Bubblers boost water efficiency
By JIM STEIERT
High Plains producers are regularly and harshly reminded that efficiency of an irrigation system dictates crop watering capacity.
It’s an old lesson, convincingly demonstrated since the 1980s. Research made low-energy precision application, or LEPA, part of modern sprinkler irrigation lexicon.
Unfortunately, hard-learned lessons get forgotten. Such was the case in 2011 in the Texas High Plains. Many irrigators lost too much water to application inefficiency in windy, hot conditions.
Small water droplets from spray emitters never got to the ground to benefit the crop. Systems lost a whopping 25%, and some even more, of the water pumped.
“We can and must do better in improving irrigation system efficiencies and crop irrigation management,” says Leon New of Amarillo, agricultural engineer and irrigation consultant for the North Plains Groundwater District.
Key Points
• Many irrigators lose water to application inefficiency in windy, hot conditions.
• Bubbler applicators on LEPA systems deliver 95% or more at ground level.
• Specialist: “Water costs money. It’s gone once you pump it.”
“For a 500-gallon-per-minute system on 120 acres, a 6% loss represented 30 gallons per minute or 0.25 gallons per minute per acre. At 12% loss, 60 gallons per minute or 0.50 gallons per minute per acre was lost, and at 18%, 90 gallons per minute or 0.75 gallons per minute per acre was lost in application.
“A 24% loss represented 120 gallons per minute, or a gallon per minute per acre. That’s a massive loss when producers are sometimes linking several wells of 100 gallons or less capacity to feed a single sprinkler,” New says.
The key to doing better in 2012 isn’t complicated or extravagantly expensive, particularly measured against adding irrigation capacity through drilling new wells.
“System capacity, whether LEPA bubble, LESA low-elevation spray, or MESA mid-elevation spray is determined by the nozzle package. There is no difference in capacity of any of these systems that irrigate 120 acres with 540 gallons per minute, or 4.5 gallons per minute per acre at 100% efficiency.
“Wind speed, low relative humidity, temperature, evaporation, runoff and seepage below the root zone all reduce efficiency. Systems must get 90% or more of the irrigation water pumped to the crop,” New emphasizes.
In 2011, nothing accomplished that better than bubbler applicators on LEPA systems that delivered 95% or more of the water at ground level for the corn crop, while spray pads were losing up to a quarter of water pumped to evaporation.
“We can’t be finished adapting. We don’t want to encounter again what we did in 2011,” New says. “Today, we have access to advanced tools and technology that can guide each of us to develop management skills to produce 900 pounds of corn, 150 pounds of cotton lint, or 8 bushels of wheat per inch of seasonal irrigation.
“The water applicator and its position determines system efficiency. Some producers say they don’t have time to flip the pads or cap from spray to the bubble mode. But when you’re losing 25% of your water, you must take time to make changes. If you don’t, hire a college student and have them change out the pads to make a needed difference in the efficiency of the system.
“Water costs money. It’s gone once you pump it. We need to get more of it on the ground to the crop, using equipment we already have, rather than drilling more wells and drawing more out of the aquifer.”
Steiert writes from Hereford, Texas.
minor tweaking: Many growers could achieve several percentage points better water use management with only minor adjustments to their bubbler nozzles.
This article published in the May, 2012 edition of THE FARMER-STOCKMAN.
All rights reserved. Copyright Farm Progress Cos. 2012.