What was done
Soybean (Glycine max L. Merr. cv. Stonewall) and sorghum (Sorghum bicolor L. Moen. cv. Savanna 5) were grown at 357 and 705 ppm CO2 in open-top chambers in the field.  Leaf and stem tissues were subsequently applied to a Norfolk loamy sand and aerobically incubated for 70 days to determine if growth at high CO2 has any effect upon tissue decomposition.

What was learned
The source of plant residue - whether it was produced in the ambient or elevated CO2 treatment - had no impact on soil carbon (C) turnover, relative nitrogen (N) mineralization, cumulative C and N mineralization, and C/N mineralized.

What it means
In the words of the authors, "these data suggest that increasing atmospheric CO2 will have little effect on composition or decomposition of field crop residues."  Hence, they conclude that "since CO2 enrichment results in increased photosynthetic C fixation, the possibility exists for increased soil C storage under field crops in an elevated CO2 world," which would in turn act as a brake to reduce the rate of rise in the air's CO2 content and mitigate whatever degree of global warming might possibly be induced by the rise in atmospheric CO2.