Estimated increase in atmospheric carbon dioxide due to worldwide decrease in soil organic matter

Atmospheric carbon dioxide (CO2) levels have risen from 260 to 340 mg kg‐1(ppm) over the last 150 years, largely attributed to worldwide industrialization and continual change in land use. Conventional tillage practices have also added to the atmospheric CO2 pool via the accelerated decay of soil organic matter. The objective of this work was to derive a simple estimate of CO2 in the atmosphere that could be attributed to tillage and decomposition of soil organic matter from arable land. The percent increase in atmospheric CO2due to a worldwide decrease of 3,2, and 1% in soil organic matter of arable land was estimated to be 20 mg kg‐1,12.5 mg kg‐1, and 5 mg kg‐1, respectively. This decrease in soil organic matter would have accounted for 6 to 25% of the 80 mg kg‐1 (340–260) increase in atmospheric CO2 over the last 150 years.