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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.

2020-04-20T11:17:22-05:00April 2nd, 2020|Tags: , , , , , |

Valuation of regenerative agriculture management

How do we value the ecosystems services that regenerative agriculture management contributes? How do we account the cost of ecosystem damages that present mainstream agriculture contributes? Some thoughts from Jerry Hatfield:

From the Regenerative Agriculture Podcast with Jerry Hatfield:

John: And because we can’t see into it very well, we struggle to understand how to value it. What is the true value of biology? And I think this is a particularly challenging question in the context of agriculture because our agricultural economics are screwed up. We have an agribusiness ecosystem that has developed in which our crops have generally become commodities, operating on very low margins, combined with the challenge that we have historically externalized many of our costs. We have externalized the environmental pollution that has been caused by some of the toxins and pesticides that we’ve used—fertilizers, nitrates in water, etc.

So, when we look at all these factors from a macro perspective, what is the value of regenerative agriculture? What’s the cost of it? And what’s the return?

Jerry: I’ve often given talks to people who’ve asked the value of carbon, and I tell them it’s priceless. But they don’t want to accept that answer.

I think we’re at the point in agriculture where we need to move away from just talking about agriculture and begin to think about agroecology. How does agriculture fit into the ecological system? What’s the value of its different ecosystem services? What is the impact of agriculture on water quality, on water quantity? What’s the impact on the biological services that we see within the soil? What’s the impact on the biological activity we see associated with that agricultural field? How do we even look at that landscape from a different perspective? So, I think that when we start looking at that context of agriculture, then we can really have a fruitful discussion about the value of regenerative agriculture.

In regenerative agriculture, as we improve carbon, we improve water. And we also improve nutrient cycling within the soil. And not only nitrogen, but phosphorus and potassium and all the micronutrients. All of those pieces are now linked together, and those things pay me dividends.

As an example, take a silt-loam soil with 2 percent organic matter in it, and assume five-foot-tall corn in the middle of August in the Midwest. This is using water at its maximum rate. That plant has about eight days of available water before it begins to be stressed.

That’s not very much. But if there’s 4 percent organic matter, the plant can go for thirteen days without water. You’ve got five more days of available water for that plant to perform to its optimum, without stress. The probability of getting rainfall during a five-day period across the Midwest is still pretty good. My point is that this is one of the ways regenerative agriculture produces value.

The other thing we see is that when we enhance nutrient cycling, we have a greener plant—a more photosynthetically efficient plant—so that more carbohydrates go into that plant. This not only improves grain production—it also continues to feed that root system so that it becomes more effective all the time.

That’s where yield stability comes from. We will become less affected by the weather variation that is going on—the longer periods of time between rainfall events.

You’ll always have parts of a field that are low yielding. The high-yielding parts of that field are always really good soils. The low-yielding parts are always those really poor soils that have low water availability and low nutrient availability.

2020-04-20T11:17:12-05:00March 31st, 2020|Tags: , , , , |

When to use inoculants to regenerate soil

In our experience, when microbial inoculants are applied as part of a different nutrition management system, they have consistently been some of the most significant ROI applications, and produce dramatic changes in soil health. Yet, many growers buy ‘bugs in a jug’ and see little or no response. When this happens, it often because the applied inoculant was put into the wrong environment, was not supported with biostimulants, or fertilizer and pesticide applications were continued. Don’t expect to continue managing everything else the same, and a microbial inoculant will change soil biology. The biology became degraded in the first place because of management practices and product applications. If these remain the same, don’t expect biology to make a miraculous comeback.

From the Regenerative Agriculture Podcast with Michael McNeill:

John: When you have a degraded system like that—where there are suppressed yields and suppressed soil health, as you’re describing it—how do you go from depressed yields of 70 to 90 bushels per acre back up to 200, with aspirations of going back up to 250 bushels per acre? How do you achieve that?

Michael: Well, it’s a long, hard task. There aren’t any silver bullets. You have to figure out what was going wrong and stop doing that—that’s number one. Number two, you’re going to have to look at what it’s going to take to remediate the soil. Has the soil become really hard—hard like a road? I get penetrometer readings where it takes 500 pounds of downward pressure to penetrate the top two inches of the soil—that’s hard. That’s just like a gravel road. A crop will not grow in that.

When they tilling it, it’s breaking up into chunks. And then when it rains, it puddles and it just seals over. And so we get no oxygen into the soil. You have to incorporate some tillage, and then you have to start providing some food for the microbial life—which is almost non-existent. It’s not non-existent, because you can bring it back—that’s the good news. If you don’t let this thing go too long, you can bring it back.

Now whether we’re bringing all of it back or not, I don’t know. But once you get it started coming back, then you can look at inoculating with mycorrhizae and some of the things—the pseudomonads, the actinomycetes—that could be missing, and stimulate them. But first, you have to get oxygen into the soil, get the water working correctly, and get the food right. There’s no magic in inoculating the soil—if it’s loaded with poison, it will kill your inoculant. You have to fix that problem first before you try inoculating. You wouldn’t have to do an inoculation, but it does speed it up—you gain about a year, maybe two years, when you do that.

I see people thinking they’re buying a magic silver bullet by inoculating, but then they continue to do the things that caused their soil to die in the first place. And they’re not winning. They’re losing.

2020-04-20T11:16:52-05:00March 30th, 2020|Tags: , , , , , |

Free online course from academy.regen.ag

Imagine being able to identify the groups of diseases or insects your crops might be susceptible to, well before they are present. 

Imagine knowing exactly how to manage nitrogen and nutrition applications to prevent possible infections from occurring. 

Both of there are possible and more when we understand redox, and the ways different products and management practices influence soil redox poising and balance. 

Olivier Husson is the best instructor I know in describing the impact and opportunities in managing redox activity in our soils. I interviewed Olivier for an introduction to the topic on the podcast here.

I very highly recommend his in-depth course that is available for free on the Academy titled: Redox Potential: Eh and pH as Indicators of Soil, Plant, and Animal Health and Quality

You will be surprised and delighted with the knowledge you gain. 

2020-03-27T15:22:21-05:00March 28th, 2020|Tags: , |

Pesticides as a cause of soil degradation

Many agronomists and farmers with three or four decades of experience describe how soil health deteriorated quickly when herbicide and pesticide use became mainstream. Michael McNeill shares his observations.

From the Regenerative Agriculture Podcast with Michael McNeill:

John: And when you say you have about 165,000 acres that you work on today, what is the scope of the work you do on each of these farms?

Michael: Most of it is working with soil health and soil fertility, and helping growers select the right genetics for the fertility programs that they’re working with. Soil health is becoming a bigger and bigger issue for me to deal with. When I first started, it wasn’t a really big issue. It’s huge now. And so I’m devoting more of my time now to soil health than I ever thought I would.

John: I’d love to talk about that a little bit—when you say that soil health didn’t used to be a big issue, and now you’re spending a lot of time on it, what changed with soil health? How are you managing it differently today than you were twenty or thirty years ago?

Michael: Well, it’s interesting that you would ask me that, John. The other day I was cleaning out a drawer in my desk, and I found some old pictures that I had taken back in 1972 or 1973 of crops that were growing. I had some close-ups and some overviews of the field. The thing that I noticed was how healthy the plants were. There were no disease lesions on them anywhere. The corn plants were just perfect. And the whole field was that way.

It’s really hard to find a field today that is that way. I was looking at the weeds that were growing along the fence rows, and they were big and healthy and looked great. They don’t look so good today, comparatively speaking. And you say, “Well, maybe that’s a good thing!” No, it’s not. The whole area that we’re farming is unhealthy. It makes me ask the question—what’s changed?

To me, the big difference from that era until today is that farmers have been drawn into big ag. You need to use herbicides. You don’t want to use a cultivator. You have to farm more land. So you use herbicides, but herbicides are doing things to the soil, because they’re all chelators. So now the plants become a little bit imbalanced in the nutrition that they’re taking up, and you find more disease—you find more insect pressure. So you start using fungicides and insecticides—more chelators, more poisons being dumped onto the ground. And you’re pretty impressed with how they work. The field is perfectly clean, and weed free—excellent. The diseases were dramatically reduced. The fungicides worked really well. The corn borers and some other of the insects that were issues went away. It was magic. The chemistry was totally magic—it looked beautiful.

But as time went on, the chemistry started poisoning the good things that were in the soil. And so, today, I’m called out to look at farms where the guy’s production has dropped off dramatically and the soil is virtually dead.

John: When you say the production has dropped off dramatically, what have you observed?

Michael: Looking at ten-year crop insurance records, the guy was getting 190 to 210 bushels per acre and had around a 200-bushel 10-year average. Excellent, excellent yields. Now it’s getting 70- and 80-bushel yields. That’s dramatic, and it will put him out of business very quickly.

John: That is very dramatic.

Michael: This isn’t just happening on a little field here, a farm there. I’m seeing 8,000- and 10,000-acre farms that this has happened to. And that really, really woke me up. I started seeing this about five years ago. I’ve been working with these growers who are asking me whether I can help them remediate that. Can I help bring the farm back? And in a three- to four-year period, we’ve had pretty good success. I would say we’re back now at where we were when this crashed.

The farmers are excited that they can now take it to a different level—to the 250-bushel range or greater. And they can see growth and potential and doing what they’re doing. They’ve moved away from GMO crops, and they’ve particularly moved away from glyphosate.

2020-04-20T11:16:10-05:00March 27th, 2020|Tags: , , , , , , |

Corn root system development

We routinely harvest only a fraction of the genetic potential our crops are capable of. Few of us actually know what a really healthy crop actually looks like anymore. Here is an image that describes what is possible.
This is a photo of corn root system from Al Trouse, from a demonstration conducted at the National Soil Laboratory at Auburn University.
The photo and notes below were shared by Jim Martindale from Cursebuster, who heard Al Trouse’s presentation to a group of Brookside consultants approximately 1979 or 1980.
In this demonstration, soil was sifted into a growth chamber so it would have a uniform density (other than gravitational pull). In this growth chamber with uniform soil density, the seminal roots reached the bottom of the chamber (6+ feet) in a few days.
Growing roots extend very rapidly though the soil until they encounter any change in soil density. When they encounter either an increase or decrease in soil density, they temporarily stop extending, and then slowly begin growing once more. If the soil density is uniform, they will extend very rapidly during the root systems establishment phase. Each growing root tip will extend for 72 hours, and stop growing after that period. The rapidly growing tips grew to the bottom of the growth chamber in 72 hours or less.
During the establishment phase, plants expand their seminal root system as widely and deeply as possible. This phase lasts for about 40 days, until the ear embryo begins to form. The outer root system boundaries are established during this phase. Future root growth does not expand past the established borders. What might this mean for cultivation close to the 40 day mark? Disturbing root systems at this point doesn’t seem like a wise idea.
Once the embryo begins to form, the root system shifts to the expansion phase, where fine roots emanate from the seminal root mass that has already been established, and fill the zone inside the established boundaries. This root system expansion period lasts until pollen drop. After the plant has dropped pollen, no additional root system development takes place.
The normal precipitation rate for Auburn University for the growing season was added with no fertilization.
Yields were estimated at 400 bushel per acre at normal plant density.
Each of the large blocks in the photo below ris 12 inches, total depth from the surface is 78 inches.
We have lots of upward potential left. I have never seen a corn plant in the field with a comparable root system.
2020-03-26T07:07:14-05:00March 26th, 2020|Tags: , , , , |

Losing a thousand pounds of carbon per acre per year

From the Regenerative Agriculture Podcast with Jerry Hatfield:

John: When I think about the differences between sustainable agriculture and regenerative agriculture, the approach we’ve taken in our work is that regenerative agriculture is all about helping plants get to peak photosynthesis, produce an abundance of carbohydrates, and move those carbohydrates into the soil, where you have a very functional carbon cycle working. You’re constantly accelerating plant health and constantly accelerating soil health.

What I’ve realized is that when we think about the entire soil-plant system—as an ecosystem—you have photosynthesis, which is the way you bring new energy into the ecosystem, and you have soil biology, which processes that energy into soil. And that total energy flow—voltage, if you will—is reflected in the carbon cycle, the carbon exchange.

How does the carbon cycle shift and change when growers begin managing soils and crops differently—with regenerative management, rather than with present mainstream management?

Jerry: We do a lot of work in corn-soybean systems. Over the past seventeen years, looking at the exchanges of carbon between the plant, the atmosphere, and the soil, we’ve shown that our typical corn-soybean system is losing a thousand pounds of carbon per acre per year. This is with maybe a deep rip in the fall and field cultivation in spring, and the only thing taken off the land is the grain of corn and soybeans.

And think about the average life of a producer. Farming forty years, they’ve lost 40,000 pounds of carbon—twenty tons. It’s a slow loss, but that slow loss is impacting the aggregate stability of their soils. The farmer realizes he’s losing productivity, that it’s different than it was before, but he doesn’t come to the realization that it’s the cumulative effect of what he’s been doing over his farming career.

That’s a dynamic that we need to consider when we talk about why fields become variable overtime. But on the other hand, we can change that system quickly. And I think this is the framework that we need to be talking about. When we go to a system where we add cover crops, and we reduce the tillage intensity by going to strip-till or no-till, we find that within one year we can change that negative carbon balance into a positive carbon balance. Then we can put more dividends from that plant back into the soil biology. We go from a negative to a positive carbon balance.

John: In a single year? That is amazing.

Jerry: Yes, and even more amazing is that over a two-year period we doubled the microbial biomass in the upper twelve inches of that profile. And these are not test plots. These are 160-acre fields, and they’re sampled at 150-foot grids. So there are a large number of samples coming out of those 160 acres. We were able to improve the biology very, very quickly.

And we’ve already begun to change the upper surface of that soil. The cover crop is giving us a longer period of time in which to take carbon dioxide out of the atmosphere—converting it into carbohydrates, putting it back into the soil, and feeding that soil biology.

I always tell producers that biology wants four things. It wants food, water, air, and shelter. These are the basic necessities of life that you and I want. We should start thinking about biology from that perspective. They want a food source, just like you and I like to eat every day. In a lot of our systems we were only growing a crop during the summer. There was a long period of time on either end of the growing season when we weren’t feeding the soil biology. It had to exist on what was there, and that’s pretty much a starvation diet. If we didn’t eat three months out of a year, we’d probably be fairly thin.

Cover crops utilize a lot of solar radiation. If we don’t have a crop growing, that sunlight is just going into the surface of the earth and isn’t doing anything for us.

2020-04-20T11:16:31-05:00March 25th, 2020|Tags: , , , , , , |

Pesticide safety assessments

A thought-provoking quote from Jonathan Lundgren on the Regenerative Agriculture Podcast:

My research focuses on two general areas. One is the risk assessment of pesticides and genetically modified crops and, basically, farm management practices in general. And then the other half is working on developing sustainable systems. So, I’ve got quite a bit of experience in understanding the ecological risk assessment in the framework that we use for trying to determine whether a particular agrochemical or something is safe or not safe. I’ve advised the US EPA. I’ve been on advisory panels for the European version of the EPA, the Brazilian government, the United Nations and their conference on biodiversity. And after twenty years of studying this, I can honestly say that when you look at the side of a jug and it says that it’s safe, that is meaningless.

You can go out and you can buy something off of the shelf and it’s labeled and it’s regulated. Nobody is watching. Nobody is watching! Risk assessment is incredibly hard. And we can get closer to the mark with scientific approaches to risk assessment, but again—when you understand the complexity of the natural world . . . ! 

Right now, just for pesticides, there are a couple of hundred different pesticides whose active ingredient is registered with the EPA. And that’s where most of the safety assessments are focused—on those active ingredients. But whenever you add an adjuvant—maybe it’s a sticker or a spreader or a defoaming agent or whatever—it changes the toxicology of that active ingredient such that the risk assessment that you’re actually performing on an active ingredient really does not hold much weight anymore. And think about all of the formulated products—there are 20,000 formulated pesticides in the US, and each of those pesticides would require an independent ecological risk assessment—each of them. 

We don’t have the first inkling of what the implications of these things are, be it glyphosate, neonicotinoids, propiconazole, or the adjuvants, which are sometimes more toxic than the active ingredient in terms of its ecological effects. And we’re not just talking about the soil, right? We’re talking about human health problems. Farmers have the highest suicide rate of any career at this point in the US. And we know that pesticide use is linked with depression. The science has been done on that. I mean, are we killing ourselves?

From: Ecosystem Diversity Prevents Insect Pressure with Jonathan Lundgren

 
2020-03-23T14:17:53-05:00March 24th, 2020|Tags: , , |

Selenium for Coronavirus, Agriculture for Public Health

The foundational purpose of agriculture is to grow nutritious food and healthy fiber. The often-repeated marketing mantra of agribusiness to justify the use of products and practices of questionable repute is “We need to feed the world.”

What if agriculture took this mantra to heart, and considered their possible role and responsibility for public nutrition and public health?

What if nutritious food as medicine were considered a national security priority, and producers were directed and compensated for producing food with a positive impact on public health?

The present panic around coronavirus is a case in point where the nutritional integrity of the food farmers produce might have a significant and direct impact on public health.

“It is generally known that Se deficiency, both in the agricultural food products and in the human organism, is associated with various degenerative diseases, notably in viral infections.”1 Lipinski describes how selenite is an effective treatment for enveloped viruses. The majority of viral infections we are concerned about are enveloped viruses,  including the common cold, influenza, Ebola, and coronavirus.

How might public health be different if all the food being grown contained adequate levels of selenium to prevent viral infections in the general population?

It seems reasonable to imagine that cold and flu infections might drop to levels approaching zero, and possibly, probably even, coronavirus would be unable to gain enough momentum to be called a pandemic.

Finland made a systemic effort to increase selenium levels in their soils and has been successful in raising the selenium status of their population according to this report.2  This is an example of the capacity agriculture has to influence public health.

The language around regenerative agriculture is still evolving. There is a well-understood need to regenerate soil health. Of equal importance is regenerating plant health and livestock health. Ultimately though, we should be having a conversation about regenerating public health.

Farmers can have a bigger impact on public health than doctors and hospitals because nutritious food as medicine can prevent people from becoming ill. This is something doctors and hospitals are not engaged in.

Lets not just “feed the world”, let’s feed the world healthy and nutritious food as medicine.

(And if you are curious about further implications of selenium for public health, look up the dozens of papers describing selenium as an effective cancer treatment on Google Scholar.)

 

Post update May 2nd, 2020. Emerging research indicates there is indeed a connection between selenium status within a population and Covid 19 cure rate.3 You can read a popular article describing the findings here.

1. Lipinski, B. Can Selenite be an Ultimate Inhibitor of Ebola and Other Viral Infections? 6, 319–324 (2015).

2. Stoffaneller, R. & Morse, N. L. A review of dietary selenium intake and selenium status in Europe and the Middle East. Nutrients 7, 1494–1537 (2015).

3. Zhang, J., Taylor, E. W., Bennett, K., Saad, R. & Rayman, M. P. Association between regional selenium status and reported outcome of COVID-19 cases in China. Am. J. Clin. Nutr. (2020) doi:10.1093/ajcn/nqaa095.

PS If you are reading this on social media, you can subscribe here and get each new post in your inbox.

 

2020-05-02T08:24:07-05:00March 23rd, 2020|Tags: , , , |

The ineffectiveness of potassium chloride as a fertilizer

The three primary nutrients fertilizer companies want to sell farmers in large quantities are N-P-K.

While many crops require as much or more more calcium than nitrogen and potassium, and as much or more sulfur than phosphorus, these nutrients are less profitable to sell, and don’t produce the marketing incentives NPK fertilizers do.

We know that we can grow all of the nitrogen our crops require. Biology can sequester and ‘fix’ some of the 35,000 pounds of nitrogen above each acre, more than enough to supply 100% of a crop’s requirements.

We know that mycorrhizal fungi and phosphorus solubilizing bacteria can solubilize abundant phosphorus and supply all of a crop’s phosphorus requirements, as long as the parent soil material contains phosphorus that can be released. (Which most soils do)

Of course, for the biology to supply either adequate N or P, there needs to be an abundant microbial population that is well supported and has a strong food source from living roots systems.

The realization of these possibilities has led many farmers to greatly reduce or completely eliminate N and P applications. This leaves potassium as the remaining nutrient common in mainstream fertilizers that growers are wondering if it is safe to no longer apply.

The answer is dependent on context of course, as it is for N and P, but for most soils, and for most crops, there are no yield benefits from applications of potassium chloride fertilization. There are significant negative effects on crop quality and soil health produced by potassium chloride fertilization.  Arden Andersen wrote about the damaging impacts of potassium chloride in Science in Agriculture.

Richard Mulvaney and colleagues have published two must-read papers on the lack of value from potassium fertilization. They indicate there is no correlation between potassium levels that show up on common soil analysis and the quantity of potassium delivered to a crop, that soil potassium levels continue to increase even with crop removal and no applications, and that there is no yield response from potassium chloride applications.

Here are a few excerpts, and you definitely want to read the full papers linked below.1,2

These evaluations leave no alternative but to question the practical utility of soil K testing because test values cannot account for the highly dynamic interchange between exchangeable and non-exchangeable K, exhibit serious temporal instability with or without air drying and do not differentiate soil K buildup from depletion. The need for routine K fertilization should also be questioned, considering the magnitude and inorganic occurrence of profile reserves, the recycling of K in crop residues and the preferential nature of K uptake. An extensive survey of more than 2100 yield response trials confirmed that KCl fertilization is unlikely to increase crop yield. Contrary to the inculcated perception of KCl as a qualitative commodity, more than 1400 field trials predominately documented a detrimental effect of this fertilizer on the quality of major food, feed and fiber crops, with serious implications for soil productivity and human health. 

By 2005, following 130 years of K removal, test values for these subplots were within the range of critical levels calibrated for North America43, which would normally be inter- preted as evidence of successful fertilizer K management. 

The most disturbing disparities involved 17 trials in which test levels were either constant or increased while crop K removal far exceeded fertilizer inputs or occurred in the complete absence of fertilization. Such obvious incon- gruities, paralleling what was found for the Morrow Plots (Table 1), leave little alternative but to question the validity of soil testing for exchangeable K.

Besides being abundant in soils and plant residues, K is notable as the only macronutrient dominated by inorganic forms in both the soil and plant, and thus availability is not dependent upon microbial transformations. 

As hypothesized, KCl fertilization was often ineffective for increasing productivity, according to non- significant responses that occurred in approximately 76% of the total trials surveyed.

Most of the responses where positive and occurred on coarse-textured, organic or highly weathered soils inherently low in K-supplying power (231 site-years); when the above-ground residues were removed (191 site-years); with crops having a shallow or low-density rooting system (62 site-years); and/or when subsoil rooting was restricted (12 site-years). In the absence of such factors, there is very little reason to expect a significant yield response to KCl fertilization. 

Yield reductions due to KCl fertilization, as documented in Table 4, can be explained by the high salt index of this fertilizer, which has been implicated as a detrimental factor for crop germination and growth and microbial processes.

Many leguminous crops are sensitive to Cl− toxicity, including soybean and alfalfa, and Cl− can reduce soil N availability by inhibiting nitrification in soils and by acting as a competitive anion that suppresses plant uptake of NO3. A further difficulty arises from the mobility of Cl− in soils, which intensifies leaching of Ca2+ as a counterion.

Producers have long been led to believe that KCl fertilization serves an essential role, not only for sustaining crop yield but more importantly, for ensuring a high-quality product that will maximize economic return. To ascertain the credibility of the latter claim, a thorough survey was undertaken of peer-reviewed and university publications that provide the most reliable source of information regarding the agronomic effects of KCl. The findings, summarized in Table 5 for more than 1000 field experiments, altogether contradict the prevailing belief in the value of this fertilizer for improving crop quality, since the frequency of positive responses was only about 8%. On the contrary, the qualitative effect of KCl was negative in 57% of the trials surveyed. In some of these trials, crop quality was reduced despite a significant yield increase.

A cumulative effect on soil physical and chemical properties would be expected since K is prone to interlayer fixation that collapses 2:1 clay minerals and converts an active, swelling smectite to an inactive, non-swelling illite. The stabilizing value of KCl has long been recognized in the construction of impervious pavement and foundations.

Unfortunately, the agronomic consequences include a loss of CEC and lower water-holding capacity, which is not conducive to crop growth and productivity. 

Since the onset of industrialized agriculture more than half a century ago, the view has been inculcated that intensive inputs of fertilizer K are indispensable for maximizing crop yield and quality and for the long-term maintenance of soil productivity. This view cannot be reconciled with the considerable volume of scientific evidence presented herein, encompassing soil testing for plant-available K and the consequences of KCl fertilization for agricultural productivity, food safety, and soil degradation.

If fertilizer K usage is to be profitable in a production setting, current recommendations that rely on soil testing for exchangeable K will no longer suffice. As a more viable alternative, producers should periodically carry out their own strip trials, for comparing yield with and without upward and downward K rate adjustment. Initially, a 3-year period would be appropriate for repeating these trials, but a longer interval could safely be employed with cash-grain cropping that limits K removal. To avoid the adverse consequences of Cl−, K2SO4 would be preferred as a fertilizer source. 

For many years, crop potassium (K) availability has been estimated by soil testing the plow layer for exchangeable K, in conjunction with potassium chloride fertilization widely promoted as an essential prerequisite for ensuring crop yield and quality. As rigorously documented in our paper, both components of chemical-based K management are seriously flawed by the lack of a scientific basis. Under the pretext of providing economic benefit for the producer and a healthy food supply for the public at large, the real purpose is to generate revenue for the fertilizer industry. 

If crop K uptake originates from huge K reserves throughout the soil profile, the question naturally arises as to whether producers can expect a profitable return from annual or biennial applications of KCl. The answer is a resounding NO.

We stand by our two principal contentions that: (1) soil testing for Exch-K is of no use for predicting crop K availability or assessing soil K buildup/depletion; and (2) KCl fertilization is often superfluous for increasing crop yield and quality and can have a detrimental effect on soil productivity and human health. Both these points are strongly supported by the extensive literature citations in our paper, covering peer-reviewed publications from field and laboratory research

The prevailing approach to K management is invariably advocated under the pretext of providing economic benefit for the producer and a healthy food supply for the public at large, but the real purpose is to generate revenue for the fertilizer industry. This is the essence of a paradox, not a dilemma.

Back to John:

In some contexts, potassium applications are indeed needed. When this is the case, we should use potassium sulfate, K-Mag, manure, compost, or sources of K other than potassium chloride. Potassium chloride is the most expensive form of potash you can buy, because it doesn’t work nearly as effectively as others do.

1. Ellsworth, T., Mulvaney, R. L. & Khan, S. A. The potassium paradox: Implications for soil fertility, crop production and human health. Renew. Agric. Food Syst. 29, 3–27 (2014).

2. Khan, S. A., Mulvaney, R. L. & Ellsworth, T. R. Further insights into why potassium fertility is a paradox. Renew. Agric. Food Syst. 30, 120–123 (2015).

2020-08-08T08:17:18-05:00March 20th, 2020|
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