# RichS Soil Lab Test Comparison



## RichS (Jan 28, 2019)

Hi all-

Newbie here, but I finally got around to doing something I've been wanting to do for years - see how various labs would report on soil all taken from the same sample - so I figured I'd share what I found. I've been hanging out for a few years at (what appears to be the-site-that-shall-not-be-named), so I have several years' worth of Logan Labs data. After discovering this site, and poking around a bit, I chose 3 other labs for comparison.

Background - The first lab tests for my soil are from Penn State in 1999. I followed their N/P/K/lime recommendations and re-tested every 3-4 years until about 3 years ago, when I got a little more interested in the details. I moved to Logan to get more detailed data and move into more sophisticated treatments. The results were a bit strange this year, but I'll leave that for a different test results interpretation thread. (They're getting close to what I want, but there's still some work to do).

These samples are from my 4,000 sq. ft. front lawn. I've focused on the front because it's more visible, and the work/cost to treat the additional 17k in back is prohibitive. It was originally mostly perennial rye and fescue, and I overseeded with TTTF 2 years ago. A physical test from 2 years ago showed a slightly silty loam - 22% Clay, 56% Silt, 22% Sand.

Because of the volume I needed, I took about 25 samples from across the lawn. For each, I stuck a hand trowel 4 inches deep and worked it side to side to create an opening. I then cut a thin slice all the way down one side, removing a 4-inch-long slice of dirt, and put it in a pail. From the other side I dug the trowel in at 3 inches and took a sample just from 3-4" deep and put that in a different bucket.

When done, I cleaned out the grass, rocks, etc., by hand, and spread the samples on some newsprint in my garage to dry out. When dry, I thoroughly mixed the samples and then filled small plastic bags, alternating 1 scoop at a time per bag, until each had about a cup of dirt in each to send away for testing.

All samples were sent USPS Priority and reports were returned by email.
•	Logan Labs: Sent 2/26; Report received 3/5/19 2:52pm
•	Waypoint Labs: Sent 2/27; Report received 3/2/19 4:00pm (impressive - the day after receipt, on a Saturday)
•	Midwest Labs: Sent 2/27; Report received 3/5/19 1:55pm
•	A&L Great Lakes Lab: Sent 2/27; Report received 3/7/19 3:09pm

Below is a tabular summary of the data, followed by some comments, and then the actual reports.

Waypoint and Midwest call out Mehlich 3 and other specific test methods on their report. A&L and Logan don't specify, but browsing their sites, it seems to be a reasonable conclusion that they use M3 also. The exception is A&L's Phosphorus, which is noted as "Bray-1 Equivalent". A note on their site implies that it's a M3 test that is then adjusted ("Mehlich-3 values correlate well with Bray P1 values, so Mehlich-3 values can be regressed into a Bray P1 equivalent number by using a mathematical operation. This allows soil test P values to be reported as a Bray P1 equivalent,").

For Logan data reported in lbs/acre, I used the assumption of 2M lbs/acre of soil at 6 inches, which converts to 1.333M lbs/acre at 4 inches. So I divided their lbs/acre numbers by 1.333 to arrive at ppm (I emailed them asking for ppm values, or to confirm this conversion method, but didn't receive a reply).

Logan reports M3 Phosphorous as lbs. P2O5 per acre, so I multiplied by .437 to convert P2O5 to P, and then performed the lbs./acre to ppm conversion.



Some things I noticed:
•	Micronutrients seem to vary the most (though Fe only varies by 21% if you discard the A&L outlier, discussed below).
•	Other findings are generally consistent - high on P, low on K and S; Ca:Mg ratio a bit low
•	A&L's Fe number appears to be using a different scale of some type. Their number of 37ppm is reported as Optimal, just as is Waypoint's 158ppm (which is consistent with Logan and Midwest)
•	A&L's 45ppm for Mn is in the high/optimum range, whereas Waypoint's 78ppm is Medium/below optimum
•	Cu values of 2.1ppm (A&L) and 3.4ppm (Waypoint) are both reported as Optimum
•	2 years ago, my B reading from Logan was 0.65. I treated with Borax for the year and had a result of 0.65 last year. I treated with an increased dose last year, and got….wait for it….0.66. The other labs all have me at 1.1+. In all the Logan results I've seen - at least 50 over the last few years, I don't think I've ever seen any over 1.0 and very few over .75. Quite interesting.

I'm not sure what to make of all of it, other than the realization that there isn't the nice set of consistent results from every lab, theoretically using the same methods on the same soil. I appreciate the graphical representations and interpretations of the Waypoint and A&L results. Unfortunately, I cheaped out the $2.50 to get recommendations from Midwest, for some reason. I'm going to see if they can do that after the fact.

Actual reports are below. I'll leave it to the many of you more knowledgeable than I to comment, correct, etc. I still have a few cups of dirt in the bucket in my garage. I'm not sure I'm up for the time or $$$ to add other labs, but I'm open to suggestions if I missed a well-known/commonly used lab that could be of interest. (I had originally planned to re-test at one or more of the labs to test for repeatability)









I almost forgot - I also wanted to address the question of sampling at the 3-4" depth vs. the full 0-4" depth. See the comparison table and results of those from Logan at the bottom. I have a few years of 3-4" results from them, so wanted to have some way to correlate results over time.





Hopefully there are a few other obsessive compulsive engineer/scientist/geek-types out there that may find this interesting. :lol:

(apologies for length, errors, etc. It's late and once I started I wanted to get this out - I'll proof and clean it up later  )


----------



## Ridgerunner (May 16, 2017)

Great post. It appears that Midwest has changed their procedures. Previously, Midwest only offered Ammonium Acetate (AA) extraction for Ca, Mg. and K and BP1, BP2 and Olsen for P with the option of M3 for P. Your Midwest report states theat M3 was used for Ca, Mg. and K. Question: Did you elect your extract procedure as M3? Was there an option to elect AA and BP1, BP2 or is M3 now their default extract?


----------



## RichS (Jan 28, 2019)

I requested the S1A and S3 tests and made no additional comments, so I assume this is currently their default procedure.

Oddly, the S1A test description says "Organic Matter, Available Phosphorus, *(P1 Weak Bray and P2 Strong Bray)* Exchangeable Potassium,", so the test description and results don't seem to be in synch.

I was going to try Spectrum Analytic, based on other posts here and what Google found as a 2016 price list of $14 for an S3 full soil test. I wrote to inquire about prices (nothing on their site) and what I got back had a price of $40 for the same test. I'm not sure I'm curious enough for that, plus shipping, or Soil Savvy's $30.


----------



## Ridgerunner (May 16, 2017)

Thanks Rich,
I called Midwest today regarding the matter as I'm planning on sending my sample in at the end of the month (or maybe not as I'm suffering a case of rock-heave anxiety) and wanted clarification.
I was told their test default is still AA and Bp1 and P2. They do have 2 tests available using M3. One of which is a version of SC3 by "special request.". They do not advertise this on their site, and it is not listed on their printable order form, but they state it is an option on their on-line order portal. It is identified as SC3M. If you didn't order on-line, then I say WTH?


----------



## RichS (Jan 28, 2019)

Very strange. I looked at their Interpreting Soil Analysis handbook https://midwestlabs.com/wp-content/uploads/2017/01/Interpreting-Soil-Analysis-Web.pdf and it does look completely different - Bray 1 and 2 Phosporous, heading of "Neutral Ammonium AA" above the main nutrients, DTPA for all of the micros - as you described.

I tried the "copy to begin a new order" on their portal and it pre-filled "S1A PACKAGE" and " S3M ". The site lists "S3" and "S3 Complete", but the order form has "S3C Package", S3M, and "S3CM". I'm guessing the M is for M3 - somehow I ended up with that. But the S1A seems pretty standard. Maybe getting the M3 version of S3 just defaulted everything to M3. The conflicting values and wording from the list of tests to the order form is certainly confusing.

But I'm glad I ended up with M3 to be comparable with other labs.


----------



## Ridgerunner (May 16, 2017)

S3C and S3CM. I transposed them&#128543;. The S3M must be the other M3 test they told me that they offered and, yes, they said M=Melich III.


----------



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

RichS said:


> I almost forgot - I also wanted to address the question of sampling at the 3-4" depth vs. the full 0-4" depth. See the comparison table and results of those from Logan at the bottom. I have a few years of 3-4" results from them, so wanted to have some way to correlate results over time.
> 
> 
> 
> ...


Thanks for posting the 0-4" and 3-4" comparisons. That's something I've wanted to investigate, but never felt strongly enough to invest the money on testing both ways.

The results are actually close enough that it doesn't seem that it makes a huge difference -- seems to me that basing one's applications from either would result in quite similar treatment plans.

It makes sense that the P would be higher in the 0-4 sample than the 3-4 sample. Phosphorus isn't particularly mobile in the soil and P is being regularly introduced at the surface in the form of mulched grass, mulched leaves, etc.

None of the other differences between the test seem like they would cause markedly different treatment

Have you been regularly applying potassium (via sulfate of potash) in recent years? That might help explain why the potassium is higher in the 0-4 sample than the 3-4 sample. (That was a finding that I didn't expect.)

Personally, I like the fact that gathering one's sample from 3-4 inches (instead of 0-4 inches) bypasses some of the potential issue of having one's test results affected by materials that are just at the surface, such as recent fertilizer applications.

Thanks for sharing!


----------

