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Growing Degree Days

cornfield pictureGrowing Degree Days (GDD) are a method used to calculate the number of heat units that have accumulated over the growing season. This measurement can be used to help you select corn hybrids best suited for your farm or to predict when the corn crop will reach maturity. Growing Degree Days can also be used to predict when alfalfa weevil or corn borers will reach the stage of maturity where they can most effectively be controlled.

Corn hybrids that are rated 80-85 relative maturity require 1900-2000 GDDs from planting to physiological maturity while 85-90RM hybrids need 2000-2100 GDDs.

The following chart contains Growing Degree Day information calculated by the Polk County UW-Extension Office based upon official temperatures reported in Amery over the last several years.

Month

2005

2006

2007*

2008

5-Year Average

(03-07)

April

174

174

165

78

143

May

223

355

361

228

284

June

615

527

580

446

512

July

671

647

648

627

614

August

587

386

570

569

509

September

452

166

398

371

371

Totals

(May - Sept.)

2722

2255

2722

2319

2433

* Information for year taken from Luck area

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