Organic Pest Control
The fight against pests through use of other, beneficial creatures is as old as humanity; one must only think to the practice of keeping cats to control mice population. With the aid of special droppers, low-flying UAVs can deploy beneficial organisms without having to set foot in the field, so as to avoid soil stress, and within a short time frame.
So far, the most established example of such measures would be the delivery of balls carrying trichogramma wasps to combat corn borers. In this way, many thousands of hectares of Italian agricultural land can be organically preserved, without the need of any chemical inputs.