Washington ? Republican Sens. Pat Roberts and Sam Brownback opposed a Democrat-written farm bill Wednesday, saying it would encourage overproduction of subsidized crops.

The Kansans voted against the Senate bill, which passed on a largely partisan vote of 58-40. The measure limits subsidies to farmers, adds new payments for crops including milk, honey, wool and lentils, and doubles conservation spending. It also bans meatpackers from owning their own supplies of livestock.

An architect of the 1996 market-oriented farm reforms, Roberts criticized provisions related to supplemental payments for grain, cotton and soybean growers when prices fall below predetermined levels.

Under the Senate bill, Roberts said, producers would only get payments through new, higher loan rates if they have a crop to harvest. Such a policy would fail farmers when they have lost crops and are in the greatest need, he said, and would weaken their ability to manage risk by paying for higher loan rates through the crop insurance program.

“This farm bill reduces guaranteed payments that exist under current law and provides incentives to overproduce, which depresses market prices,” said Roberts, who tried but failed last year to offer his own farm bill. “It takes us back to policy that does not fit the needs of producers, and it will increase the need for additional farm assistance in the future.”

Brownback said his biggest concern is that the Senate policies would encourage overproduction, and he worries its trade provisions conflict with World Trade Organization rules.

“I’m glad we’ve gotten it passed. At least in that sense, we can get it to conference,” he said.

Brownback also said he was pleased that the measure included provisions he was pushing that encourage farmers and foresters to plant trees and grasses that trap carbon dioxide in the soil.

The House passed a different version. Each chamber will hammer out a final version in the coming weeks.