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Is your pivot under pressure?

A Nebraska study is analyzing the operating pressure and overall health of center pivots.

If your center pivot sprinkler system is operating below or above optimal water pressure, especially at the distal end of the system, it is costing you money.

Uniformity is one of the primary concerns with center pivot systems, because if specific sections of the system water too much or not enough, you are either wasting water and energy, or your crop yields are less than their potential.

Nebraska Extension educator Troy Ingram, along with a team of Extension educators and irrigation specialists, has been analyzing center pivots across Nebraska for operating pressure, gathering data from the AgSense FieldCommander and Lindsay FieldNET Pivot Watch platforms.

"We have been tracking 60 pivots spread out across the state, so we have a good sample size," Ingram says. The pivots being studied also are distributed in different regions, including the Panhandle in the west, moving east to the Sandhills, south-central, east-central, northeast and across eastern Nebraska. The terrain covered in these tested pivots ranges from quite flat to heavily sloped.

"The analysis started out as a way to assess the health situation of the center pivots operating in the state," Ingram says. "We haven't done anything like that since irrigation well pump tests in the 1980s."

The goal of the analysis is to help growers establish a list of items they can check on their pivots, so they can easily remedy problems in the field.

Room for improvement

So far, the study has concluded that about 58% of the pivots in the analysis were operating below the required regulator inlet pressure for more than 5% of their operating time. About 20% were operating within the required pressure, and about 22% were operating above the required pressure for more than 5% of the time.

Researchers also found that there is typically a gradual drop in system pressure as the irrigation season progresses each year. This is likely attributed to lower groundwater levels through the growing season, as well as potential leaks that develop within the sprinkler systems.

The study found that for a single irrigation event, topography is the greatest contributor to changes in pressure in the system. Less pressure means more problems with crop uniformity, and loss of potential yield.

"If the water quality is bad, nozzles don't last as long," Ingram says. "You may also have problems with pressure regulators. Monitoring pivot pressure through the season is one way to remedy any issues that come up.

"If you have the data, you can have a local dealer do a pump test to see what you are pumping and how that compares to your sprinkler chart," he suggests. "If there are issues, you may have to renozzle the pivot to bring the pressure back up."

If you are planning to pump 875 gallons per minute, for instance, and you are actually pumping 750, you may have to renozzle to get the rate back up, Ingram explains. "With the cost of energy, it doesn't take that much to renozzle a pivot, and it is pretty easy to do," he adds.

Acting on uniformity issues early will save on irrigation costs, conserve water and help crop yields meet their potential, Ingram says.

Goals for expansion

This study began in 2018 because of questions Ingram had about the center pivots operating within his own farming operation. Initially using a gauge that was installed on the pivot below the pressure regulator to check water pressure at the end of the pivot, Ingram and the study team quickly recognized the value of pivot-monitoring data as a quicker and simpler way to analyze pressure readings.

With more than 60,000 center pivots operating in Nebraska, Ingram hopes to eventually expand the pressure study to include an even larger sampling across the state. "If 50% to 60% of the pivots in the state are not operating at design specification, we could be burning a lot of extra energy, and we are not getting uniform distribution," Ingram says. "There could be runoff problems too."

The study aims to get an accurate picture of overall pivot health.

"We want to get a picture of where we are, and then take that and offer ways farmers can make a positive change" to remedy any issues, he adds.

If you'd like more information about the pressure study, or ways to improve pressure problems on your center pivot, contact Ingram at troy.ingram@unl.edu.

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