An article on soil erosion in yesterday's Post incorrectly described Rep. Cooper Evans (R-Iowa) as not being a member of the House Agriculture Committee.

It didn't take long for freshman Rep. Cooper Evans (R-Iowa) to learn what happens to congressional upstarts of his ilk, people with bright ideas and brass enough to think they can solve a problem.

Powers-that-be swat them crisply across the chops. Evans got whacked a good one for his efforts last fall and therein lies a story about one man's venture into the political minefield of soil erosion control.

Through 45 years of federal programs, erosion control has cost taxpayers more than $15 billion (more than $800 million this year), with only mixed results on millions of acres of farmland. Farm topsoil continues to erode, and at higher rates than during the Dust Bowl years, when the new programs were born in a storm of blowing soil.

On-the-farm results are debated heatedly, but there is little doubt about this: the programs have created political fiefdoms in Congress and in the states and have generated intense and counterproductive bureaucratic competition within the Department of Agriculture.

"It is important to recognize that Congress has created that lack of unity within the department," said R. Neil Sampson, executive vice president of the National Association of Conservation Districts. "USDA won't move unless there is a mandate from the politicians."

But not even the politicians are in accord. A case in point involves Evans, who is not a member of the Agriculture Committee. He intruded on a fiefdom when he persuaded the House to put a mild conservation provision in the 1981 farm bill.

He wanted to reduce the chance that farmers participating in federal land set-asides to limit production (there are no mandatory set-asides now) would be paid for retiring land that did not contribute to conservation. In other words: don't reward the farmer who isn't serious about erosion control.

The concept is politically touchy. In the eyes of some farmers and legislators, it edges toward tying a farmer's federal crop support loans and payments to his farming practices--something akin to land-use controls.

But others see the removal of government subsidy from irresponsible cultivation as an idea whose time has come.

"If the federal government can't mandate conservation, at least it can say it won't be a party to a farmer's raping his own land by giving him price support loans and deficiency payments," said Thomas Barlow of the Natural Resources Defense Council. "If the government is going to underwrite production and keep farm prices down, it has become a part of the problem."

Sen. William L. Armstrong (R-Colo.) has proposed legislation (hearings are to be held soon) that would move the federal program in this direction. His bill would deny support loans to any western farmers who plow up arid, erosion-prone rangeland that has not been cultivated during the previous 10 years. "We must stop paying farmers to destroy our nation's soil," he said.

But the sensitivity of such ideas kept the Senate from including such provisions in its farm bill. And House conferees let Evans' even milder amendment die when the issue arose in a House-Senate conference on the bill.

Evans prefers not to talk about it, but congressional sources say the amendment was abandoned because it circumvented the Agriculture Committee, whose turf is erosion control. Evans was punished for stealing thunder on an issue that "belonged" to others.

It was not a major political event, but the vignette is reflective of the political struggle that has gone on for years over where and how to spend the prodigious amounts of money the federal government has poured into conservation programs since the 1930s.

Under the rubric of erosion control, billions have been spent on a variety of programs that, in the eyes of many in the conservation community, have only incidentally saved topsoil while creating a pork barrel that builds ponds, small watershed dams and channelizes streams. These "flood control" schemes in many instances are on-farm projects designed to increase production.

The National Wildlife Federation charged in a recent study that soil conservation has been overrun in the lust for pork. NWF found that 10 of 13 new small watershed projects of USDA's Soil Conservation Service showed less than 10 percent of their economic benefits from erosion control. That is, the projects' major benefits would come from increasing tillable cropland.

Some examples of the arm-wrestling and log-rolling in the erosion programs:

* USDA's approach to the problem has remained disjointed and compartmentalized. A years-long squabble between its Soil Conservation Service and its Agricultural Stabilization and Conservation Service is said by many to have hindered progress. Basic cultivation research--important in the erosion picture--is handled by another arm of USDA. Still another, the Extension Service, has a record of stressing higher production and discounting soil-saving cultivation techniques.

* Farmers have benefited in many ways from erosion control programs, but so have earth-moving contractors, agribusiness vendors and land attorneys. They have prospered under programs that have built 2.5 million small water impoundments and 37 million acres of expensive terraces, planted more than 8 billion trees and channelized thousands of miles of formerly free-running streams.

* The General Accounting Office (GAO) reported in 1977 that three major USDA soil-conservation programs fell short of objectives. GAO said that they had downplayed erosion control (USDA concentrated on water management and higher farm production) and that little or no effort was made to help farmers with the biggest erosion problems.

* In the view of critics, some programs are hamstrung by a highly politicized nationwide network of local soil and water conservation districts, controlled by farmers and supported by legislators bent on seeing that each area gets federal money whether it needs it or not. The National Association of Conservation Districts (NACD) opposes the targeting now being pushed by the Reagan administration to spend where the need is greatest.

* Even when executive branch efforts have been made, some have been stymied. Rep. Jamie L. Whitten (D-Miss.), the Appropriations Committee chairman and a major figure in agriculture debates, boasts of his success over 27 straight years in derailing successive administrations' efforts to alter the main ASCS cost-sharing program. The GAO study in 1977 held that much of the money had been spent on soil that did not need erosion control.

* Neither USDA nor Congress has concentrated conservation spending on the most critically eroding areas, a relatively small portion of the 413 million acres now under cultivation. States with more political pull get more money. Texas, for example, has about two-thirds less farmland erosion than Iowa but it gets twice as much federal money. Although under congressional mandate to do so since 1977, USDA still has not publicly identified the areas that most urgently need erosion-control aid.

On this backdrop, another round in the soil-erosion struggle seems likely to be played out again this year. Congress is under growing pressure--some of it from members--to take a new look at different approaches to dealing with the erosion problem. The new farm law continues present programs and does nothing to break up the intramural wrestling at USDA, but directs the secretary to stress conservation tillage and to emphasize aid to the most needy areas.

A Senate Agriculture subcommittee is planning hearings on various proposals and Sen. Thad Cochran (R-Miss.) intends for his appropriations subcommittee to take a special look at erosion and the spending priorities. No House action is scheduled, although Agriculture Committee members such as Reps. George E. Brown Jr. (D-Calif.) and Arlan Stangeland (R-Minn.) are urging that Congress more closely consider the consequences of unabated erosion to farm productivity.

Stangeland is calling for formation of a national blue-ribbon panel of experts to draw up a plan for conserving farm land and water to avert a world hunger crisis. He said recently, "We still haven't come to grips with the issues. The growth in productivity of American agriculture is leveling off . . . the roots of a world food crisis are already present. One major cause of this decline is the depletion of three major farm inputs: topsoil, water and farmland."

Others, such as NACD's Sampson, put erosion-control on a plane with national defense. "Our ability to defend ourselves may be threatened more by farm policy failure than by what is or is not happening in the purchase of new weapons systems. But the public isn't getting that story."

In theory, at least, Agriculture Secretary John R. Block agrees with that thesis, but the administration budget falls short of meeting the need that legislators and conservationists see in erosion control.

Block told Congress last fall that erosion is reaching crisis levels and must be confronted, although USDA plans no new spending on erosion programs. The administration's budget, in fact, has moved the other direction, cutting the number of soil technicians and scientists and reducing conservation spending.

Meanwhile, the administration is completing a long-range erosion control policy and action plan required by the 1977 Soil and Water Resource Conservation Act (RCA). A public comment period has just ended on a proposed plan that closely parallels conservation provisions of the 1981 farm bill.

The proposed budget for fiscal 1983 would cut $222 million from USDA soil and water conservation programs, with the biggest share--$164 million--coming from cost-sharing schemes. Only the "most urgent" public works flood control projects will be funded, and $10 million would be earmarked for grants to be matched by the states for their most critical erosion control problems.

Although Congress endorsed "targeting"--putting money where need is greatest--the administration's approach already is stirring emotions. The NACD, for example, is resisting the plan that could put as much as a fourth of the federal personnel and money in the neediest areas.

Many counties would lose the services they now get from USDA soil technicians, who would be sent to more critical areas.

Iowa Gov. Robert D. Ray, whose state loses more topsoil than any other, generally supports the administration's plan, but he worries about the political grappling and the budget restraint that erosion-control spending will feel.

"There will be turf battles," he said recently, "because Congress doesn't want to relinquish any of its control over money. We'd like the freedom to stretch our money further, but the block grants that would have done that are out. If they're interested in the future of the country, they'll put more money in this."