How to Manage Potassium

Our approach to managing potash in our consulting work is we look at soil geology and at soil biology, and we give those equal or perhaps even more credit Than we do a soil analysis. There are only a few situations where we really look at the soil test and believe what the soil test says. And those are either on very light, sandy soils with a CEC of, let's say, less than eight or nine. And on soils which have had such historical intense pesticide applications. That the biology is largely dysfunctional and is mostly dead. So in either of those types of environments, then we pay attention to what the soil analysis says. And we supplement with potassium accordingly, Mostly using. If it's a dry broadcast, we'll use potassium sulfate, Some cases kmag or sulpomag. And then, if needed, to spoon feed and side rest later on, we'll often use potassium thiosulfate. Those are really kind of the only three materials we use to address potash and our preference. If we have soils that don't have much biology, but they are heavier soils, what we've observed is that generally when we have these heavier soils, Particularly if they've had historical manure applications, we get a much larger potash release Than what is described in the soil analysis. And so SAP analysis, that tool, has really given us a lot of comfort. In managing potash a little bit differently. Because we can actually measure what the plant is absorbing and whether it needs more. So what we've observed is that in many cases, when we have heavier soils with large potash reserves, we might only put on a very small amount up front. And then we will use SAP analysis. And if needed, we will plan on applying potassium thiosulfate as a liquid. Later in the growing season. The soils are capable of delivering a lot more potash. Than what the soil analysis would indicate. Then sandy soils don't have the potash reserves. That soils do With a higher CEC and more higher clay content. So there we do often supplement and broadcast potassium sulfate. And the way we approach using potassium sulfate Is that dependent on soil biology and temperatures. And which part of the growing season we're talking about. If it's a spring crop or a fall crop, we try to apply the potassium sulfate and expect to see a release curve. That it starts releasing about 45 to 60 days after application. So we try to time that release peak to occur after pollination and blossoming. So that we have the greatest supply of potash. When we're in the grain field or fruit fill stage, Potassium chloride is an absolute no go for us. Because of the effect on biology and because of the effect on clay aging, and because of the effect on those generically referred to as energy release. So what happens with potassium chloride, of course, it has a really high salt index. And that high salt index, it's also a very strong oxidizer because of that high salt index. And so what occurs when we apply potassium chloride, it releases very rapidly, very quickly. We get an almost immediate flush of chloride and potash. The chloride also significantly increases insect susceptibility in our crops. But in the soils, we get this tremendous spike of electrical conductivity. And that EC spike is coming from two places. One, it's coming from the soluble salts, the soluble chlorides and potash in the soil solution. And secondly, it's also coming about as a destruction of the soil microbial population. And so you get this tremendous spike of electrical conductivity. But then it drops back down again. And unfortunately, it drops down even lower than it was before the potassium chloride was applied. It usually drops back down even lower right during the period when the crop needs it the most. So you get this very high spike and depends on moisture and how much rainfall you get and everything else, soil type and so forth. But that spike can last as little as two weeks from it, basically from a two week to a six week period, and then it drops off. So we end up with low energy in the soil, low electrical conductivity right at the moment when the crop needs it the most. So that's one significant reason why Richard Mulvaney and his colleagues work. They describe that it often doesn't have a positive impact on yield. And I think it's because it has the wrong energy release curve. And then the other significant reason we don't use potassium chloride is because of its clay aging effect. The short version is that if you have what is termed a young clay or an expandable clay, then you have all these small clay platelets. And these platelets can separate further apart or move closer together based on hydration, based on how much water is there. So when they dry out, the plates move closer together. When they get wet, they expand apart. And soils with these young clays that don't have enough carbon, don't have enough organic matter, often crack. And you see these wide cracks and splits in the soil profile. Aged clays or non expandable clays don't have this capacity to move back and forth. They move closer together as when they are dry, and then they stay closely put together. So this means a few things. One, it means that this clay is very compactable. You can Compact it together and it stays packed together and it doesn't flocculate again very easily. Secondly, it means that when these clay platelets move closely together, all of the cations that are stored between the two plates, like potassium cations, for example, or calcium cations, cannot be released for the crop to absorb in the future. So you might have a young clay, an expandable clay, that has a cation exchange capacity of 15, and you put potassium chloride on it for 10 years at 200 pounds per acre, 200 kilograms per hectare equivalent. And over a 10 year period, you've put on a ton of potassium chloride. And that has the effect of aging that clay and the CEC that the actual cation exchange capacity can drop from a 15 down to, let's say, a 9 or a 10. And now all of those cations that were contained and held between the clay platelets are locked up and are not available for the crop to use in the future. So when you stop to think about it, the Romans destroyed Carthage by salting the land. And potassium chloride has a salt index that's higher than sodium chloride. My understanding is that when we do a soil analysis with an acid extraction, a malic 3 or an ammonium acetate extraction, we pull some of the nutrients, some of the cations off the colloids, but mostly only those on the outside, only those on the surface of the colloids. We don't really extract the nutrients that are in between those layers for the most part. It's also my understanding that generally between those layers, the nutrients that the soil test can't access or doesn't access is mostly potassium. The majority, potassium, followed by calcium and magnesium levels that are generally in ratio to what shows up on the soil analysis. And this is actually where looking at the soil's geological profile becomes important. So it's possible to run a, what is called a mining assay and look at how many pounds in total of potash and calcium and magnesium is in the soil mineral matrix. Know that for here in North America, many of our midwestern soils will have anywhere from 40 to 60,000 pounds of potash in the top 6 inches and about 30 to 40,000 pounds of calcium. So they actually have slightly less calcium than they do potassium, and then anywhere from 6 to 9,000 pounds of magnesium. So usually the cations that are held in between those plates, my understanding is that those will be generally in ratio with the total geological profile of minerals of what's actually available.

If you need to supplement potassium during the growing season, one of the more effective materials to rapidly improve the potassium status of a crop is our hollow K, which is a very available chelated potassium that can be efficiently absorbed both through the leaves and when applied to the soil. You can learn more about Holok on our website or connect with the team at AEA at 800-495-6603. If you want to learn more information about Holokay.