Herding cattle. Counting fish. Taking an animal's temperature. Applying pesticides.

When it comes to drones, "your imagination can go pretty wild in terms of what would be possible", said Roger Johnson, president of the US National Farmers Union.

This month, the US Federal Aviation Administration issued the first permit for agricultural use of unmanned aerial vehicles. Steven Edgar, president and CEO of ADAVSO, said his Idaho-based business will use a lightweight, fixed-wing drone to survey fields of crops.