<P> Because many of today's major cities were historically founded in agriculturally rich areas, prime farmland tends to be (by virtue of its location) well suited to "growing" houses . Therefore, prime farmland is also prime developable land, and is extremely prone to conversion when in proximity to urban growth areas . This trend is further encouraged by the widespread availability of the private automobile, continuous expansion of roadways, and relatively low - priced gasoline . </P> <P> USDA prime farmland designation helps growth management and resource conservation efforts in urban growth areas to use zoning and conservation easements in order to preserve prime farmland resources, maintain local economic diversity, and establish green belts . Nonprofit organizations like American Farmland Trust specialize in helping communities use these techniques . </P> <P> Other designations used by USDA to complement Prime Farmland are Farmland of statewide importance, Farmland of local importance, and Unique farmland . </P> <P> Unique farmland is land other than prime farmland that is used for the production of specific high value food and fiber crops . It has the special combination of soil quality, location, growing season, and moisture supply needed to produce economically sustained high quality and / or high yields of a specific crop when treated and managed according to acceptable farming methods . Examples of crops are tree nuts, olives, cranberries, citruses and other fruits, and vegetables . </P>

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