ADAPTING AND IMPROVING CROPS - THE ENDLESS TASK

The Malthusian prognosis has been undermined by an exponential increas e in world food supply since 1960, even in the absence of any extensio n of the arable area. The requisite increases in yield of the cereal s taples 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 harves t index and environmental adaptation, it is not apparent how a doublin g of yield potential can be achieved unless crop photosynthesis can be substantially enhanced by genetic engineering. Empirical selection fo r yield has not enhanced photosynthetic capacity to date, but nitrogen ous and other fertilizers have done so, and there is still scope for a gronomic increases in yield and for new synergisms between agronomy an d plant breeding.