Writer: D'Lyn Ford
LAS CRUCES - As water-stingy drip irrigation systems take root across the state, a New Mexico State University scientist is looking down the road, or row in this case, at steering clear of a surge in unwanted weeds caused by a shift to this potent crop-watering technology.
In subsurface drip irrigation, water is applied directly to the plant's roots through a series of black plastic lines or drip tape buried more than a foot deep.
"Drip irrigation is the future of New Mexico, and it's just starting to catch on now," said Mark Renz, a weed specialist with NMSU's Cooperative Extension Service. "But we're also looking at a potential a shift in weed populations and timing of weed emergence."
In fact, he said, there's a possibility that many farmers' most effective weed control tools may not be up to par. The side effect of improving water efficiency is a potential boost in troublesome and difficult to manage weeds.
Since drip irrigation specifically targets the root zone, growers are likely to see the emergence of invasive perennial weed species that germinate deep in the soil. Topping the list of potential weed culprits are perennial purple and yellow nutsedge, along with persistent field bindweed. These tenacious weeds are widely known for vigorous root systems, which are almost impossible to kill once they've established a firm foothold.
"There's simply not a lot of information available on what's going to happen when we go to these drip irrigation systems," Renz said. "We need to know what weeds come up, and just as importantly, what time in the season do they appear."
To prepare, Renz is scrambling to develop a new study that will track the differences among weed populations under drip, furrow and sprinkler irrigation systems at experimental plots near Las Cruces, Deming and Artesia.
Problem weeds that aren't controlled tend to proliferate in following years, he said. By knowing which weed species thrive under a drip system, NMSU scientists adjust management practices.
"By identifying key species that are problems, and under which irrigation methods, in the future we will be able to customize management programs for the local farmer," Renz said.
Drip irrigation is widely used in many water-starved areas of California and Arizona. And while it has been around New Mexico for more than 40 years, the irrigation method has yet to take hold here because of high installation costs and immediate availability of water from the state's river systems, said Robert Flynn, an agronomist with NMSU's Agricultural Science Center at Artesia who has been experimenting with a 5-acre drip system on alfalfa for almost five years.
But extensive drought and tougher water restrictions are likely to force producers to use water more efficiently and more responsibly, he said. In many areas of the state, there simply isn't enough water to go around.
To be sure, one clear advantage of subsurface drip irrigation is that it ends the wasteful practice of spraying water into the air, Flynn said. The system simply drips underground, applying moisture precisely where and when plants need it. There's little evaporation and virtually no runoff.
For the average producer, installing a new drip system is a large-scale undertaking, and it must be done correctly, he said. Costs can vary from $500 to $2,000 an acre depending on the quality of the materials, acreage and the size of the pump and filters needed. While the longevity of a drip system depends largely on the quality of the tape, many producers expect their drip tape to stay in the ground at least 15 years.
"We've learned from previous new agricultural technologies that there is always a learning curve, and drip irrigation is no different," Renz said. "You can learn from other drip irrigation adoption areas like California and Arizona, but each state is unique. We're going to have some growing pains."
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