# Low Potassium Continues with SOP



## Lust4Lawn (Aug 4, 2020)

I started testing my soil in 2020 and immediately found low potassium. During 2021 I applied monthly applications of SOP 0-0-50 at a rate of 2lbs/K for a total of 4 applications.

This spring I tested my soil (Front vs Back yard) and was a bit shocked to find potassium numbers that didn't move at all. I called Waypoint and the friendly agronomist said that I should continue to apply SOP at the same rates but that my numbers may never improve due to soil consistency. He also said to leave clippings whenever possible to prevent potassium removal. Has anybody else experienced this?

Front Yard:


Back Yard which received 18 yards of topsoil


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## Virginiagal (Apr 24, 2017)

If you had low CEC, leaching might be an explanation, but your CEC is medium, not low. Someone else recently had the same issue (where did all my potassium go?). I found this article on potassium fixation but it is associated with specific kinds of soils and might not be applicable to you:
https://helenaagri.com/fieldlink/identifying-potassium-fixation-on-your-farm/
Another explanation might be sampling error or lab error. Is your grass doing ok? I don't have an answer but if it were me, I'd do the recommended potassium and see how things are next year.


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## robjak (Mar 31, 2020)

What were your numbers from last year?

it took me many years of using MOP to get my potassium numbers up. But they will go up.

ROB 2013 47
ROB 2014 47
ROB 2015 57
ROB 2016 72
ROB 2017 72
ROB 2018 75
ROB 2019 94
ROB 2020 121
ROB 2021 144
ROB 2022 123 I bagged alot of clippings last year and did not apply that much K


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## Lust4Lawn (Aug 4, 2020)

robjak said:


> What were your numbers from last year?


Front 2020 (Fall)


Front 2021 (Spring)


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## Wile (Sep 17, 2020)

They actually talked about this on The Grass Factor podcast. Episode 146, with Lush Lawns at 31-32 minutes in (41-42min on YT). I believe it's correlated with the CEC value.


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## Easyluck (Feb 5, 2019)

How much Nitrogen did you apply?


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## Wile (Sep 17, 2020)

^1 valid point and question


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## Lust4Lawn (Aug 4, 2020)

Easyluck said:


> How much Nitrogen did you apply?


Total Nitrogen application in the front yard for 2021 was 4.2 lbs of N. I reno'd the back yard so I wasn't wasting N on it prior to killing it off.

4/3 *.25 N*/1K via AMS (with double the water I normally use)
4/13 *.25 *N/1K via AMS, K4L Extreme Blend 10g/1k
4/27* .2* N/1K via AMS with Bifen IT .6 oz per K
5/7 *.2 N*/1K via AMS with Imidicloprid @ .6 oz per K
5/14 *.2 N*/1K via AMS, K4L Extreme Blend 10g/1k (1.1 lbs of N total to date)
5/24 *.2 N*/1K via AMS, K4L Extreme Blend 10g/1k in evening (1.3 lbs of N total to date)
6/12 5g/K Prodiamine, 2 oz/K Propiconazole 14.3, *.2 N*/1K via AMS, K4L Extreme Blend 10g/1k (Watered in) (1.5 lbs of N total to date)
6/18 *0.15 N*/1K via AMS, 2 oz/1K FeATURE, 0.15 oz per K T-Nex (YTD GDD 1421)
7/4 *.2 lbs N* of Carbon Earth 8-1-8 (This stuff is old! 25% of this is slow)
7/5 *.09 lbs N* via Urea (8.8 oz DEF/K), 0.25 oz/K Citric Acid, 2 oz/K FeATURE, 0.3 oz/K T-Nex at 7pm with AM irrigation
7/22 *.1 lbs N *via Urea (10 oz DEF/K), 3.5 oz/K Thiophanate-methyl 46.2%, 2 oz/K Propiconazole 14.3,
8/20 Azoxy .38 oz/K, 1.75 oz/K Thiophanate-methyl 46.2%, 1 oz/K Bifen IT,. 0.5 oz/K imidacloprid, *0.1 lbs of N* via DEF all mixed in one batch.
8/29 *.5 lbs N* of Carbon Earth 8-1-8
9/18 Azoxy .38 oz/K, Propi 1 oz/K, .*3 lbs N* via DEF watered in.
10/3 5g/K Prodiamine, *.25 lbs N *via DEF watered in
10/23 *.5 lbs N* AMS (Skipping areas with Poa Triv)
10/30. *.5 lbs N* AMS


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## Lust4Lawn (Aug 4, 2020)

Wile said:


> They actually talked about this on The Grass Factor podcast. Episode 146, with Lush Lawns at 31-32 minutes in (41-42min on YT). I believe it's correlated with the CEC value.


Thanks for the detailed reference. I'll check it out. I enjoy The Grass Factor show but have not listened to all of them.


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## Easyluck (Feb 5, 2019)

Potassium increased from 36 ppm to 50 ppm. Theoretically 4.2lbs of N removed 38 ppm of K, 4lbs of K added 72 ppm, and N from soil organic matter probably removed an additional 9-14 ppm (perhaps more given an ENR of 3lbs / M). So 36 - 38 + 72 - 9 is the expected ppm of K or 61 ppm. If you mulch clippings then some K is returned. If you have a sandy soil, some K could have leached.

You'll need to do more K or less N or both if you want to get K up faster. But it's a marathon not a sprint.


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## Lust4Lawn (Aug 4, 2020)

@Easyluck Thank you for this detailed response! I never realized there was a correlation between N and the depletion of K. I get a sizable amount of N from the ENR (likely during the hot summer when I don't want it) so I am pretty light on applying N in the spring to keep fungal pressure realistic. This gives me a new dimension to consider when applying N.


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## Easyluck (Feb 5, 2019)

You're welcome. Based on ridgerunners nutrient formula, if you want K ppm to reach the midpoint sufficiency level 126ppm (M3) then you'll need to apply 5.75lbs of K if you use 3lbs of N and 6.25lbs of K if you use 4lbs of N. However you shouldn't apply more than a pound of K per month. MSLN for K is 37ppm. If the grass is healthy and green looking then just stay the course and apply a 1:1 N:K ratio for the next several years.


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## ken-n-nancy (Jul 25, 2017)

@Lust4Lawn, I just noticed this thread and wanted to let you know that you're not alone in having to apply potassium (K) on a long-term basis to your lawn in order to supply the needed potassium for the grass to grow. I have soil test results going back about 8 years with a potassium level hovering around 3% that basically doesn't budge in our sandy soil (TEC in range of 4-5), despite making 2-4 applications of sulfate of potash (0-0-50) every year.

Our sandy soil leaches potassium continually, so we are nearly always potassium deficient, so I make monthly applications of 1#K/ksqft from May through August, but none after Labor Day.

I've basically just come to regard applying potassium to our lawn as a standard part of lawn care, just as we apply nitrogen (N) regularly. I've enlisted a local garden center (Achille Agway in Milford, NH) to stock a pallet of sulfate of potash in 50-pound bags so that I have a source for less expensive SOP than mail order. I use two of the 50-pound bags each year on our 12,500 square feet of lawn.

One thing I will mention, even though it applies less to you in New Jersey than it would for other lawn forum members who may be in states even further north -- various studies have regularly shown that moderate potassium applications, particularly in the fall, can significantly increase snow mold in locations that see extended snow cover in the winter.

Here are links to a few:

https://www.paceturf.org/gallery/detail/snow-mold-and-potassium
https://www.blog.asianturfgrass.com/2013/03/10-years-ago-today-a-startling-observation-about-potassium-and-snow-mold.html
http://www.hort.cornell.edu/turf/cutt/2008v4.pdf

Google can point you to many more articles on the topic.

Personally, I don't make significant potassium applications on our lawn after Labor Day, since we regularly see 60+ days of continuous snow cover in the winter, making us a great snow mold target.


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## Deadlawn (Sep 8, 2020)

ken-n-nancy said:


> @Lust4Lawn, I just noticed this thread and wanted to let you know that you're not alone in having to apply potassium (K) on a long-term basis to your lawn in order to supply the needed potassium for the grass to grow. I have soil test results going back about 8 years with a potassium level hovering around 3% that basically doesn't budge in our sandy soil (TEC in range of 4-5), despite making 2-4 applications of sulfate of potash (0-0-50) every year.
> 
> Our sandy soil leaches potassium continually, so we are nearly always potassium deficient, so I make monthly applications of 1#K/ksqft from May through August, but none after Labor Day.
> 
> ...


I'm in the same situation as you with sandy soil. What I would like to know is how do you apply 0-0-50 at a rate of 1 lb/1000 sq ft K in a drop spreader (2 lbs/1000 sq ft of product)? Or do you have a different way of applying it?


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## Lust4Lawn (Aug 4, 2020)

I'm using a broadcast spreader. I try to change the way I spread every month since I don't think my spreader is particularly accurate at these low application rates with such a coarse material.


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## Deadlawn (Sep 8, 2020)

Lust4Lawn said:


> I'm using a broadcast spreader. I try to change the way I spread every month since I don't think my spreader is particularly accurate at these low application rates with such a coarse material.


Hmmm. Maybe I need to get a broadcast spreader. I'm vacillating whether to get an Earthway or Scotts. Which one do you have? Do you like it?


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## Lust4Lawn (Aug 4, 2020)

Deadlawn said:


> Lust4Lawn said:
> 
> 
> > I'm using a broadcast spreader. I try to change the way I spread every month since I don't think my spreader is particularly accurate at these low application rates with such a coarse material.
> ...


I have a Scotts DLX and I have a mostly hate relationship with it. I would not recommend unless you can get a great price on FB marketplace.


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## Deadlawn (Sep 8, 2020)

Lust4Lawn said:


> Deadlawn said:
> 
> 
> > Lust4Lawn said:
> ...


I guess I won't be getting that one. What do you hate about it?


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## ken-n-nancy (Jul 25, 2017)

Deadlawn said:


> ken-n-nancy said:
> 
> 
> > Our sandy soil leaches potassium continually, so we are nearly always potassium deficient, so I make monthly applications of 1#K/ksqft from May through August, but none after Labor Day.
> ...


I used to have that problem, too, especially since I was using an organic (mined) source of sulfate of potash, which had somewhat larger, irregular pieces, rather than being nice, uniform, machine-packed prill as would be the case for a manufactured sulfate of potash.

The solution is that I mix it with something else to add volume. In my case, I mix with Bay State Fertilizer, which is a Boston equivalent to Milorganite. The increased volume of product makes it easier to spread the mix at the appropriate ratio. For the details, the Bay State Fertilizer comes in a 40# bag, which covers 2,500 sqft. I dump a half-bag of BSF into my Earthway 2170 broadcast spreader, then measure out (using a scale) 2.5 pounds of SOP, spread it out over the top, and use a hand trowel to mix them together right in the spreader. I then dump in the rest of the bag of BSF, measure out another 2.5 pounds of SOP, spread it over the top, and use the hand trowel to again mix them up. At this point, the hopper of the spreader contains 40# of BSF and 5# of SOP, which is the right amount to spread over 2,500sqft to deliver 1.0#K/ksqft. This approach has worked well.

I found that when I had the SOP in the spreader by itself and turned the spreader down to a low enough rate, that the irregular large particles of SOP were too big to fit readily through the opening in the spreader and thus would not spread evenly. The mixing approach seems to work very well.

I hope you're able to find an approach that works for you!


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## ken-n-nancy (Jul 25, 2017)

Deadlawn said:


> Maybe I need to get a broadcast spreader. I'm vacillating whether to get an Earthway or Scotts. Which one do you have? Do you like it?


By the way, I love our Earthway 2170 spreader. The large pneumatic tires make it easier to push (as long as the tires are properly inflated), it seems to spread quite evenly, the hopper is big enough to hold a 40# bag of Bay State Fertilizer, and it gives predictable rate control once you have "dialed in" the settings appropriately. Since I generally apply the same products all the time, I have recorded what spreader settings I use for which products to deliver them at the rate I want. For instance, I use a setting of "19" for the BSF & SOP combination I describe above, which covers 2,500sqft for me in two passes at that rate. (I prefer to spread granular products in two or more passes, if possible, to get more even distribution.)

I bought ours used on craigslist. It's just a matter of creating a search for "Earthway" and running it from time to time until one becomes available. I think I paid $50 or $60 for the one I have. At a different time, I also purchased an Earthway S25 sprayer off craigslist, although that cost me $125, which was still a big discount over the new price of about $450 when I bought it five years ago.


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## Deadlawn (Sep 8, 2020)

ken-n-nancy said:


> Deadlawn said:
> 
> 
> > ken-n-nancy said:
> ...


Wow, I hadn't thought of this method to "dilute" the SOP, but it sounds like a logical solution. Thanks for the tip! I'm wondering if using a filler like sand would also work when I don't want to add other nutrients. Granted the last thing I need is more sand!!!!!


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## frekwentflier (Oct 27, 2020)

I just ordered 2 bags of soluable SOP from Siteone that I'm going to spray. I think this is easier than trying to spread such a low amount. Mixing with other fert may work, but you have to mix it extremely well or coverage will be unbalanced. I think it's easier to just spray it.


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## Virginiagal (Apr 24, 2017)

From the soil guidelines:
"Lastly, the recommendations are for soil applications and not for foliar. Do not use these rates for foliar applications unless you immediately run the irrigation to wash the product off the leaves."
https://thelawnforum.com/viewtopic.php?t=15165


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## UDturfguy (7 mo ago)

Lust4Lawn said:


> I started testing my soil in 2020 and immediately found low potassium. During 2021 I applied monthly applications of SOP 0-0-50 at a rate of 2lbs/K for a total of 4 applications.
> 
> This spring I tested my soil (Front vs Back yard) and was a bit shocked to find potassium numbers that didn't move at all. I called Waypoint and the friendly agronomist said that I should continue to apply SOP at the same rates but that my numbers may never improve due to soil consistency. He also said to leave clippings whenever possible to prevent potassium removal. Has anybody else experienced this?
> 
> ...


You said you found "low potassium". Compared to what? If you have nothing to compare it to then it is just random numbers. If your M3 ppm is above 37ppm then you don't have a potassium problem.


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## Lust4Lawn (Aug 4, 2020)

@UDturfguy Good point. I was under the false impression that after adding multiple applications of K last year that I would move the needle more. I now understand that factors such as applied N and clipping removal I am taking 2 steps forward and 1 step backwards so to speak.

I am continuing to apply K via SOP monthly and the turf seems receptive and healthy. Spreading K will just be a part of my application schedule for the foreseeable future as part of my long game.


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## UDturfguy (7 mo ago)

Lust4lawn,
Just because you apply K doesn't mean the soil can hold the product or that the plant will be able to take it up. If you are in NJ in one of the sandier regions then chasing a number is a lost cause due to K leaching and low CEC. If you test your soil and it is above 37 ppm Melich 3 then the potential for a K deficiency is almost zero.


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## Virginiagal (Apr 24, 2017)

Your CEC is not low. It's quite close to 10 which I think of as a normal CEC. UDTurfguy is going by MLSN guidelines. Waypoint is using SLAN. I think it is fine to go by your lab's recommendations.


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## UDturfguy (7 mo ago)

Virginiagal said:


> Your CEC is not low. It's quite close to 10 which I think of as a normal CEC. UDTurfguy is going by MLSN guidelines. Waypoint is using SLAN. I think it is fine to go by your lab's recommendations.


Yes, I am using the MLSN guidelines. All other available soil test interpretation methods for turfgrass systems are extremely wasteful. Somewhere along the line of up to recommendations 2-3X's higher than necessary. Why put an element on your turf if a) the plant has zero chance of using it b) the soil can't hold it c) there is no chance of a turf response d) using correlation and calibration studies designed for commodity crops for fertilizer recommendations? SLAN guidelines are broken. The smartest scientists to ever grace the turfgrass industry have been quoted ad nauseum reflecting their dissatisfaction in all available fertilizer recommendations for the last 50 years.


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## Virginiagal (Apr 24, 2017)

Here's one of those scientists saying you can't just look at the test results and say "I'm good " if they are at or above MLSN levels. You also have to take into account the amount of nutrients being used up over the year and the amount you want to be left with in reserve. It's going to be related to how much nitrogen is being used.
https://www.asianturfgrass.com/post/one-thing-i-wish-everyone-understood-about-mlsn/


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## TampaBayFL (Jul 24, 2020)

If one is applying MOP (0-0-60), is 3lb of product/1k "safe"?

On the bags of MOP I have, they state the below. My soil test indicated I am at ~2 lb/1k of K (which I believe equates to ~35-36 ppm of K), so the directions indicate that 3 lb of product/1k is advised (or ~1.8 lb K/1k).


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## Virginiagal (Apr 24, 2017)

@TampaBayFL For MOP, you can put down 1.6 lb per 1000 sq ft in a month which will give you just about 1 lb of K per 1000 sq ft. So you would do multiple applications if you need more than 1 lb of K. Didn't your soil test give a recommendation on how much to apply over the season? Go by that rather than a bag. Different extractants will give different ppm results. We don't know what extractant the bag is assuming. For that matter we don't know what extractant Waters was using for your test. By the way, it's best to pose questions in your own thread rather than someone's else's unless you have something to add to the discussion of that person's questions.


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## Virginiagal (Apr 24, 2017)

For anyone interested in MLSN, here is how to figure things:
https://www.asianturfgrass.com/post/new-mlsn-cheat-sheet/

I have a problem making sense of the directions for estimating turfgrass usage. For one thing, it's all in the metric system and I'm used to lbs and sq ft. I'm not going to be collecting clippings to measure the volume. I suppose there is some way to measure growth potential but I don't know how. The sentences on estimating based on nitrogen supply makes no sense to me. So given a soil test with a ppm (and apparently we have to convert that to a metric measure) I don't know to put anything into their equation to come up with anything meaningful. I get the basic idea, that there is a basic level to not go below and you need to fertilize to keep above that level and how much the grass will use in a year. But on a practical level, how to make a MLSN fertilizer recommendation is beyond my ability. Throw in soil tests done with different extractants which need to be converted to a Mehlich value, it's just too complicated.

The recommendations that labs come up seem reasonable, generally ranging from 0-4 lb of a nutrient per 1000 sq ft. for the year. I think it's best to use a reliable lab in your area and go with their recommendations. For a homeowner with a normal size lawn, the costs are manageable. As for soils that tend to leach, they are going to leach no matter how much or little you apply. You could argue that they need even more fertilizer so the grass has a chance to get at least some of it before it leaches away. It's better to spoonfeed those. One thing they soil tests don't (can't?) account for is the value of clippings left on the lawn. They do return nutrients back to the soil.


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## TampaBayFL (Jul 24, 2020)

Virginiagal said:


> For a homeowner with a normal size lawn, the costs are manageable. As for soils that tend to leach, they are going to leach no matter how much or little you apply. You could argue that they need even more fertilizer so the grass has a chance to get at least some of it before it leaches away. It's better to spoonfeed those. One thing they soil tests don't (can't?) account for is the value of clippings left on the lawn. They do return nutrients back to the soil.


I'm glad to see this posted because I came to the same assumption for my lawn. I spoon feed about every two weeks. In my sand (and doubly so since I bag clippings since I dont like the mess) it just doesnt seem logical that anything is hanging around long.


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## TampaBayFL (Jul 24, 2020)

Lust4Lawn said:


> I started testing my soil in 2020 and immediately found low potassium. During 2021 I applied monthly applications of SOP 0-0-50 at a rate of 2lbs/K for a total of 4 applications


Did you get any ill effects (burning, etc) with this regimen? I am thinking of doing something similar (but with MOP at a slightly lower rate since I have some). My baseline may be worse than yours though (as I believe, if I have converted correctly) that my K is in the 35 ppm range.

This thread has been enlightening (esp with the discussions around N effecting K). I did not realize this was as significant as it is.


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## TampaBayFL (Jul 24, 2020)

Virginiagal said:


> Didn't your soil test give a recommendation on how much to apply over the season? Go by that rather than a bag.


I hope this isnt viewed as a further hijack.....but I dont trust the below (thus my question)......


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## Virginiagal (Apr 24, 2017)

@TampaBayFL That is too much potassium in one application. Call up customer service for whoever you can (Lowes? Waters?) and get the total potassium you need for the year if it's not stated. I'm going to guess the Waters may have said 3 lb, per 1000 sq ft meaning for the year, and Lowes, not knowing any better, just put it all in one application. The directions are for one application. Do they advise anything for other applications? Do you have the Waters report or just Lowes?


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## steffen707 (Apr 9, 2021)

Lust4Lawn said:


> I started testing my soil in 2020 and immediately found low potassium. During 2021 I applied monthly applications of SOP 0-0-50 at a rate of 2lbs/K for a total of 4 applications.
> 
> This spring I tested my soil (Front vs Back yard) and was a bit shocked to find potassium numbers that didn't move at all. I called Waypoint and the friendly agronomist said that I should continue to apply SOP at the same rates but that my numbers may never improve due to soil consistency. He also said to leave clippings whenever possible to prevent potassium removal. Has anybody else experienced this?
> 
> ...


Where did you get these soil tests? After using them, do you recommend them to others?

The one I did 2 years ago from the UW system was okay, but missing some info I was told.


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## Lust4Lawn (Aug 4, 2020)

@steffen707 these tests are through waypoint analytical. I learned about them here and I think that they are great. I would recommend them.


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