It's after July 1 and typically crop water use or evapotranspiration (ET) is greatest for many crops like corn, soybeans, and grain sorghum that are at or nearing the reproductive growth stage. Crop water use will depend on the crop's stage of growth as well as environmental conditions like temperature, humidity, wind speed, etc. This year, because of all the storms and some replanting, crops are at a variety of growth stages across the state. One thing it's safe to say is that crop water use varies greatly from year to year and from location to location. Several tools from the University of Nebraska-Lincoln can help you track crop water use for your crops and their growth stages, providing the information you need for more precise irrigation management.

NAWMN

Figure 1. Sample screen of reporting sites in the Nebraska Agricultural Water Management Network.

Producers, crop consultants, and others looking for timely ET or crop water use can go to the Nebraska Agricultural Water Management Network (NAWMN)  at http://water.unl.edu/NAWMN or directly to http://go.unl.edu/qqrx for the latest ET information.  Click on your county and then click on a blue balloon icon to view daily updates of National Weather Service Station data for that site. You'll be able to click on different crops to see the past day's water use for various stages of growth along with the past three weeks average water use by crop stage.

Producers, crop consultants, extension educators, NRD and NRCS personnel who operate atmometers also post ETgage readings that they collect on a weekly basis.  Click on a red balloon icon to see regular updates of information posted by these volunteers.

Producers or others using ETgages are encouraged to regularly upload their information.  To do so, please register at http://water.unl.edu/NAWMN. You will be assigned a site name to use to log in and post your weekly ETgage changes.

CropWatch Weather

Figure 2. Sample screen of precipitation report in CropWatch Weather.

CropWatch Weather has GDD and ET information for 20 Nebraska sites with multiple crops and emergence dates per site.  It also includes charts that can be used with ET gage readings to determine evapotranspiration at various growth stages.  Other CropWatch Weather features include daily updates of tables and maps of precipitation and soil temperature data for Nebraska and links to the Nebraska Rain Network, a reporting tool for growers across the state. 

CropWatch also includes links to the Useful to Usable website. It provides crop-based climate information for the Corn Belt, including historical and projected GDD and climate data. Funded by USDA, Useful to Usable is a multi-state, multi-disciplinary effort of researchers studying climate variability and change with respect to agriculture. The High Plains Regional Climate Center is one of its partners.

High Plains Regional Climate Center

The High Plains Regional Climate Center has lots of climate information on its website at www.hprcc.unl.edu. Some of its information is free and some is available for a fee. 

Figure 3. Sample screen of heating degree days as available from the High Plains Regional Climate Center.

The two main online databases are Classic Online and CLIMOD II.
With a Classic account you have access to the entire Automated Weather Data Network (AWDN) data set as well as the National Weather Service Cooperative Weather Network. It is mainly built for users who want to retrieve data on a regular or semi-regular basis. You get temperature data (highs and lows), relative humidity, soil temperature at 4 inches, wind speed, evapotranspiration (ET), solar energy, and precipitation data. You can also get heating degree days and crop dependent reports (corn, alfalfa, soybeans, wheat, grass, sorghum, dry beans, etc.) to help monitor crop growth and predicted crop growth. It can send daily, weekly, or monthly e-mails with your data. A Classic account costs an initial $100 which gives you 400 minutes. This lasts most users two to three years. The minutes used are calculated according to how much time it takes the computer server to retrieve data.

With a CLIMOD account you get free access; however, information options are a little more limited. You do not get access to AWDN stations nor do you get ET or wind data. Most people use it to get temperature and precipitation data. You can also retrieve GDD, HDD, and CDD data. This site records climatological averages for a station and record extremes for temperature and precipitation for certain stations.

For help in accessing or using these High Plains Regional Climate Center resources, see contact information on the website at http://www.hprcc.unl.edu/contact.php or call (402) 472-6706.

Gary Zoubek, Extension Educator
Judson Buescher, High Plains Regional Climate Center Intern