In alternative embodiments, the invention provides compositions and methods for the restoration of soil carbon content by carbon sequestration, or storage of carbon in a stable and sustainable form, for example, in an exhausted soil. In alternative embodiments, use of compositions of the invention and practicing methods of the invention results in a net increase in Soil Organic Carbon (SOC). In alternative embodiments, the invention provides compositions comprising, or consisting of, a combination or a mixture of seeds, wherein the mixture comprises seeds of at least one C4 photosynthesis pathway grass and at least one of any member of the genus A triplex, or in alternative embodiments, the combination or mixture comprises seeds of at least two C4 photosynthesis pathway grasses and at least one of any member of the genus
