The Senate Budget Committee voted yesterday to spend $111.9 billion on defense next year, the full amount requested by President carter and $2.3 billion more than its House counterpart approved last week.

On a narrow 8-to-7 vote, the committee approved a motion by Sen. Ernest F. Hollings (D-S.C.) which also gave defense agencies authority to spend - to commit themselves to spend in the future - a total of $120.6 billion.

Many programs, especially weapons and buildings, take several years to complete.

The spending authority is $500 million more than the Carter request and $4.6 billion more than the House committee's target.

Hollings said the Senate committee counts on saving $500 million in areas such as training and personnel turnover and adding $1 billion to procurement and to improved readiness of the armed services.

Sen. Pete V. Domenici (R-N.M.) tried to raise the spending level, saying that the savings Hollings expects will probably not be achieved. Futhermore, he noted, the President's request was based on success in the Strategic Arms limitation Talks with the Soviet Union. He noted that after the U.S. proposals were dismissed by the Soviets last week, the President talked about speeding up development of some weapons systems that had been put on the back burner.

Earlier the committee cut the President's request for international spending - both bilateral foreign aid and contributions to multilateral institutions such as the World Bank - from $7.8 billion to $7.4 billion. It narrowly beat back attempts to take even more money out of foreign aid.

The committee also approved spending $20.7 billion on natural resources, environment and energy projects. This preserves funds that Carter seeks to cut for 30 ongoing water resources projects that the administration is reviewing with an eye to killing.

The committee does not set specific program levels but sets spending targets within which authorizing and legislative committees must design their programs.

But in setting spending ceilings, the committee - as in the case of the Hollings defense proposals - sets our areas where spending should be cut or boosted. The recommendations can be rejected.

The Senate committed is expected to complete action on its budget today. Both the House and the Senate must approve a tentative budget by May 15 and a final, binding one by Sept. 15 for the fiscal 1978 spending year, which begins Oct. 1.