Optimize Your Irrigation Application Timing with SoyWater.unl.edu

Optimize Your Irrigation Application Timing with SoyWater.unl.edu

Also use SoyWater for Other Growth Stage-Specific Management Decisions

July 6, 2011

Get the most from your irrigations with SoyWater, an easy to use, irrigation management tool.  It provides timely crop water use information specific to your field and this year's growing conditions. It is available on the Web at hprcc-agron0.unl.edu/soywater/ or simply Google™ the words "UNL SoyWater."

This decision support tool was developed by the University of Nebraska-Lincoln with support from soybean checkoff funds provided by the Nebraska Soybean Board. Unlike many other management tools, SoyWater doesn't require you to install anything on your home computer or spend time learning a new software program. It guides you through four simple steps to input information so you can get field-specific irrigation recommendations.

SoyWater can help you determine how much water your field needs and when it needs it, eliminating unnecessary irrigation events. An acre-inch of water applied is equivalent to 27,154 gallons of water. Thus, saving one unnecessary one-inch irrigation event could save you 5,424,800 gallons of water on a 200-acre pivot. Moreover, you would also save pumping energy cost and time. Such savings would allow you to optimize your input use efficiency (bushels per acre per inch of water applied or energy used).

Even if you don't irrigate, SoyWater can help you fine-tune your management. Both rainfed and irrigated producers can use it to track and predict the dates when a field will reach a specific soybean stage. Pest control and disease management are much more effective if the pesticide or fungicide is applied precisely at the soybean stage that researchers recommend.

About 266 users have registered to use SoyWater since its official launch on May 1, 2010. We invite you to join this group and learn how to more effectively schedule soybean irrigation events to apply just the right amount at just the right time.

SoyWater.unl.edu sample page

Figure 1. A SoyWater crop water use table generated in 2010.

Chart of SoyWater data

Figure 2. Chart of data developed using SoyWater. Note that these figures show the user irrigating on precisely the dates recommended by SoyWater, applying just the right amount of water at just the right time.

Getting Started

To become a registered user, access the website at www.soywater.unl.edu and create a user account by inputting your email address and a password. You will receive a four-digit activation code by email. Use that code to get 24/7 access to SoyWater this year and in future years.

To get started, you'll need to provide some basic information about your field. (Note: Your information is strictly confidential – no one else has access to your field information.)

The first step is to identify the field location. An easy-to-use Google™ map tool is provided so you can locate your field based on an aerial view. SoyWater will then identify the field's GPS coordinates and use them to identify the nearest automated weather station. Data reported to this weather station will be used to estimate your crop's daily evapotranspiration (crop water use).

SoyWater then needs only four more items from you:

  1. A field name. Choose something easy to recall (e.g., Smith Pivot 5) if you have many fields.
  2. The predominant soil texture in the field. SoyWater provides a menu of choices, but if you're unsure, use the GoogleTM soil texture map tool to help you identify the soil texture.
  3. The date of seedling emergence. The emergence date is preferred, but if you don't know it, the planting date can be used instead.
  4.  The two-digit maturity group (MG) number (for example, 3.1) of the variety you planted in the field. The MG number is typically embedded in the brand's variety number. (Contact your seed dealer for details.)

Estimating Growth Stages

SoyWater uses a crop model (SoySim) to create a table showing the calendar date for each soybean vegetative and reproductive stage from emergence to maturity with corresponding and daily and cumulative soybean crop water use values specific to your field.

Once your account is established, you can log into it any time to view the updated information as the crop season progresses. As irrigation or rain events occur, you will need to input the date and amount of water applied or rain measured at the site. SoyWater estimates the first and subsequent dates when irrigation should be applied and soil water depletion amount on those dates is highlighted in yellow in the SoyWater table for that field. This recommendation is based on the soil water depletion percentage value (default is 35%) that you choose as an "irrigation trigger."

James Specht, Professor
Jessica Torrion, Research Associate
Both in the Department of Agronomy and Horticulture