Of course, you have to consider the sources here, as having to do with agriculture and soil, and energy exploration. The study was done by the National Science Foundation, a government owned organization funded by US taxpayers.
National Sciene Foundation: What it is an who funds them;
...and we all know what the Dept of Energy is about, agriculture and energy exploration.
Heres the new "study" downplaying carbonization in soil as a contributing factor to global warming. Funny how all the doubt about global warming is being generated from the ranching, farming and energy camps...for they are the ones who stand to lose the most if "green-living" ever takes off on a larger scale.