# Potassium - liquid vs granular



## davegravy (Jul 25, 2019)

Other than method of application and % of AI, are there any functional differences between liquid and granular SOP? Does liquid get incorporated into the soil and become plant available more quickly?

I ask because I have some granular and as a test I tried dissolving it in water. It did dissolve eventually but it took a long time and a lot of stirring. I imagine it would be many rainfalls before it distributed into the soil.

Is there any reason I can't dissolve my granular SOP into hot or boiling water, and then apply the solution to my lawn as a liquid with an appropriate amount of carrier water? Are there any safety issues with this, like noxious fumes?


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## davegravy (Jul 25, 2019)

@Babameca you're a chemical engineer, right? Thoughts?

I could combine with urea or AS at the apropriate ratio to get a custom-balanced fast release liquid fertilizer?


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## Babameca (Jul 29, 2019)

@davegravy There are many foliar ferts on the market that are balanced. So, your logic is sound. On the other side, K is not 'continuously' needed by the plant. Potassium is also a metal, which, I assume, resides in the soil in its ion form. Nitrogen is a gas. The mechanism those two are absorbed by the plant, their soil life is very different. So, I would stick to soil enrichment of K and dedicate spraying to Nitrogen.


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## CarolinaCuttin (Sep 6, 2019)

Babameca said:


> @davegravy There are many foliar ferts on the market that are balanced. So, your logic is sound. On the other side, K is not 'continuously' needed by the plant. Potassium is also a metal, which, I assume, resides in the soil in its ion form. Nitrogen is a gas. The mechanism those two are absorbed by the plant, their soil life is very different. So, I would stick to soil enrichment of K and dedicate spraying to Nitrogen.


I'm confused here. Elemental nitrogen (N2) is a gas, but the only plant-available forms (and the forms typically seen in fertilizers) are NO3- and NH4+ which exist as ions in solution when sprayed and in the soil. K+ is the same way, so I don't see the argument against foliar applications of potassium. What am I missing?

IMO, the real question to ask is whether or not the nutrient can enter the plant through the leaf tissue (yes for potassium) and is the nutrient likely to get bound up in the soil (no for potassium). You should be fine with a foliar or soil application of potassium, but foliar applications will give you a quicker response. Same for nitrogen.


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## bernstem (Jan 16, 2018)

Potassium is usually present in the soil as a salt. When adding it to soil, we use Sulfate (Sulfate of Potash) or Chloride (Muriate of Potash) salts. The Chloride form is harsher on soils. I would expect there is little difference in Liquid vs granular Potassium once it gets to the soil other than the extra time for the granular to dissolve.

There is, however, data to suggest that plants grown in low or medium Potassium soils benefit from foliar application of Potassium, so direct uptake by leaves happens in some plants. Though I didn't see anything about grass, it is reasonable to assume that grass can absorb potassium from leaves. From that standpoint, liquid applications may have some benefit over granular, but likely only if your soil is deficient.


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## bernstem (Jan 16, 2018)

Plants do not use Nitrogen gas (N2). It needs to be converted to Ammonia or Nitrate to be used. Urea is an intermediate form that can be converted by bacteria or by the plant itself into usable forms of Nitrogen.

Plants will absorb Urea and Nitrates through the leaves and roots. The Urea gets converted inside the plant to usable forms. Urea absorption is more efficient than Nitrate absorbtion at the leaves based on the studies I have seen. Urea is also converted by bacteria to usable Nitrogen sources which are then given to the plants through the roots.

If you want to learn more, start by looking up the Nitrogen Cycle. It gets really complex and this is just barely touching the surface of how Nitrogen is handled in plants and ecosystems.


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## davegravy (Jul 25, 2019)

Babameca said:


> @davegravy There are many foliar ferts on the market that are balanced. So, your logic is sound. On the other side, K is not 'continuously' needed by the plant. Potassium is also a metal, which, I assume, resides in the soil in its ion form. Nitrogen is a gas. The mechanism those two are absorbed by the plant, their soil life is very different. So, I would stick to soil enrichment of K and dedicate spraying to Nitrogen.


Thanks, what do you mean by not continuously needed by the plant?

My concern is that my soil test came back very deficient in K, and it may be why I've had really bad drought tolerance for years. I'm hoping to get K to the grass as quickly as possible before the summer heat arrives (if at all possible)...and based on my observation of how difficult this granule is to dissolve I'm worried it may take a while unless I help it along.


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## Babameca (Jul 29, 2019)

@davegravy I understand your impatience to get things right, but this a marathon, not a sprint. There is no overnight cure for deficiency, maybe except for N and Fe. K is stable and 'cumulative' soil nutrient. Your soil is the reservoir and it has to be replenished. I don't remember your CEC, but if it is high, it may even longer, few seasons. Finally I have to throw my biochemical diploma...wait I am not even a bio chemist :lol: 
All will be better with massive K hit.


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## Babameca (Jul 29, 2019)

@CarolinaCuttin You are 100% right about N forms for the plant. Nitrate leaches which everything gets converted to.


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## HoosierLawnGnome (Sep 28, 2017)

davegravy said:


> Other than method of application and % of AI, are there any functional differences between liquid and granular SOP? Does liquid get incorporated into the soil and become plant available more quickly?
> 
> I ask because I have some granular and as a test I tried dissolving it in water. It did dissolve eventually but it took a long time and a lot of stirring. I imagine it would be many rainfalls before it distributed into the soil.
> 
> Is there any reason I can't dissolve my granular SOP into hot or boiling water, and then apply the solution to my lawn as a liquid with an appropriate amount of carrier water? Are there any safety issues with this, like noxious fumes?


It will gunk up your sprayer, been there done that.

It's not as water soluble as you think, certainly not in the amount you can apply with granular products.

AND, it leaves a bit of white film.

Been there tried it.


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## g-man (Jun 15, 2017)

@davegravy I just checked your soil results. Potassium deficiency starts at 37ppm if you follow MLSN. You have 56ppm, therefore you are not deficient. It is low and can be improved.

You can use potassium nitrate (don't try to buy in large qty to avoid government attention) if you want to spray. From the soil remediation guide:

Potassium Nitrate 13-0-44. Apply at 0.5lb/ksqft. The nitrogen is in the nitrate form, so it moves fast and leaches thru the soil. It is applied in liquid form and needs irrigation after to avoid foliar (4oz/ksqft foliar max). Thanks Greendoc for the info.

Getting SOP to dissolve in water and agitated to spray will be a challenge. The granular will dissolve with water/rain in the soil. No need to worry about it.


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## Mightyquinn (Jan 31, 2017)

Just FYI, they do make soluble SOP for you to spray but it's hard to find locally and is cost prohibitive to have it shipped to your house. I have used some sprayable forms in the past that dissolved just fine in water but the liquids that come pre-mixed are quite expensive regardless if you find them locally. I will also note that Potassium is the second most used nutrient behind Nitrogen in your soil/grass. I think Potassium is one nutrient people kind of forget about and not realize they probably need more then they think they do. Especially if you are trying to take your lawn to the next level.


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## bernstem (Jan 16, 2018)

HoosierLawnGnome said:


> It will gunk up your sprayer, been there done that.
> 
> It's not as water soluble as you think, certainly not in the amount you can apply with granular products.
> 
> ...


I wonder if that is the carrier agents to get it to stick together and prill and not clump with humidity. Muriate of Potash should dissolve very easily. It is just Potassium Chloride (KCl) which is used as a table salt substitute. Sulfate of Potash should be a bit less soluble, but should still go into solution fairly easily.


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## davegravy (Jul 25, 2019)

Thanks for all the responses everyone



bernstem said:


> HoosierLawnGnome said:
> 
> 
> > It will gunk up your sprayer, been there done that.
> ...


The stuff I have;



It was much harder to dissolve than my urea, but it dissolved easily in boiling water (other than the bits of stone and other impurities which would need to be filtered). If it leaves a film that will accumulate over time however that's concerning and not something I want to do to my sprayer without a way to easily clean it.

As @g-man said it looks like I'm not actually deficient so I guess there's no urgency and I'm best just sticking with granular apps.


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## bernstem (Jan 16, 2018)

Sulfate of Potash is, I think, harder to dissolve in water than Muriate. I don't know what the additive used to get it into spreadable form do to solubility. My guess is they reduce clumping and indirectly reduce solubility. We should probably stick to using dissolvable forms for spraying.

Chemically, there shouldn't be any difference in the actual Potassium salt, but all the other stuff added to the spreadable probably affects stuff. My guess is that dissolvable is just the salt with no additives. Practically speaking, and ignoring foliar absorption, there isn't much difference in liquid vs granular for soil applications. Liquid might be available sooner in the soil, but it doesn't matter. Use whatever form makes you feel better, but if you apply a high rate of liquid, make sure you wash it off the leaves into the soil to prevent burning.


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## davegravy (Jul 25, 2019)

bernstem said:


> Sulfate of Potash is, I think, harder to dissolve in water than Muriate. I don't know what the additive used to get it into spreadable form do to solubility. My guess is they reduce clumping and indirectly reduce solubility. We should probably stick to using dissolvable forms for spraying.
> 
> Chemically, there shouldn't be any difference in the actual Potassium salt, but all the other stuff added to the spreadable probably affects stuff. My guess is that dissolvable is just the salt with no additives. Practically speaking, and ignoring foliar absorption, there isn't much difference in liquid vs granular for soil applications. Liquid might be available sooner in the soil, but it doesn't matter. Use whatever form makes you feel better, but if you apply a high rate of liquid, make sure you wash it off the leaves into the soil to prevent burning.


Good info, thanks!


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## HoosierLawnGnome (Sep 28, 2017)

bernstem said:


> HoosierLawnGnome said:
> 
> 
> > It will gunk up your sprayer, been there done that.
> ...


The stuff I had was this chalky powder. I bought the wrong SOP online once, it was their "water soluble" line of SOP instead of the granular. whoopsy daisy.

I slowly applied it heavily diluted over a few seasons to use it up, but it gnarled up my spreader and sprayer something awful during a few experiments.

Now I just steer clear.

Yes, another form maybe it works better??


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## bernstem (Jan 16, 2018)

@HoosierLawnGnome Interesting that soluble Potassium gummed up the sprayer. Maybe sulfate doesn't dissolve as cleanly or there was something in it.

I would be bummed if my spray solution gummed up my sprayer.


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## bhutchinson87 (Jun 25, 2018)

What about using K-Mag? The label doesn't exclusively say it is sprayable, but it does indicate that the potash and magnesium are soluble

LESCO Fertilizer 0-0-22 Elite - Product Page
LESCO Fertilizer 0-0-22 Elite - Label


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## Mightyquinn (Jan 31, 2017)

bhutchinson87 said:


> What about using K-Mag? The label doesn't exclusively say it is sprayable, but it does indicate that the potash and magnesium are soluble
> 
> LESCO Fertilizer 0-0-22 Elite - Product Page
> LESCO Fertilizer 0-0-22 Elite - Label


I used a generic version of that a few years ago thinking the same thing that I got from the local seed store and it had a TON of filler material in it so I doubt it is PURE enough to water down and spray. The only plus side is that the SGN may be a little smaller than what I got. The filler is not water soluble.


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## davegravy (Jul 25, 2019)

So I had to try to spray my SOP at 0.5lb/ksqft. I just haven't been able to spread it evenly with my cheapo spreaders. It was a lot of stressful work but I did it.

Most of the work was getting it to dissolve and stay dissolved. I used lots of boiling water and a drill to stirr, but as the solution cooled the SOP started to crystallize. Supersaturated solution if I remember the chemistry term correctly.

So I had to boil more water, and doubled the water volume (8G total). I filtered it through some old panty hose and had to rush to get it on the lawn before it cooled. It didn't clog my sprayer but the sprayer's output rate went down a bit, so maybe partly clogged.

There was a white film, similar to what @HoosierLawnGnome described, on the grass and my boots and the sprayer wand after the application dried. I hosed down the lawn right away to push it into the soil.

I flushed my sprayer with plenty of water too.


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## Groundskeeper Willie (Feb 22, 2019)

If anyone else is interested in dry, soluble potassium, https://www.seedworldusa.com/produc...fertilizer-50-lbs?_pos=4&_sid=5e08cda73&_ss=rthis product looks like the real thing. There's a lot of unbranded SOP product in baggies on Amazon that claim to be fully soluble, yet customer reviews often complain about sediment from carrier/filler.








I'm interested, but I can't vouch for it because I can't see myself ever using 50 pounds of the stuff, and the shipping price on a 50lb bag is steep. Wondering if anyone knows about this particular product first hand. It claims total solubility.

I used this same SeedWorld store for my ammonium sulfate purchase https://www.seedworldusa.com/produc...ate-21-0-0-50-lbs?_pos=1&_sid=dc74d80ad&_ss=r
This ammonium sulfate product is 100 percent soluble as the Solu-Green name asserts. 
Looking for a fully soluble potassium component to go with it.


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## davegravy (Jul 25, 2019)

@Groundskeeper Willie Interesting. Not sure where I can get that in Canada but I'm on the lookout for something similar.

Also I think I f---ed my lawn. Even though I washed the spray off the leaf right afterwards there's a burn pattern running in bands the direction I sprayed. I noticed there's still traces of white powder stuck to the grass leaves so evidently it really clung and didn't rinse off. I might have just started my 2020 lawn reno early lol


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