John Kempf

Untapped yield potential on corn

How much can you increase photosynthesis levels beyond what is considered ‘normal’ today? Beyond what is common?

How much higher might national corn yields be, if the right incentives were aligned to produce the desire for higher corn yields? Could we have a 350 bushel national average yield? Don Huber suggests we had the capacity to do so with knowledge that existed in the 70s if we had the collective desire.

From our interview on the podcast episode here.

–

John: What is the potential for plants to increase the volume of photosynthesis?

Don: The potential is 100 percent. I mean, fivefold, tenfold—depending on where we are now and what plant we’re talking about. There a number of different ways to do that.

I mentioned plant morphology, but you can also do it by increasing light intensity. You got a lot of leaves on a garden plant—a mature corn plant at tasseling time—that aren’t getting very much sunlight. They’re not photosynthesizing at their potential because of that lack of sunlight. That’s where morphology comes in.

Plant spacing—we can increase the number of ears on a corn plant. There is tremendous work being done at Purdue, for instance, in corn breeding/genetics—they’re producing five and six ears on a corn plant. If you increase the efficiency of that plant, you don’t need as high a population. You can minimize that crowding and that shading effect.

We can reduce the allelopathic effect of our plants. To increase the population in corn, it’s very critical to have even germination. If you delay germination six to eight days, you automatically reduce the size of your ear by the allelopathic effect—that auto-intoxication effect of the root exudates on an adjacent plant—by as much as 80 percent.

John: Wow!

Don: When the John Deere MaxEmerge planter came out, I remember how it was almost an instant success because it increased the soil-seed interface—the contact that gave you that uniform emergence, to minimize that allelopathic auto-intoxication suppression that you otherwise had from those higher populations. We got an increased corn population and maintained full yield potential without the allelopathic chemicals reducing the overall production potential of that particular plant.

There a number of things we could do if we needed to. Right now we’re concerned about a surplus. The biggest thing is that necessity is still the mother of invention. But there’s plenty of potential there.

In one of our brainstorming sessions at Purdue we asked Charles Tsai what the biochemical genetic potential of a corn plant was. And a couple of weeks later, when we were all together, he said “I’ve got your answer.” We were shooting for 350, 400 bushels in our research. We knew that a lot of our better farmers—back in the late ’70s—had the potential for 550 or even 600 bushels. We were trying to design some systems for them to achieve that on a field basis.

And Charles sat down, and we said “Well, is 600 bushels a realistic figure?” And he said “You’re all pessimists. The biochemical genetics of the corn plant are about 1100 bushels.” That’s what we could do if we managed the environment and the plant in a proper manner and provided the expression.

We probably won’t come close to achieving that until the necessity is there. The limiting factor is the innovation of man. And as long as we’re doing okay—as long as we don’t have that burr under our saddle to look at both the genetics and the environment—we won’t have the need to maximize the expression of that genetic material.

John: What yields did you end up achieving on your yield trials?

Don: We could get 400 bushels. We had farmers that were getting 350. Of course, the average was still 75 bushels. They were doing three or four or five times what the average was on a major piece of land. They were able to do it because they recognized that they were managing an ecology. They started out with the soil. They had a beautiful soil.

I remember visiting Herman Warsaw’s farm. You could take a steel probe and you didn’t have to lean on it. You just pushed it in the soil three feet. He had that system working very well. In some of his neighbors’ fields you’d get the probe down three or four inches and you’d have to really put some pressure on it. To get it down a foot and a half you’d be driving it in.

I can’t tell you how many of the old ping tubes are still sitting out there in the field. Those were tubes that you could drive into the soil to collect soil samples—at three and four feet. And we had to get it into our soils using a sledgehammer. Then the problem was pulling it out. You would tear the metal off of the tube with a jack, and finally you’d just crimp it over so that it wouldn’t tear up the tire, and then you left it. A lot of them are still sitting out there in those fields because we didn’t have that concept— the soil wasn’t a major part of the management program. In general, we would look at the nutrients and forget that all parts of the ecology needed to be managed—to have better percolation, to have biology, to have air exchange—and most things have to take place if you want to capitalize on the genetic potential of the plant.

John: What were the plant populations that growers were using to achieve 350-plus bushels per acre?

Don: You had the old Pioneer 3532 seed—a hybrid that picked up 95 percent of its nitrogen by tasseling time and then merely recycled it. On sandy soils it was a great hybrid because you couldn’t maintain your nitrogen availability in those sands. It would take it up and store it, but it had a yield potential of about 125 bushels at 24,000 plants, which was our standard at the time. But you could increase the population of that particular variety because it didn’t have the allelopathic effects from the root exudate with high population. It had a fixed ear. So, as you increased the population, you still maintained that same ear length. It wasn’t big like your higher-yield hybrid, but it was very stable and it tolerated high populations. So they got the yield up by increasing population.

With our other varieties—our high-yielding varieties that were hybrids—there you had a flex ear that related to the environment more dynamically. The higher the yield potential, the more nitrogen you want as ammonium. For the 3532 variety a 50-50 ratio of ammonium/nitrate was optimum for it. And you get into the higher yield and the 250- to 300-bushel yields, you want 75 to 80 percent of your nitrogen as ammonium and only 10 to 20 percent as the nitrate source of nitrogen, because you want as much photosynthesis as possible to go into the kernel. When the plant utilizes nitrate nitrogen—and most plants can utilize either form equally well—it takes 15 to 20 percent of your photosynthate to reduce nitrate nitrogen back to the amine form so that the plant can utilize it.

And so the higher your yield potential, the more ammonium nitrogen you want—to provide those amino acids for that growth, and your enzymes and everything—and less nitrate nitrogen. We always found that there was a benefit to some nitrate nitrogen because it serves as a buffer—both to limit the drain on carbohydrates—if you have a high uptake of ammonium nitrogen, nitrate will tend to balance that—but also as a stable form of nitrogen. If you run short, then you can use some of that photosynthate.

If you have molybdenum and your other nutrients available, you have part of the function of your nitrate and nitrite reductase enzymes. Again, you have a different physiological pathway. And if you’re saying, “Well, I’m going to get most of mine from an ammoniacal source,” you may forget that you also have to have molybdenum for some of those other enzymes that aren’t quite as dynamic or quite as involved as they are if you’re relying more on the nitrate source.

Those are some of the things you could do to enhance that overall photosynthetic efficiency—the form of nitrogen is going to influence your soil biology and your buffering capacity in those areas.

John Kempf2020-04-25T14:20:06-05:00April 27th, 2020|Tags: corn, Don Huber, quality agriculture book excerpt, yield potential|

Solving nematode challenges

If our soils and crops have challenges with nematodes, it is because we have managed them in a way that is conducive to developing nematode populations. Soils with balanced and healthy microbial populations can completely shut down pathogenic nematodes and prevent them from becoming a problem.

The long term solution is to rebuild soil levels of microbial active carbon (not total organic matter). Rebuilding microbially active carbon can occur quickly if we manage soils to achieve that objective.

A short term solution can be to apply high application rates of humic substances, high application rates of molybdenum, and high application rates of ocean minerals. This application can shift the soil microbial population, and enhance the species that antagonize pathogenic nematodes. It is not possible to describe what a high application rate is in a one size fits all recommendation. It all depends on your context. Rates can vary significantly based on the existing soil environment.

John Kempf2020-04-23T19:49:29-05:00April 24th, 2020|Tags: humic substances, molybdenum, nematodes, ocean minerals|

Developing disease suppressive soil

Diseases and insects only become a problem when plants are unhealthy, lacking nutritional integrity and microbiome integrity. The tools of nutrition management and microbiome management are so effective, they have been and are used as management protocols for bio warfare weapons mitigation.

From the Regenerative Agriculture Podcast with Michael McNeill:

John: Michael, we’ve been circling around this topic of soil health and the impacts of tillage, herbicides, animal manures, cover crops, and so forth. At the beginning, you mentioned that there’s a correlation between soil health and the diseases that are present. You mentioned some work you were doing in Maryland—studying diseases as a weapon. What did you learn from that experience? And how does all of that tie into what we’re talking about?

Michael: Let’s say you want to use a fungal disease as a weapon—that you can get this disease introduced into the soil. Not only does it kill a crop this year—it’ll continue to kill it into future years. So hey, that’s a pretty good weapon—you shut down a people’s food supply. They have a problem.

Well, if you have good pseudomonas bacteria in the soil, they act as a policeman in the soil, if you will, and they’ll take out the pathogenic fungi that can arise. But if you use products like glyphosate—that’s an antibiotic type of product—you’re going to kill all the pseudomonas, and then you have no protection. And it’s very easy to get a huge population of fusarium going in the soil, which probably is a pathogenic fusarium—or pythium or phytophthora. You’ve lost the natural balance. If you have that balance, though, the pathogenic fungi are not going to do much to you. Your good bacteria will clean it right up.

John: So you can actually have a disease-suppressive soil where you don’t have challenges with those pathogenic fungi. I think I also heard you mention that you were working on developing solutions to those diseases as weapons. What were the types of solutions that you were working on?

Michael: There are all kinds of approaches. If you need a fast cure, of course you’ve got to look at chemistry and the fungicides and that sort of thing. But what you find is that if you get the soil contaminated, how do you fix it? Because if you put anything on it, you’re going to kill everything in the soil. Using a soil sterilizer is not necessarily a great idea. But there is microbial life in the soil that will hold everything in balance. And if you have the right nutrition available, everything will take care of itself.

I’ll use you as an analogy, John. If your nutrition gets pretty poor, you’re going to get pretty run down, and you’re going to be very susceptible to all kinds of diseases. Would you agree?

John: Oh, I think that’s just the story of the people who are trying to sell me supplements. (Sarcasm, I take many supplements, and believe they are important.)

Michael: That’s funny—but when that occurs, you can take this supplement or this drug to prevent the disease, but you’re still improperly nourished. You’re going to get another disease, and then you’re going to get another disease. But if you get your nutrition back and properly balanced, and everything is at the correct level, your immune system starts to function properly. A good share of your immune system is in your digestive tract—there are a lot of microbes working for you.

And the soil is no different. You get those microbes working for you, you’re going to stay healthy. The soil is going to stay healthy, and so are the plants.

John: Are you saying that when you manage the nutritional balance of the soil and the microbial population of the soil, that it’s possible to grow crops that don’t have disease?

Michael: Yes. When a plant is perfectly healthy, it’s very hard to get a disease to invade it, and an insect will not even stop to look at it. Why is that? It’s because an unhealthy plant cannot convert the sugars it’s produced into complex sugars—starches and lignin—which insects and diseases can’t use. They can use simple sugars and the nitrate nitrogen in the plant. The nitrate nitrogen is taken up by the plant, and it’s immediately converted into amino acids and proteins in a healthy plant. An unhealthy plant—a plant that does not have the right mineral balance to make all those processes and cycles work—will have a pretty heavy load of nitrate in it—a fantastic food for the insect. They can detect that, and they will land on that plant and feed on it. Disease and insects are Mother Nature’s garbage collectors—getting rid of the bad stuff, the weak plants.

John Kempf2020-04-22T17:37:59-05:00April 23rd, 2020|Tags: antibiotic, disease, disease suppressive soils, fungicides, glyphosate, immune system, insects, Michael McNeill|

Eliminating the need for fertilizers with a larger root zone

A common theme from many pioneers in the regenerative ag space is that you can develop soil biology to the point where you can eliminate fertilizer applications and maintain or even increase yields. Here is Michael McNeill’s perspective on the possibilities.

From the Regenerative Agriculture Podcast with Michael McNeill:

John: We’ve been talking about a number of different things that you seem to have a very different framework on. What are some things you believe to be true that many other people don’t believe to be true?

Michael: I believe that the soil can grow an extremely healthy, high-yielding plant with minimal additions of inputs. There are plenty of minerals in the soil if you treat it properly. I think most people would disagree with me on that. They have “proven” that you have to put on fertilizers to get good yields.

John: Wow.

Michael: I’m going to stick with that, because I’ve proven it to myself—that you can do that.

John: So you’re saying that you can actually grow healthy, high-yielding crops without adding fertilizers?

Michael: Yes.

John: How do you do that? How does that work?

Michael: That’s a complex question with a very complex answer. But the key is creating healthy soil that allows plant roots to go deep into the soil, to extract the minerals they need. There’s a vast sea of minerals that are available. If you’re starting to see suppression of crop yield, and then you add fertilizer, and the yield comes back—that’s because you’re only using the top few inches of the soil. The roots are not healthy enough to penetrate deeper—to actually mine the minerals that are there. Our soil is nothing but minerals.

John: This is something that I’ve talked about as well. And the question that I often get is, “Aren’t you going to deplete the soil of minerals if you’re not adding fertilizers?”

Michael: Well, my quick reply to that is, “Try and take all the salt out of the ocean.” You can deplete minerals in a rooting zone—I’ll grant you that. But what you need to do is expand your ability to search in a bigger rooting zone. And you need to add mycorrhizae into that equation, because you want a really big rooting zone. Let the mycorrhizae work for you.

John Kempf2020-04-20T12:11:58-05:00April 22nd, 2020|Tags: eliminating fertilizers, Michael McNeill, nutrient reserves, quality agriculture book excerpt|

The challenges of managing nutrition with Brix readings

Several insightful pioneering agronomists have recommended the use of a refractometer and Brix readings as a useful management tool to evaluate overall crop quality and the effectiveness of product applications. Carey Reams popularized the idea in the ’70s and Dan Skow, Arden Andersen, and others have further developed and shared this idea.

It can be a useful, even powerful, qualitative tool as long as we understand the long list of caveats, and how to avoid being misled.

The foundational idea is that the refractive index of plant sap correlates to the content of dissolved solids, including sugars, and can be used as an overall assessment of plant health. When plants reach a certain threshold, they can become resistant to almost all insects and diseases. In principle, this has been demonstrated to be accurate and correct many times, on many farms. Putting it into practice is tricky though.

It is tricky because of Brix levels exceptionally high variability over time, weather, location on the plant, water availability, and more. It is also important (and challenging) to be consistent in extracting sap, and using the same amount of pressure to get a consistent sample each time.

Brix levels fluctuate through each 24-hour photocycle, usually peaking mid to late day because of accumulated photosynthates. In healthy plants with the proper mineral balance for good photosynthate transport, Brix levels often drop 30% or more in the leaves from evening until morning, as sugars are moved to the sugars sinks and used or stored.

Brix levels fluctuate based on weather. Plants can anticipate storms, sometimes by as much as several days, and move all the sugars possible into the roots so they can rapidly recover in case of storm damage. Brix readings should drop quite a bit in advance of a storm.

Brix levels fluctuate based on water availability. Dehydrated crops will have a higher Brix reading because the dissolved solids are more concentrated, but the crop certainly isn’t healthy.

Brix levels fluctuate at different locations within the plant. There are often big differences between old leaves and new leaves, or spur leaves and new shoot growth, or on the fruit leaf or ear leaf. It is very common for the fruit and the leaves most closely associated with the fruit to be the lowest Brix. This is true because the fruit often has the highest nutritional requirement, and is the last location for nutritional integrity to be achieved. For this reason, we can have disease and insect resistance leaves and susceptible fruit on the same plant.

Some crops have also been bred to have artificially inflated Brix reading on the fruit in the absence of nutritional integrity, while the remainder of the plant is still very low. Sweet corn is the classical example, there are others.

Each of these described fluctuations can be significant and can produce as much as a 60%-70% swing in Brix. The less healthy a plant is, the more dramatic the fluctuations.

The location and time with the lowest Brix level determine the degree of insect or disease resistance for the whole crop.

If you wish to use Brix levels effectively as a management tool, it will require committing the time to collect regular samples, at different locations on the plant, within different fields, in different weather conditions, at the exact same time of day, at least several times per week. Because of the inherent variability, effective management is a result of managing the trend, not each individual measurement.

Many growers don’t have the bandwidth to develop the degree of familiarity needed with Brix readings to use it as an effective tool. This is where sap analysis becomes a useful tool, because it requires less time, less familiarity, and because it can identify immediately which nutrients should be addressed.

To be clear, I am a fan of Brix readings, and developing familiarity with what it can tell us about a crop. However, we need to be clear-eyed about its limitations, and what is required for it to be used effectively. I know of only a handful of commercial-scale growers that use it to the degree necessary to get good results.

What aspects of Brix readings did I miss?

John Kempf2020-04-21T11:44:03-05:00April 21st, 2020|Tags: brix, refractometer|

Nutritional influence on freeze damage

It is common to hear growers describe the influence of nutrition management on improving freezing resistance. There are several possible mechanisms that reduce the freezing temperature of the fluid within the cell. We have observed freezing resistance gains of about 6 degrees Fahrenheit.

When sugar content increases, this will have the effect of reducing the freezing temperature, just like when you put too much sugar in the ice cream.

Potassium, chloride, sodium, nitrates, or magnesium are electrolytes, when the levels of these nutrients increase, it reduces the freezing temperature much like salt lowers the freezing temperature of water. Of course, there is a very large downside to having high levels of these nutrients, because a high EC within plant sap also weakens cell membranes. A delicate balance needs to be maintained with these nutrients.

Field experience suggests that elevated levels of trace minerals, particularly manganese and boron, but also zinc, copper, iron and cobalt can reduce freezing temperatures significantly, and within days or hours of application, even when plants are dormant. I don’t have a hypothesis for how this might work, I just know it does. Seaweed applications are also known to have this effect.

Here is a photo of a rye crop in KS earlier this spring. Part of the field received a foliar application of Forage Foliar blend, which includes the trace minerals mentioned and seaweed on April 2nd. There were overnight low temperatures ranging from the low to high 20’s Fahrenheit on April 10, 11, and 12. The foliar application line is clearly visible at a distance, where the untreated plants have a good bit of frost damage, and the foliar treated plants have none. This photo is of the spray line boundary, with treated plants on the lower left.

John Kempf2020-04-18T07:01:37-05:00April 17th, 2020|

Keeping inoculants on the seed

If microbial inoculants are to be effective as seed treatments they need to remain attached to the seed until they arrive in the soil. Some products, such as mychorrizal fungi inoculant, can have a fairly large particle size, and does not stick to seed very well, particularly smooth seeds such as beans.

The last thing we want to see is accumulated inoculant at the bottom of the seed hopper when we get done planting.

When you apply seed treatments yourself, lightly spray a sugar-water solution onto the seed before the inoculant is applied. This serves to make the seed slightly sticky, and microbial powders remain strongly attached to the seed.

John Kempf2020-04-11T15:39:36-05:00April 13th, 2020|Tags: inoculants, seed treatments|

Do you want high oxygen content air? Increase carbon dioxide.

Plants photosnythesize better with an abundance of CO2. Animals thrive with abundant levels of oxygen. The time periods in earth’s history when we had the largest plants, the largest animals, and the highest concentrations of CO2 and oxygen all coincide. It is intersting to imagine how the world might have been different then. It was certainly was very different than our world today, and as the levels of these gasses change in our atmosphere, we should expect plants to grow differently over time.

From the Regenerative Agriculture Podcast with Jerry Hatfield:

John: Jerry, when you spoke about growing in grow chambers, you mentioned that you saw an increase in oxygen content, as well as CO₂. This is something worth elaborating on, because I’ve observed the same thing in the field when we have plants that are photosynthesizing well.

Many people have this idea that there is a conflict between CO₂ concentrations and oxygen concentrations. And I don’t see it that way at all. When we have higher CO₂—specifically when we have higher CO₂ being released from the soil—and when we have good photosynthesis, we get higher oxygen content in the air.

Jerry: That’s correct. And that’s counter to our thought process. You only see that when you start measuring both things simultaneously. I’ve been looking at the literature on the number of papers that actually measure oxygen content within the soil—even the CO₂ content within the soil. It’s really pretty sparse.

It’s not a trade-off between oxygen and CO₂. A good biological system generates more CO₂ because the soil has more pores and more structure to allow gas exchange to occur. That keeps our oxygen content high, which then promotes more biological activity, which generates more CO₂.

John Kempf2020-04-20T11:17:46-05:00April 10th, 2020|Tags: carbon dioxide, Jerry Hatfield, oxygen, quality agriculture book excerpt|

Which does the most damage, tillage, herbicide, or fertilizer?

When growers discuss the damage to soil biology from herbicide applications, and possible alternatives, one of the first questions/justifications is: “Doesn’t tillage harm the soil more than herbicide applications?” Michael McNeill believes applied products often have a bigger negative contribution than tillage.

From the Regenerative Agriculture Podcast with Michael McNeill:

John: You’ve iterated several times that you have to stop doing what inflicted the damage in the first place. What I heard you saying was that it’s really the herbicides and fungicides and the insecticide applications that are causing this degradation of soil health. And I heard you mentioned that these herbicides and these various pesticides that people are applying are actually chelation agents.

Why do you believe that these products are the causal agent for the suppression of soil health? Couldn’t it also be the extensive tillage that we had for a number of decades and some of these other contributing factors?

Michael: Well, I have some farms that I feel are way over-tilled. They’re organic farmers. They really do till excessively, in my mind. But it doesn’t seem to be bothering the soil at all. It isn’t quite as good as I’d like to see it, but as long as they’re keeping their organic matter up, preventing erosion, using cover crops, and that sort of thing, the tillage in itself doesn’t seem to be doing as much damage as I originally thought it would.

Now, having said that, you have to be careful which tillage tools you use. A disc is not a very good tillage tool to be using—it causes compaction, it fractures the soil structure much worse than a tined implement that you could pull through—whether that be a v-ripper or a narrow-pointed field cultivator. These kinds of things do not seem to do the structural damage that I see with things like the disc, or even like a moldboard plow or a field cultivator with sweeps on it.

John: In essence, you’re saying that tillage doesn’t have the damaging effects on soil health that the herbicides do, from your perspective.

Michael: It’s not as bad as the herbicides, not as bad as anhydrous ammonia, and not as bad as the high-salt fertilizers. They tend to be more of an issue. And when you put them all together, it overwhelms the soil-life system.

John: I understand the impact of anhydrous ammonia and salt fertilizers—both of those are very oxidizing and can have the potential to produce a lot of damage to the soil’s microbial community. But I don’t understand how herbicides would have that same effect. You mentioned herbicides being chelating agents. From your perspective, how is it that herbicides and these various pesticides have such a damaging effect on soil health?

Michael: We have not paid a lot of attention to micronutrients in the soil. Micronutrients are extremely important to plant growth. And they are readily and easily chelated by the pesticides that we use. And once you tie them up, you start shutting down significant pathways. That’s where my physiology training and background came into play—when I started seeing a lot of these physiological processes being shut down.

An example people are probably familiar with is that if you chelate manganese and tie it up, you shut down the shikimate pathway. When you shut that down, diseases can move in very quickly, because that’s sort of the plant’s immune system, if you will. If you shut that down, you have to buy fungicides. You put on the fungicides to protect your plant from the disease that’s invaded, and then you start killing more of the fungal life in the soil. And it’s a vicious, vicious cycle that you’ve set up.

John Kempf2020-04-20T11:17:36-05:00April 8th, 2020|Tags: anhydrous ammonia, degradation cycle, Michael McNeill, pesticides, quality agriculture book excerpt, salt fertilizer, soil health, soil regeneration, tillage|

Considerations for spraying microbial applications

To produce the most effective response from applications that contain living microbes, we need to consider the path through the sprayer nozzle and the environment on the leaf surface or within the soil once the product is applied.

It is best to have spray pressures below 55 psi to reduce or avoid sheer at the nozzle. Higher pressures can produce a sheer force with a markedly negative effect on living organisms in the solution.

When applying products that are suspended in solution and with larger particle size, such as mycorrhizal fungi which can have a spore size up to 50 microns, use larger nozzle and screen sizes. We generally recommend a 50 mesh screen or even no screen in some cases.

When applying products to the soil surface that will not be incorporated, add humic substances or dark-colored material such as molasses to the solution to protect organisms from UV. I suspect (but don’t know for certain) that this may be less necessary when applying to the leaf surface, since organisms which can survive on the leaf surface can likely handle UV exposure.

Combine the inoculant with a biostimulant to develop a ‘synergistic stack’ of products that produces a much greater performance than either product by itself. These could be materials such as humic substances, seaweeds, food sources, prebiotics, enzymes, etc.

And by all means, avoid adding antimicrobials into the spray solution, at any concentration. This means you don’t use water that contains chlorine, chloramines, or anything with a similar antimicrobial purpose. Don’t add ionic or salt forms of boron, zinc, manganese, or copper. After all, in the right concentrations, each of these minerals are very effective antimicrobials. We need to consider not only the solution in the spray tank but also the concentration of the droplet when it begins drying on the leaf surface or soil surface.

Field experience indicates it seems to be ok to add chelated or complexed forms of these minerals that aren’t immediately absorbed by the microbes in the solution, yet are quickly absorbed by the plant while the droplet is still liquid on the leaf surface.

John Kempf2020-04-06T18:14:27-05:00April 7th, 2020|Tags: biostimulants, foliar feeding, inoculants, microbials|