Roody

Standard industrial agriculture is heavily dependent on synthetic fertilizer, which is mostly produced from natural gas with the Haber-Bosch process. The carbon in the natural gas is a by-product that is disposed in the form of carbon dioxide into the atmosphere. This is a form of digging up carbon, converting it into a gas, and warming the atmosphere--analogous to burning it in a car engine or electricity generator..

Organic agriculture does not use synthetic fertilizer, but manure. The carbon from manure is accounted for in the biological carbon cycle so there is no net increase in warming gases.

Yes, organic farming does contribute to AGW in other ways, as others posters have pointed out. But the total effect is much less than from standard farming with synthetic fertilizers.