Résumé
All soils that are now farmed have been formed or modified by late Cenozoic events. Where these events have been dramatic with glaciers and plate tectonic processes actively intervening, old soils have been obliterated and replaced by newer, inherently more fertile materials. In more placid regions, soils that originated on Tertiary and even Mesozoic landscapes persist, and continue to evolve towards states of low fertility. The inherent fertility of soil, a renewable resource, is largely ignored in modern mechanised agriculture in favour of chemical fertilizers largely mined from non-renewable deposits. A saner attitude once existed, still exists in at least part of the Third World, and should be re-examined as a possible basis for future strategies.