KIMBERLY, Idaho — A University of Idaho researcher says a water-efficient irrigation method he helped devise was effective in potatoes during 2017 trials and is poised for significant expansion in the coming season.

UI Extension irrigation specialist Howard Neibling and his Washington State University counterpart, Troy Peters, worked in conjunction with Bonneville Power to develop the first pivot using low-elevation sprinkler application in 2013.

LESA sprays water in a flat pattern from low-pressure nozzles dangling about a foot above the ground — low enough to pass beneath the crop canopy and eliminate drift without excessive runoff.

Their prototype system, tested in Nevada, included a single pivot span fitted with LESA hoses. They tested another LESA pivot span the following summer in an Arco, Idaho, grain field, finding it delivered roughly double the water to the soil on especially hot and windy days, compared to the conventional spans. The technology has rapidly spread since then, with several farmers in Eastern Idaho using it to meet groundwater consumption reductions mandated under a recent water call settlement.

During the summer, Neibling worked with two potato farmers on the Rexburg Bench and one in Osgood who agreed to convert a single pivot span irrigating potatoes to LESA.

“The objective was to make sure we could make it work in potatoes, and if there were problems, figure out what they were and if we could solve them,” Neibling said.

Through his trials, Neibling discovered LESA spans should be 3 feet apart in potatoes for full coverage, compared to 5 feet apart for rotational crops. In fields with small hills, he said dragging nozzles sometimes dug into the soil and exposed tubers, causing a small volume to turn green.

But Neibling’s worries that nozzles would become entangled with potato vines didn’t come to fruition. Furthermore, one of the spud growers made changes in configuring towers that significantly reduced the depth of pivot wheel tracks compared to his conventional pivots — something Neibling plans to study in greater depth next season.

Neibling said the potato trials demonstrated spud growers can reduce irrigation by at least 10 percent under LESA without hurting yield or quality. One of the growers plans to upgrade to a full LESA pivot in his potato rotation next season, and the other two plan to continue evaluating a single span.

Neibling still advises potato growers to use zip-ties to raise LESA hoses above their spud canopy, thereby preventing dragging nozzles from exposing tubers, or from spreading pathogens.

Next summer, Neibling plans to study how much of the usual LESA water savings growers might sacrifice by raising hoses just above crop canopies.

Growers in Rupert and the Idaho Falls area installed more than 20 full LESA pivots last winter for use during the summer, with funding assistance from USDA’s Natural Resources Conservation Service.

Josh Miller, district conservationist with the NRCS field office in Idaho Falls, said about 15 growers within his area alone submitted LESA funding applications for next season, prior to an Oct. 13 deadline. Miller said it costs $5,000 to $7,000 to retrofit a pivot to LESA, but buying a new pivot already configured LESA costs about $2,000 extra.