Organic has it's own problems. It uses far more water and electricity, more land, and a lot of the "natural" insecticides they use have their own environmental problems, such as coal coke and creosote.
While it has its upsides to industrial farming, it's by no means a 100% viable alternative. Additionally, even organically grown crops are affected by the nutrient leeching, as that's a product of carbon load in the air.
The best way to offset your carbon footprint when it comes to food is to follow the following three principles. Shop local, shop seasonal, and shop less.
Buying from local producers, either directly from them, through farmers markets, or from "farm to table" stores (which is the most common way in urban environments) dramatically cuts down on the carbon load. Same thing with buying seasonal, as buying off season products implies those products had to travel here by pollution belching planes and ships.
Lastly, shop less. Food waste is a leading contributor to ones carbon footprint. Never stockpile perishables if you are constantly throwing portions of them away.