WASHINGTON (AP) _ The Senate approved a farm bill Friday that carries no major changes in agricultural support programs but breaks new ground in environmental protection in setting the nation's agricultural policy for the next five years.

The 70-21 vote came late in the afternoon, following compromise on scores of amendments that had bogged down the Senate for days.

Floor managers cautioned their colleagues that the budget summit negotiations with the White House would inevitably mean changes in the planned spending of $54 billion over the next five years, spending that must be done through annual appropriations bills.

The House is near passage of its version, and a conference between the two houses will be necessary to agree on a single bill to send to the White House - where President Bush is expected to get veto recommendation s from agencies concerned that the bill costs too much.

Agriculture Committee Chairman Patrick Leahy, D-Vt., who pushed for many of the environmental changes, said the bill ''is the most progressive farm bill I've seen since I've been here.''

''It is an environmentally conscious farm bill. It is one that allows us to do the things Americans want,'' he said.

Among the environmental breakthroughs in the bill is a ban on the export of agricultural chemicals illegal in the United States.

The bill also establishes standards for use of the phrase ''organically grown'' and lays down new policies designed to protect wetlands and forests.

The Agriculture Committee's ranking Republican, Sen. Richard Lugar of Indiana, said changes in the bill may be necessary once budget negotiations are completed with the White House.

We feel that agriculture should pay its share,'' he said.

Republican Leader Bob Dole of Kansas, who also is a member of the Agriculture Committee, said, ''For the most part we are proceeding with the philosophy we put together in 1985,'' as the White House and congressional leaders planned all along. But he added: ''The problem with the 1985 farm bill was that it cost about $80 billion in program outlays. We no longer have $80 billion to spend.

Before recessing for the weekend, the House fought off an effort to eliminate government subsidies to honey producers. The Senate earlier in the week cut the subsidies from its bill.

The Senate, in the space of an hour, cut 23 amendments from a list of 40 ranging from red tape reduction to wetlands conservation.

The House and Senate both voted Friday to use the farm bill against Iraq by cutting off U.S. loan guarantees the country uses to buy American wheat, rice, lumber, cattle and commercial goods such as tires and machinery.

Sen. Nancy Kassebaum, R-Kan., conceded that the sanctions could hurt Kansas wheat farmers but said human rights considerations, including reports of government torture of children, outweigh economics.

''I can't believe any farmer in this nation would want to send his products, under subsidized sales, to a country that has used chemical weapons and a country that has tortured and executed its children,'' she said.

The Senate also voted to restrict loans to the Soviet Union by preventing banks from offering credit at a lower rate to the Soviets than to farmers, unless the funds are used to buy U.S. agricultural products.

The amendment, approved 64-32, pertains to banks, savings associations, credit unions or any entity that has deposits insured by the federal government.

One of the stickiest disputes resolved Friday was between Great Lakes and Gulf Coast senators about the amount of food aid to foreign countries that should be shipped out of Great Lakes ports.

Sens. John Glenn, D-Ohio, and John Breaux, D-La., agreed to a formula that will enable Great Lakes ports to bid on the shipping.

The compromise limits the Great Lakes to 240,000 tons of food aid cargo annually and allows them to use less costly foreign ships that fly an American flag and use American crews.

The bill establishes price-support programs for commodities and sets policy for nutrition programs, agricultural exports, soil and water conservation, agricultural research and extension work, food inspection and other responsibilities of the Agriculture Department.

The administration's chief concern clearly was budgetary.

Immediately before floor debate began, Secretary of Agriculture Clayton Yeutter and the Office of Management and Budget said they would recommend a veto if the cost of the bill were not decreased.

The Senate fought off two efforts to increase target prices. A plan by Sen. Thomas Daschle, D-S.D. to help small farms would have increased payments to a certain level of production, then cut support below the target prices in the original bill.

A proposal by Sen. Max Baucus, D-Mont., would have tied target prices to the consumer price index, less 4.3 percent, to help farmers fight the rising costs of production.