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SDI uses less water, but needs more maintenance

Randy Uhrmacher is one of the early adopters of subsurface-drip irrigation in Nebraska, at least on a full quarter-section scale.

He installed a T-Tape SDI system in 2005 on a quarter section previously irrigated by gated pipe. It had been a pain to move water through the near-perfectly flat field with gravity irrigation, and he ruled out replacing that system with a pivot because of a farmstead building that prevented full rotation.

So his answer was SDI, a system that, after the seventh season in 2011, has caused him few problems and cut water use vs. gated pipe delivery by 70%. “I feel that on average, I’ve used 30% less water than a pivot would have used on this field.”

He’s also burned less diesel to run the well due to fewer hours of pumping.

“SDI isn’t for every farm,” says Uhrmacher of Juniata. “If this had been a quarter section with rolling terrain and no pivot obstruction, a pivot would have been my choice.”

He’s subdivided the field into four sections, or zones, of 37 acres each, irrigating them one at a time in 12-hour shifts. Uhrmacher uses a valve to manually switch the water between zones. Since his installation in 2005, SDI controls have become more refined and can be set automatically. “All four sections are watered in two days.”

Emitters are on the tape, which is buried 14 to 16 inches deep and 60 inches apart. Crops are planted on 30-inch rows.

After seven seasons of use, annual irrigation water application is about 5 inches. This year, however, with well-timed rains, he irrigated only twice, applying just 1.4 inches total.

That won’t happen every year, but Uhrmacher harvested the best corn yield ever on the quarter section in 2011, and he believes he may have over-irrigated in the past with the SDI, especially on low spots in the field.

“I installed for the first time a John Deere water capacitance probe in the field this year, and I trusted its soil moisture readings,” he adds.

Trade-off

“With SDI, you spend less time irrigating and can get by with less water applied, but it takes more management than a pivot does.”

The system requires flushing, which he does during the first irrigation. He then cleans the filter after that first irrigation to remove any rust that may have been left by the well.

Leaks due to rodents or other animals posed some problems through the years. “The worst thing I’ve experienced is badger holes, but gopher damage to the tape is more common. I can find the location easy enough because the water surfaces right above the leak. It’s actually easier to fix than a flat pivot tire,” he says.

Back in 2005, Uhrmacher took advantage of a USDA surface and groundwater cost-share program — part of the Environmental Quality Incentives Program — to help offset some of the installation costs.

That’s another consideration with SDI — investment costs are higher than for center pivots.

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WATER FROM BELOW: SDI may not be for every irrigator, but Randy Uhrmacher found one quarter where it fits just right.

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

All rights reserved. Copyright Farm Progress Cos. 2012.