While the FAA has until September 2015 to allow high altitude drones (above 500ft) in US airspace, there is a proliferation of small, low altitude drones (below 500ft) fitted with color and IR cameras to survey individual fields a quarter square mile or more at a time. The Minneapolis Startribune has a good story on this. Farmfest is held every year at Redwood Falls, Minnesota. The data is used to plan fertilizer use and can save $10-30/acre.
Hyperspectral returns from crops is the topic of the August, 2014 issue of the ASPRS publication PE&RS.
Even though most cameras are smaller and lower quality images than many installed in full sized survey aircraft, it is a perfect application for Hexagon Geospatial’s AutoDTM software to get LiDAR points from Ortho imagery, it is crowdsourcing surveying of areas as often as the farmer chooses to do it, hopefully sooner and they can share their results with other groups/governments for current databases of ortho and LiDAR or short term change detection between higher quality sensor flights. If each farmer does not want to use it themselves, regional agriculture groups can help them process the data. To get more information about AutoDTM just contact firstname.lastname@example.org