Calibrate Before You Irrigate

October 28, 2010 05:23 AM
Calibrate Before You Irrigate

Like gasoline powers a car, water fuels the growth of Richard Dobbins’ corn and soybean crops each July and August.

“We often get a 50-bu. to 60-bu. yield response from just 5" of water applied during that time frame,” says Dobbins, who owns North Concord Farms near Albion, Mich.

Dobbins’ 2,800 acres of crops are planted on light soils and hilly terrain, and roughly 1,000 acres are irrigated. This year, he worked with Farm Journal Associate Field Agronomist Missy Bauer to evaluate the uniformity of his irrigation applications.

Bauer placed calibration cups about every 10' along the center pivot and then measured the volume of water collected in each.

“The volume of water in the cups should be consistent from one end of the center pivot to the other,” Bauer explains. “When you find a cup with an inconsistent amount of water, you need to make a correction.”

Lyndon Kelley, irrigation educator for both Michigan and Indiana through a partnership between Michigan State University (MSU) and Purdue University, offers these timely management tips for maximizing the efficacy of your irrigation practices.

  • Make sure your irrigation application is uniform. There are simple catch-can measurement systems available that you can use to evaluate the uniformity of application in your irrigation system.


  • Know your actual application. A catch-can system will also tell you the actual application rate of your irrigation system. Your system provider or the resources on the MSU Extension Web site can provide you with tools to print a corrected timer chart if needed.


  • Assure yourself that you have an adequate water supply. A pump capacity of 5 gal. per minute per acre (¼" per day) will meet all of your crop needs except during hot, dry spells of 15 days or more. That means a 500 gal. per minute pump can provide 1" every four days on 100 acres.


  • Schedule irrigation applications.Determine the appropriate amount of water to be applied to each crop at the correct time to avoid yield loss and conserve water. Under-watering will reduce yield potential and leave valuable crop inputs underutilized. Overwatering is equally bad, as it can waste natural resources and push nutrients out of the root zone.

Kelley recommends growers seek more information on effective irrigation management practices at MSU Extension’s St. Joseph County Web site ( Click on the Irrigation link on the lefthand side of the page to locate expanded discussions of these tips, as well as additional resources.

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