# Potassium leaching



## Jeremy3292 (Apr 30, 2020)

Does anyone know if potassium leaches from a lawn? I'm concerned with these ferts that are something like 8-1-8 or high in K that I may be putting too much down on a regular basis. I know once your P is solid you really don't have to worry about it but I am not so sure about K. Anyone have any thoughts?


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## BermudaBoy (Jun 27, 2019)

Too much potassium doesn't affect your lawn but if you have a lot of potassium you probably have an equally high level of nitrogen that may be a problem unless you desire to mow a lot.


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## sirwired (May 21, 2020)

Get a soil test; they will tell you recommended fertilizers for your specific situation.


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## Jeremy3292 (Apr 30, 2020)

I've gotten 3 soil tests this year. I'm wondering if anyone can explain if K does leach from soils or not like P.


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## Ware (Jan 28, 2017)

Jeremy3292 said:


> I've gotten 3 soil tests this year. I'm wondering if anyone can explain if K does leach from soils or not like P.


Moving this discussion to the soil fertility subforum.


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## Ridgerunner (May 16, 2017)

Jeremy3292 said:


> I've gotten 3 soil tests this year. I'm wondering if anyone can explain if K does leach from soils or not like P.


Yes. Leaching is dependent on a number of factors including solubility, soil texture, CEC and AEC and whether the nutrient is a cation or anion. Generally speaking, K can leach faster than P, but much slower than Nitrate.
Why do you ask?


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## Mightyquinn (Jan 31, 2017)

Most soils will be deficient in Potassium as it's the second most used element by the grass behind nitrogen. Without a soil test you will never really know for sure what your soil is like and what it needs. For Bermuda, I think a good rule of thumb is to go at a minimum of a 2:1 ratio of N:K and you could even go up to a 1:1 ratio but that all depends on whether you are catching your clippings and what your soil test says.


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## Jeremy3292 (Apr 30, 2020)

Thank you for the responses. As I noted before, I have gotten 3 soil tests this year; that was not an issue. I was more curious about K levels and how they fluctuate. Most people will tell you once you get your P right it will generally stay there for a long time bc P does not leach from soils very rapidly at all. So I then began to wonder if K does not leach like P or not.

@Mightyquinn I always return my clippings to the ground except during a scalp. I was wondering if something like an 8-1-8 as a maintenance fert would eventually be too much K as it is a 1:1 with N. But if K is used by bermuda a lot like N, then the answer to my question would be no...


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## Mightyquinn (Jan 31, 2017)

Yeah, I think a 8-1-8 would be fine to use but I wouldn't apply more than 6-7 lbs. of product per 1,000 sq/ft or around .5 lb of Nitrogen and Potassium per application and apply every 2-4 weeks unless there is some slow release in that.


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## Ridgerunner (May 16, 2017)

As Quinn pointed out warm season turfs uses potassium in an N;K ratio of between 4:3 and 1:1. Anecdotal evidence on golf courses has shown when N and K is applied at those ratios, K levels can be maintained at a stable year over year basis (via soil test results). Consequently, it would be fair to conclude that the lion's share of K loss is due to plant usage rather than leaching. Regardless, if you can maintain stable K levels from year to year, it won't mater if K loss is due to plant uptake or leaching- you've got it covered.


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## Jeremy3292 (Apr 30, 2020)

Mightyquinn said:


> Yeah, I think a 8-1-8 would be fine to use but I wouldn't apply more than 6-7 lbs. of product per 1,000 sq/ft or around .5 lb of Nitrogen and Potassium per application and apply every 2-4 weeks unless there is some slow release in that.





Ridgerunner said:


> As Quinn pointed out warm season turfs uses potassium in an N;K ratio of between 4:3 and 1:1. Anecdotal evidence on golf courses has shown when N and K is applied at those ratios, K levels can be maintained at a stable year over year basis (via soil test results). Consequently, it would be fair to conclude that the lion's share of K loss is due to plant usage rather than leaching. Regardless, if you can maintain stable K levels from year to year, it won't mater if K loss is due to plant uptake or leaching- you've got it covered.


Thank you both for the insight; that is good information.


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## Mightyquinn (Jan 31, 2017)

Ridgerunner said:


> As Quinn pointed out warm season turfs uses potassium in an N;K ratio of between 4:3 and 1:1. Anecdotal evidence on golf courses has shown when N and K is applied at those ratios, K levels can be maintained at a stable year over year basis (via soil test results). Consequently, it would be fair to conclude that the lion's share of K loss is due to plant usage rather than leaching. Regardless, if you can maintain stable K levels from year to year, it won't mater if K loss is due to plant uptake or leaching- you've got it covered.


You make what I say almost sound intelligent :lol:


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## Ridgerunner (May 16, 2017)

You had the insight to get to the heart of OP's inquiry and provide an informative answer. I had to save face somehow.  


Mightyquinn said:


> Most soils will be deficient in Potassium as it's the second most used element by the grass behind nitrogen. Without a soil test you will never really know for sure what your soil is like and what it needs. For Bermuda, I think a good rule of thumb is to go at a minimum of a 2:1 ratio of N:K and you could even go up to a 1:1 ratio but that all depends on whether you are catching your clippings and what your soil test says.


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

Jeremy3292 said:


> Most people will tell you once you get your P right it will generally stay there for a long time bc P does not leach from soils very rapidly at all. So I then began to wonder if K does not leach like P or not.


The short answer is that phosphorus (P) in the soil is very stable and does not leach much at all. On the other hand, potassium (K) is readily leached from the soil, particularly sandy soil.

I have a sandy loam soil in my lawn and need to make regular monthly potassium (K) applications to maintain (K) levels, as confirmed by annual soil tests. This is typical for sandy soils.

As a side note, people may be wondering that if phosphorus (P) is stable in the soil, why is there so much concern about overapplication of P being bad for water sources and causing algae blooms? The issue is _not _that the phosphorus leaches through the soil and goes into groundwater -- that isn't a problem, as phosphorus is tightly bound to the soil. Rather, the problem with P overfertilization is *runoff* -- heavy rainfall after fertilizer application can cause the recently-applied phosphorus to run off in surface waters to streams, rivers, ponds, lakes, bays, etc., where it causes trouble.

The problem with phosphorus runoff is particularly an issue with water soluble forms of phosphorus, such as most synthetic fertilizers. More organic sources of phosphorus are less of a problem, but are still subject to runoff if there is enough rainfall to cause the applied fertilizer particles to get lifted up and wash away. Even worse than either of the above is erosion of phosphorus-rich soil.


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