Americans have a choice:
* Either treat the world's most productive cropland as a finite, nonrenewable resource to be ''mined'' for maximum short-term profit.
* Or else maintain the nation's rich soil as a fully renewable resource through good farm management.
The difference is that the second option pays off with soil which will become even more productive for future generations. Yet this book warns coolly that if erosion continues at present rates ''it would take only 100 years to wash away every single acre of cropland in the United States.'' How rapidly this 100-year ''window'' narrows depends on which assessment you accept about new demands placed on America's 413 million acres currently devoted to crops and the additional 127 million acres of potential cropland.
Some experts such as Julian Simon, a University of Illinois economist, argue that the world is in no danger of running short of food or cropland. Others take present needs, add new factors such as raising corn to produce gasohol for fuel and paving over more cropland for shopping centers or nuclear power plants, and conclude that a crisis is approaching.
Farm-bred Neil Sampson makes his own stand clear and compelling.
''Every farmer,'' Sampson writes, ''has both the opportunity and obligation to become a conservation farmer.''
This message is for ordinary urbanites as much as for the farmers and ranchers and the policymakers who have spent years arguing over the various conflicting projections of cropland needs. (The projections are presented side by side in this book and its valuable appendices.)
Sampson argues that more than 50 years of research has given farmers all the information they need to win the battle against erosion. And he argues that this battle must be waged by farmers, because ''public programs don't save soil or manage water. Farmers do.''
Sampson's own eight years as a government soil technician working closely with farmers convinced him that most farmers share a sense of stewardship toward their land. When farmers degrade rather than improve their land, he explains, it is largely because of economic pressures. He is particularly critical of government programs that penalize farmers who use conservation techniques while rewarding those whose intensive methods produce short-term high yields but ultimately ruin their land's productive capacity.
Along with groups such as the Natural Resources Defense Council and his own employer, the National Association of Conservation Districts, Sampson points to the 1930s as the source of many current problems. In an intriguing history of federal involvement in agriculture, Sampson shows how early pick-and-shovel experiments in erosion control ballooned into a massive, self-perpetuating public works program. The legacy is that cutting down on America's yearly 6.4 billion-ton loss of soil is considered a big-bucks federal responsibility -- rather than an essential goal which can be achieved by relatively inexpensive farming practices applied locally.
Sampson's aim is to change the public's mind. He argues that an aroused public can create ''a sustainable agriculture.''
In a paragraph summing up this book's high goal, Sampson writes:
''A sustainable agriculture is one that produces the food, fiber, energy, and other crops that we need as a nation, including a marketable surplus that can be sold abroad. It produces this on the average year, not just during times of unusually good weather. It can stand a bad year by drawing on stored fertility and moisture in the soils; stored water in reservoirs; stored wealth in financially secure farms; and stored food products in the granaries of farmers, industries, and government. It can profit from a good year by setting aside extra commodities or making an extra effort to see that they are sold abroad, without driving prices through the floor and creating financial hardship and ruin among producers. In addition to meeting our food needs, a sustainable agriculture would reduce the waste and pollution of water, provide better wildlife habitats, slow the advance of desertification and soil salinization, reduce the loss of prime farmlands and fragile topsoils, and, in general, make rural America a far more healthy, satisfying, and financially rewarding place to live.''
Achieving this goal depends on the voluntary effort of farmers. But, Sampson insists, it also depends on the other 97 percent of Americans learning about the challenges facing agriculture, writing their congressmen, and perhaps signing up to help through one of the many government and private groups working to keep America's fields green.