# Waypoint S3M vs. SW1



## ROJ_3030 (Sep 28, 2019)

Hey TLF,

This will be my first year getting a proper soil tested and I'm debating between the S3M and SW1 test from Waypoint. I have cores pulled and ready to send in and I'm located in the central Michigan area if that helps with my question.

In the soil test thread, https://thelawnforum.com/viewtopic.php?f=24&t=3124, it's mentioned that if you suspect high pH or have hard water to use the SW1 test. I am on a well with minor hardness and I have no clue about my soil pH at this point.

Does the SW1 test just provide more data and would there be any drawbacks to it over the S3M?

-Jacob


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## bhutchinson87 (Jun 25, 2018)

They provide the same data, the difference is in the extraction method (Olsen and Ammonium Acetate vs Mehlic III), checkout Ridgerunner's Soil Test Thread. Given that you're in Michigan, I would go with the S3M test.


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## Ridgerunner (May 16, 2017)

bhutchinson87 said:


> They provide the same data, the difference is in the extraction method (Olsen and Ammonium Acetate vs Mehlic III), checkout Ridgerunner's Soil Test Thread. Given that you're in Michigan, I would go with the S3M test.


Good synopsis of the different extracts. :thumbup: However, your guess on which test should be used is suspect. There are regions around the Great Lakes in the U.S. and Canada that have very alkaline soils. IMO Michigan is likely to be higher pH soil. 
@ROJ_3030 If you select the SW*, you should be coverd no mater the pH of your soil. ammonium acetate will extract Ca. Mg and K accurately regardless of pH. That test uses Olsen which is best for high pH P extraction and I believe that test also includes/provides Mehlich 3 extraction for P which is good for useful low pH P values. Maybe @g-man can confirm that the SW* test includes both M3 P and Olsen P as he has used Waypoint and analyzed many of their tests for folks.


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## bhutchinson87 (Jun 25, 2018)

Ridgerunner said:


> Good synopsis of the different extracts. :thumbup: However, your guess on which test should be used is suspect. There are regions around the Great Lakes in the U.S. and Canada that have very alkaline soils. IMO Michigan is likely to be higher pH soil.
> @ROJ_3030 If you select the SW*, you should be coverd no mater the pH of your soil. ammonium acetate will extract Ca. Mg and K accurately regardless of pH. That test uses Olsen which is best for high pH P extraction and I believe that test also includes/provides Mehlich 3 extraction for P which is good for useful low pH P values. Maybe @g-man can confirm that the SW* test includes both M3 P and Olsen P as he has used Waypoint and analyzed many of their tests for folks.


Good point, that's what I get for assuming lol. I can confirm that the SW3 test does use Olsen and M3 for P levels. That's the test I used earlier this year which is in my soil test thread.


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## g-man (Jun 15, 2017)

Some areas of michigan near the lake and sandy have low pH. The rest is high pH. I would just error in the side of assuming high pH and use the SW1 or Midwest labs. SW1 uses Olsen and M3 P. The SW3 is the SW1 + Nitrogen + salt testing for $5 more. I think SW1 should be enough.


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## ROJ_3030 (Sep 28, 2019)

Wow, this forum blows my mind. I can't believe the amount of reach and knowledge that is available here. Thank you all for the input! @bhutchinson87 @Ridgerunner @g-man Looks like I have some new reading material ahead of me from Ridgerunner.

This was a new construction house that I fully landscaped myself. The builder kept all the native soil and "flipped" it back over some questionable fill to build up the grade. The soil is what I'm considering to be sandy loam and I have at the minimum 4-6" across the whole yard.

The cost is so low for testing in general that I might just do the SW3 for my first test and go from there. I'm sure in the future the S3M will be sufficient.

This was about a week ago as we tried hard to pull consistent 4" plugs. And yes, we got rocked by snow mold this year!





Thanks again!
-Jacob


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## SCGrassMan (Dec 17, 2017)

I always do S3M personally. I have absolutely no reason for this decision.


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## Ridgerunner (May 16, 2017)

> I'm sure in the future the S3M will be sufficient.


That would depend on the soil pH that is reported on the first test. Or, maybe you meant to distinguish between SW3 for a first test and SW1 for subsequent tests. The controlling factor is to select the correct extract test based on soil pH.


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## ROJ_3030 (Sep 28, 2019)

Ridgerunner said:


> > I'm sure in the future the S3M will be sufficient.
> 
> 
> That would depend on the soil pH that is reported on the first test. Or, maybe you meant to distinguish between SW3 for a first test and SW1 for subsequent tests. The controlling factor is to select the correct extract test based on soil pH.


You're correct, I poorly worded that statement. For this year I'll use the SW3 and then let the pH drive which test I use moving forward.


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## Lust4Lawn (Aug 4, 2020)

I performed an SW1 test last fall and an M3 test this spring. For my PH 6.5-7 there is no discernable difference in the data.


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## ragga (May 5, 2019)

I recently had the sw3 run with ph=7.8 soil and the P from Olsen came back as 15 ppm whereas the P from the included m3 came back 35 ppm. My understanding is that results from the two methods will be increasingly discrepant as ph increases above 7.

IF you don't know your ph is 7 or below, and you aren't worried about spending a few extra few $, i would get the SW and rest easy knowing you are covered. Personally, I used the same thinking and went for sw3 and added soluble salts just to cover as many bases as i could.


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