Genetically modified maize. Tractor in a field of genetically modified (GM) maize plants Zea mays, during a field trial. This GM maize has had one application of a Glyphosate type herbicide to which it is resistant but which has killed weeds. This herbicide is neutralised on contact with the soil and leaves no groundwater pollution which is a problem with herbicides used with non- GM maize. The GM maize has had its DNA (deoxyribonucleic acid) genetic code modified to withstand the new herbicide. It is controversial whether GM foods are healthy to eat. This field trial was conducted by Agrevo in Lincolnshire, England.