New Mexico State University engineers and the boards of supervisors for the Central Valley and Peñasco Soil and Water Conservation Districts (SWCD) have developed a novel herbicide sprayer that will provide an efficient and cost effective way to eradicate invasive plant species. The sprayer will soon be available to ranchers in the districts.

Invasive plant species, such as mesquite, creosote and certain types of juniper, pose a problem in the arid Southwest, using precious water resources that might otherwise support beneficial grasses or cause the erosion of land.

The sprayer is the culmination of more than 10 years of research conducted by Don Alam, who was district conservationist for United States Department of Agriculture’s, Natural Resources Conservation Service and the board of supervisors for the Central Valley and Peñasco SWCD’s at the time. Alam retired in 1998 and has since returned, now working part-time for the district.

It all began when Alam learned that a local rancher’s wife, Norma Brennand, began experimenting spraying a concentration of herbicide and water that was different than that specified by the manufacturer of the herbicide. Norma’s husband, David, is currently a member of the board of supervisors for the Peñasco SWCD.

“Her kill rate was twice what we were achieving,” said Alam, referring to the amount of invasive brush that she was able to eradicate.

So Alam began spraying various amounts and concentrations of herbicide and water over plots in different grid patterns. He identified the various concentrations and grid patterns that were most effective in killing certain species of woody brush. He found that spraying a 2 percent solution of water and herbicide in small 10 cubic centimeter squirts on a 6-foot grid pattern resulted in a 93 percent kill rate of juniper and mesquite.

“I tested all kinds of variations,” said Alam. Eventually, Darrell Brown, manager of the 4-Dinkus Ranch near Artesia, approached the NMSU College of Agriculture about developing a herbicide sprayer that could duplicate Alam’s efforts. The project eventually landed with the College of Engineering’s Manufacturing Technology and Engineering Center (M-TEC), which has expertise in engineering, manufacturing, product development, prototyping to assist businesses and individuals throughout the state.

M-TEC engineer Wesley Eaton, along with engineering student Kamren Pierce and other M-TEC employees, used Alam’s criteria and designed and built a grid sprayer that can be pulled or carried with a vehicle across rangeland while spraying the solution.

“We incorporated a GPS (global positioning system) unit that tracks the distance traveled so that the correct amount of solution is sprayed at the proper intervals,” explained Eaton, who started working on the sprayer in January of 2008.

The engineers created a touch screen that allows the operator to specify the grid pattern and amount of solution to be sprayed. A 36-foot spraying boom adjusts in height up to 7 feet to reach over the brush canopy while valves and nozzles deliver the solution in precise locations. A smaller version of the grid sprayer has been adapted for use with ATVs that can operate on rough terrain.

The grid sprayer is a cost-effective alternative to aerial spraying, which can cost up to $48 an acre and can be cost-prohibitive to private landowners. The grid sprayer could reduce costs to approximately $10 an acre, depending on the chemical concentration. It also allows a more targeted application of herbicide, preventing the eradication of beneficial vegetation.

While the grid sprayer is currently being tested, it will soon be available for rangeland use in the Central Valley and Peñasco districts.