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 farming techniques.
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. During the latter half of the 1980s they reached a level of 4.2 metric tons per hectare. But now the growth curve has flattened out, with no increase in average productivity thus far in the 1990s.
I am encouraged by the potential of new agricultural technologies now on the horizon, including drought-resistant plants and crops that use the sun's energy more efficiently. But recent slow productivity gains, together with the socioeconomic restraints on adoption of new technologies so prevalent in the third world, make slower yield gains in future years seem inevitable. And adverse weather will continue to be an important worldwide factor as well.
The earth has little unused land suitable for farming and only a modest potential for expansion in irrigation.
Consider rice, the primary food source in Asia, home to more than half of humanity.
Dr. Robert F. Chandler, founding director of the International Rice Research Institute, points out that rice production on that continent nearly doubled from 1960 to 1988, with only a 12 percent gain in the number of hectares devoted to the crop.
He also says that there has been no appreciable increase in the acreage planted with rice since 1977.
Almost all of the Asian land suited to this vital crop is already in use. In some heavily populated countries, including China and Japan, the amount of land available for food production is actually decreasing.
Considering the likelihood of much slower gains in crop yields than experienced in recent decades, plus limited land and water for expansion in farming, it is evident that only a two-pronged strategy can assure global food security in the next century:
* A worldwide effort toward a more efficient food system through research, education, and appropriate funding. Governments must support agricultural development and avoid unnecessary regulations that discourage productivity.
* Stepped-up programs in the fast-growing third world aimed at bringing birth rates down to the replacement level. This is particularly needed in the more than 100 countries still increasing in population by more than 2 percent annually. Much must be accomplished by local people, but nations that can afford to give foreign aid should reconsider priorities and devote a greater proportion to assisting the less fortunate in their family-planning efforts.
I believe the world has the resources and the technology to avoid a food production catastrophe. Now we have to muster the will.
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