April 11, 2003

LINCOLN, Neb. — Irrigation water use will be a critical issue across much of the state this summer, a University of Nebraska irrigation engineer said.

With ground and surface water levels declining, Nebraska growers need an irrigation strategy to ensure systems pump efficiently and distribute water consistently, said Dean Yonts, irrigation engineer at NU's Panhandle Research and Extension Center at Scottsbluff.

Growers need to be sure their sprinkler irrigation systems are applying water uniformly, which is especially important this drought year, the Institute of Agriculture and Natural Resources specialist said.

"If we apply too much water to one spot and not enough to another, we've not effectively used that water to the best of its ability to do something for us."

Yonts advises against running sprinkler irrigation systems to apply light, frequent applications early in the season when much of the water can be lost to soil evaporation, he said.

"Before the crop canopy develops, the water evaporates with each application," he said. "Once a canopy is established, the protection beneath the canopy allows the crop to use the water before it's evaporated in the air."

Sprinkler height also is important. Yonts said sprinklers closer to the ground won't necessarily save growers a lot of water compared to those located above a corn canopy.

"Evaporation loss is not all that critical compared to what the runoff may be," he said. "Sprinkler devices in the canopy lose the ability to spread water over a large diameter. When sprinklers are in the corn canopy, they can only shoot water four or five feet at most."

Soybeans and dry beans could benefit from sprinklers closer to the ground, but if the field is in a corn rotation, it may not pay to risk the runoff in the corn, he said.

If growers have the water available, creating a reservoir of water for the crops will be important. "If you are going into the season knowing it will be dry, you may want to apply a little bit of water going into planting. Sugar beets would especially benefit from this," he said.

Farmers in areas facing restrictions will have to reduce pumping by decreasing how much water the crops consume. For example, corn can be stressed early in the season and then irrigated starting about two weeks before tasseling. Surge irrigators that lack the means of reusing irrigation flows from the lower end of a field may want to stress the lower end rather than to allow the water to run off.

Yonts said "the real criterion in a short water situation (with all types of irrigation systems) is to apply as much water as you can, but don't get runoff."

Crop choices also can be changed, he said. Shorter season crops or something that uses less water, such as soybeans or sorghum, is another option.

Crop residues are another important tool in conserving water this year, Yonts said. Good residue cover reduces evaporation losses and saves moisture.

Also, maintenance and equipment readiness will save time when irrigation is critical this summer, Yonts said. Repair leaky gates and gaskets and look at spray nozzles.

"Check nozzles that had to be replaced last year," Yonts said. "We have to remember one or two of those sprinklers cover a lot of area. We could be applying way too much or not enough."

4/11/03-SA

Sandi Alswager Karstens
IANR News and Photography
(402) 472-3030

Department: Biological Systems Engineering