[biggreg]

A bit on testing for CEC:

[biggreg]

Effective CEC is the number of exchange sites at any given ph.

The barium cloride compulsion test can be a direct measure of effective CEC at any ph. This test isn't normally done.


Summation of the base cations and estimated acidity from the lime buffer or calculation from a routine soil test Is the estimated CEC @ph 7.0 or TCEC.

CEC is used by some state universities to adjust SLAN Mg K or P fertilizer recommendations.

For the purpose of balancing soils via BCSR ratios, the CEC @ 7.0 is the scale that is used.

[VortexPower420]

Really interesting stuff. The article on "muck soils" is interesting.

[biggreg]

Thanks. I've been an information leach on this forum since 2010. Time to give back what I've learned in this area of growing.

[biggreg]

My main message to all testing their recycled, peaty, lightweight, mucky muck, non mineral soil, container soils is to:

Make the lab weigh in the sample to get an accurate mg/kg and Meq/100g report

Measure your own bulk density in g/cc

Convert the mg/kg to mg/l and meq/100g to meq/L to give the numbers perspective. That is the key. Unlike with mineral soils which the report is pretty much reads both mg/kg and mg/l with the same number, ppm and CEC need to be looked at volumetrically in soils less dense than 1g/cm3 to have meaning.




From there you can balance cations by weight or adjust to typical levels per volume.

[biggreg]

I'm curious to compare our soils.

What's your CEC meq/100g
What's your bulk density?
Meq/L? (Also can be expressed meq/100cm3, just move the decimal)
Target ph?
Base cation ratio goals?
Suffiency levels goals ( in mg/L)
Micronutrient level goals? (In mg/L)
Teqniques for correlation and calibration of these tests to actual results?
Favorite labs?

Also let's share our at home testing tequniques, ph testers, bulk density, lime requirement tests, EC, other meters, etc.

[biggreg]

On labs so far I've found that run the Mehlich 3

1. The never scoopers

MB Labs in B.C. Canada
They claim to not even own a standard weighing scoop. You specify which extractant. Their standard is a locally developed Kelowna extraction. They will sub the Mehlich3 upon request.

They run a pretty complete standard package for home gardeners that includes : Nitrogen (N), Phosphorus (P), Potassium (K), Sulfur (S), Sulfate, Organic Matter, Major & Minor Elements–including: B, Ca, Co, Cu, Fe, Mg, Mn, Mo, Si, Na, Zn, pH & Conductivity (Salinity) cost $73.50 CAN ( exchange rate helps)

Exact scientific in WA. They don't own scoops either. Must request Mehlich 3

Soiltest lab in WA. Same as above

I was told by a Midwestern lab that labs in WA do not scoop due to wacky soils.



2. The scooper labs that say they will weigh with a real analytical balance upon request, you should call first. It's not their standard. Make sure to check their assumptions on CEC calculations, mineral soil conventions will throw the test.

Spectrum Analytic ( extra handling charge)
Rock river labs
A&L Great Lakes
Agvise ( must request Mehlich 3)


3. The scoop only labs: the ones who say no

Logan
Midwest
Brookside
Dairy one
AgSource
Ward labs
American Ag lab






I will keep calling around to add to the list.

[biggreg]

Hey, just found this info:

4. Labs that don't weigh the sample at all--Volumertic testing.

Looking into all these lab's methods, I decided to look into labs in North Carolina, knowing that state has lots of histosol crop land.

Dr. Mechlich worked for the North Carolina Department of Ag where he developed the Mechlich 3 test with Carolina histosols and mineral soils in mind. His Mehlich lime requirement buffer test was also designed with higher organic matter soils. Maybe the Mehlich is the right test for our soils?

Labs in this state seem to all report volumetrically mg/dm3. They test a volume of soil without weighing. Also they give an calculated bulk density. They measure the mass of the dried sample and apply an equation to arrive at the field moist volume.

https://www.ncagr.gov/agronomi/sthome.htm
If you are a North Carolina resident, the Mehlich test is free if you are willing to wait 8 weeks for results. ( they have waiting times on their site)
A&l eastern is also in that state and tests organic soils in the same way.
https://watersag.com/service/soil-analysis/ Is another one.

With a volumetric test mg/dm3 and a bulk density, we could convert it back into mg/kg if we wanted to look at it in soil mass ppm.

[biggreg]

Three ways the Mehlich 3 tests are performed by labs on our organic soils:

1. By mass. Organic Soil is weighed in via analytical balance---legit
2. By mass. Organic Soil is weighed in via mineral soil calibrated scoop----NOT LEGIT!
3. By volume. A 2.5cc volume of organic soil is measured in. ----legit

[biggreg]

The Mehlich ( may-lik) lime buffer seems to be the most accurate test for organic soil lime requirement. Tell the lab your target ph for a lime amount needed.