“Measuring the organic content of soil is an easy way to assess soil health. Most conventional farms have an organic content below 2 percent. Virgin Midwestern prairie used to be 7 to 8 percent. Good soil has a deep black color, because carbon is black; it's rich and actually smells good.
As noted by Candelario, a French initiative called the 4 Per 1,000 Initiative3 found that if we were to increase the carbon (the organic matter) in all agricultural land around the world by a mere 0.4 percent per year, the annual increase of CO2 in the atmosphere would be halted, because so much carbon would be drawn from the atmosphere.”