Sap pH as a susceptibility indicator

Bruce Tainio pioneered the use of plant sap pH as an indicator for disease and insect susceptibility in 1988. We have used this tool in our consulting work since the beginning, and have found it invaluable. Today, pH is included in lab sap analysis because of Bruce’s work.

More recently, we have learned from Olivier Husson’s work, that measuring pH by itself is incomplete, since the environmental parameters organisms require to become virulent are at least two dimensional, as they are determined by both Eh and pH, not by pH alone.

Bruce wrote this outline we shared in our newsletter in 2010, and it is still relevant today.

Plant Tissue pH = Energy
By Bruce Tainio

While laboratory soil and tissue tests are good and necessary tools, we often don’t receive the results for several days, or even up to two weeks in some cases. On a growing crop, that can be too late. With this in mind, we developed a diagnosis of plant health based on liquid pH values of plant tissue sap, which has been used in our biological program at Tainio Technology & Technique since 1989.

Simple to use and 100 percent accurate, a quick plant tissue pH test is an instant snapshot of the state of health of any plant and can tell us the following information:

  1. Enzymatic breakdown of carbohydrates (sugars) for proper growth and vitality of the plant.
  2. Risk potential for insect damage.
  3. Risk potential for foliage disease attack.
  4. Nutritional balance in the growing crop.
  5. Quality of nutrition in the fresh fruit or vegetable crop to be harvested.
  6. Shelf storage potential of fresh fruits and vegetables.

The table below is a general guideline to determine what tissue pH means. With this scale we can predict the probability of insect and disease resistance or susceptibility.

The dictionary defines pH as “a number equal to the logarithm of the reciprocal of hydrogen ion concentration within a solution.” That’s a mouthful, but more simply put, pH represents the percentage of hydrogen ions in a solution. In our case, the solution is the liquid of the plant cell, or the sap.

It is important to know that a change in the pH level of a solution of just one unit equals a tenfold change in the hydrogen ion concentration. If the pH is increased or decreased by two units, the hydrogen ion concentration changes by a hundredfold! Thus we can see why what appears to be only a slight shift in pH can spell disaster for the farmer.

A neutral pH of 7 within the cell fluid means it contains 100 percent saturation of cations other than hydrogen (in other words, the sap contains no free hydrogen ions). At a plant’s ideal cellular fluid pH of 6.4, the saturation of cations other than hydrogen is about 88 percent. At 88 percent saturation – principally of calcium, magnesium, potassium and sodium – the ionization and activity of these elements generates an electrical frequency of between 7.5 and 32 Hertz, which is one of the “healthy” frequency ranges of all living cells.

To decrease cellular pH to 6.0 is to lower the saturation of the above four principle elements to 80 percent, thus lowering the plant’s frequency to a level of lower resistance to bacterial, fungal and viral plant pathogens.

Studies have shown that insects are attracted to a tree or plant by the tree or plant’s frequency. If the saturation of Ca, Mg, K and Na increases to over 88 percent saturation, the frequency from these ions in the cell are increased, and consequently, insects are attracted to the higher-than-normal cell frequency.

The same process occurs in animal and human cells. Hydrogen accumulation in the cell tissue means the saturation of Ca, Mg, K and Na is decreasing, thus causing the frequency to decline. This low frequency leaves the cell an easy target for disease.

Oftentimes we see both insect and disease problems occurring at the same time. This can happen when insects attack due to a high plant tissue pH, and the tissue becomes weakened in the localized areas of attack. Next, localized, rapid energy loss (a drop in pH) occurs at the insect-damaged spots, resulting in tissue disease attack of those areas on the plant.

When a pH shift of a half point (0.5) or more from the ideal 6.4 occurs in the cellular liquid, a laboratory tissue test should be taken to determine exact imbalances and which materials should be applied.

Tissue pH Rule of Thumb
Low pH + Moderate Brix = Calcium Deficiency
Low pH + Low Brix = Potassium Deficiency
6.4 pH + High Brix = Balance

In the interim, for a quick adjustment to bring up the pH, calcium can be foliar applied in small amounts per acre. To quickly bring down a pH that is too high, on the other hand, small amounts of phosphate can be applied to the foliage. These types of quick fixes are usually only temporary, however, and should only be used while awaiting a complete tissue test analysis.

Like most busy people, we have neither the time nor the patience to puree the two pounds of plant tissue it takes to get enough for a conventional pH meter readings; so we use the Cardy Twin drop pH tester, made by Horiba. With this pH meter, a reading can be taken out in the field in less than one minute. We just take a few leaves, roll them up into a tight ball, and squeeze out a few drops of sap using a garlic press. Be sure and use a good quality stainless-steel press, as a cheaply made garlic press will break.

Generally, the more mature leaves on the plant will give the most accurate picture of the plant’s health, level of resistance or susceptibility to problems. Since the plant spends most of its energy supporting new growth, the pH of new leaves will not reflect the pH of the rest of the plant as a whole.


An indirect method of determining the energy levels of a plant is to measure the carbohydrate (sugar) levels in the cell liquid. For this test, a refractometer is used to determine the level of sucrose in the cellular fluid. This reading is referred to as the brix scale.

Within a given species of plant, the crop with the higher refractive index will have a higher sugar content, a higher mineral content, a higher protein content and a greater density. This adds up to sweeter-tasting, more nutritious food with a lower nitrate and water content and better storage characteristics. Such produce will generate more alcohol from fermented sugars and be more resistant to insects, reducing the need for insecticides. Crops with higher sugar contents will also have a lower freezing point and therefore be less prone to frost damage. Soil fertility needs can also be ascertained from this reading.

The brix levels should not be taken as an exact measurement of a plant’s vitality, but rather as a guideline. Stored sugar is not a cellular energy source until its carbon-hydrogen-oxygen molecular links are enzymatically broken apart. If this line breaks or energy release occurs faster than the cell can use it, then that energy is lost into the air. This condition usually occurs when the liquid pH of the cell is below 6.4 and most often indicates low Ca and high K.

The reverse can also occur – if the links between the carbon, hydrogen and oxygen molecules of a sugar are broken too slowly due to low enzyme activity, the plant becomes starved for the energy it needs for growth. This is usually caused by low manganese or zinc, or from high nitrogen/high tissue pH levels, coupled with drought stress.

As a general rule, we can say that when a plant has a low tissue pH and a moderate brix level, there is usually a calcium deficiency involved. On the other hand, a low pH with a low brix level usually indicates a potassium deficiency. The ultimate goal is to achieve a pH of 6.4 with a high brix level.

Plant tissue pH management is a relatively small but invaluable investment of your time and budget, which cannot only help you prevent disease or insect attacks, it can stop them in their tracks even once they have gotten started. This means better yields, bigger profits and most importantly, less need for chemicals.


2021-07-16T13:35:05-05:00July 19th, 2021|Tags: , , , |

The value of targeting applications with sap analysis

One characteristic of top tier growers is the desire to make decisions based on manage-able data. I have been an advocate of sap analysis to evaluate the need for product applications and to evaluate product performance for almost a decade. In that time, many growers have embraced sap analysis and can’t say enough good things about how it has saved them money by reducing fertilizer inputs, how it has made them money by increasing crop yields and quality.

A few growers look at the cost of sap analysis and say, “I can’t afford that.” If you are a small scale market gardner, that may be the case. If you are a professional grower managing a professional enterprise, you can’t afford not to use sap analysis. If you choose not to use it, you chould be clearly aware that those growers who do are rapidly becoming the low cost producers, with the highest profitability.

Mike Omeg from Orchard View shared his experiences with sap analysis on our podcast interview, and I believe you will find them valuable.

Mike: I started the process of focusing on the soil. Many folks have done the same thing, but I started to put on every biological stimulant and inoculant that was available to see what worked. As one would expect, there are some products that work better than others.

What I really learned was that hindsight is indeed 20/20. I found that spraying inoculants onto the bare soil just didn’t make sense, without having material there to protect everything that you’re putting on―to feed everything that you’re putting on. It didn’t make sense. I began to put on material before and after my mulch, because there are some things I wanted to be covered by the mulch and in contact with the soil, and there are other things that I wanted to have on top of the mulch, to add some biological horsepower to the natural processes and to kickstart the natural processes of breaking down that mulch and having it go to work for us in the soil.

One of the things that I began doing was using a lot of fish products. I landed upon a product that I really liked that’s made with salmon and crab. It really pushed forward our soil enhancement efforts, and we saw direct benefit in the crop. We were still a conventionally managed orchard, but we applied this fish product onto the soil and onto the foliage of the trees, and we saw a big return on our investment.

We tried lots of other fish products. As you know, many are available in the market. Some of them work better than others. But the ones we found that were made with salmon and crab here on the West Coast really pushed us forward in our efforts. They’re one of the base components to all my nutrition programs.

John: What other nutritional applications are you using today, and how have they shifted over the last decade or so, since you started experimenting?

Mike: We use nutrition as it’s necessary now. We’re able to do that because we utilize a technique to monitor what’s going on in our orchard in real time throughout the entire season, and that technique is sap analysis.

For many years, in about January or February, I would sit down and I would look at all of the returns that we had for the orchard. I would then look at maybe a couple of leaf samples that we had pulled during the growing season and maybe a soil sample. And I would write down everything I was going to do the following season, and we would follow that recipe. We would make minor tweaks, depending on the size of the crop―if we were going to have a light yield or an average yield or a heavy yield. Maybe we would have a disease problem that started developing, so we would boost a nutrient or two. But we essentially would just follow what was written down on the back of the envelope in the winter. Eight months from when something had been written down, we were doing it.

But an orchard―or any farm―is not a static system. There are all kinds of in-season changes that require us to change our approach in nutrition. But there was no technology that I had confidence in that could tell me what was going on at any moment in my orchard.

Sap analysis changed that. Every two weeks we take a sample―from the time the first leaves are expanded until right before leaf drop. The entire growing season of our orchard, we’re sampling, and we’re sending those samples off and we’re getting the results back and we’re calibrating every nutrient application we put on based on those samples, because we have a real-time picture of what our trees have need for or what they have excess of. Every nutrient in every tank we spray is there because the sap analysis has indicated it needs to be there.

It’s very difficult for me to give generalities about what nutrients we apply. I would love to do that―I’d love to say that our nutrient program is based on X, Y, and Z. But I honestly can only say that fish is something that is in virtually every application. The other nutrients depend upon the results of the sap analysis.

John: How similar are your current types of nutrient applications to what they might have been before you were using sap analysis? Are there still general similarities? Were you applying similar trace minerals? Perhaps a different way of asking the question would be, what were the changes that sap analysis indicated that really surprised you or that were unexpected?

Mike: That’s a great question. I’ll give you some examples.

Before I started doing sap analysis, I would put on semi-loads of triple-20 foliar fertilizer. I would put on large amounts of zinc in the spring, thinking that the trees needed zinc in order to generate bigger leaves, because we all know that bigger leaves on the tree mean more carbohydrates being generated for the tree to size those cherries, and that’s what our goal was.

I’d put on lots of triple-20 and lots of zinc. What I found was that I was shooting myself in the foot because my trees did not need zinc; they did not need triple-20. The potassium I was applying in that triple-20 was pushing calcium out of my trees. When we started doing sap analysis, I found myself putting on oodles and oodles of calcium, and no triple-20, because the trees had become deficient in calcium.

Over time, I was putting on more calcium than I ever could have imagined. And I was putting on no potassium and very little, if any, zinc. That was a big surprise to me, because our baseline program was actually harming our genetic potential of the trees to generate the returns we wanted. I never would have known that I was actually taking away from the potential of the tree unless I had done sap analysis. So that was a big surprise.

I think it was Bill Gates who said something like, “People generally overestimate what they can do in one year and underestimate what they can do in ten.” I love that saying, because as we’ve gone through time, we see things happening in the sap analysis that are surprising.

For example, like I said, we applied lots and lots of calcium when we first started this process years ago. What we see now is actually that our calcium levels are quite good. I never thought I would have said that, given how much calcium we put on. But through the various activities we’ve been doing―focusing on our soil and our foliar nutrition, based on sap analysis―we’ve gotten our calcium levels up to where I’m comfortable with them.

Believe it or not―I never thought I would say this in a million years―we actually had a difficult time keeping our nitrogen levels up in the last growing season. I found myself actually putting on a large amount of nitrogen, relative to what we’d done in the past, because our nitrogen levels weren’t high. We needed them to be higher. That was a big surprise.

I never would have done the right thing and put on nitrogen, and backed off on our calcium applications, had I not had sap analysis right there in front of me, showing me the trends in those two nutrients and allowing me to take action to correct them.

John: We’ve certainly observed that adopting sap analysis is one of the hallmarks of really exceptional growers. Because if you’re not testing, and if you’re not measuring, then you’re just guessing. There are many growers who have historically been comfortable with guessing, and that’s rapidly shifting and changing.

Mike: It sure is. There are probably growers out there who are so in-tune with their crop that they might be able to look and be lucky. Then they tell themselves that they’re never wrong. And boy, that’s a mistake.

I think that sap analysis has been foundational in allowing me to efficiently use the biologically intensive techniques I’ve been using on my farm and to have a return on investment. I don’t sell my fruit direct-to-consumer―I sell my fruit into the wholesale market. I don’t have the luxury of my own brand―my face on the package, so to speak. My fruit is anonymous in the marketplace. The only thing that my fruit has to speak for itself in the marketplace is the size and quality of the fruit.

Because of that competitiveness in the market, I have to make sure I am very efficiently managing my inputs, because I don’t receive a brand premium. I get a premium price because my quality is above average, generally. Nobody’s perfect, and it’s not always that way, but the quality of my fruit is above average. And it needs to be if I want to compete in the wholesale market.

The use of bio-intensive practices has to be done in a way that ensures a return on investment, because these expenses are added expenses versus the conventional fruit that I’m competing against in the marketplace. They often require higher levels of management and labor―which, of course, are two of the more expensive things for a business.

But by doing sap analysis, I am able to make sure that I’m hitting the mark with these techniques to the best of my ability. That adds a very important boost to the return on investment, because we’re targeting them perfectly. The efficacy of that investment becomes quite high when, instead of just guessing with something that’s an expensive input, you’re putting an expensive input right where it needs to be at the right time, in the right amount. The return on investment is quite substantial when you start doing that.

You can learn more about sap analysis from Crop Health Labs.

2020-06-23T13:03:13-05:00June 30th, 2020|Tags: , |

When micronutrient levels in tissue analysis don’t correlate with field observation

My frustration with tissue analysis a decade ago that lead to our use of sap analysis was that tissue analysis results did not correlate to disease and insect pressure, which the literature indicated should be possible. Tissue analysis also did not correlate with field observation of deficiency symptoms. Michael McNeill discusses how accumulated pesticides residues in the soil profile can chelate micronutrients, and continue to hold them in chelated form even after they have been absorbed by the plant. The chelation constants of many pesticides are much stronger than naturally occuring chelation agents like amino acids and organic acids.

From the Regenerative Agriculture Podcast with Michael McNeill:

John: Michael, what is something that you’ve puzzled over for a really long time? What’s really caught your attention in the agriculture space that you’ve been working on?

Michael: Well, something that I’ve finally figured out, I think, was the impact of the lack of availability of micronutrients in our crops. I was doing tissue testing, for example, and I had adequate copper and iron and manganese and magnesium and calcium—everything looked good. What I didn’t realize was that a lot of those minerals were chelated. They were tied up into a form that the plant could not use—yet they showed up on a chemistry test when we tested the tissue. And when I finally figured that out, then everything started to gel for me.

John: I think what you’re saying is that these various minerals and trace minerals were being chelated inside the plant tissue by the herbicides and fungicides that growers were applying.

Michael: Yes. When I tested the plant, it had adequate levels. But when I looked at the plant, it was showing deficiency symptoms. You could look at it and just tell that there was a zinc deficiency or a manganese deficiency; it was obvious. But when I tested it, it was fine. Why was that? And it’s when I learned about this chelation issue and how it can be such a problem.

John: This is something we’ve been monitoring for a number of years. And it seems that, in some cases, sap analysis reports those a bit more accurately. And perhaps that doesn’t take all the chelation into account—but of course it’s still extracting nutrients that are held within the plant sap, and it’s still possible for them to be chelated. We do see the sap analysis correlate more accurately to what the plants are actually showing visually.

Michael: I would agree. I think the sap analysis has been a good step forward. When I figured out this chelation effect, that’s when it really gelled for me and I could understand why I was seeing deficiency symptoms in what, on paper, looked to be an appropriately healthy plant.

Why we don’t use Horiba meters to measure nutrients in plant sap

Laboratory leaf sap analysis has given us remarkable insights into plant nutrition. We have learned a great deal about nutrient interactions and plant nutrient absorption of different products and in different environments, and have become champions of sap analysis. 

Occasionally I am asked how we might use the Horiba meters to measure sap contained nutrients in the field, rather than submitting them to a lab.  

I don’t consider Horiba meters to be a viable option if we really want to manage plant nutrition properly. Here are a few reasons why: 

  1. We need to know the levels of many more than four or five nutrients. Knowing the levels of only nitrate, potassium, calcium, sodium, pH, EC, and Brix doesn’t begin to approach the thoroughness of data needed to make informed decisions about nutrient management. For example, manganese influences potassium absorption, and boron influences calcium absorption, to a significant degree. Trying to manage the macronutrients without knowing the levels of the trace minerals promises to be an exercise in frustration and mismanagement.
  2. Nitrate is only one of many possible forms of nitrogen contained within a plant. In a healthy plant with proper protein synthesis, upwards of 80% of the nitrogen will be in the form of enzymes – complete proteins, which don’t register at all on a nitrate meter. It is possible to have a crop with abundant levels of total nitrogen and record a non-detect nitrate on a Horiba nitrate meter. With lab-based sap analysis, nitrate, ammonium, and total nitrogen are all measured separately. Our goal is to have abundant total N, with nondetectable levels of ammonium and nitrate. A goal that we achieve quite regularly.
  3. In many cases, (not always) in-field analysis with the Horiba meters is conducted on the sap contained within the petiole, rather than in the leaf. Yet, we know the petiole is a nutrient and water transport pipeline, and nutrient levels in the petiole sap can fluctuate by as much as 30-40% at different periods during each 24-hour photocycle. With what other analytical methods would we accept a possible 30+% error margin? None, of course. We can reduce this margin of error by collecting samples at the same period of each day, but this doesn’t resolve the challenge that the nutrients contained within the petiole don’t always reflect what is present in the leaf.

In –  lab analysis of leaf sap overcomes all of these challenges. This is why we only use the sap analysis from Crop Health Labs.


2020-03-16T13:52:03-05:00January 10th, 2020|Tags: , |
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