Measuring Organic Matter

All the soil maps and surveys reference Organic matter by percent. Does anyone know exactly how that is calculated? Is is by weight or volume?

If I had an acre of land; and it had 1% organic matter. How much organic matter would one have to add to raise it to 2% for example? If I took a cubic foot of soil, weigh it; and multiplies by .01 that would be the weight of organic matter (roughly) that needed to be added, correct? Anyone with experience in this?

on land judging team for FFA 1978-79 we didn't have a lab and judged soil composition based on sight, touch, crumble test, regional attributes, local characteristics/natural resources etc but I did recall the percent is derived from the total mass (how much in how much) and found this detailed procedure with the data sheet and formula. lab procedures to determine organic matter and here are other test options

and, this, if you don't have a lab, is how we used to determine soil makeup Soil Judging Manual

[snip]The soil properties, soil conditions, and soil uses in this guide provide a brief overview; the definitions and information are not intended to be all encompassing – they simply provide a brief discussion of the subject covering most situations that will introduce participants to the idea of soil judging. [/snip]

Take the soil dry it, maybe at 170F
weigh the water less soil
Now heat the soil 350F+. This will burn all the carbon in the soil
weigh the soil again the difference is the amount of organic matter.

As for how much organic matter to add. 3 inches
3inch of mulch by 1 acre is 403 cubic yard of woodchip per acre.
The mushroom+microbes will do the hard job of bringing it deeper into the soil horizon.