Researchers, engineers team up on saltcedar control system

The U.S. Bureau of Reclamation has a new tool in its efforts to control invasive saltcedar at Elephant Butte and Caballo reservoirs in southern New Mexico.

Left to right: NMSU engineering students Wyatt Kartchner and Eric Freeh, along with M-TEC staff engineer Wes Eaton, look over a carpet-roller herbicide application system they designed and built to help the Bureau of Reclamation control invasive saltcedar.

Developed by New Mexico State University, it’s a tractor-mounted rig for wiping herbicide directly onto saltcedar plants. It can be used on regrowth following mowing or on newly established plants. It covers a 24-foot swath at a time, without harming the grass and other plants growing under the saltcedar.

The supersized, heavy-duty carpet-roller applicator system was designed and built by staff and students in NMSU’s Manufacturing Technology and Engineering Center, working with Kirk McDaniel, a professor in the Animal and Range Sciences Department, and Brent Tanzy, resource management specialist with the Bureau of Reclamation’s Elephant Butte Field Division.

The bureau has been fighting saltcedar around the reservoirs since the 1950s, Tanzy said. The invasive, fast-growing plants, also known as tamarisk, are notorious for using large amounts of water, replacing native vegetation and increasing the intensity of brush fires.

There are 6,000 to 7,000 acres of saltcedar at Caballo Lake and about 5,000 acres at Elephant Butte, Tanzy said. “Historically we have mowed it, but we have been trying to move beyond the mowing.”

Saltcedar plants grow back quickly after mowing. Spraying the mowed plants with herbicide also kills the grass and other native vegetation that the bureau would like to re-establish.

With funding from the bureau, McDaniel has been researching the use of carpet-roller applicators to wipe herbicide directly on the saltcedar without damaging the grass. He and graduate student Jose Franco determined the optimal rate of application and the most effective time of year to apply the herbicide.

But commercially available carpet-roller applicators, made for use on turf or row crops, were not big enough or rugged enough for the field situations at Elephant Butte and Caballo. McDaniel and Tanzy approached Wes Eaton, a project manager and engineer at M-TEC in NMSU’s College of Engineering, and described what they needed.

Eaton hired three engineering students – Wyatt Kartchner, a civil engineering senior from Cliff; Beau Bradberry, a mechanical engineering technology senior from Cliff; and Eric Freeh, a mechanical engineering technology junior from Alamogordo – in summer co-op positions to work on the design and fabrication. They started the design work in late May and the finished product was ready for the field by the end of August.

“They did a great job,” Tanzy said. “This is pretty significant, because it is reviving and improving a methodology that was developed in the 80s for brush control. Those were really small rigs at that time. This rig – I don’t know anybody else who has one this size.”

The rig uses three eight-foot carpet rollers, one at the front of the tractor and one on each side at the rear that can be lowered like a boom from a vertical to a horizontal position. A system of adjustable nozzles applies the right amount of herbicide to the carpet-covered rollers. The rollers rotate opposite the direction of the tractor’s forward movement so that the herbicide is effectively wiped onto the surface of the saltcedar as the rollers pass over.

The rig was first used on saltcedar growing over saltgrass on the upper end of Caballo Lake on Sept. 10.

“It went very well,” McDaniel said after the first day’s trial. “It looks like it’s going to work perfectly for what we’re trying to do. Next year at this time we will know the results.”

The area being treated had been mowed about a year ago and the saltcedar plants had grown to a height of four to six feet.

“We may not be able to eradicate it but we want to manage it more effectively,” Tanzy said. After several seasons of alternating mowing and herbicide application, he said, “by attrition I think we can actually eliminate it in certain areas.”

McDaniel said the system could be effective in a variety of heavy brush control situations. “It’s not just for saltcedar.”

Karl Hill

Sept. 18, 2007

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