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.
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.
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.