The Legislature further declares that it is in the public interest for local officials and landowners to retain agricultural lands which are subject to contracts entered into pursuant to this act in parcels large enough to sustain agricultural uses permitted under the contracts. For purposes of this section, agricultural land shall be presumed to be in parcels large enough to sustain their agricultural use if the land is (1) at least 10 acres in size in the case of prime agricultural land, or (2) at least 40 acres in size in the case of land which is not prime agricultural land.