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Calculate water needs

David Nielsen and his
research team sat down and burned the midnight oil pouring over long-term field
data that showed a relationship between crop yields and irrigation
applications. The trends they discovered confirmed what Nielsen had suspected:
It was possible for farmers to calculate water needs in advance of crop needs.

The ARS team, based in
Akron, Colorado, went on to create a compact disk or Web downloadable program
called the MultiCalculator. The program has proven to be a hit. Nearly a
thousand copies have been obtained by central Great Plains farmers, while
downloads have been brisk, Nielsen reports.

The reason for this
popularity stems from the fact that the MultiCalculator is not only based on
realistic field information but also is easy to use. Nielsen says the
MultiCalculator uses three simple Excel spreadsheets that include a yield
calculator, water calculator, and ethanol-water calculator. Plus, it can be
used to predict nonirrigated crop yields.

Using The Program

To begin to use the program,
first estimate how much available soil water your fields have. This information
can be obtained from soil-moisture probes in respective fields. Or, for your
general area, you can contact your land-grant university or state metrological
service.

With current moisture
content in hand, tab to a table on a different screen that helps make this
estimate, giving multiplication factors for various soil types.

For example, fields
predominantly consisting of silty loam, you would multiply the depth of the wet
soil by 2.2 to get the number of inches of soil water available for the crop at
planting time.

Next, going to step three of
the program, select the crop to be irrigated, your fields’ locations (currently
the program only provides locations for eastern Colorado, western Kansas, and
western Nebraska), and then guess the percentage of average precipitation
expected during the growing season. You can get historic precipitation data for
your specific area from your state’s meteorological website.

After inputting this
information, the program will instantly project yields for your fields based on
actual field data. The calculator provides this for 18 crops, including cereal
grains, seed legumes, oilseeds, and forages.

The water calculator also
works in reverse, beginning with choosing a crop and then selecting the target
yield. It tells how much water you’ll need to achieve that target yield.

The program also provides an
interesting facet called the Ethanol-Water Calculator. This tool figures how
many gallons of water you’ll need for each gallon of ethanol produced from the
crop.

Download the MultiCalculator
by going to http://www.ars.usda.gov/Services/docs.htm?docid=19206).

For a CD version, call Nielsen
at 970/345-0507 or e-mail him at david.nielsen@ars.usda.gov.  

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