[Redbaron]

Grass. Primarily the grass that grows between the rows and becomes next years beds. But also grass clippings from the yard to a lesser extent. Most people don't realise that the trick to long term deep carbon sequestration is the roots of living perennial grasses and forbs. They pump lots of carbon deep in the soil in the form of exudates that feed mycorrhizal fungi, which in turn feeds all the rest of the soil biology.[1] The waste product of all that biological activity is humus. Because the soil is never broken by the plow or tiller, that carbon sticks there.....up to thousands of years potentially.[2] Tilling in organic matter does help, but it takes a whole lot more and the plowing releases almost as much as is added. The exudates no till method is better from this POV and VERY economical.