Farmers adopting precision agriculture techniques
By Jean Caspers-Simmet
simmet@agrinews.com
Date Modified: 07/15/2010 4:05 PM
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KANAWHA, Iowa —Farmers at last week's Iowa State University Northern Research Farm field day at Kanawha learned about precision agriculture tools and saw a demonstration of a tractor equipped with autosteer.
Matt Darr, an ISU ag and biosystems engineering professor, said nationwide one out of every two producers is using some level of precision agriculture with 40 percent of producers using yield monitors and 45 percent of producers using either a light bar or auto steer. About 85 percent of the machines at farm cooperatives use light bars. Variable rate technology adoption is 25 percent.
Darr said ISU research shows that a light bar will pay for itself in three years on a 300-acre farm.
At the heart of all precision farming systems is the global positioning system receiver, Darr said. What separates quality and cost of receivers is how they correct the satellite signal to overcome errors caused by the atmosphere, terrain or satellites being slightly out of orbit. There are three common methods of GPS correction.
Single frequency GPS receivers use the free Wide Area Augmentation System correction service and typically function within 12-inch accuracy during pass-to-pass field operations.
"This is suitable for non-critical guidance, including tillage, spraying and seeding/drilling," Darr said. "They are also used for autoswath systems on sprayers, but accuracy will decline in larger fields."
Dual frequency correction offers advances over single frequency correction and provides pass-to-pass accuracy within 4-inches or better, Darr said. This works well for precise auto steering for planting and for planter section control. It requires a yearly subscription that can range from $800 to $1,500.
Real Time Kenematic, or RTK, correction is the most accurate GPS correction because it uses a privately-owned reference station located close to the GPS receiver. RTK can provide one-inch pass-to-pass accuracy and is the only GPS correction that provides year-to-year position stability. RTK allows controlled traffic, strip tillage/fertilization/planting and extremely precise autosteering. Darr said that although RTK receiver costs have come down, the investment is still high from a cost and complexity standpoint.
RTK networks maintained by groups of implement dealers are available for a subscription fee. The cost is similar to a dual frequency subscription.
For farmers not near an RTK network or in an area where line-of-site communication to the RTK base is not possible, the Iowa Department of Transportation's new RTK network, Iowa Real-Time Network, or IaRTN, is a solution, Darr said. DOT's Iowa Real-Time Network, consists of 82 RTK base stations throughout the state. Each station is connected to a central data server maintained by the Iowa DOT. Access is available free of charge.
These base stations have been organized as Continuously Operating Reference Stations, or CORS, and a cell phone is required to receive the RTK correction, Darr said. The GPS receiver must be a CORS-enabled receiver or have an add-on cell phone modem to access the network. A dedicated cell phone service is used and requires a data-only plan which can range from $25 to $50 per month.
"You have to look at what works best in your area," Darr said. "If your equipment dealer has a network that works in all your fields, you absolutely want to stay with a radio-based system. If you have area without network coverage, you will want to look at using the Iowa DOT system."
Investing in a $2,000 light bar for a sprayer can cut chemical costs by 4 to 8 percent per year, Darr said. In areas with rugged terrain, the savings have been as much as 17 percent.
Investing in things like row control can reduce seed bills by up to 4 percent, and yields will improve by eliminating overplanting.
"Using a suite of precision ag technologies can put money in your pocket," Darr said.