Soybeans and corn are not sown together in the same filed; nevertheless, most farmers are reluctant to use the herbicide on their corn.

One very effective herbicide is safe for corn, but soybeans are damaged even by the herbicide's residue, which remains in the soil more than a year after the herbicide is applied.

Soybeans, corn and cotton that tolerate high doses of herbicides and fend off pests — technologies that benefit rich-world farmers — are nearly all the choices we have.