Whoa. Aren’t yields of corn and soybeans increasing year by year? Yes, but imagine how much greater the increases would be if the soil organic matter (mostly carbon) was equal to the original level before tillage began. 

What has caused most cropland to lose about half of its carbon? The top three reasons are: tillage, tillage and tillage. The greater the volume of soil disturbed, the greater the loss of carbon.

Don Reicosky, a retired soil scientist with the USDA-ARS in Morris, Minn., completed years of research on a wide range of tillage implements, measuring carbon loss (as CO2) immediately after tillage with a collection device he designed. 

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Of course, you can’t ‘see’ CO2 as it escapes from the ground. But picture the CO2 as the dust cloud when you disk or cultivate dry soil. Greater depth and greater intensity of tillage makes the carbon loss worse. 

The loss is proportional as we go from full width shallow tillage to plowing 6 inches deep to subsoiling 14 inches deep. Simply, the more air that’s allowed to mingle with soil particles, the more oxygen from the air combines with carbon in the soil and is released into the atmosphere as CO2.

If tillage causes the loss of Carbon…