Aaron J. Hand, Managing Editor
and Daniel C. McCarthy, Senior News Editor
Photonics goes to work before the corn even begins to grow. For example, Dicky-john Corp., a farm equipment supplier in Auburn, Ill., makes an LED-based sensor that lets corn farmers know how many seeds they have planted.
Dicky-john's seed counters consist of a tube that fits into a row unit, and each uses a photovoltaic cell to register when a seed breaks the optical path of a near-infrared LED. Rates for sowing corn planters can go up to 40 to 50 seeds a second.
Various photonics technologies are used to analyze plant growth, assessing whether the corn has enough fertilizer, for instance, or whether pesticide use is harming the vegetation. Taking a closer look at corn, crop consultants can use portable near-IR sensors in the field to determine whether the plants are short of nitrogen, said Charles Hurburgh, an agricultural engineer at Iowa State University in Ames. If they are, and if the crop is large enough, farmers can add fertilizer. The idea, he said, is that putting less nitrogen into the system at the beginning of the season means less pollutant runoff.
Photonic methods are also useful for weed control in cornfields. The Weedseeker is an LED-based weed detector made by Patchen Inc. of Ukiah, Calif., that has been marketed for four years for use on other crops, mainly cotton. But John Hummel, an engineer with the Agricultural Research Service and a researcher at the University of Illinois in Champaign-Urbana has found the Weedseeker effective on corn and soybean crops as well.