from MnDOT Aeronautics
Many airports rent airport property for agricultural operations as a way to maintain that property and generate revenue for the airport. While areas away from the Airport Operations Area (AOA) have few limitations as farming moves towards the runways addition care and concern must be used. At some point farming becomes unacceptable and the land must be kept open. Ground based navigational aids may place some additional restrictions on farming. VORs and NDBs have ground planes of underground wiring and ILS localizers and glide slopes are susceptible to interference from vehicles.