# Selecting the right extrantant



## ragga (May 5, 2019)

I am looking to submit a soil test soon and am leaning towards using Waypoint Analytical. They have many options and methods available across sites. Two years of testing with Soil Savy have come back with ph values of 7.25 and 7.37, which I attribute mostly to irrigating with extremely hard water (30+ grains) that, according to my local water report, is ph 7.8. It is the ph >7 that leads to my question regarding the proper extraction to use.

Mehlich 3 is the default test used at the nearest lab to me (IA). From what I understand, the Mehlich 3 is solid, widely used test but may not be the most accurate for alkaline soils over ph7. Waypoint also offers the Olsen for P, Ammonium Acetate (K, Mg, Ca, Na) and DTPA (Cu, Fe, Mn, Zn). They also have a Saturated Paste Extract that includes Co3 and HCO3,

So my questions are: Is it worth it to bother with any of these other methods for soil that is only in the ph 7.2-7.4 range? Or just stick with Mehlich 3? How about the saturated paste given my hard water situation? I'm not sure exactly what i would do with the additional info there..

Any advice would be greatly appreciated


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## g-man (Jun 15, 2017)

If you think you have a high pH, ask for the SW1 using waypoint analytical in Memphis TN or go with midwest labs.


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## ragga (May 5, 2019)

Thanks for your reply, g-man. The SW line uses a mix of Mehlich 3 and Ammonium Ascetate, with Olsen for P, and is the one they advertise for alkaline soils - makes sense to go with that. Any thoughts about the Saturated Paste Extract?

Thing is, the agronomist at Waypoint said that the Ammonium Ascetate is best suited for higher ph like in the 8+ range. He was suggesting that, for only slightly elevated ph, it wouldn't really be necessary to try any of these other ones.

Then again, I recently saw @Greendocon the youtubes advocate for the Olsen any time ph is above 7. I dunno, maybe I'm overthinking it lol


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## Ridgerunner (May 16, 2017)

> So my questions are: Is it worth it to bother with any of these other methods for soil that is only in the ph 7.2-7.4 range? Or just stick with Mehlich 3? How about the saturated paste given my hard water situation? I'm not sure exactly what i would do with the additional info there.


You don't specify, but I assume your stated pH numbers are based on the results for pH from your SS test. If so, SS uses a weak acid solution and not de-ionized water. Consequently, their reported pH results are going to be lower than what the results would be from a standard 1:1 pH test. Soil Savvy used to state that the difference could be 0.5 of a point of pH. So your actual pH is more likely 7.7 - 7.9 rather than 7.2-7.4.
A saturated paste test reports only the amount of nutrients that are available in the water solution and only for the day the soil sample was taken. Values can change (sometimes quite significantly) from day to day. Results are of no value for calculating nutrient adjustment and fertilizer application rates. It's a tool used primarily for diagnosis. I wouldn't suggest that you get that test other than to satisfy curiosity.
IMO M3 data becomes less reliable the higher the pH of the soil. Olsen and AA will give more useful and dependable data for higher pH soils.


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## g-man (Jun 15, 2017)

Since you suspect that your pH can be higher, i think it is wise to go with the SW1($26.50), for this time. If the pH is at 7.3, then sure next year you can save $10 and go with the M3 ($16.50).


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## ragga (May 5, 2019)

Very interesting, Ridgerunner. I didn't know that the other test would low-ball ph like that. 7.7-7.9 would be right in line with the 7.8 stated in my local water report, too. I am definitely eager to see what a better test would show, and after a year of ammonium sulfate as my main N source and a couple apps of elemental sulfur!

I mention the saturated paste test only in regards to calcium carbonates/bicarbonates that may be building up from the hard water. Is there anything that can be done about that if they were to come back elevated?

thank you both for your help!


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## ScottW (Sep 16, 2019)

I'm not certain that the pH of your soil would be significantly affected by the pH of your local water supply.
My tap water routinely measures pH 9.5 or higher. My soil pH last year was 7.2. Before that it was a couple tenths higher because I had overshot with the lime a couple years prior, but left alone with no intentional pH adjustments, even watering with my pH 9.5 municipal water, it will slowly acidify.
Midwest soil is generally more alkaline than ours over here on the east coast.


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## ragga (May 5, 2019)

it would definitely be interesting to sample a non-irrigated plot adjacent to my house and compare :thumbup:


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## ragga (May 5, 2019)

Well, the non-irrigated plot, which is maybe 100 feet from my yard came back as ph = 7.4, whereas my irrigated yard came back at 7.8. I guess the ph of your water does have an effect


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