AMES, IOWA — The U.S. Department of Agriculture said it will accept 1.7 million acres, equal to about 90% of the total acres offered, under the 45th Conservation Reserve Program.

Secretary of Agriculture Tom Vilsack announced the sign-up total July 22 during a speech in Ames.

“For 27 years, lands in C.R.P. have helped to conserve our nation’s resources and played a part in mitigating climate change,” Mr. Vilsack said. “American farmers and ranchers continue to recognize the importance of protecting our nation’s most environmentally sensitive land by enrolling in C.R.P.”

The U.S.D.A. said it received nearly 28,000 offers on more than 1.9 million acres of land, “demonstrating C.R.P.’s continuing appeal as one of our nation’s most successful voluntary programs for soil, water and wildlife conservation.” Offers are accepted based on an Environmental Benefits Index comprised of five factors: wildlife enhancement, water quality, soil erosion, enduring benefits and air quality.

Currently there are 26.9 million acres enrolled on 700,000 contracts, the department said. C.R.P. allows eligible landowners to receive annual rental payments and cost-share assistance to establish long-term, resource-conserving covers on eligible farmland during the 10- to 15-year contracts. The program pays land owners about $2 billion annually.

In addition, the U.S.D.A. said that over the past four years it has set aside significant acreage under the C.R.P.’s Continuous Enrollment Programs to target habitat conservation on especially important land. More than 1 million acres of C.R.P. Continuous Enrollment Programs were dedicated in March 2012 to conserve wetlands, grasslands and wildlife, the U.S.D.A. said. Farmers and ranchers have offered more than 370,000 acres under Continuous C.R.P. sign-up this year, a figure the U.S.D.A. said was “impressive given that the lack of a farm bill extension last fall meant that C.R.P. enrollment only reopened this. Lack of a comprehensive farm bill this year has resulted in uncertainty for achieving further enrollment objectives under Continuous C.R.P.,” the U.S.D.A. said.