SPRINGFIELD, Mass. (AP) _ Rep. Edward P. Boland, author of the amendments which barred U.S. aid to the Contras in Nicaragua, announced today that he will retire after 36 years in Congress.

''I've decided to call it a day,'' the 76-year-old Democrfat said at a news conference at Our Lady of Hope School, surrounded by supporters in the Irish neighborhood where he was born and raised.

''The parades are all over. The give and take of the campaign trail no longer beckons and the time has come when the bell tolls on a career that has been for me an exhilarating and fulfilling experience,'' he said.

Speculation that he might retire led three Democrats - Springfield Mayor Richard Neal, former Mayor Theodore Dimauro and state Rep. Kenneth M. Lemanski of Chicopee - to announce they were interested in the seat, provided they didn't have to oppose the incumbent in a primary.

Boland did not endorse anyone to succeed him.

The Reagan administration's frustration with the Boland Amendments inspired the diverion of profits from arms sales to support the Contras. That operation became a focus of the Iran-Contra investigation and the recent indictment of former Marine Lt. Col. Oliver North and others.

The reserved Boland came to Washington with the man who would later become the speaker of the House, Thomas P. ''Tip'' O'Neill, in 1952. For more than 20 years, the two friends roomed together in an arrangement they described as a real-life ''Odd Couple'' with Boland, the neat and tidy half of the pair.

Many expected him to follow O'Neill into retirement in 1986, but some believed that Boland stayed, in part, in the hopes of taking over the chairmanship of the House Appropriations Committee.

Boland is the No. 2 Democrat on the powerful panel and would be in line for the chairmanship if Jamie L. Whitten of Mississippi retired. Whitten, who is a year older than Boland, has already announced plans to run for re-election.

The son of Irish immigrants who settled in Springfield's Hungry Hill district, Boland was elected to the Massachusetts House of Representatives at age 22 and never lost an election in a half-century in politics.

Boland served as chairman of the House Intelligence Committee from 1977 to 1985.

He remained a bachelor until 1973, when he married Mary Egan, then the 35- year-old president of the Springfield City Council. They have four children.