Lawmakers reached agreement Thursday on an election-year overhaul of farm programs that would boost subsidies by about 70 percent, the lead Senate negotiator said.

The agreement ends two months of talks and could affect several important Senate races this fall.

Senate Agriculture Committee Chairman Tom Harkin said the agreement includes his proposal to reward farmers for improved environmental practices. At a cost of $2 billion, that plan would be the largest single new program in the farm bill, said Harkin, D-Iowa.

The legislation will replace farm, nutrition and land-conservation programs set to expire this fall. The new bill would expire in 2008, a presidential election year.

While details of the agreement were yet to be announced, it was known that the accord would increase total agriculture spending by about $7.4 billion a year.

Negotiators were stalled for weeks over issues that included subsidy rates for corn, soybeans and other crops; White House plans for expanding the food-stamp program; and a proposal to require meat and produce to be labeled with their country of origin.

Other disagreements involved limits on payments to individual farms, a new dairy subsidy program and a ban on meatpacker ownership of cattle.