Senate Republicans prevailed by a slim margin yesterday on a key farm-bill vote that kept alive the administration's drive to reduce subsidies paid to grain and cotton farmers.

The Senate voted, 49 to 45, not to table an amendment by Sens. Robert J. Dole (R-Kan.) and Richard G. Lugar (R-Ind.) that would freeze target-price payments for one year and reduce them in later years. The farm bill reported by the Agriculture Committee provided for a four-year freeze on income-support payments to farmers. Earlier this week, the Senate rejected by three votes a Lugar amendment to limit the freeze to one year.

Buoyed by the close vote, Majority Leader Dole and Lugar devised the new proposal that included the freeze but added other provisions for cutting the bill's cost. Yesterday's vote left the package as pending business when farm bill debate resumes next week.

"Sen. Dole controls the floor, but I don't feel he has the upper hand," said Sen. John Melcher (D-Mont.), leader of the campaign to retain subsidy payments at current levels for four years.

Yesterday's vote came at the end of a week of farm-bill debate highlighted by parliamentary gambits that included a move by Dole preventing consideration of a Melcher proposal to cut about $7.6 billion from the bill while leaving intact the subsidy payments.