Er where to start
Firstly what crops had you in mind ? As far as I know there are no crops that can only be bought as GMO. So just say no and buy your stuff elsewhere . Food does not need that monsanto flavouring
Secondly You could always compost any GMO plants you have already that I think should take care of that
David
Living in Anjou , France,
For the many not for the few
http://www.permies.com/t/80/31583/projects/Permie-Pennies-France#330873