May 2, 2002

NDSU Ag Engineer Says Precision Ag Technology Can Boost Management and Returns

Despite its initial cost, precision farming has excellent potential to help farmers improve management and economic returns says a North Dakota State University agricultural engineer.

"Variable rate application has become feasible due to several new technologies including fast computers and powerful graphical and informal management software," says Vern Hofman of the NDSU Extension Service. "These technologies are now small enough to be easily carried in a tractor cab."

That technology allows producers to cut costs in new ways, Hofman notes. "Instead of making fields larger to reduce costs, precision farming will allow farmers to apply crop inputs to individual parts of a field while using large machinery."

Hofman has been using yield monitoring technology in his precision agriculture studies for six years. "It is an excellent way to determine crop variability," he says. "If a producer is thinking of moving into precision farming, a yield monitor may be one of the best places to start. It is advisable to collect yield data over three or four years to see trends occurring in a field. If low yields are consistently showing up in an area, can you make changes to improve the production capabilities? If you are losing money, should something else be done?"

The first step toward applying inputs at variable rates is to do regional soil sampling to provide data about the variation in soil conditions throughout the field. Once the soil type is determined and a projected yield is set, the data can be processed into maps to provide information for variable rate controlling devices. "All areas of a field can have different amounts of inputs including fertilizer, seed, and pesticide application done based on its production capabilities or needs," Hofman explains. .

Once this prescription map has been developed, it must be executed by an application implement. A differentially corrected GPS receiver determines implement position in a field. The GPS receiver is coupled with a computer in the tractor cab that determines fertilizer and seed rates based on the position. The computer operates application rate controllers that are connected to the computer and adjusted for the implements they control and calibrated for the materials it will apply.

"After that, it is usually a matter of turning on the electronics, selecting the application map for the field from a menu and proceeding down the field," Hofman says. Information on position in field and rate of application are usually displayed on the console in the cab.

They key components of a variable-rate application system are:

• GPS Receiver. Mounted on the tractor cab, the GPS receiver takes signals from satellites to determine the application unit position.
• GIS Map Reading Software. Geographical information system (GIS) software installed in a computer reads a GPS-linked prescription map that is prepared in advance, usually from soil test information obtained from the field regions.
• Computer and Electronic Control. Mounted in a tractor cab, this unit operates the software and controls the metering unit speed. Controller units may use a variable speed electric motor or a hydraulic motor.
• Metering System. Usually driven by the tractor’s hydraulic or electrical system, this motor delivers a specific amount of material (fertilizer, seed or pesticide) per revolution. Motor speed is controlled electronically from the cab and thus material volume can be controlled. A system must be calibrated to determine the amount of fertilizer, metered per revolution. This is done by operating the motor for a period of time, the weight is determined and then the amount is compared to the desired amount. Adjustments are made and the planting begins.

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Source: Vern Hofman, (701) 231 7240, vhofman@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu