Rev.K: I'll be the first to say that I'm no expert, but if you're using carbon sequestration to capture emissions in the soil, does that not mean you can't till that soil because doing so would release the carbon?

The half life of Cabon-14 is 5,700 years. So if you're trapping carbon in soil that you can now no longer till, do you not need a constant supply of soil to keep you going?

How much carbon can the soil actually hold?

Again, I'm no expert.

It works, more or less, like growing a forest does.  You don't till grasslands used for grazing, so grazing depleted land restores the top soil, capturing carbon, until it becomes fully restored and reaches full saturation.  At which point you are just cycling atmospheric carbon through grass/cows.  So restoring depleted soil can capture carbon, just like restoring forest can capture carbon, up to a point.  Grassland and forestland store roughly the same amount of carbon.

The issue is that covering the earth in either grassland or forests doesn't really matter because the carbon capacity is limited to what the biosphere can hold in an instant of time while the carbon released by burning fossil fuels represents millions of years worth of Earth's carbon that was buried deep underground separated from the biosphere.