As water supply concerns continue to mount, especially in the central U.S. and westward, irrigation researchers and manufacturers are devising new ways to preserve the precious resource. This year, T-L Irrigation, Hastings, NE, re-launched its Precision Mobile Drip Irrigation (PMDI) system to do just that.
PMDI’s design actually combines two commonly known technologies. In-line drip hoses take the place of nozzles or sprinkler heads on center pivot or lateral-move systems. Drip lines are spaced at 60-inch intervals, and as they are pulled through a field, emitters within the driplines deliver an even water pattern across the full length of the irrigation system.
Emitters are spaced every six inches and put out about two gallons of water per hour (at 15 pounds of pressure). Studies have shown total water use efficiency at almost 95%.
The system has been tested and sold in the High Plains for crops such as corn, soybeans, milo and cotton. Most recently, T-L is developing a set-up for a farm operation in Texas that is aiming to raise 200-bushel corn with 12 inches of irrigation water per year.
“We’re seeing the most response in areas that are deficit irrigating,” says Dave Thom, vice president of marketing with T-L Irrigation. “They have limited water, and they’re trying to get as much crop out of every drop of water they have available.” Interest is also coming from areas that put allocations on farmers – growers receive a set amount of acre-inches per year from a water source, and they want to stretch that as far as possible.
Vegetable growers will be interested in the technology as well, seeing as the system doesn’t apply water to crop leaves — which can promote disease development.
Factors To Consider
Thom notes that PMDI offers some considerable advantages over conventional approaches. For instance, the system eliminates leaf evaporation and wind drift. “You could be out there irrigating in 40 mph winds, and nobody even knows you’re watering. You don’t see any water moving around the field, it’s just quietly dripping,” he says.
In addition, PMDI drip lines run behind the system, so wheels run on dry ground. This avoids deep wheel tracks, a real problem in some soils and cropping conditions.
Cost wise, Thom says a PMDI system is priced about the same as a mid- to high range center pivot sprinkler package. It is universally available for all new or used pivot or linear irrigation systems.
The pivot controls remain the same just like any other sprinkler package, so growers can use variable rate irrigation. T-L has teamed up with AgSense, Inc. to provide Web-based irrigation management through its Precision Link product. The technology allows full remote pivot control and monitoring capabilities.
Growers will need to make sure their water source is clean enough — and in some cases they’ll need to filter water so it doesn’t clog emitters. (Thom notes that the system uses the largest emitters on the market, so they won’t have as many problems as buried drip tape can run into.) Then too, hoses get longer and longer as they extend out on a pivot, trailing up to 60 feet behind the end of the system. Growers should monitor these longer driplines to make sure they stay straight.
Thom says that although PMDI does require some additional management over conventional center pivot and lateral move equipment, user experience has shown the benefits of improved watering efficiency far outweigh the extra effort.
The PMDI design was actually patented 10 years ago, utilizing a hose used in the gold ore mining industry. The manufacturer of that hose discontinued the product, but last year T-L teamed up with Netafim Inc., a world leader in drip irrigation technology, to supply a comparable line.
Thom says this type of highly efficient application system really dates back to the 1980s, when Dr. Bill Lyle and Dr. Leon New at Texas A&M University developed low energy precision application (LEPA) of water in farm fields.
Instead of sprinklers delivering water over the crops, LEPA systems feature smaller sprinklers hanging down from the pivot span pipe above. Very close to the ground, a nozzle gently bubbles water onto the crops. Because the bubbler is so close to the ground, growers lose a lot less water to evaporation than with traditional spray irrigation. Plus, these low-pressure LEPA systems use less electricity.
“We tried to bring LEPA technology to Nebraska, but it was pretty much a failure,” says Thom. “We had more water, tighter soils and more slopes to our fields, so water just ran off.”
He felt that such a system could still be very efficient in Nebraska — and similar regions’ — conditions if they could find a way to make the water stay put. “I imagined if we could spread water out wider, then it would soak in, then the LEPA concept would work here too,” Thom says.
So the PMDI concept was born. Thom says though the system was absent from the market for several years, it’s time has truly come. “From here to the West Coast, everything in between, all we read about or hear about is saving water or water shortages,” he says. “Almost everything we do as a pivot manufacturer revolves around how we can save water. We’re directing all research and development toward that goal.”