Irrigation Scheduling Equipment

It’s nearing mid-May and crops should hopefully be emerging soon! For those of you utilizing watermark sensors for irrigation scheduling, it’s important to install those shortly after emergence so you can monitor soil moisture fluctuations long before you ever need to think about irrigating.  I’ve found that our cooperators who install these early after emergence are far more confident in the readings than those who install them closer to irrigation time.  That’s why we no longer install these for anyone past June 15.  

In case you’re wondering what is a watermark sensor, it’s a 3″ sensor filled with fine sand with a fiber glass mesh around it that measures how much energy it takes for the plant roots to extract moisture from the soil.  The sensor measures this in a unit of energy called kilopascals or centabars…units that don’t mean much to you or I.  That’s why we’ve created charts that convert these units to inches of depletion/foot-terms with which we are more familiar!  We recommend farmers install one set at 1′, 2′, and 3′ depths in their fields to monitor when their soil reaches at least 35% depletion.  The basic rule of thumb based on research by Dr. Suat Irmak at UNL is to take the average of the top two sensors prior to the reproductive stages of the crop and the average of all three sensors once the crop has reached the reproductive stages (tasseling or flowering).  When the average of these sensors reaches 35%, we suggest you consider scheduling an irrigation.  

The other tool we use are Evapotranspiration (ET) Gages.  The green canvas cover mimics the leaf surface and essentially as the cover is exposed to different environmental conditions such as wind and low humidity, water is moved out of the tube through the canvas cover and the depletion is noted on a site gage on the front.  This tool has helped farmers visually better understand why their crop did or didn’t use water for any given week as they can look at the ET gage and consider the weather conditions and the influence they had on what the crop used.

On average, our farmers have saved 2.0-2.5″ of water in corn and soybeans since participating in this program.  This program called the Nebraska Ag Water Management Network began in 2005 and now has over 500 cooperators State-wide in Nebraska.  More information about the Network, the tools and charts I described above, and videos demonstrating the equipment can be found at:

About jenreesources

I'm the Crops and Water Extension Educator for York and Seward counties in Nebraska with a focus in irrigated crop production and plant pathology.

Posted on May 9, 2011, in Irrigation Scheduling and tagged , , , , , , . Bookmark the permalink. Leave a comment.

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