Three years ago, very much unannounced, a reporter stopped in this little southwestern Iowa community to see what farmers and the Department of Agriculture were doing to control soil erosion.

It wasn't a bright picture. Soil loss in this hilly livestock and crop area ranged as high as 35 tons an acre each year (5 tons a year is the USDA's "tolerable" level) and the farmers' push for more production was relegating soil protection to the back burner.

In fact, erosion was so severe in this and 15 surrounding counties that the USDA's Soil Conservation Service called it one of the most critical areas in the country. A special targeting program was set up to give the area special care and attention.

Here in Cass County, the SCS man on the scene was William E. Willis II, one of the agency's scores of veteran soil conservationists across the country. In no particular order, a conservationist is a scientist, a technician, a bureaucrat and, perhaps most of all, an evangelist and teacher.

One thing that came through about Bill Willis, who eats his lunch from a black lunch pail, was his frankness. He complained that many of the farmers he worked with were too bound up in tradition, too unwilling to make the kinds of changes in cultivation techniques promoted by the SCS.

But being an evangelist, a man who had to go out and win adherents to the cause, Willis kept after it. He is still here, now in his 11th year in Cass County, running his little shop in the one-story, one-stop USDA service center on the edge of town.

In the three intervening years, however, the farm economy in this part of the country took a nose dive. When that happens, almost everyone in agriculture agrees, the often costly procedures farmers must follow to conserve their soil simply go to pot.

"There still is an ethic out here, and people still will try to preserve their soil, but the economic pressures are so severe that many farmers must give conservation a lower priority," Willis said.

Willis acknowledged that average soil loss has not been reduced much, if at all, in the past three years. But he said he thinks the payoff is coming. "The federal targeting program is starting to pay and I think we're going to see a reduction in soil loss pretty quickly," he said.

One of the reasons, he said, is the boom in "no-till" cultivation. Back in 1980 and 1981, only about six Cass County farmers were no-tilling their land -- that is, planting their crops directly into the previous year's crop stubble without first plowing the soil. By not plowing, erosion is stemmed, although the method involves greater use of toxic herbicides to control weeds.

"Last year, we had more than 100 farmers doing no-till on about 10,000 to 12,000 acres," Willis said. "It's getting hard to keep track of the numbers, there's so much of it going on. We're really beyond the experimental stage here now and the cost savings -- very important in times like these -- are coming through to farmers."

Through the foggy lens of memory, it appeared last month that there were more terraces on the hillsides, more of those expensive structures built to slow the flow of water and reduce gullying and topsoil runoff.

"Well, that's right," Willis said. "In an ordinary year, we'll build about 150,000 feet of terraces through an SCS cost-sharing program . But in 1983, when all that land was idled with the payment-in-kind program, the land was there to work with and we went after it all year. We put in 211,000 feet of terraces. Then in 1984, it went back down to about 150,000 feet installed."

Terracing is increasingly expensive, however. Two years ago, it cost $1.60 to install a foot of terracing; today the cost is around $1.74.

"We used all of our cost-sharing money last year, but the economic crunch is settling in for real here in rural Iowa, and I'm afraid we're getting on the edge of not getting all our cost-share funds spent because of the economic situation," Willis said.

"I get some satisfaction from pecking away at it, although I'll not see the job done in my lifetime," he added. "To get to the 5-ton soil-loss level, we have to make farming profitable, and we'll have to put more cost-share money out here at a higher rate."

Now, with the program in Cass County showing the potential for payoff, the Reagan administration has poised its budget scalpel over the SCS. Willis is distraught about that.

"If they shut off the SCS, where I've built a career based on retirement, it would leave me out on the job market. I've got a family to support and they wouldn't fare too well. I'd be irate," he said. "In the 11 years I've been here, we've built the program in this county and I hope we've built a better land ethic. If that is not nurtured and sustained, it is 11 years down the drain."