16 Pa. Stat. § 11943
All counties are hereby authorized to enter into covenants with owners of land designated as farm, forest, water supply, or open space land on an adopted municipal, county or regional plan for the purpose of preserving the land in the designated use. Such covenants and extensions thereof shall take effect upon approval of the court of common pleas of the county in which such land or the major part thereof lies. The land owner may voluntarily covenant for himself and successors and assigns in right, title and interest that the land will remain in open space use as designated on the plan for a period of five years commencing with the date of the covenant. The county shall covenant that the real property tax assessment, for a period of five years commencing with the date of the covenant, will reflect the fair market value of the land as restricted by the covenant.
16 P.S. § 11943