Every night all week, a special mass has been said here in the little white church on the prairie. The services, like everything about St. Patrick's Church, have been plain and unpretentious.

It is corn-picking time, and some men come to worship straight from the fields in blue jeans and flannel shirts; five or six younger women carry babies over their shoulders; and the Rev. John Richter, the church's shaggy-haired priest, sheds his white clerical robes as soon as the last hymn is sung so he can mingle with the parishioners in an open-necked shirt and blue windbreaker.

The church plans to hold the same kind of short, homespun service Thursday when it hosts Pope John Paul II in his only stop in rural America.

"This is one place in the country where the pope's visit is not going to be turned into a sideshow," Father Richter, 28, said last night. "This will be a much different kind of experience than he'll get anywhere else on the trip.

"We want this to be a prayerful visit of the pope to a simple country parish. You're not going to see anyone selling T-shirts or bumper stickers around here."

The prospect of the spiritual leader of seven million Catholics visiting a parish with only 205 members (counting a baby born last week) has understandably excited the people of Irish Settlement, a community with no stores, schools, or street signs.

But it hasn't awed them.

"Being farmers we're able to deal with crises without showing a lot of emotion," said John Connor, who operates a 1,000-acre farm across a dusty road from the church.

The pope is scheduled to spend about 20 minutes here. And only parishioners and a handful of reporters will see him during that time.

But church leaders hope the setting, deep in America's heartland, will oblige the pope to address some of the most profound social and economic questions that will be raised in his week-long trip to the United States.

"We don't know what the Holy Father will speak about," says Bishop Maurice J. Dingman of the Diocese of Des Moines, which includes St. Patrick's. "But the setting is made to order for him if he cares to address rural issues."

Land ownership is something that Dingman, an outspoken opponent of corporate farming, hopes the pope will address either at St. Patrick's or at an outdoor mass at Living History Farms, a 600-acre outdoor museum on the outskirts of Des Moines.

"The family farm was what made our country great, but it is rapidly disappearing," says Dingman, who as chairman of the National Catholic Rural Life Conference, has organized a project to investigate land ownership patterns and management. "We don't have to say bigger is better. We can say small is beautiful."

In organizing Pope John Paul's four-hour visit to the Des Moines area, his only stop west of the Mississippi, Dingman, one of the nation's most liberal bishops, has tried to stress simplicity. And as chance would have it, the visit falls on the Catholic feast day of St. Francis of Assisi, the patron saint of Italy, who is best remembered by his humility and poverty.

Thus, there will be no motorcade, no visit to any cathedral, and no VIP section for the pope in Iowa. Instead, John Paul will be met by 150 elderly and handicapped people at the airport, visit St. Patrick's, and say mass to a crowd expected to reach between 200,000 and 500,000 people gathered in a pasture.

"I hope we can give the pope a feeling of rural American while he's here," said the bishop. "I'd hope he'd go back to the Vatican and say to himself, 'The future of America is in small towns and countrysides.'"

St. Patrick's is a political advance man's dream. It is old, remote and picturesque, a poignant, reminder of an America that existed a century ago.

It sits on a grassy knoll about 16 miles southwest of Des Moines and is adorned with a colorful rectangular spire that rises to treetop height. The church cemetery sits nearby.

Irish settlers first built a log church on the 40-acre site in 1852. When they outgrew the structure, they built the white frame church that stands today, creating considerable local controversy by using milled lumber rather than logs. Still visible are the tie rods that hold the building together after wind blew down the walls during construction.

The church is one of a dying breed. The names on the century-old tombstones behind it are carried on by today's congregation. They are solid Irish names, like Laughlin, Connor, Kiernan, Walsh, and Harrington. The grandchildren and grandchildren's children farm the same land the immigrant newcomers did a century ago and they attend the same church. They are more American than Irish now, however. "That place is so American you could cut it with a fork," says Jay Anderson, director of research at Living History Farms museum. "They go to church. They vote Democratic. They're exactly what Tom Jefferson had in mind when he wrote about the American yeoman."

"I don't think you'll find many parishes this close," Leo King said the other night. "After services you'll find all of us hanging around for a half hour or so. We talk about corn prices. We talk about politics. When something happens, people rally around. When Don Lynch went to the hospital last week, the word got around in no time. Everyone turned out and picked his corn."

If St. Patrick's is taking the pope's visit in stride, the rest of Iowa isn't. The pope's visit is the biggest thing that ever happened here, and no one lets you forget it. At the Des Moines airport, pope posters sell for five dollars, pope T-shirts for $6.50 and pope buttons for $1.50. A sign outside one downtown tavern today said, "Join us for our pope party at 4 p.m."

Published reports that Des Moines (Iowa's largest city) would be flooded with visitors scared people half to death. Meanwhile, fearful that crowds would be embarrassingly small, the Catholic diocese yesterday put spot announcements on radio and television telling people there will be plenty of room for everyone to see the pope.

But what was perhaps more revealing of the mood here is this incident: Last week a lawyer went into a local district court, asking that the trial of a client charged with operating a house of prostitution be postponed until after John Paul's departure.

"The papal visit creates immense possibility that the standards of morality in the community may be magnified fifty-fold," said attorney Alfredo Parrish. The judge agreed. The trial was reset for November.