Howard Neibling

The University of Idaho’s Howard Neibling at a variable-rate irrigation pivot and control panel.

Howard Neibling helps farmers irrigate more efficiently.

“A lot of water users are being more careful with their water and trying to stretch,” said the extension water management engineer at the University of Idaho Kimberly Research and Extension Center. “Basically, what I’ve been doing for a long time is helping growers get the most production for the water they have. A lot of that is minimizing losses and making sure they time their applications to avoid water stress.”

He helps growers evaluate the efficiency of their irrigation system and determine if changes are warranted.

“I present to growers that you have a whole palate of options depending on how short you are (on water) and how much you want to save,” Neibling said.

He likes to focus on water-delivery efficiency.

Average amounts of pumped water that get into the soil range from 60-70% for hand- or wheel-line sprinklers up to 80% for a conventional center-pivot nozzle placed 5 or 6 feet off the ground, Neibling said.

About 90% of water gets into the soil if delivered by a Low Elevation Sprinkler Application system 30 to 36 inches above the ground, and 92-94% if the LESA is placed down into the plant canopy. Drip irrigation can be 95% efficient or more depending on the approach used.

Those rates account for losses from evaporation, leakage or deep seepage from over-application. They are lower in windy or dry conditions.

Researchers at UI, Utah State University, Brigham Young University and BYU-Idaho have been studying variable-rate irrigation, which adjusts sprinkler pivots or individual nozzles according to water need. Electronic controls customize applications to areas that are wet already, or especially dry, for example.

“Variable-rate makes the most sense where you have non-uniformity in soils in a field, or have areas of rock,” Niebling said. “We are trying to say we have variability out here, and how do we set our systems up to manage it?”

Such systems don’t pencil out where water is plentiful and inexpensive, but can produce major savings in other locations.

“In the Rupert (Idaho) area or other areas where there are rock piles or rock blowouts, you could program this so when it goes over a rock pile, it shuts off,” Neibling said.

Variable-rate systems also can help save on chemicals applied via irrigation.

Drip irrigation is also advancing. From a connection to a groundwater pump or filtered surface water, tubing or drip tape is rolled out and placed at the desired depth.

Neibling has been watching developments in mobile drip irrigation, in which lengths of drip tubing replace sprinkler heads on a pivot. Potential benefits include uniform application as the pivot moves around the field, less wind drift and water concentration at the root instead of foliage to make the plant less disease-prone.

“We are seeing some usage,” he said. “Again, it’s more expensive. But if you don’t have enough water to grow a decent crop, it may make sense to you.”

Neibling said costs to convert to various systems include about $8,000 per pivot to go from sprinkler heads 5 to 6 feet off the ground to LESA set at 30-36 inches, or about $12,000 if they’re at 18-24 inches because more heads are needed for narrower spacing.

The cost is $20,000 to convert a pivot to mobile drip, with water filtration accounting for about half of the pricetag.

“With the uncertainty coming from climate-change effects, we may have less water and higher crop demand,” said Neibling, who works with soil-moisture sensors as well as irrigation systems. “So we’re going to have to manage water even better in the future.”

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