Sub-surface irrigation demonstrates moisture savings

Images of water spaying over fields may be a thing of the past if growers adopt the latest technology by installing sub-surface irrigation in their operations.

Robert Bergquist, micro-irrigation manager for Toro, said that when pivot irrigation began in southwest Nebraska in the 1980s and 1990s, three concerns were conveyed by naysayers: It was too expensive, it would be hard to get enough water from the pivot (water previously ran down the rows) and the technology was too complex.

Bergquist said that as he’s demonstrated how subsurface irrigation works, he’s hearing the same things 35 years later from growers. He said fellows have a hard time wrapping their heads around the technology of the system; it’s hard for them to believe enough water can be delivered and they think the system will be too expensive.

At the Oahe Farm and Ranch Show this summer, Bergquist showed examples of the Aqua-Traxx tape that offers emitter options from 4- to 24-inch spacing. Highly engineered, the zigzagging in the tape actually provides the turbulent flow path, he said. The little outlets utilize laser burn-ins to let water out. This design allows nitrogen to be added at the pump-site and used like a side-dress application.

The drip tapes are tubes buried beneath the soil surface for multi-year use, according to company literature. The technique of burying less expensive Bi-Wall laterals was pioneered in the American Southwest decades ago and has been improved by researchers. The technique is now being used throughout the world on a wide range of grain, forage and fibers crops including alfalfa, corn, cotton, soybeans and sugarcane.

The system uses rigid PVC pipe for sub mains and flushing manifolds and are maintained for multiple crop use. The system is expected to last for up to 35 years when properly designed, installed and operated. The tape is manufactured to best fit the design of the field. Soil types, water conditions, field size, shape and topography all come into play in setting up the system.

“If the system is to apply an inch of water on the field, we strive to get 95 percent or greater uniformity,” Bergquist said. “That would mean the driest parts of the field would get .95 of an inch and the wettest would get 1.05 inches. That would go directly into the root zone with no leaching and no runoff.” And that would apply, too, if fertilizer were added at the pump head.

Looking at the field, visual evidence of the system is at the pump site and vent sites for flushing the system at the end of the season.

Advantages include increasing yields by growing healthier plants that receive the water when they need it. It also allows irrigation of odd-shaped sections of fields. It reduces energy costs by operating at lower pressures and fewer hours than pivots and reduces the volume of water applied.

It’s a water saver, Bergquist said. It’s putting water in the root zone. If you put on 10 inches on the surface with a pivot, you may get 7 ½ inches in the root zone. With subsurface, when you apply 10 inches, at least 9 ½ inches gets in the root zone.

“It’s like a 2-inch rain at the first of August, that’s huge,” he said.

For more information, go to toro.com or call 308-991-8555.