Unless there is one master gene for yield, which I'm guessing there is not, engineering for yield will be very complex. It may happen eventually, but through the coming decades, we must assume that gene engineering will not be the answer to the world's food problems.

Man can and must prevent the tragedy of famine in the future instead of merely trying with pious regret to salvage the human wreckage of the famine, as he has so often done in the past.

As far as plants are concerned, they can't tell whether that nitrate ion comes from artificial chemicals or from decomposed organic matter.

Water covers about 70 percent of the Earth's surface. Of this total, only about 2.5 percent is fresh water, and most of this is frozen in the ice caps of Antarctica and Greenland, in soil moisture, or in deep aquifers not readily accessible for human use.