The Republican-controlled Senate Budget Committee yesterday rejected President Reagan's proposals for drastic cuts in government support of agriculture as it balked at domestic-spending reductions to match the big defense cut it approved Tuesday.

The panel voted, 13 to 9, to reject Reagan's program, which included $6 billion in deficit reductions for next year, and then approved, 14 to 8, a proposal to cut deficits by $200 million by freezing farm programs at current levels for a year.

The committee's bipartisan rejection of Reagan's farm proposal, coupled with earlier votes on other domestic programs, left it far behind the goal for domestic spending cuts set by committee Chairman Pete V. Domenici (R-N.M.).

By combining defense- and domestic-spending cuts, Domenici hoped to cut projected deficits by $50 billion to $60 billion next year as a first installment on halving them to less than $100 billion within three years.

The committee exceeded Domenici's goal on defense but began losing ground yesterday as soon as it took up domestic spending.

By voting only to freeze farm spending, Sen. Slade Gorton (R-Wash.) said, "We're going to fall far short of the necessary goal in deficit reduction. Simply voting for a freeze on every budget [category] down the line is simply going to be inadequate."

But farm-state senators contended that agriculture is being asked to bear too much of the deficit-reduction burden at a time of crisis in the Farm Belt.

"This is no time to eliminate the safety net for agriculture," Sen. Charles E. Grassley (R-Iowa) said. "Agriculture must play a part in the deficit reductions but not such a Draconian part," Sen. J. James Exon (D-Neb.) added.

On the administration's behalf, Domenici had proposed radically reducing price-support programs, terminating direct operating loans, phasing out federal crop insurance and establishing various user fees.

Domenici said it is too early to predict failure for deficit-reduction efforts on domestic spending. "I didn't expect anything better than this in the midst of an agricultural crisis," he said in reference to threatened bankruptcies across the Farm Belt.

He said the committee could still regain lost ground on such major issues as Social Security and Medicare. Domenici is proposing major Medicare cuts and elimination of cost-of-living increases for Social Security benefits for one year.

The farm vote meshed with a pattern in which committee members of both parties generally embraced a budget freeze but rejected more drastic cuts proposed by Reagan in his fiscal 1986 budget.

The committee voted to reject Reagan's proposal to eliminate the Small Business Administration, voting instead to recommend a two-thirds cut in its direct-loan program. It also accepted the administration proposal to eliminate postal subsidies for profit-making mailers and political organizations and end a rural-housing program run by the Farmers Home Administration.

The panel voted, as Reagan wanted, to kill direct loans under the Export-Import Bank but approved additional funds to help finance foreign purchase of U.S. products, including increased interest subsidies and a $1 billion "war chest" to protect domestic producers from "predatory" overseas competition.

It rejected Reagan's proposals to phase out rural electrification loans and sewer grants, terminate funding for the Strategic Petroleum Reserve, reduce power-generation subsidies and impose user fees for navigation and recreation purposes.

In many other areas, from energy conservation to water-project construction, it rejected Reagan's proposals for spending cuts, opting to freeze spending at current levels.

In initial votes on nondefense spending, the committee approved only half of the spending reductions proposed by Domenici to achieve a target of more than $50 billion in deficit reductions for next year.

After voting on foreign aid and trade assistance, science, energy and environmental spending, farm programs and commerce, the committee had approved about $4.7 billion in deficit reductions for next year, while falling about $9.6 billion short of Domenici's goal for these areas of spending.

By contrast, it had voted Tuesday to approve even bigger cuts in Reagan's military buildup than Domenici had recommended, amounting to $79 billion over three years instead of Domenici's proposal for a $66 billion three-year cut.

Even before yesterday's voting, Domenici conceded that the committee was unlikely to approve domestic-spending cuts needed to halve deficits by fiscal 1988, the Senate Republican leaders' goal.

"I don't have any strong hope I'll win a $60 billion deficit-reduction package," Domenici said.

Senate Majority Leader Robert J. Dole (R-Kan.) also issued a veiled warning that defense cutbacks must be matched by similar restraint in domestic spending.

"I want to see what some of those people who voted to cut defense will do" on domestic spending, including major direct-benefit programs, he said. "I think before we pass judgment on the [committee's] work, we ought to see the total picture, not just a piece of it," said Dole, speaking of Tuesday's defense vote.

The balance between defense and domestic spending is critical because the panel's votes are subject to ratification in a final package that could be jeopardized in committee and on the Senate floor if deemed too far out of balance.

Moreover, Dole has indicated that he would consider the committee's work largely as a draft to present to the White House for further negotiations on deficit reductions, and his bargaining leverage could be weakened if the committee falls short on domestic-spending cuts demanded by Reagan.

As in Tuesday's defense votes, yesterday's were along bipartisan lines, often with Democrats sponsoring the winning proposals, picking up enough Republicans to prevail even though they are outnumbered on the committee, 12 to 10.

Throughout yesterday's deliberations, senators with strong home-state stakes in particular spending programs zeroed in on specific Domenici proposals and often defeated them.

For instance, Sen. J. Bennett Johnston (D-La.) prevailed on a proposal to reduce but not end spending for filling the Strategic Petroleum Reserve.

At another point, when Sen. Howard M. Metzenbaum (D-Ohio) was arguing against continuation of favorable debt treatment for power-generating authorities, a program dear to the Pacific Northwest, Gorton retorted:

"He [Metzenbaum] is asking us to do things totally inconsistent with what he's done with the St. Lawrence Seaway. We simply canceled that indebtedness."