Just when we thought all we had to worry about was unemployment, the deficit, Nicaragua and the MX, here comes ABC News to tell us that the American farm is dying.

In an hour bristling with awesome statistics and stunning scenery, "Vanishing America" (Channel 7, tomorrow at 7 p.m.) tells us that the independent farmers of this nation are drowning in cascades of their own wheat. And if you think of independent farmers as straw-chewing old-timers with 40 acres and six cows, think again.

We're talking about big: 12,000 acres, say. We're talking about spreads worth $9 million or more, growing so much wheat that 30 hired cutters take five days to harvest it. We're talking about the people who grow 96 percent of America's food.

"The more they produce," says Rep. Tom Daschle (D-S.D.), "the cheaper the product. The cheaper the product, the lower the income. The lower the income, the greater the pressure. The greater the pressure, the more they try to produce next year. And it goes on and on."

Joe Fanger of Pierre, S.D., (pronounced "peer") owes $800,000. He grosses $450,000 a year but spends $465,000, losing $15,000 even in the best of times. "Everybody's stuck by me," he says, his eyes glittering with tears, but his equity is running out. The farm his grandfather started will go to auction sooner or later. Last year, with "the best crop ever," he still lost money.

The film's best sequence shows Fanger and his crew racing to harvest 2,500 acres against a tornado alert as a gigantic black storm rolls majestically toward them over the magnificent billowing plains. He made it that time, but some of his neighbors didn't, and Marshall Frady takes us in this smoothly assembled "Closeup" documentary to a farm auction, a scene of quiet bitterness and flashing tempers.

The camera work, the clean editing, the good connections with people bear the unforgettable stamp of John Korty's style, and sure enough, there he is, listed as executive producer for the firm associated with ABC in making the picture. Pam Hill was the network's executive producer.

Last year, Frady reports, 34,000 farms were lost to rising production, falling prices and inflated costs, in the worst down swing of the cycle since the Depression. Part of the blame, Frady says, belongs to the 1979 embargo on exporting wheat to the Soviet Union, since lifted, and upon Washington's historic inability to form a coherent farm policy. But partly it is just the American tradition of more: buy more land, produce more wheat, expand and expand for the sake of expansion itself.

He asks--and the baffled, seamed faces of the farmers ask, too--what is happening to "the most efficient farming system in the world" and the vast, rich land that economics are forcing into ever larger tracts. He speaks of the Payment in Kind program that left a third of the fields fallow last year but is only a short-term response to this crisis of plenty.

In the end, there is no answer, and we are left gazing out across those superb rolling vistas under the big skies of Montana, Nebraska, the Dakotas, and wondering what is going wrong.