# How do you calculate ppm to 1k square foot?



## SaltyBouy (Jun 3, 2020)

Hey folks,

I just got my soil test back and would like to make some adjustments. My report is in ppm and am trying figure out how much to add to the lawn in square footage. Or should I just make amendments and retest?

Here are my test results.



I did not get a CEC fro the test but I do have clay soil. Not sure what to do with high Magnesium. 
My plan is to add ammonium sulfate for N
SOP for K 
I'm curious if I should add gypsum to reduce salt? It could also help with the high magnesium which I think may be a big part of my compaction issues but I don't want to mess with my ph which is surprisingly good, thoughts?

Thanks!


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## Virginiagal (Apr 24, 2017)

I suggest you get a soil test from an established lab like Brookside or Waypoint. They will give you fertilizer recommendations for a whole growing season rather than for just one application. You cannot trust the pH reading from these online companies.
https://thelawnforum.com/viewtopic.php?t=16135
https://thelawnforum.com/viewtopic.php?t=26242

Gypsum would help if you do have a salt problem. Gypsum doesn't change the pH. Using lots and lots of water to get the sodium to leach is also part of the process. Water is a precious commodity in California. You should get some local advice. Here is how to contact the UC extension office:
http://cesacramento.ucanr.edu/UC_Cooperative_Extension
The extension office may also be able to recommend soil labs.


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## SaltyBouy (Jun 3, 2020)

Thanks! Bummed to find out my test is bunk. Time and money wasted, thats what I get for trusting a paid advertiser. I thought it would be easier to find a local test lab especially with UC Davis nearby but their site is very involved and I can't figure out what test to order. The hunt continues.

Thanks again!


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## g-man (Jun 15, 2017)

The top thread in this folder gives you options. Stuff in california seems to always be more of a challenge, so mail it to a out of state lab using USPS.


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## Virginiagal (Apr 24, 2017)

It looks like UC Davis does only research testing, doesn't provide routine soil testing for individuals. Call the extension number and ask them what labs they recommend and what specific test to request. You want pH, CEC, the cations (like potassium, sodium, calcium, etc.) and phosphorus (an anion), and probably micros (like iron, zinc, copper), though the micros can be skipped. While you're on the phone with them you could also discuss sodium. Is excess sodium common in your area?


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## Virginiagal (Apr 24, 2017)

The test should also include electrical conductivity (EC).

Here is a brief email explanation of saline, sodic, and saline-sodic:
https://www.agvise.com/wp-content/uploads/2020/06/interpretation-saline-sodic-soils.pdf


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## Virginiagal (Apr 24, 2017)

Read the parts of this article that talk about which soil test extractants are best for California:
http://calag.ucanr.edu/Archive/?article=ca.2016a0007
Choose those extractants when you order your next soil test.

You should also make sure a buffer pH test is done. You can't trust the pH reading on the YardMastery test, but if it's below 6.5 a buffer test would tell you if any lime is advised (probably wouldn't need much). If it's really 6.3, you might just leave well enough alone.


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## Natron (Aug 23, 2021)

Hi Salty,

I'm in your neck of the woods. Virginiagal and g-man have already given you great advice. I can lend some local perspective.

I went with A&L Western for my soil test http://www.al-labs-west.com/services.php?section=Soil Analysis as they have a location in Modesto and I believe were recommended in the forum. Turn around was quick and it didn't break the bank. See my lawn journal for an example report.

Another (slightly pricier) local option is https://sunland-analytical.com/. Most of the landscape contractors I work with use them. I believe they are cheaper than Waypoint (CA).

Hope this helps.


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## g-man (Jun 15, 2017)

That A&L west western looks to have all the proper tests and decent price. :thumbup:


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## SaltyBouy (Jun 3, 2020)

Thanks everyone! I have my homework for the weekend. I think I'll do my father in laws yard next and do mine again in a few months since I already put down some N. 
We put down super drought tolerant Buffalo grass last summer at his place. I can start to get his soil going in the right direction before it warms up. 
Thanks again!


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## Ridgerunner (May 16, 2017)

:thumbup: advice from Virginiagal and gman

regarding calculations:

Every pound of any nutrient in its elemental form that is added to one thousand square feet of lawn will add 21.78 ppm to the tested value levels of that particular nutrient. *Need to rephrase:* _To determine the amount, in ppm, that one pound of any particular fertilizer product will supply of the elemental form of the desired nutrient, you need to determine what percentage of the product molecule is that particular elemental nutrient._ Then multiply 21.78 by that percentage to determine the total ppm that will be added per pound of the fertilizer product applied.

Example:
One pound of ammonium nitrate per thousand square feet of lawn will increase N levels by how many ppm?
ammonium nitrate: NH4NO3 is slightly less than 35% N (nitrogen). 
21.78 X 35% = 7.62 ppm
Every pound of ammonium nitrate applied to one thousand square feet of lawn will theoretically add 7 ppm to N levels.

Every pound of P2O5 (the phosphorus in the fertilizer bag) that is added to one thousand square feet of lawn will theoretically (in a "controlled lab" environment) add 9.56 ppm to tested P (phosphorous) levels.

Every pound of K2O (the potassium in the fertilizer bag) that is added to one thousand square feet of lawn will theoretically (in a "controlled lab" environment) add 18.07 ppm to tested K (potassium) levels.

As reality seldom aligns to theory, it's simpler to calculate using 9 when applying phosphorous and 18 when applying potassium. We're throwing hand grenades, not darts.


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