I think agricultural uses are going to be one of the main drivers of commercial drones and other robotic technologies, so I love stories like this. From The Economist:
[Lettuce] is a fiddly business. Not only does lettuce need to be fertilised and weeded, but also "thinned" so that good plants do not grow too close to each other, inhibiting growth. Much of this is still done by hand. Labourers, who tend to be paid per acre, not per hour, have little incentive to pay close attention to what they pull from the ground, often leading to unnecessary waste.
Enter Lettuce Bot, the brainchild of Stanford-trained engineers, Jorge Heraud and Lee Redden. Their diligent robotic labourer, pulled behind a tractor, takes pictures of passing plants. Computer-vision algorithms devised by Mr Redden compare these to a database of more than a million images, taken from different angles against different backdrops of soil and other plants, that he and Mr Heraud have amassed from their visits to lettuce farms. A simple shield blocks out the Californian sun to prevent odd shading from confounding the software.
When a plant is identified as a weed—or as a lettuce head that is growing too close to another one—a nozzle at the back of the unit squirts out a concentrated dose of fertiliser. If this sounds bonkers, it turns out that fertiliser can be as deadly as a pesticide, which is why farmers usually sprinkle it at a safe distance of 10-15cm from the plants to be nourished, so as to dilute its effect. So the robot not only kills weeds and excess heads, but feeds the remaining crops at the same time.
The battery-powered system crunches the image data fast enough to work with 98% accuracy while chugging along at a bit less than 2kph. In September Blue River Technology, a start-up founded by Mr Heraud and Mr Redden, raised $3m from Khosla Ventures, a venture-capital firm active in agribusiness. The launch of a fully operational, ruggedised version of the robot is planned for next year. Mr Heraud is coy about Lettuce Bot's cost, but says it will be competitive with manual labour.
Its creators are also working on a machine capable of excising weeds mechanically using a rotating blade. (Indeed, the robot was originally conceived as an automated lawnmower for parks and other public places but legal issues—think spinning metal blades in areas frequented by children—prompted Mr Heraud and Mr Redden to turn to agricultural users instead.) That would make it a boon to California's "organic" farmers who eschew the potent, weed-killing fertiliser.
Next in Mr Heraud's and Mr Redden's sights is corn (maize), America's biggest crop. Teaching the robot to deal with plants like tomatoes, where distinguishing weeds from the crop can be hard even to a trained human eye, will take longer. But where Lettuce Bot treads, other salad bots are sure to follow.