PHENOMENAL gains in crop yields since World War II have
contributed significantly to the growth of the United States
economy. Enhanced productivity per acre has assured abundance at
home and enabled us to sustain a high level of grain exports to
customers abroad, as well as to countries with occasional needs to
supplement home-grown supplies.
By doubling or even tripling the yield of several crops, US
farmers have avoided the need to expand acreage under cultivation.
Thus we have the luxury of vast parks and nature preserves,
spacious lawns, golf courses, and other recreational facilities.
Further, in the interests of soil conservation and erosion control,
much land that was once farmed is now being "given a rest."
Will the average number of bushels or tons of produce per acre
continue to climb?
Long-term US Department of Agriculture (USDA) records of
estimated crop yields contribute to an answer. In no year prior to
1946 did the US produce a corn yield averaging more than 35 bushels
per acre. About that time, better nutrition through the use of
fertilizer, superior protection against pests, and new seeds
carrying genes for greater vigor began to have a combined effect.
During the 1960s, corn yields rose to an average of 71 bushels
per acre and during the 1970s to 90 bushels. A high of 118 bushels
per acre was reached in 1985. But the mean yield for the subsequent
eight years (1986-1993) was only 112 bushels. This average includes
1992, when a phenomenal 131 bushels per acre were produced; it also
includes the drought year of 1988, when only 84 bushels per acre
were recorded, and 1993, when excessive rains in the Midwest
dropped the average corn yield to just over 100 bushels per acre.
Looking ahead, we must recognize that adverse weather often will
have the last word on yields, regardless of the use of scientific
A study of USDA records and similar data from other countries as
published by the United Nations Food and Agriculture Organization
indicates that the rate of yield increases is tapering off wherever
farmers have widely applied modern agricultural methods.
For example, during the 1960s, US wheat gained in yield over the
1950s by an average of 3.8 percent annually. That was a period when
more growers began to overcome soil nutrient deficiencies with
fertilizers. The gain in the 1970s over the 1960s averaged 1.9
percent per year. But since 1980, the average annual rise in yield
has been a little less than 1.5 percent.
Many third-world countries have increased crop yields
significantly in recent years - the so-called Green Revolution.
They will continue to make further gains as more farmers use
scientific crop-enhancement practices.
But where greatly increased productivity has already been
achieved, recent gains are modest or negligible. Mexican farmers,
for example, now obtain very good yields of wheat. …