Soil organic matter is probably one of my top ten curiosities. I have this debate with myself about the efficiency of attempts to
build it in a short time. No doubt many have successfully discovered and executed successful strategies, but it's a seriously deep art & science requiring a substantial commitment. It's the numbers I find daunting. I started scratching on a napkin, but, rather than sharing that addition and subtraction, I'll provide this neat little summary I found here:
https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_053264.pdf
"An acre of soil 6 inches (15.2 cm) deep weighs approximately 2,000,000 pounds, which means that 1 percent SOM weighs about 20,000 pounds per acre. Under average conditions it takes at least 10 pounds of organic material to decompose into 1 pound of organic matter, so it takes at least 200,000 pounds (100 tons) of organic material applied or returned to the soil to add 1 percent stable organic matter under favorable conditions (“What Does Organic Matter Do In Soil”, Funderburg 2001, Samuel Roberts Noble Foundation)."
After that sinks-in, managing (to keep) what you already have become job number one.