LUBBOCK, Texas - LEPA, LESA, LPIC, MESA.
Try to roll those four acronyms off your tongue five times real fast. Sounds like some ancient druidic chant designed to make certain the sun comes up again tomorrow.
Well, the confusion doesn’t stop with pronunciation difficulty. All four stand for efficient center pivot irrigation systems and are sometimes clumped together under the LEPA (Low Energy Precision Application) moniker.
But all four bring something unique to the field, and each has a specific niche where it may work better than the other three.
Dana Porter, an irrigation specialist with the Texas Cooperative Extension Service, stationed at Lubbock, has worked with and tested all four arrangements in several cropping systems and says each works well. Level of water use efficiency varies slightly.
Here’s the official definition of LEPA, according to the Natural Resources Conservation Service (NRCS): Low Energy Precision Application (LEPA) is a water, soil, and plant management regime where precision down-in-crop applications of water are made on the soil surface at the point of use. Application devices are located in the crop canopy on drop tubes mounted on low-pressure center pivot and linear move sprinkler irrigation systems.
Low Pressure In Canopy (LPIC) is a system that may or may not include a complete water, soil and plant management regime as required in LEPA. Application devices are located in the crop canopy with drop tubes mounted on low-pressure center pivot and linear move sprinkler irrigation systems.
“Dr. Bill Lyle used the acronym LEPA for the irrigation system that Jim Bordovsky and he developed for the Texas High Plains (at) the Texas Agricultural Experiment Station at Halfway,” says Terry Howell, Research leader, USDA-ARS Water Management Research Unit at Halfway.
“According to guidelines and publications by Bill and Jim, the LEPA name applies as much to a management philosophy as to irrigation hardware,” he says.
“LEPA is a package deal,” Porter says, “that generally includes drag hoses running in alternate furrows. So with LEPA growers have one dry furrow and one wet.”
LEPA systems, to qualify for EQIP funding, also must include furrow dikes or residue to hold water in the rows.
“True LEPA systems also must be designed with rows in circles (for center pivot systems; straight rows for linear systems),” she says.
LEPA systems work best on flat terrain and relatively sandy or loam soils where runoff is not as likely as in heavier, tighter soil.
“LEPA shines for deficit irrigation applications,” Porter says. “It can achieve 95 percent water use efficiency, if designed and managed properly. LEPA also works well in low water quality situations because the hoses apply water to the soil and keep salts off crop leaves.”
LESA, Low Elevation Spray Application, uses spray nozzles instead of the drag hoses. Porter says LESA systems typically put nozzles less than 2 feet above the soil surface.
“This is still a low pressure system so evaporation loss is much lower than with older technology high pressure systems. Also, LESA poses less runoff potential than LEPA systems so we can use it on more rolling terrain and on tighter soils.”
Porter says the spray systems also offer better potential for chemigation. “We can apply fertilizers with drag hoses, but spray systems allow us to apply materials to the crop canopy,” she says.
LESA water use efficiency hits 90 percent or better, “with proper management,” Porter says.
LPIC, Low Pressure In Canopy, irrigation, offers a bit more flexibility than either LEPA or LESA, Porter says. “It’s something of a hybrid of LESA and MESA. LPIC may be more common in grain sorghum or corn, where the nozzles drop into the crop canopy. Growers may adjust nozzles to spray up into the leaves. LPIC is pretty much the same as LESA.”
Main differences could be the crop selection and the height of the nozzles.
MESA, Mid Elevation Spray Application, puts nozzles higher above the soil surface than either LPIC or LESA. “MESA units will not be as elevated as traditional high pressure center pivot systems,” Porter says, “but could be as much as 5 feet above the ground.”
She says growers who don’t want to drag hoses through their crops, possibly moving disease organisms from one part of a field to another, may prefer to have nozzles a bit higher.
“Also, the contour of some fields may adapt better to higher elevation nozzles.”
Porter says spray pattern and water distribution may be better with hoses higher above the soil and the crop. Spray nozzles' technical specifications, she says, include height spray pattern and throw distance.
MESA systems will lose a bit more water to evaporation but not as much as with less efficient high-pressure center pivot units.
Porter says farmers may place hoses further apart on MESA systems and still get uniform distribution of water.
“I’ve had good results from LEPA, LESA and MESA systems on cotton and peanuts,” Porter says.