Research improves water-application uniformity, penetration
By CAROL RYAN DUMAS
The years have brought enormous efficiencies to agricultural irrigation, with equipment manufacturers continually improving their hardware.
"Some are doing things like working a lot on nozzles and new nozzle packages, and we're seeing more uniform water distribution," said Howard Neibling, University of Idaho extension water management engineer.
Others have concentrated on improving water-application uniformity through tall-crop canopies, but all have concentrated on reducing wind drift and improving penetration into the soil, he said.
At this stage in the evolution of irrigation-equipment design, systems "are not reducing losses a lot but doing other things that help with crop production," he said.
Efficiencies are aimed at how much water is getting to the plant through evapotranspiration -- or ET -- and decreasing transmission and evaporation losses, surface runoff and deep percolation below the root zone.
"If we're going to improve efficiencies, we have to minimize losses and maximize ET crop use," he said.
Newer systems have reduced water use through improved water-application uniformity. Growers don't overwater some areas and underwater others, he said. Some system hardware allows growers to apply more water at one time, so there are fewer irrigations, less evaporation, deeper root zone infiltration and healthier crops without runoff.
"It's been a continual movement the last 20 years," he said.
Although the acreage irrigated by low-pressure pivot systems, hand lines and wheel lines is increasing, there is still a lot of ground under surface irrigation. As the surface systems wear out, many growers are moving to pivots, improving efficiencies and cutting labor costs, he said.
"We're definitely moving away from surface irrigation; it's labor intensive. You could manage more land yourself with pivot irrigation," he said.
Cost of labor, an uncertain labor supply, worker liability, improved efficiency, better yields and quality are all driving the change.
"Lenders are more apt to finance farmers with sprinkler irrigation," he said. "Almost all new equipment sold is low-pressure pivots. Power costs (of high-pressure pivots) have driven a lot of people to low-pressure pivots."
The most efficient systems are drip and micro spray irrigation, but they're expensive, and only growers with high-value crops would consider it. It works very well on Idaho's onion crop, he said. It cuts water and nitrogen needs in half.
Low energy precision application is also quite efficient, but needs refinement. "In the past, we've seen a lot of runoff," he said.
Neibling and a counterpart in Washington state are working on a grant to study the system.
"We may be coming to the conclusion LEPA is good for some of our soils and not others," he said.
As a system, however, it is as efficient as irrigation can be. For the foreseeable future, LEPA and low-pressure pivots will rule the industry, he said.