A SENSOR that calculates exactly how much nitrogen a crop needs is slashing fertiliser use in field trials. The system will not only save farmers money but also reduce fertiliser run-off, and so reduce nitrate pollution of water courses. “This pollution problem is serious. It’s much bigger than we’d even like to talk about,” says Jim Schepers of the US Department of Agriculture, who is leading the work.
The system, which is mounted on a tractor, shines rapid pulses of red and infrared light onto the leaf canopy of the crop, and sensors detect the reflected light. Healthy leaves absorb…
