Precision spraying is spraying chemicals only on the weeds or plants that need them, instead of over a whole field. Cameras on the sprayer look at the ground as the machine moves. Software recognises each weed or each crop plant, and the nozzle above that spot opens for a fraction of a second. It is also called spot spraying or targeted spraying.
The usual method is a blanket spray. A tractor pulls a boom, a long bar with a nozzle every half metre or so, and every nozzle sprays all the time. But weeds often cover only a small part of a field. So most of the weedkiller lands on bare soil or on the crop, and the farmer pays for chemical that does nothing useful.
How does a precision sprayer see? Cameras are fitted along the boom, and each one watches a strip of ground just ahead of a few nozzles. A small computer on the machine runs a computer vision model, which has been trained on hundreds of thousands of labelled photos of crop plants and weeds. The model looks at each camera frame, marks every weed and works out where it is. When that weed passes under a nozzle, the computer opens the nozzle's valve for a fraction of a second. This happens on the machine, in milliseconds, often with no mobile signal. This is called edge AI.
Consider a spraying contractor in Akola district, in Maharashtra, who sprays soybean fields for farmers and charges by the acre. One farmer's 10-acre field needs a weedkiller spray. A blanket spray would use 4 litres of herbicide, at about ₹1,000 a litre: ₹4,000 in all. The camera sprayer finds that weeds cover about a quarter of the ground. It sprays only those spots and uses about 1.2 litres, which costs ₹1,200. The farmer saves about ₹2,800 on that one spray, and less chemical reaches the soil and the nearby water.
Most Indian farmers have small fields and earn little from each acre. Few of them can buy a new machine. So Indian makers fit the cameras to the sprayers and tractors that farmers or contractors already own; see agricultural machinery. Spraying drones are another way to spray, from above.
Less chemical is good for the farmer, but it means lower sales for chemical makers and their dealers, whose sales agri-input channel management software tracks.
How is it different from hyperspectral imaging? A precision sprayer's cameras see ordinary colours, close up, and act within milliseconds. Hyperspectral cameras, usually on satellites, aircraft or drones, see hundreds of narrow bands of colour. They can spot a disease or a shortage of nutrients across a whole field, but they do not control a nozzle.