A new sensing system developed by Agricultural Research Service scientists scans corn plants across an entire field, allowing farmers to apply fertilizer where it's needed most.

The new sensing system is one of the latest advances in precision agriculture, in which farmers use the latest high-tech devices to help them raise crops more efficiently and with minimal impact on the environment.

Agricultural engineer John W. Hummel and information technology specialist Scott T. Drummond of the ARS Cropping Systems and Water Quality Research Unit in Columbia, Mo., developed the system. It can be mounted on a tractor or combine to collect plant spacing data from early in the season through harvest. By tapping into overhead satellites--global positioning system (GPS) technology--the scientists can determine exactly how many plants are located in specific areas of the field.

Using commercially available photoelectric sensors, scientists place an emitter on one side of the row and a receiver on the other side. An infrared light beam shines across the row from the emitter to the receiver. The sensors are fast enough to measure the time the beam is interrupted by a cornstalk.

Taking into account how fast the tractor is moving, scientists can determine the diameter of the cornstalk and the space between adjacent plants. The computerized sensor also differentiates between cornstalks and weeds.

By knowing the corn plant population in different sections of the field, a farmer can determine how much fertilizer needs to be placed in each section. This can save the farmer money on fertilizer as well as help the environment.

The sensors do not touch the plants, so the system can be used at any time during the growing season. Also, the system has no moving parts and is thus more durable. The researchers have tested their system only with corn, so far, but the software probably could be adapted for other row crops.

ARS is the U.S. Department of Agriculture's chief scientific research agency.