Because farmers cannot easily find out how plants in the centre of a field are faring, patches can dry out and die. Agrosense of Israel (WO 02/079376) suggests setting up a small dummy field alongside a real field. The dummy is made from one-metre squares of a woven fibre, variously dyed to match the colour of the maturing crop.
Some dummy squares of each colour are kept stone dry; others are kept wet by wicks which hang down into a water bath. The dummy crop squares provide a reference for how the real crop should be looking if properly watered. A crop duster plane with a thermal-imaging camera flies low over the field. Patches of real crop that look like the dry cloth squares reveal which areas are parched.
