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Corn+Soybean Digest

Simple Yet Sophisticated | Student Adapts Equipment for Variable-Rate Application


One young farmer tailors his family’s farm equipment to keep up with precision agriculture.

When J.D. Riffel finishes his Kansas State University master’s degree in agronomy next year, he plans to head back to the family farm near Stockton, KS, where he’s already testing precision-ag technology with a custom-made, variable-rate fertilizer applicator.

As an undergraduate in agricultural technology management, Riffel’s simple modifications converted the farm’s anhydrous-ammonia applicator to accommodate variable-rate application.

“It could be built less expensively than commercial ones,” he says. “We have a lot of terraced ground and point rows, so we need lots of flexibility across the implement. The manufactured ones are more rigid and wouldn’t fit the contours of the ground as well.”

At K-State, Riffel scaled down his design to apply liquid nitrogen (N) with the university learning farm’s narrower equipment. He uses the equipment to study the results of varying N prescriptions on 11 acres of grain sorghum based on soil electrical-conductivity maps, grid sampling, yield maps and other factors.

“I’m using coulters and injector tips to place the N in the ground on 15-in. centers. It could be adapted to use spray nozzles for surface applications if the researchers do a placement-method study, too,” he says.

Riffel has pieced together the variable-rate technology equipment from various sources, starting with a heavy steel tubing frame. His custom-building success could encourage other growers who view variable-rate technology as being only for large operations.

You don’t always need to spend a lot of money on equipment and soil samples for variable rate, he says. “Some of our equipment at home actually was very easy to convert with a few extra modifications.”

Starting with some simple sketches, Riffel took measurements to begin building the main frame and determining the transport and working heights of the unit.

He found a 200-gal. poly tank and a hydraulically driven centrifugal pump from his local sprayer dealership. Using a 3/8-in.-thick, 4x4-in. steel tube, he constructed the main frame.

“I made my own tank cradle by rolling some sheet metal and reinforcing it with steel tubing,” Riffel says.

Next, he mounted Clymer Coulters’ spring-loaded coulters on a ¾-in. steel plate on a 4x4-in. frame to make three-point mounts to lift the applicator.

After selecting mount locations, Riffel used poly fittings to assemble plumbing, including a flow meter, flow-control valve and an electric on/off ball valve.

“The plumbing was one of the harder things to figure out when I was trying to keep it simple and compact,” he says.

He built his own injectors and mounted them directly behind the coulters and ran high-pressure tubing from the manifold to each injector.

“I needed a way to direct fluid to 12 coulter units so I made a manifold out of a sprayer wet boom and threaded nozzle bodies,” Riffel says.

The injectors are made from stainless steel with a diaphragm check valve to minimize dribbling when the flow is shut off, he says. The injectors also are adjustable vertically and horizontally to allow for placement directly in the slot created by the coulter.

To complete the applicator, Riffel wired an EZ-Boom controller with an EZ-Guide 500 guidance system and attached the hydraulic hoses to the pump.

To make the implement’s use and storage more convenient, he built a simple cart using a steel frame with 4-in. castors on the base.

“I can roll it into place to hitch it to the tractor, and I can roll it over against the wall in the shop for storage with no hassle,” he says.

After using the applicator in the field, Riffel says there isn’t much he’d change, but he’d make some improvements to electronics.

“Fertilizers are so corrosive that the wiring connections are corroding,” he says. “I am going to replace some connectors with Weather Pack connectors to prevent this from happening.”

Riffel notes that variable-rate technology complements yield data that most modern farm equipment collects. While many farmers use harvesting equipment with yield monitors, few know what to do with the data, he says. That’s something he hopes to change, starting with his own farm and his neighbors’. 

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