New optical sensors "read" crops and weeds, then automatically adjust the variable rate of fertilizer and herbicide applications.

New technology in optical sensors promises to improve nitrogen use efficiency and lower the cost of weed control. Numerous products new to the market or still in prototype stages of development show real potential for significantly reducing chemical loads and nutrient runoff, saving input dollars and, in some cases, improving yields.

Earlier this year, Redball LLC, Benson, Minn., was named distributor for the GreenSeeker optical sensing and fertility application system in the South and Midwest by NTech Industries. The California-based company introduced GreenSeeker in 2002 after a dozen years of development and testing by Oklahoma State University (OSU) and NTech researchers.

GreenSeeker features optical sensors that use red and NIR (near infrared) light to assess the color and health of crops as an application rig moves across the field. Plants absorb red light as an energy source during photosynthesis. Therefore, healthy plants will absorb more red light and reflect higher amounts of NIR light than unhealthy plants.

Collected data is then used in real time to drive variable-rate applications of nitrogen fertilizer or other crop inputs. As a result, plants get the optimal amount of fertilizer they need rather than an average applied over an entire field. Cloud cover does not hamper operation and the technology can be used day or night.

One Technology, Multiple Uses

GreenSeeker uses the same advanced optics and computer circuitry as the NTech WeedSeeker that senses and…