The House Agriculture Committee, buoyed by an unprecedented compromise between farm groups and environmentalists, yesterday approved an ambitious package of conservation measures designed to improve water quality and protect wetlands on the nation's farms.

The committee reached a compromise after several weeks of wrangling with environmental groups. Committee members and commodity groups, reflecting the interests of farmers worried about draconian restrictions on land use, drafted an early version of the conservation provision that environmentalists found unacceptable.

But in a protracted series of working sessions, a compromise was worked out on key provisions that lobbyists on both sides agreed they would not challenge later.

Committee Chairman E "Kika" de la Garza (D-Tex.) called the final product "probably the most ambitious effort we have ever had in the history of farm legislation. It's a good package for farmers and for the environment."

The session also completed committee debate on the entire farm bill, expected to move to the House floor for consideration after the July 4th recess. The Senate committee still has not completed work on its version of the bill.The package includes the first provision in a farm bill for a water quality program aimed at controlling the quantity and types of chemicals leeching into local water supplies as a result of pesticide and fertilizer runoff.

Environmentalists had wanted a mandatory program, but settled for a voluntary plan monitored and implemented by the Department of Agriculture. Congressmen had made it clear they would not vote for a mandatory program.

"We wanted a beginning," said Maureen Hinkle of the National Audubon Society. "We think farmers need to become part of the solution; with this legislation they have the opportunity to step forward and put their land into the program."

Another first for environmentalists was a program allowing farmers to receive a payment to stop growing crops on wetlands. The government will fund the restoration of the land to its natural state and pay farmers up to $250,000 to keep it permanently out of production.

The most bitter and long-running controversy, however, involved existing "swampbuster" legislation that takes subsidies away from farmers who drain and plant crops on wetlands.

The committee spent hours in closed and open session redefining "wetland" and modifying its application. "Providing this guidance," said Rep. E. Thomas Coleman (R-Mo.), "was the most important thing we did."

Under the legislation approved yesterday, farmers violating swampbuster will not have their program benefits terminated immediately, but instead will be required to pay a $750 fine and restore the land.

Environmentalists also succeeded in changing the language of the measure so that farmers will be liable for fines not just for planting crops on wetlands but simply if they "alter the land."

Hinkle commended the committee for "deciding their own environmental future instead of having it happen to them," but noted that environmental groups had additional concerns that had not been addressed in committee. These, she said, would be raised on the floor of Congress if arrangements could not be worked out beforehand.

Committee members nonetheless remained optimistic: "These negotiations were as good as negotiations of this type can be," said Illinois Rep. Edward R. Madigan, the committee's ranking Republican. "I think we're moving in the right direction and I hope environmentalists will look at this as an opportunity for cooperation rather than to take advantage."