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Time to fine-tune your irrigation efficiency

One silver lining to this year's drought -- if you irrigate, that is -- is that issues with your irrigation systems will stick out like a sore thumb.

There are countless ways that the uniformity of center pivot irrigation applications can be affected: blown pipe, leaking gaskets, bad sprinkler spacing and low water pressure are just a few that can cause your system to either under- or overwater in parts of your field, ultimately limiting your yield potential. Normally, these may not be as clear to see. Not this year, says University of Nebraska Extension irrigation specialist Bill Kranz.

"It takes a year like this to more fully see how some water distribution systems are growing older or underperforming. Little problems that affect water application uniformity can reduce yield," Kranz says. "In a 'normal' year, these likely wouldn't be visible. This year, however, the impact is visible and the yield reduction is likely to be more evident."

If you've got the chance to get up in the air to survey fields from a bird's-eye view, that's the best way to get a clear snapshot of where you may have issues in a given irrigation circle. But, if that's not a possibility, you can also use the following field survey method, according to Kranz:

  1. Identify the position of the problem sprinkler or gasket from the pivot point.
  2. Go to the area of the field where the center pivot is perpendicular to the crop row direction. Go to the point that would be the same distance from the pivot point identified in Step 1.
  3. Hand harvest and weigh the grain produced in 20 feet of each row for four to six rows on either side of the problem. The graph came from a field in western Nebraska and shows how sprinkler spacing can impact grain yield in a dry year. Similar response should be expected for the other issues listed.

"Most of the problems are easy and relatively inexpensive to fix. However, depending on the location of the problem along the pivot pipeline, the economic impact of a single sprinkler or gasket problem can be significant in the amount of yield reduction it causes," Kranz says. "Assessing your irrigation water delivery system now -- when the system is working its hardest -- can help you see exactly where the problem is on the pipeline as well as the effect it’s having on your crop. Also remember that problems like those you identify in 2012 likely have been having a subtle impact on grain or forage yield for a number of years. This means that even though the yield impact is more significant in 2012, a small yield loss likely occurs even when rainfall is more normal."

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