American Farm Bureau leaders visited Japan earlier this year to demand better access to Japanese markets. They came home impressed by that nation's deep concern about soil conservation.
''The Japanese,'' says Carrol Chaloupka, president of the Texas Farm Bureau, ''told us they're worried about our farmers ruining land they rely on for their food.''
Since the United States supplies 60 percent of the world grain trade and 17 percent (by value) of all agricultural trade, the state of its farmlands is a global concern. But what is true for the US is true throughout the world - food-producing topsoils are being lost or ruined at an alarming rate.
The Carter administration's Global 2000 Report - one of the best-documented assessments of the world resource challenge - warned: ''While on a worldwide average there was about four-tenths of a hectare (one acre) of arable land per person in 1975, there will be only about one-quarter hectare (three-fifths of an acre) per person in 2000.''
Two years later, the report's principal author, Gerald Barney, says he sees little that would change that projection. ''The No. 1 problem facing the world is the problem of soil protection,'' he warns.
Many nations are awake to this problem. The Global 2000 Report now is a best seller in its German, Japanese, and Spanish editions, despite sluggish US sales.
In a sense, a global test of Reaganomics is taking place. Many other nations wonder whether or not the Reagan administration's commitment to less government intervention and reduced federal spending will improve American agricultural productivity.
If the US can find a cost-efficient soil-conserving way to increase farm output substantially, this will relieve global food supply pressures. It will give third world countries more time to learn how to feed their exploding populations. But if even wealthy America can't halt the damage being done to its soil, poorer nations will be in still deeper trouble.
Meanwhile, information about the world's farming potential remains incomplete and controversial.
''Land degradation, or desertification, threatens to blunt agricultural efforts to keep pace with the global population surge,'' warns Harold Dregne, a Texas Tech University professor, in a US Department of Agriculture report. Dr. Dregne, who is director of the International Center for Arid and Semiarid Land Studies, admits that ''worldwide rates of land desertification are impossible to determine with any degree of reliability because little field information is available.'' Yet he estimates that ''only 40 percent of the world's available land is being farmed,'' with perhaps only 3.5 billion acres out of a total of 6. 2 to 8.6 billion acres now producing crops.
Dregne forecasts that ''per capita food production will likely increase in developed countries, primarily on the continents of Australia, Europe, and North America, spurred by improved land management techniques and, in some cases, the reversal of moderate desertification.'' But he concludes that ''the large majority of the developing countries (primarily in Africa, Asia, and Central and South America) will have difficulty increasing food production.''
''Although desertification could be halted, and even reversed, in these developing nations, the deceptively slow degradation process is frequently overlooked, and the cost of reversing current desertification is steep,'' he says. ''This, combined with the additional expense of expanding cultivation to new lands, will make it difficult for these developing nations to increase food production to meet rising populations.''
The Global 2000 Report draws similar conclusions. It states:
''Environmental, resource, and population stresses are intensifying and will increasingly determine the quality of human life on our planet. These stresses are already severe enough to deny many millions of people basic needs for food, shelter, health, and jobs or any hope for betterment. At the same time, the earth's carrying capacity - the ability of biological systems to provide resources for human needs - is eroding. The trends reflected in the Global 2000 Study suggest strongly a progressive degredation and impoverishment of the earth's natural resource base.''
The report calls for worldwide action to protect ''farmlands, fisheries, forests, minerals, energy, air, and water.'' It projects that world population will grow from today's 4.5 billion to between 5.9 and 6.35 billion by 2000.
Because of this, the report predicts that, by the turn of the century, the resulting increased demand for agricultural products could double the real price of food and seriously damage the soil. As more fragile lands are opened up to meet agricultural demand, the report warns, ''Serious deterioration of agricultural soils will occur worldwide, due to erosion, loss of organic matter, desertification, salinization, alkalization, and waterlogging.''
Projecting ''an accelerating deterioration and loss of the resources essential for agriculture,'' the report states that ''this overall development includes soil erosion; loss of nutrients and compaction of soils; increasing salinization of both irrigated land and water used for irrigation; loss of high-quality cropland to urban development; crop damage due to increasing air and water pollution; extinction of local and wild crop strains needed by plant breeders for improving cultivated varieties; and more frequent and more severe regional water shortages - especially where energy and industrial developments compete for water supplies, or where forest losses are heavy and the earth can no longer absorb, store, and regulate the discharge of water.''
The main change affecting the 1980 report's findings, Dr. Barney says, is that world oil prices have risen faster than anticipated. He explains that ''the United States continues to pursue policies that will lead to a substantial deterioration of the soil resource base of this country by the end of this century.'' He says higher oil prices can only add to the massive investment needed to reduce soil losses. These emphasize the need to take corrective action now rather than later.
But even widespread agreement that a problem exists does not guarantee a consensus about possible solutions.
Neil Sampson, executive vice-president of the National Association of Conservation Districts, outlines the basic problem clearly in his recent book ''Farmland or Wasteland: A Time to Choose.'' He writes: ''We stand, in most places on earth, only six inches from desolation, for that is the thickness of the topsoil layer upon which the entire life of the planet depends . . . . Continuing to grow food year after year without appropriate soil conservation management wears out the soil as surely as though you ran a factory at full production without investing in repairs or maintenance. The factory would soon wear out; the land is no different.''Mr. Sampson, a former US Department of Agriculture soil scientist, estimates that, with current erosion rates, ''it would only take 100 years to wash away every single acre of cropland now being farmed in the United States.'' The remedy, he says, is to realign government farm programs to offset the current economic pressures on farmers. These force them into farming for short-term profits rather than maintaining their soil's long-term productivity.
But just as neighboring farmers often choose very different farming practices , so do agricultural experts have different views as to what should be done.
There are at least three distinct lines of argument:
* The environmentalist leaps to the conclusion that emergency actions must be taken immediately to preserve the world's seriously endangered land, water, and air. The Global 2000 Report, as cited above, has moderated and documented this viewpoint.
* The supply-side economist insists that, given a free rein, market forces will automatically protect natural resources to the degree that is necessary and cost-effective. The extreme statement of this position comes from Julian Simon, a University of Illinois economist, who maintains that vast land, food, and energy resources remain untapped.
* The cautious optimist or government bureaucrat concludes that persistent soil erosion calls for international action but that the world already has the tools in hand to correct the situation. Soil Conservation Service chief Peter Myers puts this case well.
For the environmentalist, any of the countless erosion-torn fields from Montana to Louisiana is just one tiny example of massive worldwide abuse of agricultural land, forests, and fisheries. In this view, the deteriorating global situation demands urgent action to protect vital natural resources endangered by uncontrolled exploitation.
Robert J. Gray, director of the nonprofit American Farmland Trust, says that until the world's governments give higher priority to curbing soil erosion, ''we will continue to damage our soils and we will create more serious problems.''
A supply-side economist, however, takes a very different perspective. In dollar-value terms, a badly eroded field has lost any present worth as agricultural land, because of the natural balance of supply-and-demand forces. When and if demand for agricultural products increases, it may make economic sense for a farmer to rehabilitate this field.
According to an economist with Resources for the Future, Pierre Crosson, it is probable that further breakthroughs in agricultural research will provide new high-yield techno-logies enabling the world to feed and clothe itself even better than at the present time. In this case world needs will be met with fewer acres per capita because each acre devoted to agriculture will become increasingly more productive and therefore increasingly more valuable in dollar terms. The most suitable land's increasing market value for agriculture will automatically provide the incentive for its owner to protect it from erosion or from being swallowed up by urban sprawl.
Midway between the environmentalist and the economist, the mainstream expert sees any highly eroded field as a challenge that demands a complex mixture of corrective measures. Thus farmers need both technical and financial support for action that will restore their fields' productivity and reduce off-farm effects such as flooding, clogging of shipping channels, and water and air pollution.
According to the middle view put forward by many US Department of Agriculture officials, the federal government should share the cost of repairing past damage and preventing future soil erosion because of the high cost of the cure and its general public benefit. But rather than ask the government to spend money on a crash program, those who hold this view call for local, state, and federal governments to formulate new coordinated policies which consistently encourage conservation rather than exploitation of land and other precious natural resources.
Without a new public commitment to building rather than depleting the world's soils, Robert Gray warns, ''the steady increases we've had in yields per acre will level off.'' He says that ''we have built a highly sophisticated and complex agricultural machine, but many factors, including soil loss, could throw a monkey wrench into this machine.''
Tomorrow: Stop paying farmers to ruin the land