Preface



 The roots of the technological revolution in
agriculture of the past century can be traced in the
history of scientific discovery and the development of
university research and training programs. Dramatic
improvements in production per hectare and per farm,
however, are a comparatively recent phenomenon. The first
major breakthroughs occurred in the biological sciences
with the development of hybrid maize in the 1930's,
followed by the expanding use of complete fertilizers and
improved weed and pest control technology following World
War II. Scientific knowledge in the basic and applied
agricultural sciences continues to advance at an
accelerating rate and is the basis for confidence that
food and fiber production can keep pace with growing world
demand.
 It is clear that not all farm households and family
members have benefited equally from technological
progress. Yields per hectare and per agricultural worker
vary greatly among the regions of the world, among
countries within regions, and among farms within each
country. As a result, average farm incomes and the
percentage of a nation's population engaged in agriculture
also vary greatly among countries and regions. While the
overall pattern of differences can be explained with
reference to natural soil fertility, rainfall, product