CO2 Emissions from Food Production

I'm afraid most of that CO2 is released a few hours after eating that cabbage.

I seem to remember reading something about research about CO2 uptake by various plants done by or for NASA - I think they were planning what types of plants to grow on orbiting/interplanetary craft, where the uptake and emission amounts would be critical. Back in the 70's I think it was - Google may turn up something but I would go through old Popular Science articles. Any County Agricultural Extension office or university with agricultural programs could likely help as well.

Here on Terra Verde, I'm sure that CO2 uptake can be calculated, but emission ratings would likely be futile because of where crops are grown versus where they are transported to be consumed. It is hard to predict a given distance of transport because of the way food is distributed - I grew up in Arizona near a large citrus production, yet the citrus we consumed was trucked in from California and Florida. I think most of the juice we drink in the US comes in on the Tropicana now anyway!

A lot of crops go in a maze of directions depending on supply and demand as well as time of year and fuel prices, and don't forget about Government intervention.

Just a WAG, but if you consider all the fuel burned in cultivation
and transport, (including manufacture and transport of fertilzer etc.),
I'd be willing to bet a shiney nickel that there's a net increase in
amospheric CO2.

Check with the US department of agriculture if you live in the US (and pay taxes as a citizen) if you are not then don't. Consult with your own countries government.

The US goverment conducted many studies of agricultural products to determine how much ventiliation is needed. I know a common application and one that has got much ridicule was a US government study to determine how much methane and other compounds were emitted from cattle. Although very funny, but very freightening (what else is the god damn goverement doing with my money?) it provided sound findings that helped farmers and others in the cattle industry design ventilaiton systems.