An optical sensor lets a microprocessor-driven spray system figure out how much nitrogen fertilizer to apply. The sensor looks at the ground to sense the amount of living cell mass and plant photosynthetic potential (basically how green it is). The system, called GreenSeeker, from Ntech Industries Inc., Ukiah, Calif. (www.ntechindustries.com), operates in real time without GPS or field mapping, supplying fertilizer for every 2 square feet. Current agricultural-spray systems involve time-consuming GPS-guided, acre-by-acre field mapping and wasteful broadcast spraying.

"The GreenSeeker was used to top dress 10 fields, from 90 to 160 acres," says agronomist Kenneth Failes. "We saw increased yields of four and nine bushels in our fields. That means a significant return in dollars to the farmer," he adds. The technology is slated for use in cotton, barley, corn, and soybean fields.