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Variable rate cuts water use up to 15%

Ed Lammers of Hartington needed information before he could begin using variable-rate irrigation technology on his farm. “When I started irrigating in 2009, I began noticing that parts of the farm were producing better under irrigation,” Lammers says. “This made me realize the high variability of the soil types on my farm.”

CropMetrics LLC utilized several pieces of data collected during grid sampling of the land to develop an irrigation application map based on soil type, topography and historic yields.

The Zimmatic system that Lammers used initially could vary the application rate in up to 12 “slices” of the center-pivot circle, varying the watering rate by slowing down or speeding up the pivot, according to the prescription for each slice. But the CropMetrics map was so precise that Lammers says it could have been broken into 60 slices if the pivot system would have had the technology to handle that kind of precision.

Control systems developed in Australia and studied for many years in the U.S. have proven that variable-rate irrigation can reduce water usage by up to 15%, says Bill Kranz, University of Nebraska Extension irrigation specialist.

“In northeast Nebraska, where irrigators might apply 6 or 8 inches during a growing season, that savings may not sound like much,” Kranz says. But multiply water conservation and accompanying energy savings over several pivots and many years, and the economic advantages can be significant, he adds.

At a glance

Speed control and zone control are both methods of variable-rate irrigation.

Lammers now experiences less yield variability.

Variable-rate irrigation reduces water usage up to 15%.

Now, Lammers hopes to retrofit his older Reinke pivots with equipment that will allow him to utilize variable-rate irrigation prescriptions on more land. Pivots must have GPS installed, and there is expense involved in bringing older systems up to date with new control panel technology.

While variable-rate speed control used on the Lammers’ farm is one method, growers can invest in the equipment and technology called zone control, providing more precise watering with individual sprinklers or banks of sprinklers on the pivot controlled independently of each other according to a prescription field map.

Kranz says that researchers continue to focus on varying application rates over smaller field units. So far, field conditions and cost may be obstacles to implementing some of the most precise possibilities. Researchers are also concerned about where to place soil water sensors within each managed slice or zone on variable-rate irrigation fields, so the information collected is most useful to growers.

Kranz says that variable-rate irrigation might offer opportunities, particularly for growers of high-value crops like edible beans, sugarbeets, seed corn and potatoes, for instance. “On the other side, if you can realize 5 more bushels of corn per acre, that adds up” over the entire pivot, he says.

Lammers also uses University of Nebraska-Lincoln’s Web-based SoyWater irrigation scheduling tool to identify the crop stage of his soybeans and to assist in timing of irrigation on his fields. Reducing as many variables as he can, Lammers hopes to boost overall productivity.

“Yield-wise, there are so many variables for farmers,” Lammers says. “This year we had to contend with two wind storms that caused greensnap in corn, high temperatures at night during the growing season, and then frost.” So yield variation is a fact of operating, he says.

But, he believes that reducing the variable of water on his crops through variable-rate irrigation helps reduce the range of yields he experiences by increasing productivity on lighter soils. It also improves water and soil conservation on his land, Lammers says.

For more information on variable-rate irrigation and new irrigating technology, contact Kranz at 402-584-3857, or email


IRRIGATING THE BY SLICE: The center pivot Ed Lammers has equipped for variable-rate irrigation applied differing water amounts in 12 slices of the circle in 2011. It could have irrigated by even more slices of the field.

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

All rights reserved. Copyright Farm Progress Cos. 2012.