Accurate, cold-weather, variable-rate application of anhydrous ammonia is a dramatic step forward for Doug Zink, a farmer in Carrington, North Dakota.

He’s taken up the challenge with the Maxflow VRC. The machine pumps liquid NH3 into the soil according to a prescription map, at up to 170 pounds per acre. The operator has sectional control, a manual foot switch to minimize loss at turns, and a field that is ready to seed when the work is through.

“This is the best anhydrous applicator I’ve ever had, and I’ve had a lot of them,” Zink says. “Most of the time, things don’t really live up to what you’re told. But this does.”

Zink applies the NH3 at 9 mph with a new 42-foot vertical tillage coulter, the Salford RTS. It will cut through 2 inches of frost and up to 1 foot of snow. In less than two weeks, Zink had fertilized about 8,000 acres of soybean residue. He was going through a 1,500- gallon tank of NH3 every 90 minutes.

“You can put on 140 pounds of actual nitrogen or just 40 pounds at 9 mph. It’s just so accurate,” Zink says. “You don’t have to worry about anything.” The cab tells the operator how much is in the tank. When there’s 10% left, an alarm goes off.

The key to the system is high pressure, keeping the NH3 liquid until it is sealed in the ground, according to Cameron Stewart, president of MaX-Quip. The company specializes in handling and metering compressed gases from many industries. Pressurized liquid NH3 is easier to handle and can be metered more accurately. It eliminates vapor loss and opener freezing.

Continuous pressure is generated by the tractor’s hydraulics, tied into a MaX-Quip positive displacement van pump driven by a hydraulic motor. The pump is mounted close to the nurse tank with the intake below the nurse tank belly. Varying the motor speed varies the flow rate.

“Higher pressure with smaller lines lets you accurately deal with reduced rates at the low end and accurately push more product through at high rates,” states Zink.

An automatic rate controller, using signals from a flow meter and a ground speed indicator, can adjust the motor speed on-the-go. The rate can also be varied by a task controller with a map and GPS signal. On-off valves on the distribution manifold keep the system fully pressurized.

“If you only need 30 pounds, you now can get it with consistency and accuracy. At all rates, high manifold pressure is easier to handle than low manifold pressure,” Stewart says. “For variable rate, high pressure provides almost instant response from zone to zone.”