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Insect and disease attraction to plants with reducing sugars

How is it possible for a high Brix plant to be resistant to insects and not provide them with an abundant food source when insects are attracted to sugars? The key insight is that plants contain different concentrations of different carbohydrates at various levels of plant health. The goal for optimal plant health is to have all photosynthates and soluble sugars such as glucose and fructose converted to non-reducing sugars in each 24-hour photoperiod. This means a healthy plant will have a high Brix concentration and very low levels of reducing sugars.

From the podcast interview with Don Huber.

John: Are there any negative health consequences of plants having high levels of fructose and glucose?

Don: Yes and no, depending on what other stresses there are present. If you have a deficiency of manganese, for instance, it can’t store the reducing sugars―glucose and fructose―that are being produced through photosynthesis. It can’t store them as sucrose, and so they become very attractive reducing sugars, and they become very attractive to insect pests and to a number of plant pathogens.

Manganese is a critical factor for that sucrose-phosphate synthase enzyme that converts glucose and fructose into sucrose for storage. If you’re deficient in manganese, you’ll have high reducing sugars―glucose and fructose. As insects like aphids fly over these plants, they can detect that high reducing sugar, and for them, it’s a red flag saying, “Hey, come in for dinner!” But if those sugars are converted to sucrose and stored there, you don’t see that attraction.

Reducing sugars come out of the root system―they’re the root exudates that are attracting Pythium and Phytophthora and Aphanomyces and those other oomycete pathogens―root-rotting pathogens.

Later:

John: Don, you described how the carbohydrate profile can attract aphids. Are there other insects that can be attracted by the carbohydrate profile?

Don: A lot of them are. I don’t know that all of them are, but many recognize the difference between the reducing sugars, and they don’t seem to be attracted to the non-reducing sugars nearly as much. You’ll see that association. When we get the minerals balanced for the plant, you’ll see all of those problems start to disappear or be very minor.

P.S. I appeared as a guest on The Modern Acre podcast in this episode.

Soil glyphosate limiting manganese availability

We have observed many soils that do not deliver manganese well in spite of having large manganese reserves in the soil profile. In most cases, this is a result of manganese oxidation. Manganese oxidation can result from chemistry interactions, but a great deal of manganese oxidation occurs as a result of fusarium overgrowth from accumulated glyphosate applications.

Here are some thoughts Robert Kremer shared in our conversation on our podcast interview:

John: Coming back to the conversation about glyphosate and AMPA, how does glyphosate—and the accumulation of glyphosate and AMPA over extended periods—impact overall soil health?

Robert: We know that there are some indirect effects of continuous use of glyphosate on soil health, because we usually measure a lot of the biological parameters when we set up soil assessments. We see that there are some effects on some of the beneficial bacteria that are involved in plant growth promotion, such as producing plant growth regulators that stimulate root growth and other beneficial bacteria that will produce pathogen-suppressive compounds. We’re noticing that glyphosate tends to suppress those beneficial groups of bacteria, so that has an effect on subsequent plant growth as well. So we feel that there’s a problem there.

I briefly mentioned the effect on some of these microorganisms that are known to cause certain micronutrients to be immobilized, and therefore not available for plant uptake. One of these is manganese. And manganese, of course, is very important for the activity of many enzymes that are involved in many of our metabolic pathways. If it’s tied up, you may have poor photosynthesis. You may have poor amino acid formation because you don’t have enough of it to satisfy the needs of the enzyme.

We’ve found, for example, that fusarium that will colonize the roots of plants that are treated with glyphosate. Fusarium is a manganese oxidizer, so it will immobilize manganese. If it’s on the root system, manganese is not going to be taken up. And if it’s built up in the soil—whether there’s a genetically modified crop there or not—it’s going to remain in the soil. It’s going to continue to immobilize manganese. If you don’t have a lot of available manganese, that’s going to affect the overall soil health as well.

There are a lot of other things. Glyphosate may exchange with phosphorus in the soil, and then you have problems with either excess phosphorus, or, if phosphorus isn’t being taken up by the plants, it can become an environmental problem. We discussed the quality of the organic matter, because we basically just use two crops as the source of the organic residues being returned to the soil. If we don’t have the microbes there to decompose them, or if there’s not a diverse enough quantity of organic substances to help build up soil organic matter, then that will affect soil health as well, because—like I mentioned before—organic matter is one of the key indicators for good soil health.

2020-07-20T22:09:29-05:00July 21st, 2020|Tags: , , , |

Change ‘pathogens’ to ‘beneficials’ by changing the soil environment.

if the pathogens can’t bring about that compromising of the availability of manganese by converting it to an oxidized form, the fungus is essentially just a good saprophyte in the soil.

Don Huber describes for us once again that ‘disease’ organisms can only produce an infection in the correct environment. In a healthy environment, these same organisms develop symbiotic relationships with the plant. Our task as farm managers is to manage the environment properly, and crop ‘dis-ease’ vanishes.

You can listen to the entire episode here.

Don: A lot of your nutrient relationships—where you have microorganisms that are responsible for changing the valence states of various minerals so that they’re more available or less available. And you have those going on in both directions at the same time in some capacities. It’s an issue with manganese or iron or some of those things. Some of the secondary functions come into play so that all of that can take place and manifest in a very positive manner. Even though what you might be looking at—or the tests that you have—may not show the complete picture, you have to realize that it has to be going on, in order to complete the cycle.

And so, it’s a matter of either developing the techniques or understanding how all of those organisms interact—the ecological niches that make the system work. Everything isn’t just one big pool with somebody stirring the whole thing around. You really have a community of functions that are taking place at the same time, but you don’t have the same gas station at every corner or a grocery store at every corner. You have each one of those different functions taking place in its own little scheme of things. So the overall system is a very functional and very dynamic relationship relative to the plan. And it’s neat.

John: One of the pieces that you and I have discussed in the past is the challenge that we are seeing today with manganese availability. I would say that as much as 80 percent or more—perhaps even 90 percent or more of the crops that we work with today—come back showing inadequate levels of manganese. What are the major factors that contribute to that?

Don: Manganese has a very dynamic relationship with the soil, and also with many of the fungi. There are organisms—mycorrhizae—that increase the uptake of manganese, as well as zinc and phosphorus and some of the other nutrients. So, if they’re not functional, you miss that ability to absorb and to interact with a tremendous volume of the soil—where that mineral might be in short supply.

The other thing is that you have bacteria that are responsible for the valence state. You have the oxidizing groups. You have the reducing groups. The plant can utilize only the reduced form of manganese—the Mn2+ form. Mn4+ form is non-available, but we see it primarily in the soils that have high phosphate levels or high oxidative relationships—the manganese can be there and yet not be available for uptake. We see it with many of our pathogens, because the pathogens utilize manganese oxidation as a virulence factor.

We looked at several thousand isolates of Gaeumannomyces graminis, which causes take-all all over the world. We evaluated those and we found that there was one characteristic that was common in all virulent farms—manganese oxidation. If the wheat had oxidized manganese, it would never resist the disease. The same thing for rice blast. The same thing for isolates of Streptomyces scabies and a number of other pathogens. The ability to oxidize manganese to a non-available form—and to compromise the resistance of the plant to those pathogens—if the pathogens can’t bring about that compromising of the availability of manganese by converting it to an oxidized form, the fungus is essentially just a good saprophyte in the soil.

Same thing with many bacteria. So, we see these direct effects on mineral availability being involved not just in growth and quality and nutrient density, but also in susceptibility or resistance to disease. You have the virulence relationship of the pathogens with bacteria and fungi in the soil, and that’s related to those minerals that are necessary for the plant’s defenses. Those minerals are also directly related to the growth and resistance of the plants to those pathogens in their overall physiological function. It all fits together very nicely if the system is balanced—if it’s favorable.

And that’s one of the things that we can adapt to. When we’re farming, we’re really managing an ecology. It’s not a matter of a silver bullet for this problem or a stinger missile for another. It’s really a matter of having ecology work for us and support the plant. And if we don’t do that and we upset the system, then we compromise the overall quality and productivity potential we have in our soil.

John: You said that there are a number of pathogens that are dependent on manganese oxidation. And if they’re unable to oxidize manganese, they just become saprophytes in the soil profile. Are they dependent on that manganese oxidation directly—do they individually require it? Or are they just producing a manganese-deficient plant that is now susceptible to invasion?

Don: Both of those statements would be correct. They don’t necessarily need the oxidation. Some of them are also reducing organisms. In other words, if you change the environment—or if you change the association that they have with other organisms—then they may be strong reducing versus strong oxidizing organisms.

We see that especially with the Pseudomonads and a number of other organisms—you change the soil environment and they can benefit you, or they can be synergistic, or they can even be a direct pathogen, involved in compromising that resistance. The microorganisms use those minerals just like a plant does, or just like we do. Our metallo-nutrients, or strong transition elements, or electron transfer and physiological processes, are the cofactors for enzyme function. We don’t require very much of them, but if you don’t have that specific cofactor that’s involved for an enzyme, that enzyme isn’t going to do any work for you—it’s just another protein that’s sitting there. And about 80 percent of our proteins in plants are what we call metallo-proteins, where the metallo part is a cofactor. It’s a small part, but a very critical one, as far as function of that physiological pathway.

John: In essence, what you’re describing is that as long as plants have adequate availability of reduced manganese, they have resistance to all the diseases that you described.

Don: It would be very, very critical for that resistance—for the physiological functions in in the plant—without those minerals.

If you have read this far, you are welcome to join us for a webinar June 19th, at 11 AM EDT where we will discuss how to increase reduced manganese availability in soils.

2020-06-11T07:43:44-05:00June 12th, 2020|Tags: , , |

The problem, and large opportunity of manganese availability

Most agricultural soils today do not supply adequate levels of manganese to a crop. This is a foundational problem, because of the need for manganese in the water hydrolysis process at the beginning of photosynthesis.

When water is absorbed from the soil, and used for photosynthesis, the first step in the process is that the water molecule needs to split into H and OH, hydrogen and hydroxyl. This process is called water hydrolysis. Without this crucial first step, the photosynthesis process is blocked or greatly reduced. The water hydrolysis process is completely dependent on manganese to function. The macro ingredients needed for photosynthesis are chlorophyll, sunlight, water, carbon dioxide, and manganese. Even if we have generous levels of the first four, when manganese is low, it becomes the bottleneck that slows down the photosynthesis process.

We observe inadequate manganese levels in plants almost universally. You can observe it visually, quite easily in most plant species. The leaf vein should be at least as dark green as the area between the veins. When the veins are lighter in color than the area between the veins, this is an indicator of a low-level ‘hidden hunger’ manganese deficiency, and manganese being a limiting factor in the photosynthesis process. You can observe this easily on most plants, crops, cover crops, and so-called ‘weeds’.

I have learned from experienced agronomists that this systemic challenge with manganese has not been present historically. We now know that glyphosate, AMPA, some other pesticides, and oxidizing microbial communities all contribute to manganese being chelated and oxidized in the soil, and not available for plants to absorb. Many soil have generous levels of manganese in the profile, it only needs to be released. I will be hosting a webinar on Friday June 19th at 11 AM EDT describing the cultural management practices and tools that can be used to release the locked up manganese in the soil profile. You can sign up to attend here.

Robert Kremer discussed these interactions in our fascinating podcast interview:

John: In our experience working with many different farms, I would say, just off the top of my head, that greater than 90 percent of the farms we work with have experienced severe manganese deficiencies. I wonder about the long-term effects of this. When you have glyphosate accumulation, you have this shift in the fusarium population, and you have oxidizing organisms that are immobilizing manganese. What are the long-term implications of that manganese immobility in the soil profile? How long does it take before that manganese might be released and converted back into a form that the plants can actually utilize?

Robert: Yeah, that is a concern. I think there are several issues here. You have the effect of the shift in the balance of the microbial diversity. It’s shifted toward a lot of manganese oxidizers, causing manganese not to be available. I think that over time, if one were to alter the management to include, let’s say, cover crops—or at least different crops within the rotation—this could stimulate other types of microorganisms that will help free that manganese, or that will at least compete with those oxidizers to reduce their impact. So that would be one possibility. And how long that will take, it’s hard to say. It may take a couple of seasons, or maybe less. That’s something that really needs to be looked into. 

The other issue is something we mentioned previously: how much manganese can be immobilized or chelated by the residual glyphosate and the residual AMPA? That, I think, is a very serious issue—especially in soils where the texture is such, or the level of phosphorus is so low, that you don’t have any competition with the glyphosate or AMPA. They will obviously chelate or immobilize manganese as well. I don’t think we have any real good information on how long that can happen or what the extent of that situation is as far as tying up manganese over the long term. Taking all that together—the shift in the microbes, the residual glyphosate and AMPA, and the basically continuous corn-soybean rotation—if that continues, the manganese problem may persist.

John: When you speak of bringing crops into a rotation to help reduce some of that manganese and to increase its availability, what are some crops that are really effective at having a reducing effect and shifting the biology and the availability of manganese in the soil profile?

Robert: I don’t have any specific ones in mind, but certainly when you have a diversity of cover crops in a mix, there will be some that will support different microbial communities that are able to mobilize these micronutrients, and others that can actually mobilize the nutrients themselves. A common example is the use of buckwheat, or some of the brassica crops, which can mobilize phosphorus or neutralize nitrates. 

And then let’s say you add something like sorghum to the rotation—grain sorghum or sweet sorghum. From my experience, sorghum has a keen ability to host a lot of mycorrhizal fungi in its root system. And mycorrhizae are very adept at mobilizing many nutrients—not just phosphorus. If you could add a crop like that, or other crops that can host mycorrhizae, that would be a very good way to get around the manganese problem, to improve regrowth, and to improve the overall diversity of the microbial community.

Low level manganese deficiency in peaches:

2020-06-11T06:52:31-05:00June 11th, 2020|Tags: , , , |

Cell division for fruit size and quality

Potential fruit or grain size is determined during the cell division period immediately after pollination. The cell division process can continue for as little as 5 days, to as long as 40 days, but most crops have a 10-14 day cell division window. During this window, the cells in the embryo are rapidly dividing, 2-4-8-16-32-64 and so on. At the end of this 10-14 day window, cell division stops completely, and the remainder of the fruit fill or grain fill period is focused on cell expansion, filling each cell with proteins, sugars, and water.

Fruit that are tightly packed with more smaller size cells are firmer, store better, are crisp, and crunchy. Fruit with more cells can be much larger in size when all the cells are filled with water and nutrients. Fruit with more cells are resistant to cracking and splitting. In general, almost all the fruit quality characteristics we seek can be improved by increasing the number of cells formed during the cell division period, with the exception of some fruit where excessive size is a negative.

The nutritional factor which limits the number of cells formed during the cell division period is calcium, because calcium is needed to form the cell membranes for all the rapidly dividing cells in the fruit embryo.

An easy step to produce exceptional quality and yield is to ensure a peak of available calcium during the cell division period.

This means any soil applications of calcium need to be timed so the peak of the release curve coincides with the crops peak demand curve during cell division. Applying gypsum or limestone on tree fruit in the spring is much less effective than a fall application, because it doesn’t release quickly enough to be available during cell division right after pollination.

In almost all cases, when fruit express physiological symptoms of inadequate calcium, which we call blossom end rot, bitter pit, or cork, it is because there is inadequate calcium supply during the cell division period.

Quite often, this inadequate calcium level in the plant or in the embryo may not be the result of low calcium in the soil. Poor calcium absorption can be the result of excessive potassium, low boron, or low manganese availability in the soil. Any of these conditions will limit calcium absorption, and thus negatively impact fruit quality.

I have been framing the discussion around fruit, but these concepts hold equally true for grain crops.

These grapes are still 3-4 weeks from harvest, and each berry is about 60% of mature size. When was the last time you bought grapes like these? Would you like to grow crops at an equivalent level of health and quality? If so, managing calcium and the associated nutrient interactions during the cell division stage becomes a top priority.

The first thing you will cut is all potassium applications until after the cell division stage is completed. To achieve this, you likely needless fertilizer application, not more. And most likely also timed very differently.

2020-06-09T20:19:17-05:00June 10th, 2020|Tags: , , , , , |

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