If such a contract is made with any landowner, the city or county shall offer such a contract under similar terms to every other owner of agricultural land within the agricultural preserve in question.

However, except as required by other provisions of this chapter, the provisions of this section shall not be construed as requiring that all contracts affecting land within a preserve be identical, so long as such differences as exist are related to differences in location and characteristics of the land and are pursuant to uniform rules adopted by the county or city.