Who will farm the land if the banks take over?

American farmers are wasting the land upon which the strength of the United States depends. Between 4 and 6 billion tons of topsoil are moved each year by various forms of soil erosion. On 12 percent of the nation's croplands and 17 percent of the range lands, soil losses are so severe that those lands will be unproductive within a few short decades.

Although these trends do not lend themselves to any certain predictions, they suggest that the equivalent of between 25 and 62 million acres could be lost in the next 50 years. In the past decade, an additional 10 million acres of land with excellent physical characteristics for growing crops was converted to urban , industrial, and other nonagricultural uses. Asked why these damage levels and losses are occurring, many farmers respond that the financial crunch and technological treadmill they find themselves on today give them no choice.

In the rarefied atmosphere of Washington, D.C., it is too seldom recognized that public laws, regulations, or programs don't save soil or manage water. Farmers do. They manage those resources as part of the day-to-day work of their private business. In soil conservation, as in crop, livestock, or family financial management, they do what they have the knowledge and skill to do, the finances and equipment to carry out, and what seems, in their own private calculation of costs and benefits, to be the ''right'' thing.

Protecting farmland involves additional costs. The farmer must pay to make investments in soil productivity, construct conservation practices, or forgo income when cash crops are replaced by soil-building crops. But these investments seldom, if ever, result in immediate cash returns. The profits from protecting farmland accrue slowly, largely to future generations.

So how is the farmer to justify such added expenditures? The market does not recognize or reward him. A bushel of corn produced under careful soil stewardship brings no better price than a bushel produced on land being allowed to wash or blow away. The fact that the conservation farmer had a higher cost of producing his corn is of no consequence to the buyer. So today's farmers, caught in a vicious cost-price squeeze, are forced into deficit financing, biological as well as economic. The severity of the situation can be readily seen on the land, and on the balance sheets.

American agriculture is precariously close to bankruptcy. Farm debt is at least $200 billion, up from $175 billion at the end of 1980. The US Department of Agriculture predicts 1982 net income to be $13-$18 billion - the lowest farm purchasing power since the depression. Part of this is due to the general recession affecting all Americans, but much of today's stress is due to the nature of the market that national farm leaders have intentionally created. Today, more than ever before, the American farmer produces for a global market.

This global market has allowed farmers to vastly expand their production and has been a real boon to the US economy. Over $40 billion in sales abroad helps the US pay for imported oil and other products. But this situation is inherently unstable, and having one-third of US farm produce moving into an unpredictable, volatile market affects all prices, domestic as well as foreign.

Economists call the situation a ''thin'' market. Most nations produce 95 percent or more of the food they consume, then import the rest. As a result, a 5 percent change in their annual production, due to relatively minor weather variations during the year, can either double their import needs or eliminate them entirely. What is, to that nation, a relatively small variation in crop size is, when added up into an international market, a major event that can move prices by as much as 25 to 50 percent in a matter of months.

The supply of American farm products cannot be turned on and off that rapidly , however, so farmers, or the government, must find some way to manage in an atmosphere of increasing uncertainty and stress. Whether or not that is even possible is a question that plagues national policymakers, but one thing grows more and more certain: the current situation is untenable and threatens to bankrupt both America's farmers and the nation if not changed soon.

Another 1930s-style farm depression would not, however, be just a repeat of that social and financial disaster. The rates of land damage inflicted today as farmers fight for survival using their high-input, big-machinery technology are more serious than at any time in human history and threaten to damage the land so badly that economic recovery could be seriously threatened.

Fighting for short-term economic survival by mining the land's fertility is a workable strategy if it can be kept relatively brief. The problem, of course, is that it is perilous in the longer term, and the actions of the past decades are catching up with us. The future is now. Government must act, and soon. The solutions will not be easy, as past farm policy efforts have proven. But they must be sought.

The longer the nation delays, the more difficult the solutions will become. Half of the national farm debt is secured by the land's value, yet soil erosion and farmland conversion continue to eat slowly but inexorably into that value. What will be gained if farmers default and the land ends up in the hands of banks, holding corporations, insurance companies, or government agencies? Who will farm it then? Will we end up with a new class of peasant farmers in America , working land for major institutions or governments? How much good land will be left, after this period of waste is finished? Enough, surely, to meet our needs for survival, but what about our ability to rebuild a strong national economy?

One thing is certain - these are not questions that concern only farmers. Every citizen who expects to continue buying the necessities of life with a reasonable portion of his income should demand action to prevent the destruction of America's farm industry and the associated waste of the resources that have made, and could continue to make, the US a strong and wealthy nation.