What is really eroding in America

Soil erosion worries President Reagan and millions of other Americans. The news media carry frequent scare stories about loss of topsoil. But Department of Agriculture surveys show that less land is eroded now than in the 1930s. And the quality of cropland shows improvement in surveys from the 1950s to the 1970s.

Furthermore, analyses by University of Illinois economist Earl Swanson indicate that government programs to force farmers to change their farming practices have little or no economic support.

Yearly ''loss'' of 3 million acres of farmland to ''urbanization'' has been proclaimed by the National Agricultural Lands Study (NALS) of the Carter administration, supported by Secretary of Agriculture John Block, and publicized widely by environmentalist organizations and the media.

This assertion is simply preposterous.

It is contradicted by all the other available evidence, much of it very solid scientifically. The true figure is roughly one-third of the heavily publicized 3 million-acre figure.

That is, the 1970s were no different from the average for 1950-70 of about 1 million acres a year, a figure which Thomas Frey of the US Department of Agriculture documents extremely well and which he courageously defended against strong official pressure to change it. And only a portion of that 1 million acres is cropland, the rest being pasture, wasteland, and so on.

Furthermore, this change represents only a microscopic proportion of US land. Total urbanized land is less than 3 percent of US area. And we are making more new cropland each year - roughly a million and a half acres - from irrigating deserts and draining swamps than we are ''paving over.'' Most important, despite the assertions to the contrary, total US cropland has been going up and not down since the 1960s, owing to increase in demand for food - but at the same time producing a food glut.

The 3 million-acre figure is a governmental scam, disavowed even by the NALS's research staff after that agency shut down. The sole apparent basis for the NALS estimate was a faulty Soil Conservation Service resurvey in 1975 of a small portion of the observations in a 1967 survey.

Discussions of the ''loss of prime land'' often hinge upon misunderstanding of economic principles. Take the example of the new shopping mall called Market Place near Cham-paign-Urbana, Ill. The mall land has greater value to the economy as a shopping center than it does as a farm, wonderful though this Illinois land is for growing corn and soybeans. That is why the mall investors could pay the farmers enough to make it worthwhile for them to sell.

An example should bring out the point.

Suppose that, instead of a shopping mall, a corn and soybeans farmer sold the land to a person who would raise an exotic new crop which would be sold abroad at a high price. The land clearly would be more economically productive raising this than corn, as shown by the higher profits as compared with corn and soybeans and as also shown by the amount that the new farmer is willing to pay for the land.

A shopping mall is similar to this new farmer. It seems different, however, because the mall does not use the land for agriculture. Yet there is no relevant economic difference.

Why do government agencies put out the misinformation about farmland? Why do news media feature scare stories about it? There are a variety of likely reasons. Here I speculate about one cause only: that we feel something is wrong with our country and its productivity but do not want to put the blame where it belongs - on our institutions, our culture, and ourselves.

The food we eat and the housing in which we live come mostly out of muscles, nerve, hearts, and minds, rather than out of land. Developing better farming methods, draining swamps, irrigating deserts, and growing a vast number of vegetable crops hydroponically each year in central Illinois give many times the output per acre that our ancestors produced. And no end to the yield improvements is in sight if we continue to do research.

So what ism the problem? As I see it, the problem is that we don't want to work as hard as we did in the past (or as the Japanese work now). We prefer entertainment television to self-improving books (our book production per person is about half of West Germany's). We natives do not want to take risks to open businesses the way new immigrants did, and still do. We want to feel we are entitled to receive retirement payments many times in excess of what we put into social security, even if we are not poor and do not need public welfare support. We prefer to accept welfare payments instead of working at unpleasant jobs that we therefore fill with illegal immigants.

Our politicians do not have the will or the incentive to fight public opinion on these matters. Every interest group figures it ought to grab what it can for its members.

Of course we do not like this picture of ourselves, and we do not want to blame ourselves. So we focus our worry upon non-embarrassing nonproblems such as soil erosion and urbanization of farmland, instead of on our lack of will and nerve. If this analysis is correct, we are not doing ourselves any favors in the long run by concentrating our worry upon unfounded environmental scares such as soil erosion and urbanization of farmland.