Just a couple of observations on this that might interest you.
Generally if you are just comparing the growing of plants then there might not be that much difference but it is important to take in the wider picture.
Where has the seed come from? - Some GM warehouse or last seasons crop?
Where has the fertiliser come from? - Overseas and petroleum added or collected from animals, mulch crops and fallen leaves?
Where has the energy associated with the farming technique come from? - Hydrocarbons or muscle?
How far does the food have to travel before consumption? Vast distances or Zone 2 to Zone 1 or at the most a local Farmers Market.
What is the nutritional benefit of the food - weight for weight? Is it mostly water and flavourless?
What toxic residues, GM and other issues are there to consider?
What is the mindset of the consumer likely to be? - One with the planet and a sustainable society in mind or dollars and more environmental destruction in mind?
I reckon you might be trying to compare two very different things here and there is more to the carbon equation than just what is left in the soil!
Good question and good luck answering it !
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