Evapotranspiration: Needs and Water Availability at Champion, Nebraska .

The following graphs are generated from data taken from the High Plains Regional Climate Center located in Lincoln .  The HPRCC operates an automated weather station that collects weather data, including precipitation and evapotranspiration information.  This Champion site was put into service in 1981. 

The site collects potential ET and, then, the HPRCC uses a formula to compare the growth stage of a plant to the actual ET data.  Using the HPRCC server, we asked it to compute the ET rate for medium season corn for each day for 1993 through 2004.  The following charts show HPRCC data for 12 years.

“ET required” is the amount of water the HPRCC says a medium season corn crop will need in order to meet maximum yield.  The light blue shaded area is the precipitation received during the growing season.  The green shaded area that is visible is the amount of water that must come from irrigation or from the soil profile for the plant in order to make maximum yield.  The line with the diamonds is the average amount of water that is needed according to the Champion station.  The line without marks is what Dr. Derrel Martin reports is needed.  The line with the squares shows how much water needs to come from the soil or from irrigation.

Summary

The Champion station data combined with UNL corn plant needs data shows evapotranspiration needs to be at least 5.06 inches greater than Dr. Derrel Martin’s data.  We note what Dr. Martin’s reports because it is being used by all of the policy makers and is being used at educational classes held throughout Southwest Nebraska . The ET requirement reports say that the lowest ET numbers are to the west.  As the one moves further east in Nebraska , the ET requirements go up.

Here, we are looking at one data station that collects ET data in Southwest Nebraska .  Other stations are located in McCook, Curtis, Dickens, and Ogallala. 

The Champion data for the last 12 years shows that there is a need for an average of 18 inches of water to come from irrigation or the soil profile during the growing season.  The non-growing season precipitation and the soil type you have will determine how much of that can come from each source. 

The effective root zone for mature corn is 2.5 feet.  To estimate the amount of water available from the soil profile, multiply 2.5 by your soil type. 

If you have a fine sandy loam soil and the soil profile is fully water charged, then there would be between 3.75 and 5.00 inches of soil profile water available to you.  The balance must come from precipitation during the growing season or irrigation.

Assuming your soil profile is saturated, in the 12 years we consider here, you will need the following amounts of irrigation.

The difference between the blue and the green areas must come from irrigation or from water stored in the soil.  Refer to the above tables to see what the soil holding capacity is for your soil type.  The yellow line is the amount of water required according to Derrel Martin.  The green area above the yellow line is the amount his average ET number underestimates the need by.

The following graphs are for the comparison purposes.

For Champion, Nebraska

For McCook, Nebraska

For Holdrege, Nebraska