Variable-rate Fertigation Has Emerged

By Tharran Gaines

Imagine being able to apply variable-rate liquid nitrogen through a center pivot irrigation system while, at the same time, varying the amount of water being applied. According to Caleb Schultz, precision ag manager for J.R. Simplot Company in Wray, Colorado, such technology is no longer a dream but a reality.

Schultz was one of the first to use a new reflex variable-rate fertigation (VRF) system introduced by Agri-Inject, a manufacturer of chemigation systems and fertilizer injection pumps based in Yuma, Colorado.

Matching Flow to Changing Conditions

As Neal Saxton, director of global sales for Agri-Inject, explains, the reflex intelligent injection-control system was actually introduced nearly two years ago to provide responsive control of fertilizer or chemical flow into the system to match changing irrigation conditions. Whether the variable flow rates are the result of a corner span extending, change in pivot speed, or changing flow rate from the pump, reflex senses changing water flow rates and automatically adjusts the rate of the injection pump to ensure consistent fertilizer dosing.

“Since then, we’ve used that flow-based injection technology to develop intelligent injection control for VRF,” he relates. “Now, you can apply fertilizer through the pivot to either match flow rate or to match a fertilizer prescription, just as you vary water applications to a prescription. In fact, reflex even allows you to variable-rate water and fertilizer applications independently.”

Schultz says his experience with VRF began in 2014 when he programmed a system on a customer’s field for a flat-rate fertilizer application, even though the pivot was programmed for variable-rate irrigation. The reflex system compensated for an increase or decrease in the amount of water applied to different sections of the circle to maintain an even fertilizer application over the entire crop.