Notwithstanding any other provision of law, for the purpose of reducing the costs of farm programs, assisting farmers in turning their land to nonagricultural uses, promoting the development and conservation of the Nation’s soil, water, forest, wildlife, and recreational resources, establishing, protecting, and conserving open spaces and natural beauty, the Secretary of Agriculture is authorized to formulate and carry out a program during the calendar years 1965 through 1970 under which agreements would be entered into with producers as hereinafter provided for periods of not less than five nor more than ten years. No agreement shall be entered into under this section concerning land with respect to which the ownership has changed in the three-year period preceding the first year of the agreement period unless the new ownership was acquired by will or succession as a result of the death of the previous owner, or unless the new ownership was acquired prior to January 1, 1965, under other circumstances which the Secretary determines, and specifies by regulation, will give adequate assurance that such land was not acquired for the purpose of placing it in the program: Provided, That this provision shall not be construed to prohibit the continuation of an agreement by a new owner after an agreement has once been entered into under this section: Provided further, That the Secretary shall not require a person who has operated the land to be covered by an agreement under this section for as long as three years preceding the date of the agreement and who controls the land for the agreement period to own the land as a condition of eligibility for entering into the agreement. The foregoing provision shall not prevent a producer from placing a farm in the program if the farm was acquired by the producer to replace an eligible farm from which he was displaced because of its acquisition by any Federal, State, or other agency having the right of eminent domain.