The Carter administration opened a public campaign of "friendly persuasion" with the Senate yesterday in a drive to fill four-fifths of 152 newly created federal judgeships by April 1.

Attorney General Griffin B. Bell held a news conference to expound on president Carter's efforts to fill the choice jobs on the basis of merit rather than traditional Senate patronage.

Carter signed an executive order yesterday that set standards for merit selection, urged senators to use voluntary commission to choose candidates and required affirmative efforts to recruit more women and minorities as judges.

Bell said he recognized that not all senators would pick their candidates for the 117 new district judgeships by commission. "Some will refuse," he said. "But we hope and except they will use an open process."

Sen. Llyod M. Bentsen (D-Tex.), for example, sent Carter and Bell his choices for 10 new judges in Texas without waiting for the president's merit guidelines.

"I am the merit commission for texas," he told a Dallas newspaper months ago.

But Bentsen said in a telephone interview that he was confident his nominees would meet any standards. "I want you to know how far I've gone," he said. "I have picked the first black from Texas, two women, a Mexican American and a Jew."

He used a confidential group of advisers to screen more than 200 possible candidates and submitted his final list to a state bar association for approval before forwarding the 10 names on to Washington, he said.

Other senators, including Edward M. Kennedy (D-Mass.), the incoming chairman of the Senate Judiciary Committee, also started their selection process before the president set his merit standards.

Kennedy did use a voluntary commission, however, to pick 15 finalists for the four new judgeships in Massachusetts, an aide said. A black and a woman are expected to be among Kennedy's selections, another aide said.

Bell said yesterday that is important to get more qualified women and minorities as judges because it would build public confidence in the system of justice. At present there are only nine women and 29 Blacks and Hispanics among the 525 sitting federal judges.

The attorney general, who was a federal appeals court judge for 15 years, said he would not hesitate to ask selection commissions to reopen their search if the process was unfair or failed to produce qualified candidates.

An official of the Virginia NAACP already has complained that Sen. Harry F. Byrd Jr.'s commission didn't adequately seek out blacks and women. Byrd reportedly forwarded the names of 10 white males for new judgeships in Virginia.

Bell said he welcomed media and public scrutiny of the administration's choices to fill the judgeships, the most ever to be appointed by a president.

"I know that the public sometimes loses patience that the president can't come in and with one fell swoop, by fiat, carry out his campaign promise" for merit selection, Bell said. "But by the time we finish selecting these 152 judges, we will have substantially carried out his pledge."