Oklahoma State University

Water Balance in the Root Zone Introduction, Soil Physics,Oklahoma State University


Water Balance in the Soil Root Zone



D.L. Nofziger and Jinquan Wu



Water management is of great importance for preserving water resources, efficient use of water by plants, and minimizing excessive leaching of soil chemicals. This program enables the user to specify the capacity of the root zone of a soil to store water, the amount of water in the root zone at a particular date, and the type of irrigation practiced in the area. The program uses daily rainfall, irrigation, and evapotranspiration to calculate the amount of water in the root zone and the amount of drainage below the root zone and displays a variety of graphs and tables. Since the results depend upon the weather, calculations are performed for 9 years. The user can view the results for a single year or for the entire collection of years. The program is designed to enable the user to see the impact of the soil water holding capacity upon the amount available for plant use, the amount drained below the root zone, the impact of irrigation upon these amounts, and the way these values change from year to year.


Latest Version:

2005.05.04,  May 4, 2005
Version History



A manual outlining the purpose, model, and simplifications used in this program is available here.


Computer Platform:

The software is written in Java and runs as a Web Start application. The Java  run-time package and Web Start software are  available free of charge from Sun Microsystems, Inc. The program was developed and tested on various Windows platforms as well as on Linux and MacOS X. We recommend 256 MB or more of Random Access Memory. Approximately 40 MB of disk space is required. 


Link for Java Software:

Before a Java Web Start program can be used on a computer, the supporting software must be installed. This is needed only 1 time per computer no matter how many different applications use it. Sun Microsystems Inc provides this package free of charge at http://java.sun.com/ or it can be downloaded here. If this is the first time you are using it, just download the file from the site above. Follow the instructions given there for installations. I recommend that you accept the default values proposed in the install process. 


Download/Execute Program:

The program is available with weather data for several locations below. If you use the program more than one time, you will be given the option of storing it on your local computer. You can then start the program without coming to this page with a web browser.

Southeastern United States

Canterburry, New Zealand



D.L. Nofziger, Department of Plant and Soil Sciences, 368 Ag Hall, Oklahoma State University, Stillwater, OK 74078. 

E-mail: david.nofziger@okstate.edu

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