Hi Darrin, the test I used was the test from Midwest Labs that John Kempf talks about. It tests for everything in the soil. I don’t know how the test works but it’s supposed to reveal the total reserves you have in your soil. It extracts far more than a M3 does so long as the nutrients are. Example, in my case magnesium and potassium are barely any higher on the total test than a M3 but iron shows up at 5000ppm vs 100ppm and my phosphorus shows up at 600ppm vs 150ppm. Sandy soils, at least mine won’t have the huge reserves that clay soils will have.