Interestingly, hemp having significantly less root mass than another common row crop (corn) grown under similar conditions challenged assumptions about hemp’s superiority in carbon sequestration.
Substitution of fiber hemp for corn did not affect soil greenhouse
gas emissions from a Kentucky cropping system
“To test hemp’s reputation as a more climate-friendly crop, we compared soil greenhouse gas fluxes, root mass, and soil carbon from hemp and corn over 2 years.
We found that hemp and corn released similar amounts of greenhouse gas equivalents.
Corn did release more nitrous oxide 1 year, and hemp released more methane early in the season, but these differences balanced out when everything was converted to CO2-equivalents.
One difference was found in the root biomass. Corn had almost four times more in-row root biomass than hemp, which means corn put more carbon into the soil, where it has the potential to stay longer.
As hemp’s root input was less than corn’s, this suggests that hemp may not contribute as much to soil carbon storage.
However, between-row root measurements are needed to scale these findings to the field level.
Our results indicate that fiber hemp may not be as climate-friendly as previously believed and requires more research at a larger scale.”
Click here to download the study [PDF].