The Reagan administration yesterday acted on its own to implement emergency farm-credit relief spurned as inadequate by Senate Democrats, and the Senate remained mired in a bitter partisan dispute that delayed the expected confirmation of Attorney General-designate Edwin Meese III.

As a weary Senate met beyond midnight in its second late session this week, leaders of both parties hit an impasse after a day of exchanging offers aimed at resolving the farm dispute and ending a Democratic-led filibuster blocking a vote on Meese.

Shortly after midnight, Senate Majority Leader Robert J. Dole (R-Kan.) took the floor to tell colleagues that deal-making was off, that the Senate will meet today but not Sunday and that members should prepare for round-the-clock sessions starting Monday, if necessary, to force a vote on Meese.

"I think it's fair to say we're going to stay on the Meese nomination. We're not going to make any deals," said Dole, adding: "Rest up on the weekend. Get a lot of sleep. Get a lot of rest . . . starting next Monday, we're going to be up all night."

Minority Leader Robert C. Byrd (D-W.Va.) responded: "Apparently, the decision has been made to stay with Mr. Meese and let the farmers go to hell." Byrd, saying he had been in the Senate leadership 19 years, added: "I've never seen anything like this."

In what had become a political cat-and-mouse game, the administration seized the initiative early in the day when Agriculture Secretary John R. Block, acting on instructions from President Reagan, imposed the contested new rules without awaiting agreement with the Democrats.

Then, the Democrats, claiming that the provisions fell short of farmers' needs, continued filibustering in hopes of winning new concessions, including favorable conditions under which the Senate next week can consider broader credit relief.

The provisions embraced by Block were aimed at making it easier for farmers to qualify for loans and at enticing banks to make loans available, which Republicans said would help financially distressed farmers and Democrats said were only cosmetic changes.

The new provisions included assurances that "adequate" funding would be available for direct government loans and federal guarantees of commercial loans.

They abandoned a requirement that farmers show a 10 percent profit to qualify for loan guarantees; farmers now must show only that they can break even.

They also increased the portion of a loan that the government will guarantee, up to the maximum of 90 percent over the life of the loan.

Block's move, coupled with earlier threats by Dole to hold the Senate in session into the weekend, prompted a renewed attempt to iron out the dispute early yesterday after a tentative agreement fell apart late Thursday.

But, late into the night, leaders of both parties were arguing critical procedural points that could determine the fate of further credit-relief legislation before farmers face the financial pinch of spring planting. These included 14 amendments, subsequently reduced to seven, that Democrats hope to have considered next week as riders on African famine-relief legislation.

To smooth the feathers of Democrats offended by a letter he sent Thursday, Block wrote another one that avoided language the Democrats said they considered insulting. In his second letter, Block made clear that Reagan was a party to the deal, and he omitted an earlier reference to administration opposition to further farm relief legislation.

Also, Dole agreed to give Democrats a chance to vote on more far-reaching credit-relief legislation in connection with the African relief legislation, schedeuled next week.

Many farm-state senators want to make sure that the Senate has a chance to vote on a broader measure expected to be approved next week by the Democratic-controlled House.

It would advance payment of price-support loan money from fall to spring to help farmers get past their immediate credit crunch and provide $3 billion in new loan guarantee authority. Dole has predicted that the Senate will defeat this bill.

Faced with politically tricky votes on further farm legislation and angered about Democratic challenges to their leadership prerogatives, Republicans were insisting on procedural safeguards that Democrats contended would stack the deck against any further legislation.

"I'm going to stay here till the cows come home to see that Bob Dole is not molested on this," Senate Agriculture Committee Chairman Jesse Helms (R-N.C.) said, reflecting GOP suspicions that Democrats intended to embarrass Dole, a charge that Democrats vehemently denied.

As negotiators dickered over farm-credit amendments Democrats might offer to the Africa drought-aid bill, Helms also threatened to offer amendments on such issues as abortion, school prayer and busing. "If they want to stretch this out, I know how to do it," Helms said.

If Democrats had won little of substance, they nevertheless filled the airwaves with claims of vindication, laced with denunciations of the Reagan administration.

Even though Democrats rejected the provisions announced yesterday by Block, Sen. David L. Boren (D-Okla.), leader of the filibuster, said he was "very, very pleased" that Block accepted the modifications "that we got him to make."

"Those are things that were not happening, that were not going to happen, until we began our action," Boren said.

Accusing the administration of procrastinating on farm-relief measures announced shortly before the Nov. 6 elections and questioning its will to carry out the new provisions, Sen. Edward Zorinsky (D-Neb.) said, "This administration has done for farmers what Bonnie and Clyde did for banks."

Zorinsky also ridiculed charges that the extra Democratic demands amounted to a potentially budget-busting government bailout for agriculture. "It's an industry worth saving unless someone in this room has found a way not to eat," he said.

Asked if it presented a problem for Republicans, Rep. Jim Leach (R-Iowa) said, "You bet your life. There is a possibility of a generation of farmers holding an administration responsibile for presiding over the bankruptcy . . . of rural America."

Dole, saying Democrats were left "out there naked" by the Reagan-Block move, accused them of continuing to delay because they are "holding out to the bankers."

However, even Dole conceded that Democrats sensed a political advantage in their cause. "Let's face it. They feel they can't lose on this issue," he said.

Although the farm fight presented Dole with his first real leadership test since he assumed the Senate's top post last month, Democrats were gentle in their treatment of the new Republican leader, despite his jibes. "I think he Dole is acting in the best of faith," Byrd said. "His problem is downtown the administration ."

However, as the day progressed and bickering increased on both sides, Republicans increasingly portrayed Democrats as trying to erode Dole's control of the Senate while Republicans rallied to his support. This appeared to polarize members along party lines in a way not usually seen so early in a congressional session.

In announcing administration implementation of the liberalized credit terms spurned by Democrats, Block said, "It's time to end the fooling around and start putting some certainty out in the country . . . they farmers don't need any more uncertainty."