Save the soil

The food on your table depends on farmland that is disappearing at a rate causing international alarm. Like oil, when it is gone, it is gone. The challenge - and the emerging solutions - are of greater long-range significance for humanity than the most sensationally headlined events of the day.

That is why the Monitor devoted four double pages to ''Soil: the crucial resource'' last week. It is why full attention should go to exploring the potential crisis during America's postponed (but not for long) congressional hearings on the proposed National Topsoil Preservation Act of 1982. It is why international momentum must be developed in line with the World Soil Charter adopted by the United Nations Food and Agricultural Organization last year.

Saving the soil may seem remote, especially to city dwellers bringing home plastic-swaddled tomatoes from supermarket bins. But it is not remote to farmers seeing their topsoil blown away, contaminated, or exhausted, and having to decide to cherish the land or abuse it for quick profit. There will be nothing remote about it to anybody's grandchildren if present trends continue:

* A multiplication of the world's desert acres from 2 billion to 7.5 billion by the end of the century, for example.

* In the US, the globe's leading agricultural country, such severe soil losses on 12 percent of the cropland and 17 percent of the rangeland that these will be unproductive in a few decades.

Various countries and international agencies are struggling with the problem and its cure. The agroforestry movement headquartered in Kenya, for example, is trying to improve the use and preservation of land through planting trees and crops together in ways to enrich each other and the soil.

But, just as the United States plays the leading role in food production, it is looked to for a lead in policies and practices to maintain the land as well the abundance it produces. Increasing productivity - so that more food can be grown on dwindling acres for an increased world population - may help, but only in the short run.

In a sense the buck stops with the farmers. Many, such as the Amish, need no urging to use prudent methods in which crops, livestock, and land form a harmonious cycle of production and renewal. Others destroy fertility through intensive short-term means for immediate results, leaving the future to take care of itself.

The latter means can unfortunately be encouraged by some government subsidy programs. Among current proposals are ones to make subsidies dependent on appropriate conservation practices.

The specter of federal interference need not be raised as it was when Rep. Morris Udall of Arizona and Sen. Henry Jackson of Washington vainly fought for national land-use planning legislation in the 1970s. The Senate twice passed such a bill. It offered a light federal hand, with aid to states to come up with their own plans. In Mr. Udall's words it said: ''States, we want you to do some land use planning and we're not smart enough to do it for you.''

Such a governmental attitude might have aided ancient civilizations that let their lands decline. There is growing agreement that some national pressure will be needed to use land more wisely in the United States if the localities and farmers do not do so on their own. In present economic conditions farmers may plead they cannot afford conservation measures. Here congressional debate could be useful in determining how far taxpayers might be expected to help in preserving what is, after all, a national resource.

Issues like this could be aired in the hearings on the modest topsoil act now proposed by Mr. Udall and Rep. Neal Smith of Iowa. It calls for stockpiling and replacement of topsoil on public and other lands affected by federal projects. But its ripples could go far in stimulating awareness of the subject.

The kinds of examples the US could give were suggested in the federal follow-up to the Global 2000 report, whose warnings have become better known than its recommendations in recent years. The latter include:

* Federal technical and financial assistance to state and local governments wishing to develop land preservation policies.

* Financial incentives to encourage conservation and preserve farmland.

* Seeing that federal programs (loans, sewers, highways) do not unnecessarily spur farmland conversion to other uses.

* State and local use of growth management tools to discourage farmland conversions.

Here is food for thought as the world gives thought to food - and to the crucial resource it grows in.