While we refer to our "lawn" only in parentheses since the grass is full of dandelions, clover, and whatnot and never gets fertilized (except with the chicken tractor), I do occasionally feel guilty about the grassy areas.  Granted, on our farm, grassy garden aisles make sense, but most like-minded people think all lawns are evil.  However, as I mowed Thursday, I started wondering whether the carbon dioxide coming from our mower might not be offset by the carbon being sequestered in the soil as grass blades and roots turn into humus.

Sure enough, independent scientists (in addition to the lawn-care "scientists" you might expect to feel this way) report that lawns do act as carbon sinks.  A minimal input lawn like ours that only gets mowed with no other treatment sequesters about 147 pounds of carbon per lawn per year (after you subtract out the carbon released by the mower).  The abstract I read didn't mention lawn size, but I'm assuming they're using the American average of a fifth of an acre, which matches up with another study that reports each acre of lawn sequesters a net of 760 pounds of carbon per year.

Of course, cover crops will put the puny carbon sequestration powers of a lawn to shame.  Sorghum-sudangrass will pump a massive 10,565 pounds of carbon per acre into the soil, and oilseed radishes don't do so bad either at 3,200 pounds of carbon per acre.  In fact, a 120-year-old northeastern woodland only clocks in around the carbon sequestration powers of oilseed radishes, and you can still grow tomatoes in the oilseed-radish ground during the summer.

Which is all a very long way of saying --- if you're considering making a patio or leaving that area as lawn, go for the lawn.  But if you really want to sequester carbon fast, plant some cover crops.