Adapting and improving crops: the endless task

The Malthusian prognosis has been undermined by an exponential increase in world food supply since 1960, even in the absence of any extension of the arable area. The requisite increases in yield of the cereal staples have come partly from agronomic intensification, especially of nitrogenous fertilizer use made possible by the dwarfing of wheat and rice, in turn made feasible by herbicide development. Cereal dwarfing also contributed to a marked rise in harvest index and yield potential. Although there is still scope for some further improvement in harvest index and environmental adaptation, it is not apparent how a doubling of yield potential can be achieved unless crop photosynthesis can be substantially enhanced by genetic engineering. Empirical selection for yield has not enhanced photosynthetic capacity to date, but nitrogenous and other fertilizers have done so, and there is still scope for agronomic increases in yield and for new synergisms between agronomy and plant breeding.