David Hest 1

December 14, 2010

7 Min Read

Promoters of optical crop-sensing systems have been talking about a just-around-the-corner heyday for almost 10 years. But relatively few farmers have made use of the new technology, especially when compared to the potential acreage it could serve across the Corn Belt.

Now optical sensing systems mounted on farm machinery, airplanes and satellites may be on the verge of more widespread adoption, sensor technology companies say.

Until last year, when it was joined by new sensor systems from Ag Leader and Topcon, Trimble’s GreenSeeker system was the sole player in machine-mounted optical crop sensors in the U.S. The entry of two new players and Trimble’s purchase of GreenSeeker developer NTech Industries in 2009 are lending credibility to optical sensing.

“It is not mainstream yet. But the adoption of optical sensing systems by major precision ag companies has bolstered our sales,” says Russ Linhart, a GreenSeeker sales specialist for Trimble, who held a similar post for NTech. “The technology has enough credibility that mainline companies have picked it up. So farmers feel some safety in adopting the technology.”

Satellite-based optical sensing systems also may be primed for a growth spurt. Private companies are in the process of deploying new satellite systems that can fly over key farming areas every week or less — rather than in today’s typical 16-day schedule. This could improve the usefulness of satellite imagery.

“Along with use of optical sensing systems for variable-rate applications, we have seen even more interest in using imagery for crop monitoring,” says Luke Faleide of Agri ImaGIS Technologies, a major provider of satellite imagery and image-analysis software tools. “That is something that more timely imagery would help.”

In contrast to machine and satellite-based systems, aerial optical sensing systems appear to have taken a step back in recent years. Although imagery taken from airplanes is available in many areas, no large providers have stepped into the Corn Belt marketplace since John Deere introduced its OptiGro Imaging System in 2006 and left the business barely a year later.


Sensor benefits

Optical sensing marketers say the key benefit of their technology in corn and wheat is that it makes it possible to apply varying rates of nitrogen across a field by measuring actual crop needs. The goal is to optimize yield by using only as much nitrogen as is needed, benefiting the pocketbook and the environment. 

They say that sensor systems address a reality that a growing cadre of university fertility scientists has emphasized in recent years: It’s virtually impossible to predict the amount of nitrogen that will be released by soils during the growing season, not to mention predicting in-season nitrogen losses. So it’s difficult to know how much supplemental nitrogen to apply. Differing soil types, organic matter levels, and other variables compound the challenge by releasing varying amounts of nitrogen across individual fields.

“Fields that have variations in organic matter and high and low areas can really benefit from variable-rate nitrogen application,” says Roger Zielke, product manager for Ag Leader’s OptRx crop sensor system. “There is a lot of money being left on the table with uniform application rates.”

Whether mounted on farm machinery, airplanes or satellites, optical sensors work roughly the same way to measure a crop’s nitrogen needs.

In ground-based systems, for example, crop sensors shoot a beam of light at the growing crop, then take ongoing readings of specific light wavelengths that bounce back. The reflected light measures crop vigor associated with variations in green plant color. This correlates with nitrogen status and the crop’s yield potential. An on-board computer then interprets the reflected light readings to adjust nitrogen rates in real time.

Aerial systems work similarly. But since they rely on sunlight, they can’t assess crops when there’s cloud cover.


Adoption challenges

While they are optimistic about the future of optical crop-sensing systems, marketers admit that convincing farmers of their benefits has been a slow slog compared to pitching the advantages of navigation systems, planter row shutoffs and other precision ag technologies.

“I think even farmers who typically are early adopters of precision technology struggle to understand how an optical sensor works and whether they can trust it,” says Ag Leader’s Zielke.

Education is the key, adds Carol Snyder, advanced solutions and training manager for Topcon’s CropSpec sensor system. “There has been a big increase in growers who want to be able to apply variable-rate nitrogen on the go by using optical sensors,” she says. “They are excited about the idea, but they need to learn more about how to best use it in the field and validate rates that are needed by the crop.”

As more farmers and crop consultants use crop-sensing systems and more university crop sensor research is conducted, farmers, in general, are becoming more comfortable with the technology, says Trimble’s Linhart. “We are making progress. We are getting more growers coming up to us at farm shows saying they have been watching the technology and they are buying into it,” he says.


Optical sensing systems

Here’s a review of the major optical crop sensor options:

Ag Leader OptRx. Ag Leader introduced the OptRx system for use in corn in 2010. For 2011, Ag Leader also will support its use in wheat. OptRx was developed in conjunction with Holland Scientific, for which Ag Leader is the sole worldwide distributor for production agriculture markets.

OptRx sensors measure visible and near-infrared light reflected from the crop canopy to determine a vegetative index used to set varying nitrogen application rates. The system includes boom-mounted sensors, plus a Canbus module that carries sensor data to software contained in Ag Leader’s Insight or Integra displays.

Ag Leader recommends using three OptRx sensors on booms less than 80 ft. wide. Five sensors are recommended on wider booms. Sensors retail for $3,000 each. The Canbus module retails for $1,500. The cost of a five-sensor system is $16,500, plus the cost of an Insight or Integra display, if needed. For more information, visit www.agleader.com.

Topcon CropSpec. The CropSpec sensor system, which was available on a limited basis in 2010, will have its full U.S. launch in 2011. It was developed in conjunction with Yara International, a fertilizer and industrial chemical manufacturer based in Norway.

The sensor system uses two sensors mounted on each side of the application rig cab roof to measure red and red-edge light reflecting from the crop. The sensors are mounted at a 45° to 55° angle, which allows them to take readings from several crop rows contained in roughly a 3-meter ellipse.

The two-sensor CropSpec system retails for $19,500. It interfaces with the Topcon X20 display/controller, which retails for $5,665. The company plans to add compatibility with additional Topcon displays in the future. For more information, visit www.topconpa.com.

Trimble GreenSeeker. The GreenSeeker system has been available in the Corn Belt since 2005, first from NTech Industries and from Trimble since its purchase of NTech in 2009. It was developed in conjunction with crop scientists at Oklahoma State University as an outgrowth of a related product, the WeedSeeker optical sensor weed-control system.

GreenSeeker sensors measure red and near-infrared light to assess plant vigor and determine appropriate nitrogen application rates. In addition to corn, GreenSeeker has been used for variable-rate nitrogen applications in winter and spring wheat, sorghum, canola, cotton, barley and Bermuda grass. It also has been used for variable-rate applications of growth regulators and defoliants in cotton.

Trimble recommends use of six GreenSeeker sensors for booms greater than 60 ft. and four sensors for shorter booms or side-dress rigs. It is available in two configurations: one for use directly with the Trimble FMX display, and a second for use with the Trimble Nomad handheld computer, which can interface with John Deere GreenStar monitors and various controllers, including Raven controllers ranging from the Raven 440 to the Viper Pro.

GreenSeeker FMX configurations retail for $13,495 for six sensors, and $9,995 for four sensors. Configurations including the Nomad handheld computer retail for $19,995 and $16,495 for six- and four-sensor systems. For more information, visit www.trimble.com/agriculture.


Satellite systems

Crop imagery from satellites is available from many companies across the U.S. and worldwide. Images taken at 16-day intervals by the same Landsat satellites often are available from multiple sources. Large U.S. satellite imagery providers include TerraServer (www.terraserver.com), Satellite Imaging Corporation (www.satimagingcorp.com) and Agri ImaGIS Technologies (www.satshot.com).

Smaller, more maneuverable satellites have been launched by private companies in recent years, including Surrey Satellite Technology Limited (www.sst-us.com) and RapidEye AG (www.rapideye.de). These satellites will shoot images of key agricultural areas more often, says Faleide of Agri ImaGIS Technologies. “Our goal within the next couple of years is to be able to provide new images of the same Corn Belt geography every three to four days,” he says.

About the Author(s)

David Hest 1

David Hest writes about precision agriculture, electronics and communications technologies and trends affecting production agriculture.

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