Washington growers here, is that when I obtain some ranges from the literature, many of these come from actually Chile, where they do much more nutrient analysis in fruit. And what we observe here is everything in red is above or in the higher range of that nutrient concentration. So to point out here, that the way I see it, that we are more on the high level or toxicity levels of that curve in Washington. | Values in the table which sit above the reference range from the literature are highlighted in red, showing that the majority of the nutrient levels were above the reference range for all three years. Only 2023 nitrogen content is shown to sit within the reference range. |
| This is advancing on its own. Okay, so I would like to touch a little bit on the calcium concentration. Calcium is such a relevant nutrient that is used everywhere in the world for fruit quality, and because it’s not an element that leads to any level of toxicity as far as we know, sometimes we don’t know the benefit in concrete. So here what I wanted to show is these four sites that had very similar levels of calcium concentration. The only one that was slightly higher in concentration was this site number two, but there was no statistical difference in most of these sites especially when we compare within site fruit that was firm versus fruit that was soft. The soft fruit here is in blue and the firm in red. So this is just to point out that there was no difference in calcium concentration in the fruit | A bar graph appears which shows the percentage of calcium in both firm and soft cherries at each of the five tested sites. The x-axis shows the sites by their number and the y-axis shows the calcium content by percentage in a range of 0 to 0.12. Site number two shows the highest percentage of calcium in the fruit but there are not large differences in the calcium content either between sites or between the soft and firm fruit at each site. |
| But the other thing of importance is that, site number two that had slightly higher levels of calcium in the fruit, was also the one that apply less amount of calcium in the orchard. You can see the amount of calcium that we apply. This is in pounds of units of calcium and the proportion that is applied in spray application versus soil. | A table appears below the chart stating the amount of calcium that was applied at each site. This table is separated between total calcium pounds applied to the soil and the amount sprayed. Site two is shown to have had 16 pounds of calcium applied to the soil and 3 pounds sprayed. This is far lower than the other sites which had showed less calcium content in the fruit. |
| And the other thing that I wanted to show here is that, regardless of the difference, some of these sites that have higher levels of calcium in general were site number four and five. These were the ones that had poor fruit quality overall in terms of firmness and fruit size, while these three sites here, one, two, and three were the ones that had in general better fruit quality. | A text box appears on screen stating that ideal fruit firmness is above 300 g.mm^-1 and that ideal fruit size is above 25 millimeters. |
| Okay so I already touched on the importance and the results that we have had here in Washington. This of course might not relate necessarily to the experience that you might have in your region when there is a deficiency on any element. It’s probably that the correlations that much stronger just because, by adding a nutrient that is in deficiency, we normally will see a positive response. But it needs to be in that level of deficiency. So when we think about management then, how do we deal with this, not only the variability of the orchard but also this complexity of the interactions? And how are we understanding what level of that curve we are? | Slide titled “Management” which contains a picture of cherries growing on a tree. |
| I came up with these four factors in the order that I think they are of relevance. First of all is to understand the variability of our blocks, and secondly to identify and prevent possible limiting factors. And this is not only thinking about what I mentioned of light and light interception, water, providing adequate water, and root health in general, but also preventing possible limiting factors in the ground such as a high salinity levels or barriers to root growth. Once we have that identified and prevented if possible, we can estimate the rate of our crop based on the yield and then we can continue monitoring. So these will be the steps that I’m going to go through in in this moment. | A bullet point list appears outlining the four factors for management: variability, preventing limiting factors, estimating rate, and monitoring. |
| Okay so for variability, there’s several tools. Many of these are tools that you might have available in in your country and they vary in terms of cost and the detail of information that you can gather. So for example, I use a lot of Google Earth. This is a free application and in some cases you can go into this the history of the block. And for example in this is an Apple block that we been working on, we call it the Smart Orchard Project, and in this case I was lucky to find a year where they put a shade net, so reflective cover. So it highlighted the differences in vigor in that orchard so it was more like a vigor difference or variability. We also run there the Green Atlas. Some of you know that technology which is pretty much a vision system that can lead you to evaluate growth or for yield. So there’s many apps now that are available that are doing that. We have used drone technology with a colleague of us here in Washington (indistinct), and so this is an image provided by him where he estimate evapo-transpiration based on drone image. But we also have more older technology like the easy mappings here down below which pretty much give you an idea of the salinity and texture of your soils. And there’s newer technology, one of them is the soil optics. Some of you have heard of that. That can help you to identify variability especially in physical conditions which can be very useful. Whatever the tool you use, the importance here is that you identify that variability in your block and to not mix the evaluation of these sections. You can prioritize, you can do them all if you have the budget, or you can just decide which is the area that you want to focus on or identify a problem. So understanding this variability I think is very relevant | Slide titled “1. Variability” containing a bullet point list of the mentioned technologies for tracking variability. Example images of the output maps are provided for each type. |
| Second is within that variability then, identifying what are those limiting factors, or what are the conditions in those areas above ground and underground, especially underground because it’s harder to see. I always recommend to do this, dig a pit, look at the roots, and look at the soil profile. To understand, one the root health, and sometimes when we don’t have the experience, one easier technique is just to compare a good and a bad site. So you can identify what how does it look that volume of roots between the sites of extreme conditions. Also look at how your water moves, the irrigation distribution in your orchard can be very relevant in some areas especially hill slopes. Lack of water or excess of water can lead to many problems and root death. And of course many physical barriers. Here in Washington we have to deal with calcium carbonates in the soil that vary in depth and that can prevent not only water movement, but also the root growth. | Slide titled “2. Limiting factors” contains a photo of cherry roots which have been dug up from the soil. A bullet point lists highlights underground limiting factors to tree growth such as root health, lack or excess of water, and physical barriers. |
| So this is just to give you an example of this process that can be very simple in a diagnostic process. This is a site that I visited in 2019 of low production. The grower was a concerned about the low productivity of the orchard, but a lot concerned about this yellowing of the leaves. And when he will ask some consultants to come, the quick response was to apply a iron or manganese. These symptoms are very unique to iron deficiency so that would be kind of a good solution to prevent that symptom or to deal with the symptom, but he was also having some areas with dead trees. | Slide appears containing a photo of a cherry orchard. The leaves of the trees show significant yellowing. A bullet point lists outlines the plant symptoms of low production, yellow leaves, and dead trees. |
| So the way I did this analysis, as I mentioned before, I looked in the Google Earth and we identified areas with good and bad conditions. | An aerial view of the orchard from Google Earth is shown with colored dots indicating areas of good and bad conditions in the orchard. |
| Then what we did is we dig a pit. And so in this case, it will not always be like that, we found very fast the problem. And in this case, there was a layer of a compacted clay that was preventing the water from moving through the profile at about 8 inches of depth. And so you can see that there’s no roots or very few roots alive and the soil is looks very moist. In this case, there was no growth beyond this point. | Slide appears containing a photo of a soil pit. There is a clear demarcation between the regular soil and the greyish compacted clay layer, and the soil above this layer looks very moist. No roots are seen growing close to the clay layer. |
| So the problem here was not the iron chlorosis as the cause but that was the consequence and the problem was actually the drainage there was a limitation in drainage. And an easier way if you haven’t seen a soil pit before and you couldn’t identify the problem in here was comparing with this area where the trees were growing much greener and in healthier and it was very clear to see those differences because, not only was the soil drier, meaning that the water was able to drain better, but also the amount of roots that we see in this profile. So that was a very simple way to understand that limiting factor. | An additional photo appears of a soil pit in a healthier part of the orchard. No clay layer is visible and the soil appears drier. Roots are seen growing throughout the soil. |
| Okay so we go now to number three in the steps for management. Which is to determine that rate, and here again we’re going to try to simplify it and think about it as the demand of the trees minus the supply, which could come from many sources. And we have to apply an efficiency especially for elements that are mobile like nitrogen. | The formula for rate appears which shows that rate equals demand minus supply divided by efficiency. |
| So when we think about the demand there’s a couple of methods. One that I like is the one that considers the demand as the uptake of nutrients by the fruit, the leaves, the roots, and the wood. | A pictographic formula for demand appears which shows that demand is the sum of the fruit, leaves, roots, and wood. |
| But when we want to determine how much we need to apply year after year in a mature block, a full productive block, we will think about only the fruit. Because, and this might vary between in different conditions and situation, but in most cases the roots, generally the roots will turn over and so the carbon or the energy and the resources will return to the soil and continue to be available. The same here in Washington, most of the growers will prune and that pruning material will go back to the soil. Its chipped and reincorporated and unless we have a very wind day, most of the leaves will remain on that floor and be recycled. So it continues to be recycled in the ground. | The part of the equation containing leaves, roots, and wood is circled in red. A |
| So we consider the demand as the extraction of the fruit from the orchard. There has been other studies that consider also tree growth. And that could be possible in situations where you’re not incorporating the pruning wood. You are taking it out, or you are in a situation where you think that the leaves don’t remain in your ground, or other condition especially at the beginning of the establishment of your orchard. | Text appears highlighting that tree growth demand could be a part of the equation in some situations. |
| When we think about the fruit extraction, with this study that I mention before, we also determine that fruit extraction for these three different varieties for each year. And what we learned here, and I believe this is good news so we don’t have to repeat it every year and each grower doesn’t have to do it in their own site, is that we didn’t see a huge variability between the between years, between sites, and between varieties. So what I’m providing here is a range of the extraction levels in terms of pounds of nitrogen or element per ton of fruit. | Slide titled “Fruit Extraction” presents a table showing the estimated nutrient removal via fruit extraction. Columns list 10 key nutrients in pounds per US ton of fruit. Rows compare multiple cherry cultivars and values are shown as ranges. A note below the table highlights that extraction levels did not differ across cultivars or years. |
| So just to give you an example of how to use this information, I have an example of 10 tons. These are US ton, the short tons, multiply, in this case, for the upper range of demand in ‘Chelan’ for example and simple mass. 47 pounds of nitrogen are needed in this orchard, nine pounds of phosphorus, 64 of potassium, and 7 pounds of calcium and so on. So you can estimate what is what you are taking out of the orchard using these values, in my opinion, with confidence. | A handwritten equation appears below the chart illustrating an example calculation converting yield in tons to nutrients removed. |
| Now once we have the demand, we now need to subtract what is supplied by the orchard. And that could be in the soil, what is there as minerals in the soil, but also what is coming from the water. So we do have experience, some orchards in Washington that are irrigated by the Colombia River for example, are very high in nitrate. So they provide quite a big amount of nitrogen throughout the season and that will vary. The same thing in Chile, I know that in Central Valley there’s a lot of water that has high levels of calcium for example, so you have to consider that in the supply. | Slide titled “Supply” contains an illustration of small trees being watered via irrigation line. |
| And a very simple way that I utilize, and it has not been as popular because it doesn’t correlate always, but it’s a good tool that you can use as a complementary tool, is to compare and do the soil analysis and try to keep the ranges within these values that I’m sharing here. If we have the ranges within these values, we will consider that there’s no extra need or correction that needs to be done for for the soil. I point out here that the method that we are utilizing is important, because there’s several methods that are around that will not neccessarily relate to these ranges. | A chart appears outlining the ideal ranges for 12 key soil nutrients. The first column contains the soil nutrient name, the second column contains the ideal range of this nutrient in the soil, and the last column show the method that can be used to boost this level in the soil. |
| You probably notice that in that table I don’t have nitrogen. One of the limitations of nitrogen in the soil is that it’s very mobile and so we can’t really rely very strongly in those values when we do soil analysis. So we made it a little bit simpler especially for Washington Growers. We had an estimation that, for every percent of organic matter provided in the soil, we can estimate between 8 to 17 pounds of nitrogen per acre. So with this information, we can at least estimate how much is provided because of that organic matter of your soils. But we also can calculate by doing water analysis the amount that that is provided by the irrigation. And again, the soil analysis needs to be used as a complimentary tool and not as the only source of information. | Slide titled “Supply” contains a photo of roots growing in the soil above a layer of compacted clay. A bullet point list outlines the mentioned system for estimating nitrogen needs as well as highlighting that this method should be used as a complementary tool. |
| The third part this is the factoring. So we have demand minus supply, and we need to apply a level of efficiency. And this is where it becomes more complicated because the level of efficiency is very local to your operation. | Slide titled “Efficiency” contains a close up photo of plant roots. |
| Important things to consider are the timing of the application, and the timing will relate to two main things. One is the root growth, so when the roots are starting to grow in in your orchard, and that might vary between root stocks. As a general term we know that the roots will start growing around 15 degrees Celsius or 59 Fahrenheit and with moisture levels of 50 to 70, which also correlates well with the more microbiological activity and mineralization. | Bullet points appear which outline that root growth begins at the stated temperature and moisture levels. |
| And the other thing to consider is to understand: when is the maximum demand of a nutrient, in this case nitrogen, for example, for cherries. What we have learned in the past is, there’s a more recent work done by Patrick Brown that shows this information too, that higher demands are between that fruit set and maturity of the fruit and also after harvest. That’s when the tree is taking up more nutrients or the larger percentage of nutrients through the soil and the root system. | Additional bullet points appear outlining that maximum nutrient demand is between fruit set and maturity of fruit as well as after harvest. |
| A precaution that I want to share, and this probably is not news to the growers that are looking to the roots and planting their trees, there is a large variability in uptake and timing of uptake between rootstock. This is a picture shared by Matthew Whiting of a ‘Mazzard’ root stock and a ‘Gisela’, and so you can see the amount of roots that are very different. In a very preliminary work we did this year, we are comparing this root growth between rootstocks and we already see a difference between ‘Gisela 12’ ‘Maxima 14’ and ‘Gisela 5’ in terms of growth. | Slide titled “Rootstock differences” contains two photos of cherry root systems, the top image is of the ‘Mazzard’ rootstock and the bottom is from a ‘Gisela’ rootstock. The root system in the top image is significantly larger than the root system of the bottom image. A line graph beside the photos show the difference in root growth of three different rootstocks, G12, G5, and MxM14, from May to August. There are clear differences in the root growth of these three rootstocks with G5 initially having less growth than the other two but rapidly overtaking them in early July. |
| I’m getting to the end so Carolina, you can make me a sign if we are good on time. And one thing I didn’t want to forget when we think about the efficiency, I mentioned that period of time that there’s higher demand through the root system, but also we have learned that there could be a good opportunity for foliar application especially during the fall. The picture here is not the best stage, that is maybe too late. But it’s just to highlight that in the fall, there has been a work, we did some work with Matthew Whiting in relation to that application of urea and zinc. But there has been other reports prior to us that have shown similar results. The impact of this foliar application? When the roots are no longer active or the plant is no longer active it’s because there is a remobilization from the leaves, to the storage, to the roots. So when we apply this, we think that the system kind of turns around and is moving things downwards that will be used. And we know this for sure, that the cherries will use these resources for this first stages of development of full bloom and first stages of cell division. It’s also very useful for elements that are not mobile like boron for example, or zinc, not very mobile in the plant and you need them earlier in the season. So fall application of nitrogen or micronutrients like zinc and boron are very common here. And also we repeat this application during the Spring for boron and zinc, especially when we know that there are some deficiencies. Which, here in Washington soils are very low in boron in general. And the efficiency level are generally thought in the best case scenarios of 80%. | Slide titled “Foliar Spray” contains a photo of a cherry orchard in the autumn with orange and yellow leaves. A bullet point list highlights the benefits of foliar sprays in the fall and spring and also that the efficiency max is 80%. |
| Okay so to finish here, and I promise this is one of the last slides. Just to summarize what I just presented, so just to give an example, if we have 10 tons of uh ‘Chelan’ and we use the upper level of nitrogen demand. We have that 47 pounds of nitrogen, right? And let’s consider we have 1% of organic matter which is very common here in Washington. There’s much more nitrogen or organic matter I know in central Chile and southern Chile especially. But that would lead us to 17 pounds of nitrogen per acre if we think about that upper level of supply so that leads to 30 pounds of nitrogen. | The formula for rate appears again along with handwritten notes of an example calculation as outlined in the audio. |
| Now the question is again: what is your efficiency level? If we think that we have some limitations and we want to correct those we can consider 50% of efficiency in the lower end, and that would lead us to 60 pounds of nitrogen demand in this 10 tons per acre block. But if we have everything done very well, we use the good timing, maybe we’re using drip irrigation or fertigation and we can split the application of nitrogen several times, which it is more efficient, we can go to up to 80% efficiency. And so it’s almost half the amount of nitrogen needed in this block. Depending on the source of the fertilizer you’re going to use you have to multiply that by that factor. | The word “Efficiency” is circled in the formula and an example equation for both 50% efficiency and 80% efficiency are written on the screen. |
| And last then, we need to monitor. And so how do we assess that that efficiency level applies? That we use it correct? Then we can monitor by evaluating those yields and fruit quality, but also we can use this leaf tissue analysis. And there’s several references on the levels that will tell you if you are within that range of adequate nutrition. | Slide titled “4. Monitor” which contains a simplified chart of nutrient needs in cherries as well as a bullet point list outlining that you should monitor yields, and do leaf tissue and fruit analysis. |
| So in summary, this is the last, manage variability, identify your limiting factors, could be underground or above ground, estimate the rate based on the yield of your orchard, and improve the efficiencies in terms of timing, especially identifying when are your roots growing and when you have the most efficiency, and then monitor your block to assess that practice. | Slide titled “Summary” contains a bullet point list of the 5 key suggestions for management: managing variability, identifying a preventing limiting factors, estimating rate based on yield, improve efficiencies, and monitor. |
| So with that I finish. I’m going to be back for the Q&A, and thank you very much again Carolina and Lisa for the invitation. | Thank you slide containing the author’s contact information. |
| For Bernardita, foliar calcium application by uh fertigation, when to start those applications? | Host of Q&A session appears on screen. |
| Yeah ,so first of all remember that you might not always need calcium. So my first recommendation would be that you do a soil test to see if you actually need it or not. The calcium in general is not as mobile as nitrogen, so it remains in the soil quite a longer time especially if your soil has calcium carbonate or is a type of alkaline type of soil. Now if you are thinking of applying because you have low levels of calcium in your fruit or if you have low calcium level in in your system, it has been very well reported that early applications are more efficient. And the reason for that is that calcium is used for developing the cell walls of the fruit, so the timing of calcium needs to be available in that moment of cell division. But also, because it’s already been well reported, not only in cherries, but in other fruit crops is the xylem functionality. so the xylem is the pathway that calcium gets into the fruit and the xylem will decline its functionality throughout the life of that fruit. And so it’s more active at the beginning, and that’s where you can actually be able to get calcium into your fruit. So early applications, this is through the soil or fertigation, much more efficient than foliar application given the system that the plant has to take up calcium, which is through the roots. Now there is some evidence, although it’s much more contradicting, with foliar application the efficiencies are very low. But if you are willing to try that, the early application will be again be my suggestion. Again, try to monitor those calcium levels because in most cases we actually don’t need that extra calcium application. | Bernardita appears on screen. |
| Next question, for you too: If you do too much nitrogen in the fall, can the tree struggle to go into dormancy in the winter? | Host of Q&A session appears on screen. |
| So probably I’m going to start with the same answer that I gave to calcium. So remember that the fall application will be in cases where you did your nitrogen analysis in your leaves and you evaluated your crop and you see that the trees maybe had a very high crop load. And so you demanded more of those trees and also you have maybe some level of deficiency. You see small, short growth and so you identify that you have a limitation and you need to apply more nitrogen. That’s when I would recommend that fall application. And second, when we’ve done that, and we did our work with Matthew recently with the application of urea in the fall, we actually had no impact in that hardiness. And we did more than the going to dormancy evaluation, we evaluated the hardiness of those in the winter and in the spring. So we had no impact on that hardiness level of the trees. But again, there has been some reports where if you have high vigor in your trees, regardless of you applying more or no nitrogen, there has been some data that suggest that you can delay that going into dormancy and impact that hardiness level. It’s not data that I have seen, but I know that it has been reported. | Bernardita appears on screen. |
Link to YouTube video: Impact of Nutrient in Sweet Cherry Quality. Bernardita Sallato
