Wireless networks aren't just for getting our laptops on the Internet. They are finding a place in agricultural fields.

Research under way with the assistance of Martin A. Hebel, an associate professor at Southern Illinois University Carbondale, could assist farmers wirelessly measure surface temperatures of crop canopies to determine a crop's stress level and the need for irrigation. Hebel, who is in the Electronics Systems Technologies program in the School of Information Systems and Applied Technologies, is working with researchers from the U.S. Department of Agriculture in Bushland, Texas, in developing a wireless infrared temperature system to monitor crops.

The research applies to center pivot irrigation systems, which involve elevated rolling sprinkler equipment that rotates on a fixed pivot and moves in a circular pattern in fields. Crops in need of irrigation are "stressed" and run hotter than healthy crops, Hebel said.

By positioning infrared sensors on irrigation pivot arms, the sensors can look down at the crop canopy as the arms move through the field and wirelessly send data to a control system that determines irrigation needs.

The collaborative research began in 2007 when Susan O'Shaughnessy, a research agricultural engineer with the USDA's Agricultural Research Service, contacted Hebel because of his work with microprocessors and wireless radio frequency modules. O'Shaughnessy needed to expedite a wireless prototype for field deployment, and Hebel's "expertise and previous work in agriculture fit well," she said.

Hebel helped facilitate a design and improved designs for a narrow field-of-view infrared thermometer (IRT) by testing two different infrared sensor types and developing code to manage and transmit data from the IRT, O'Shaughnessy said. The IRTs measure the surface temperature of the crop canopy and with GPS, or global positioning system, the system determines the location of the stressed crops in a field. Temperature data from the IRTs are transmitted to a computer at the center pivot, and the computer automatically manages the data at midnight to determine the stress level of the crop. Irrigation begins later in the morning if the stress level is above an established set point, she said.

Hebel and O'Shaughnessy said that the wireless IRT is less expensive than wired counterparts.

"The cost savings come from not having to run thermocouple wire and the elimination of dataloggers," O'Shaughnessy said. "Wireless sensors can easily be relocated and there is no maintenance of wires from weather and rodents."

Machines going through the fields can destroy sensors set in the ground, Hebel noted.

"If you can irrigate more specifically where the water is needed you can practice water conservation, which is a important consideration in several areas of the country," he said.

The current field test involves two sensors that view each treatment plot from opposite sides, O'Shaughnessy said. The plots are 45 feet in width. There are 24 wireless sensors on the pivot lateral covering a radius of 856 feet or a circular 52-acre field

Hebel's work "was key to prototyping our wireless sensors in a timely manner and in developing code that allowed the IRT sensors to send data every five minutes and sleep in between transmissions to reduce battery consumption," O'Shaughnessy said.

Hebel said the technology continues to evolve, with a push for low-powered devices that can operate off a small set of batteries that can last for months.

"What we have found is that wireless sensor networks are feasible in production agriculture if a moving sprinkler system is used as a platform for these sensing devices," O'Shaughnessy said.

The technology for using wireless infrared thermometers to monitor crop canopy temperatures has widespread application in agriculture, she said.

"We are using this technology to automate irrigation scheduling to make the process simpler and less time intensive. This is important since many farmers are now managing multiple fields," she said. "Others use crop canopy temperatures to identify the drought stress characteristics among the varieties of the same crops to help breed the most suitable variety for a particular region."

Hebel's research also includes other various agricultural applications, including using a microcontroller, accelerometer, and wireless system network transceiver to measure forces when "shaker" machines vibrate trees while harvesting the citrus. He has assisted in the project at the University of Florida Citrus and Research Education Center, developing sensors that measure the "shakers" distribution of force on citrus at the time it breaks free from the tree. The goal is to find the optimum forces for harvesting to not damage the citrus or tree.

Work is now under way on what force is needed for best uniform yields, he said.

Hebel said he enjoys the programming for data collection, instrumentation and monitoring. He is able to apply this work in his undergraduate classes, and many of his students are going into fields that include agricultural applications, he said.

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