Prime farmland

Prime farmland is a designation assigned by U.S. Department of Agriculture defining land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops and is also available for these land uses.

Prime farmland "has the soil quality, growing season, and moisture supply needed to produce economically sustained high yields of crops when treated and managed according to acceptable farming methods, including water management.".

In general, prime farmlands have an adequate and dependable water supply from precipitation or irrigation, a favorable temperature and growing season, acceptable acidity or alkalinity, acceptable salt and sodium content, and few or no rocks. They are permeable to water and air.

Prime farmlands are not excessively erodible or saturated with water for a long period of time, and they either do not flood frequently or are protected from flooding.

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.

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.

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