Nitrogen: shovelling or spoon feeding, it’s all about timing

Very few corn growers still apply the full load of nitrogen at or before seeding time.

Although a solid foundation of pre-seed nitrogen is applied in late fall or early spring, it’s generally accepted that too much nitrogen at any one time leads to leaching, volatization and denitrification.

This holds true regardless of the season or the type of nitrogen, according to the Fertilizer Institute.

Agri-Inject, a fertigation company in Yuma, Colorado, agrees with that group’s research. Agri-Inject specializes in designing and manufacturing chemical injection products for agriculture.

The two organizations state that closely matching nitrogen timing to nitrogen use minimizes nutrient loss and maximizes return on investment.

“By postponing a portion of the N treatment until the crop is better able to utilize the nutrient, plants take up the nitrogen more quickly and efficiently,” the Fertilizer Institute says in its reports on the practice. “That means growers get more from their fertilizer investment, and fertilizer losses that contribute to environmental concerns are lessened.”

It said the best management practices for corn production are split applications and late season applications, better known as spoon-feeding nitrogen or just-in-time nitrogen.

There is unanimous agreement that spoon-feeding and just-in-time nitrogen is the smart route, but the discussion has become focused on timing and resources required to accomplish the task.

University of Missouri researchers have studied the timing issue for 20 years and concluded that corn yields always improve when nitrogen is applied as late as tasseling. In studying rescue nitrogen application, they concluded that they “failed to find corn that was so late and so pitiful that rescue N was unprofitable.”

Erik Tribelhorn founded Agri-Inject in 1983, and has been dealing with that tricky timing question ever since.

“Researchers agree that a positive response to nitrogen application is seen when nitrogen is applied around the time of tasseling. The corn plant, however, takes up 20 percent of its total nitrogen after R2,” Tribelhorn said.

“Much of that late-season nitrogen is used by the corn plant for grain fill. The difficulty in addressing the late-season need most efficiently is that most application systems can’t operate much beyond the tasseling stage.”

He said corn growers with pivot irrigation systems can spoon-feed nitrogen to the corn crop throughout the entire period of nutrient uptake, avoiding the peaks and valleys inherent in other application methods.

“Corn plants don’t eat nitrogen; they drink it,” he said.

“It makes sense to feed the plant at the same time it’s taking up water. With today’s injection systems, you can precisely match the nitrogen delivered to the needs of the corn plant throughout its entire life cycle.

“More than half of a corn plant’s sulfur uptake occurs after VT/R1. As a result, many farmers apply 28-0-0-5 through their pivots during the critical late stages of grain fill.”

Beck’s Hybrids in the United States conducted trials of variable applications last year, making a strong economic argument for nitrogen fertigation.

Two corn hybrids received 30 pounds of UAN via fertigation at the VT stage. Compared to irrigation alone without UAN, the response to UAN applied at VT was an additional 29 bushels of corn. The return on investment from nitrogen alone was US$98.98 per acre.

Just-in-time spoon-feeding nitrogen through fertigation appears to make the most sense in terms of return on investment and environmental protection, say researchers.

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