Real Savings on Center-Pivot Farms: A Case Study


Courtesy of Arable

UNL and Nature Conservancy partner with Arable to establish a network of sensors for better access to local weather data. Fifty miles is a long way to drive to check a rain bucket on a center pivot. That's the challenge Chase Johnson dealt with whenever he wanted to know exactly how much rain fell on one of his pivots.


Johnson started farming about two years ago in York County, Neb., and as a beginning farmer, time management is a high priority.

When Johnson met with Trenton Franz, University of Nebraska-Lincoln hydrogeophysicist, and Adam Wolf of Arable, they asked him about what was important to him as a beginning farmer. The first thing that came up in Johnson’s mind was being able to reliably monitor rainfall.

"I`ve got farms that are 40 to 50 miles apart," Johnson says. "I talked with Trenton Franz and said, `I`d like to know reliably, how much did it rain and when, and how far do I have to drive to turn a pivot on or off?` I had met Adam, and he told me about these Marks."

For the last two years, Johnson has been one of several irrigators involved in a network testing Arable`s Mark sensors in Nebraska. The project is funded by The Nature Conservancy with support from UNL, the Daugherty Water for Food Global Institute and the South Platte Natural Resources District.

The multiyear project involves a network of 20 Marks installed throughout Nebraska — including the two on Johnson`s fields. An additional one is located at the Testing Ag Performance Solutions (TAPS) field at the West Central Research and Extension Center at North Platte, and 17 more are in growers’ fields as part of a the Western Nebraska Irrigation Project. The goal is to validate the technology and demonstrate the value of having access to local rainfall data.

The Mark, which has a flying saucer-shaped acoustic rain gauge on top, has the ability to measure rainfall and distinguish it from hail and other objects.

"If you`ve ever been inside a shed with a corrugated tin roof while it rained, you can hear the sound. Your intuition can already calibrate it — maybe not to the exact millimeter — but you can intuit that heavier rain is louder than lighter rain. If you`ve been in your house when a hailstorm happens, it`s a high-pitched `tink` rather than a low-pitched `thunk,`" explains Adam Wolf, CEO at Arable. "We can distinguish those by the pitch of the sound. Rhythm is another factor. For example, raindrops are more staccato [with a short, detached duration] than a human voice."

Using the sensor`s radiometer, the Mark can also measure radiation. With this information, along with its spectrometer to measure normalized difference vegetation index (NDVI), the sensor can calculate evapotranspiration (ET) using a modified Penman-Monteith method. Connected to the Arable web tool and smartphone app, the sensor provides hourly updates to growers for the location. Wolf says the ability to measure both ET and rainfall locally gives users a more complete picture of their water budget.

  • NE farmer Chase Johnson manages fields up to 50 miles apart. “I`d like to know reliably, how much did it rain and when, and how far do I have to drive to turn a pivot on or off?”
  • Knowing when to shut off his pivot remotely saved him 3 hours in the car, 1” of water per acre, and $500, more than paying for the Mark system.
  • "Between fuel and everything, it`s probably close to $1,000 in savings," Johnson says. "It`s a huge time saver."

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