Drip irrigation helping fine-tune scheduling

LITTLE ROCK, Ark. — University of Arkansas researchers and scientists are using subsurface drip irrigation techniques to help refine irrigation scheduling recommendations. They’re also trying to determine if the technique can provide better yield stability and reduce water usage.

Phil Tacker, Arkansas Extension irrigation specialist, said the university provides farmers with a powerful irrigation scheduling tool. “We’ve conducted soybean irrigation studies with the help of the Arkansas Soybean Promotion Board, and we want to make sure our irrigation scheduling program recommendations address newer production practices.”

The program has been revised over the years and is used by other states, but it can always be made better.

Larry Purcell, a UA physiologist on the project, said most of the irrigation scheduling recommendations are based on production practices that are many years old. Purcell is an advocate of using earlier maturing cultivars, narrower rows and higher population densities with quicker canopy closure.

Current recommendations don’t take into account the higher populations and narrower row spacings used on earlier maturity groups.

Tacker said the three-year research project can also lay groundwork for developing recommendations if subsurface drip irrigation becomes a practical and affordable alternative for row crop farmers. “There’s an interest in subsurface drip irrigation, but we’re not currently promoting it as something many row crop farmers should switch to. We’ve put some in to see what it takes to install and to evaluate how it works.”

Tacker said the first drip irrigation was installed in cotton near Keiser, Ark., in 2002. Soybeans were added this year.

What’s the verdict so far?

“As far as a really precise control of irrigation water, it’s good,” Tacker said. “The water is put in at the roots in a controlled amount with better efficiency. Subsurface drip is 95 to 100 percent efficient as compared to center pivot irrigation at about 85 percent and flood and furrow irrigation, which is something less. Drip also requires significantly less pumping capacity on a per-acre basis than flood or furrow.”

Subsurface drip irrigation also offers the advantage of being able to apply precise amounts of nutrients directly to the roots for quick crop uptake.

Much of the well water in Arkansas typically has high pH and iron levels that can cause problems for drip irrigation. Drip tubing has small openings that can be plugged by and calcium and iron deposits.

“Drip shows promise as an irrigation system, but the real question is how does it compare cost-wise to conventional irrigation systems? We already have some effective irrigation methods,” Tacker said. “Does it give enough advantage to warrant the cost?”

Chris Tingle, Arkansas Extension soybean specialist, has been involved in devising planting systems and plant populations for the research. He’s enthusiastic about the project. “Being able to use this new technique is allowing us to better define the water use curve for Arkansas soybeans.”

As an irrigation tool, Tingle said, drip irrigation may be more justified for commodities other than soybeans. “We could see it used in soybeans if the economy someday justified it. But it’s a sizeable investment for the landowner and farmer.”

Dick Oliver, a UA researcher, said vegetable producers can justify the use of subsurface drip irrigation because they’re watering a smaller area and a high value crop. He said the system has the advantage of slowing weed emergence and growth.

Lamar James is an Extension communications specialist with the University of Arkansas.

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