# How long does P & K last



## Big Boy Stan (Aug 27, 2020)

I received the following result from my soil test in August showing my P and K levels in a good place. How long can I expect the them to stay in the good zone without adding any to the soil? Will I need to add P & K in the spring or any time in 2022? Or just stay with a pure N fertilizer?


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## Lawn Noob (Jul 26, 2020)

Do another test early spring and then you'll know.


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## Mightyquinn (Jan 31, 2017)

Phosphorus doesn't usually get depleted from the soil too fast and is pretty stable for the most part. Potassium on the other hand is the second most used nutrient behind Nitrogen and can get used up but I assume you are mulch mowing your clippings back into the lawn which helps supply Potassium back to the soil and roots. So your numbers may not go down all that fast. I wouldn't worry about it and just get another soil test done about this time next year to see where you are at and if the numbers have changed significantly.


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## g-man (Jun 15, 2017)

If you mulch mow, the values will stay there for a while. You could re test your soil in 3 yrs.

If you bag, then you are throwing away some of the P and K with your clippings. How much? It depends on how much N you are using, how long your growth season is, etc. Re test in a year to see how much change you get in a season.


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## Big Boy Stan (Aug 27, 2020)

Thanks all. I do mulch my clippings (as well as fall leaves) when mowing. I just finished a 2#N/k (4.25# of urea) fall N blitz. 
I'll stick with just N for the spring green up app and see how the lawn performs through the season. If all goes well, I'll skip the 2022 soil test.

Thanks again


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