Booms vs. big guns


Irrigation study shows ways to save water, energy and money


study of big gun vs. boom irrigation systems in Skagit County may help growers save money as well as water.
In summer 2007, Don McMoran, agriculture and natural resources educator at WSU Extension Skagit County, and Troy Peters, extension irrigation specialist at WSU Prosser, teamed up to compare the efficiency and uniformity of big gun and boom irrigation systems.
“The manufacturers said that boom systems were 85 percent efficient in comparison to the 60 percent efficiency of the big guns, but I wanted to prove or disprove that based on our own studies,” McMoran said.
McMoran and Peters raised $4,000 through donations from various local organizations for equipment and did evaluations on two big gun systems and two boom systems on potato fields.
“The biggest difference was in water consumption,” McMoran said. “We found that you can save 10.9 million gallons of water per year (with the boom system) based on the irrigation of 100 acres at 9 inches per year.”
The boom system is closer to the crop, so the water is only traveling in the air for a fraction of a second. The big gun’s lower efficiency is due to the much longer time the water spends traveling from the nozzle to the soil, which makes the water more susceptible to evaporation and wind drift.
“It’s hard to see it happening because water vapor is invisible,” Peters said. “Out of sight, out of mind.”
The boom system also distributes water more evenly, which can improve crop yields, uniformity and quality.
Despite the significantly higher cost of a boom irrigation systems — $10,000-$20,000 more — the study shows that growers not only will save water in the long run but energy too.
“The boom systems use only half the pressure the big guns use,” McMoran said. “Therefore, they only consume half the fuel or energy. By switching you could save $6,000 to $9,000 per year with each system.
“These savings, over the life of the boom system, will more than pay for the additional upfront costs if the pump is diesel or gas powered. As fuel prices increase, the financial benefits of converting from a big gun to a boom also increase. This may not be true, however, if the pump uses electrical energy.”
McMoran and Peters have received worldwide accolades for their research, which will not only help local growers but also leave more water for the natural environment, Peters said.
“It’s going to bring awareness to the new ways and technology of irrigation,” McMoran said.
Due to their success, McMoran is brainstorming similar studies they could do to further assist growers in Skagit County and beyond.
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