Before 1950 most of the increase in global food production came 抽om an
increase in farmland and improved farming techniques. . Inereased
harvests stemmed from development of high-yield "miracle' yarieties of
wheat and rice were capable of producing two_or three harvests a year,
increased use of chemical fertilizers, and massrve investments in jrrigation
systems in developing nations. The introduction of new types of rice and
wheat that Yesponded better to fertihizers increased crop yields between the
