High and dry

Thirsty crops can now be spotted from the air, say researchers in California.
Since plants with enough water have cooler leaves than dry plants, airborne
thermal imaging cameras should be able to tell the difference. The problem is
that heat radiated from bare soil between crop rows confuses cameras. Steve Maas
and his colleagues at the US Department of Agriculture’s research station at
Shafter, California, have solved the problem by combining thermal data with
digital images to calculate the percentage of ground covered by leaves. “We
could tell the day after we turned the water off in our test fields,” Maas
says.