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Get the most out of your pivot

With high grain prices, farmers need yield uniformity across their field to take full advantage of their input expenses, including irrigation. In Nebraska, pivots have become the norm, comprising around 82% of irrigation systems, compared to only 60% a decade ago.

Aaron Zimmerman operates center-pivot irrigation on his rolling farm ground in Pierce County. He has installed programmable panels on his pivots so he can automatically slow the sprinkler over higher, sandy ground that needs more water, and speed it up on lower, wetter soils.

At a glance

Pierce County farmer seeks more efficiency through his pivots.

Pay close attention to pressure and sprinkler spacing.

Keep nozzles out of corn canopy unless they are spaced between
5-7.5 feet.


Efficiency is the key for Zimmerman. “We watch our pressure,” he says. “Our wells taper off at the end of the season when the water table is lower, so we may have to speed up the engine to keep the pressure up on the sprinklers.”

Tune-up tips

Zimmerman’s preseason pivot tune-up usually includes checking pressure, chemigation valves and unplugging a few sprinkler nozzles. He operates an electric motor and a diesel engine on separate pivots. When he chose a diesel engine, Zimmerman took the time to find one that had the power to do the job and that ran in a cost-effective manner. But fuel efficiency is just part of the picture.

“Sprinklers and nozzles are at the heart of the system,” says Bill Kranz, University of Nebraska Extension irrigation specialist. “Select one that is most appropriate depending on your field conditions.” He says for center pivots “irrigation uniformity depends on the spacing of the sprinklers.”

Kranz and Derrel Martin, a fellow UNL Extension irrigation specialist, have been developing methods to improve irrigation efficiency for years. Kranz says, “Poor water application uniformity resulting from inappropriate sprinkler spacing or surface runoff can greatly affect overall grain and forage production.”

A few dollars spent on sprinklers could mean thousands of dollars in increased yields.

“Keep spacing [between nozzles] down,” Kranz says. Spacing should provide for at least 150% overlap. He also suggests keeping nozzles out of the crop canopy unless spacing is reduced to 5 to 7.5 feet between sprinklers.

Running at lower pressure has positive results, but there are management challenges, too. “Get out in the middle of the field to make sure water is where you want it to be,” Kranz says. “Check for runoff when the sprinkler aligns with the row direction on the slope.”

Water may be visible running down the row, particularly in lower-pressure systems where the wetted diameter is considerably less than high-pressure systems, he says.

Kranz notes that UNL and Texas A&M University research indicates that evaporation and drift are often overestimated. He says that there is usually only between 1% and 3% water loss in the air. “Small water droplets evaporate the most,” he says. “But most water droplets put on by the sprinkler are larger.”

Zimmerman operates medium-pressure sprinkler systems with drop nozzles placed just above the corn-crop canopy. Kranz says that pivots with end guns, like those on the Zimmerman systems, may not have adequate pressure to operate the end gun if the pivot is running at reduced pressure. Some systems could require the addition of a booster pump and a smaller end gun, or even elimination of use of the end gun.

“With these record corn prices come record inputs, keeping the margins the same but the risks are higher,” says Zimmerman. “With the large dollar amounts we put into each acre, we need to do everything we can to ensure a return.”

You can learn more tips on improving efficiency and effectiveness of center-pivot irrigation by contacting Kranz at 402-584-3857 or Martin at 402-472-1586.

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EFFICIENT IRRIGATION: Aaron Zimmerman (right) and his brother, Ryan, routinely give their center pivots a preseason checkup.

This article published in the May, 2012 edition of NEBRASKA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.