# Low P and K in Soil test



## Marlon (Jun 25, 2019)

Hello,

I recently ran a soil test on newly installed *Bermuda* sod (4/2019). Cores were take at 4" and sent out for testing here in Charlotte, NC. Soils are definitely clay based due to poor drainage.

Results:


P and K are dismal. The %HM (humic acid) is an indication of organic matter and this should be above 1%. pH a little on the high side as well.

I've love to get some insight as to how I should start amending this soil. I typically fertilize with Milorganite and have done K correction with SOP.


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## g-man (Jun 15, 2017)

Welcome to TLF.

Just like you read it, low P and K. pH is at 7.0 and not super high (8).

They are recommending 5-10-10 at 20lb/ksqft for the season and that's a good recommendation. For Bermuda you can use 10-10-10 at 10lb/ksqft per month instead of season to encourage spreading when it is actively growing.

Organic matter beingn low is common in new construction. It will take years to build this up. Roots from the lawn will die as new ones are developing, thus incorporating OM into the soil. This is called root cycling. You can help by mulch mowing. Mowing the fall leaves. You can also aerate and topdress with compost.

While all of this is great, for Bermuda is not that impactful. Bermuda is a good weed that can grow on concrete as long as it has sun and water.


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## Marlon (Jun 25, 2019)

I was thinking of SOP but maybe just stick with 5-10-10 or 10-10-10? I plant to mow down to 0.8 with an automower; my Honda rotary will choke. This of course is mulch mowing.

I also want to install inground irrigation - does Bermuda benefit from this?


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## g-man (Jun 15, 2017)

If you want to go the SOP route, it also good.

For pitassium
SOP (0-0-50) at 2lb/ksqft months that the grass is growing

For phosphorus
MAP (11-52-0) at 2lb/ksqft months that the grass is growing

Or

Triple super phosphate (0-46-0) at also 2lb/ksqft.

For N
Use urea (46-0-0) or AMS (21-0-0), per the Bermuda Bible.


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## Marlon (Jun 25, 2019)

You say 2lb/ksqft months - are you inferring this needs to be applied monthly during the growing season for Bermuda?


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## g-man (Jun 15, 2017)

Yes, but of a could/should rather than a needs. This is to improve your soil nutrients, but you should be able to grow bermuda just fine as it is.


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## Marlon (Jun 25, 2019)

On a separate note, I plan to cut at 0.8" with an automower - only because my Honda rotary can't get down there without butchering the blades. I don't want to invest in a reel mower. My question, with an automower, would I need irrigation installed or would the constant mowing help with this? Thanks for you assistance.


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## g-man (Jun 15, 2017)

An automower is a robot mower? My neighbor has one and it uses a string trimmer to cut the grass. The cut is very bad since it is a tear vs. clean cut.

The mower you use is irrelevant to the water requirements. You will need to apply up to 1.5inches of water per week per ksqft. This needs to come from rain, above ground sprinklers or in ground.


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## Marlon (Jun 25, 2019)

No, these robotic mowers cut like a real - very sharp blades.


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## g-man (Jun 15, 2017)

Yes I know there are robotic mowers with blades.

https://twitter.com/PenderSuper/status/1164533613695660032


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## adgattoni (Oct 3, 2017)

Marlon said:


> On a separate note, I plan to cut at 0.8" with an automower - only because my Honda rotary can't get down there without butchering the blades. I don't want to invest in a reel mower. My question, with an automower, would I need irrigation installed or would the constant mowing help with this? Thanks for you assistance.


FYI I don't think you will like the cut with the automower. Bermuda has two vertical pieces: a brown stemmy piece, and green leaf tissue on top. When the grass gets taller, the stemmy pieces get taller. If you go from a 2" rotary cut to a 0.8" automower cut, you will see tons of the brown stemmy pieces (if not entirely brown). The business park I work in has a section of bermuda maintained with an automower and IMO it looks terrible. Probably 60% green and 40% brown stems. From a distance the turf looks yellow-green like it's been scalped or hasn't been fertilized.

Re: irrigation. They are really two separate topics. You will need to water the lawn somehow in NC for the lawn to look it's best. With bermuda you could generally just let it go off of rainfall and it won't completely die, but there will be periods of time where the turf looks thin. Whether you get an in-ground system or move sprinklers around your property is really up to your wallet IMO.


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