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Fertilizing on the fly

Nitrogen losses due to excessive rainfall have cost Midwest corn growers millions of dollars in yield losses over the past four years.

As fields dried out enough to support ground equipment during those years, many farmers applied rescue nitrogen with conventional sidedressing equipment or high-clearance applicators. But many fields never dried out in time for farmers to make those applications.

Fortunately for farmers in some areas, aerial application equipment was available to fly on dry urea (46-0-0).

In central Iowa, three bright yellow Air Tractors owned by Agri-Tech Aviation of Indianola were a familiar sight last summer as they applied nitrogen to approximately 24,000 acres of nitrogen-depleted corn. Some of the fields they treated had received 15 inches of rain in two weeks in mid-June.

One of the Air Tractors is a Model 502, which holds 2,900 pounds of urea. The other two are 402 models that hold 2,300 pound of urea. Sometimes Agri-Tech also used a smaller Cessna Ag Wagon.

Application charges vary depending on how close a customer's fields are to an airport. Aerial fertilizer application costs more than spraying because the planes are handling a lot more volume so more time is spent loading and flying to and from fields. A typical rescue rate was 100 pounds of urea (46 pounds of N).

Agri-Tech is owned by Terry and Debbie Sharp. Their two sons, Jay and Wes, are the third generation in the business, which was started in 1947 with the help of Terry's father, Weston Sharp.

Unless this turns out to be another wet spring in the Corn Belt, the demand for flying on dry urea probably won't be as great as it was last year. But the Sharps plan to have three Air Tractors available if the need for rescue nitrogen arises.

“We can switch from applying liquids to applying dry urea in about two hours,” says Jay.

And some farmers are interested in a planned application of dry urea as opposed to a rescue application.

A lot of the urea the Sharps applied last year landed on saturated fields. Obviously, there was no way to incorporate it. Consequently, most of the urea was either treated with Agrotain by a fertilizer dealer or purchased as SUPERU.


Agrotain is a nitrogen stabilizer that reduces volatilization losses of urea. Volatilization is the loss of nitrogen into the air and occurs when urea contacts moisture and urease, a soil enzyme. Agrotain is a urease inhibitor.

SUPERU is a urea-based fertilizer from Agrotain that has two active ingredients, a urease inhibitor and a nitrification inhibitor. As mentioned previously, the urease inhibitor protects against volatilization losses. The nitrification inhibitor slows bacteria growth and helps keep nitrogen in the ammonium form longer so it is less susceptible to denitrification and leaching.

It takes several people and a lot of support equipment to keep the planes in the air. Two Rivers Cooperative was supplying fertilizer to the planes at the Pella, Iowa, airport when these photographs were taken. Agrotain was applied to the dry fertilizer at their plant and hauled to a parked fertilizer tender in trucks. From the tender, the fertilizer was transferred to boxes on a flatbed trailer, where the boxes were weighed.

Matt Van Weelden is the agronomy service manager at Two Rivers Cooperative. He views aerial application primarily as a rescue operation because it is weather dependent. “You need a shot of moisture to take it in,” he says.

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Agri-Tech Aviation, Inc.


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