House-Senate negotiators last night struck another compromise on a $370 billion catchall spending bill for fiscal 1986 as Congress struggled wearily to wrap up work for the year and go home, possibly today.

The agreement trims $1.3 billion off a $298.7 billion allocation for defense and earmarks $6.3 billion in a Pentagon reserve fund for pay, pensions and readiness-related programs in order to meet objections of House members who rejected an earlier version of the bill. It also continues to provide for renewed production of chemical weapons and a ban on space testing of antisatellite weapons.

But, to avoid further strife over congressional compensation, House negotiators agreed to give senators a $7,500 increase in their existing $22,500 limit on fees from outside speeches, despite earlier House objections to the increase.

The agreement, needed to continue funding for several major government agencies that will run out of money tonight, goes to the House and Senate today for final approval. President Reagan, despite earlier resistance to defense-spending cutbacks, has indicated that he will sign the measure, according to Senate Appropriations Committee Chairman Mark O. Hatfield (R-Ore.).

In a major achievement of the first session of the 99th Congress, both houses approved a compromise, five-year farm bill that redirects U.S. agricultural policy, at little if any savings to the taxpayer. The bill now goes to Reagan, who has not indicated whether he will sign it.

The House also gave final approval to legislation, already passed by the Senate, that orders a reorganization of the troubled Farm Credit System and opens the way for possible future financial assistance from the government. The president has indicated he will sign the credit measure.

Hopes faded for an accord on another key bill -- the budget reconciliation measure -- that would cut back a wide array of spending programs enough to reduce deficits by $70 billion to $85 billion over three years.

Negotiators, hung up largely over taxes to support the "Superfund" toxic-waste cleanup program, were attempting to reach a compromise. But Senate Majority Leader Robert J. Dole (R-Kan.) and others acknowledged that the reconciliation measure might get lost in the rush toward adjournment.

Budget leaders had been pressing for enactment of the program cutbacks on grounds that failure to do so would give Congress a black eye on the politically sensitive deficit-reduction issue. They also contended that failure to act would aggravate difficulties in reaching deficit targets established in the sweeping legislation passed last week to force a balanced budget.

Apparently anticipating that the reconciliation bill would remain sidetracked, the House Ways and Means Committee approved a seven-month extension of several programs that would otherwise expire without action on the reconciliation bill, including a 16-cents-a-pack tax on cigarettes. Without action, the levy would drop to 8 cents.

The House Rules Committee last night balked at clearing the measure for floor action today, leaving its fate in doubt.

"By extending, we're clearly indicating we're not interested in reconciling," complained Rep. William M. Thomas (R-Calif.).

"The longer you extend it the temporary measure , the more improbable it is we're going to get a reconciliation agreement, and there's a lot of savings in that," said Rep. James R. Jones (D-Okla.).

Negotiators on the separate catch-all spending measure were fine-tuning an earlier measure that was unexpectedly rejected by the House late Monday, largely because of concessions to the Reagan administration on defense spending and weaponry.

As yesterday's bargaining session started, Hatfield said the White House was insisting on cutbacks in domestic spending but no further reductions in funds for the Pentagon.

After conferees nailed down $250 million of the $300 million in domestic spending cuts demanded by the administration, Hatfield begged for what he called a final "contribution" to meet the target. "The Lord loves a cheerful giver," he said, and his colleagues eventually scraped together the cash from Interior Department programs.

The final hangup was over defense spending, where a critical issue was earmarking of the reserve to prevent it from being used as a slush fund to ward off cuts under the new balanced-budget act. House negotiators won on this point as well as the $1.3 billion cutback, warning that failure to make the changes would invite House rejection of the measure.

House members also gained approval of a proposed weapons-procurement change aimed at limiting costs that defense contractors can charge to the government.

In tying up loose ends, the conferees agreed to ban all but legally binding contracts from being let as the Synthetic Fuels Corp. is terminated under the legislation. That apparently would doom one if not two projects that western senators had been seeking to exempt.

The conference also dropped a provision that would continue to penalize states that had not raised their drinking age to 21.

But senators held firm for a $7,500 increase in the current $22,500 limit on income they can earn from speech-making. House conferees reluctantly agreed to the increase for senators, apparently fearing that, if they rejected it, the senators would insist on trying to impose Senate ethics rules on the House.

House members tried to hold off resolution of the outside-income issue until defense was resolved. When the Senate balked, House members moved to pull out of an agreement to allow resumption of chemical-weapons production.

Congress also moved yesterday to aid dependents of the 248 soldiers killed in the crash of a jetliner in Newfoundland. The package would temporarily continue housing entitlements for the victims' dependents and raise the current $35,000 death benefit to $50,000.