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Counting Weeds



Laura Lengnick of the Beltsville Agriculture Research Center wrote about 
the difficulty of counting and taking "biomass from randomly selected 
"representative" areas within the plots." For what it's worth, this 
reminded me of my days [in the 1970s] working with an agricultural 
consultant with a pilot's license. The aerial infrared photographs yielded 
a tremendous amoung of useful information about crop fields, including weed 
infestations. Living organisms, such as weeds, have their own unique 
infrared "signatures," such that it is even possible to distinguish a 
water-stressed plant from a well-irrigated plant, or a diseased plant from 
a healthy plant.

I haven't kept up with the progress of aerial infrared photography as a 
scientific methodology. But when I read about spy satellites whose cameras 
are able to resolve objects less than a meter in length from outer space, I 
can't help but think that somewhere in the Beltway, maybe in the USDA 
itself [the CIA for sure], is someone who could help. Somewhere in the 
computer trade magazines, I remember reading about how information [e.g. 
the points or intensity of the light] from photographs or even bacterial 
colonies could be scanned into a computer and analyzed. So, conceivably, if 
you had a field "mapped" photographically, you could then use a computer 
program to direct you to what would be a representative sample of the field 
and count the various species and take your measurements and samples.

Back in the '70s, the farmers we worked with using the infrared photos 
taken from private aircraft could pinpoint problem areas in fields, 
sometimes only a few square feet, needing special attention or soil 
amendments. The accuracy meant big savings in input costs, by directing 
inputs and remedial actions to precisely where they were needed, rather 
than treating whole fields. I believe this is called precision farming 
today, and with geographic information systems [GIS] technology is precise 
to within inches. 

Joel Grossman
Santa Monica, CA