Benchmarks for corn development

June 13, 1996 3(13):83

Joe Lauer, Corn Agronomist

Knee-high by the Fourth of July" is a common benchmark we use to describe the progress of our corn crop. Many benchmarks are used to describe weather effects on corn, but typically calender date and growing degree units (GDU) are most commonly used. This year the temperature pattern during May and June has been cooler than average. A question I have been getting is, "How far behind is the corn crop this year?"

Table 1 describes average benchmarks expected for corn grown using chisel tillage at Arlington, WI. Early in corn development, each leaf collar requires about 50-60 GDUs to emerge. During the first couple of weeks in June we typically accumulate about 14 GDUs per day. Thus, each leaf collar requires about 3.5 to 4.5 days to emerge. On average, corn produces four leaf collars (V4) by June 3 and typically 380 GDUs have accumulated since planting on May 1. In 1995, corn planted on May 1 reached V4 on June 7 after accumulating 397 GDUs. This year a chisel tilled field planted on April 26 was at V3 on June 10; only 340 GDUs have accumulated.

Using the calendar as our benchmark, corn planted early at Arlington is about 10 to 12 days behind in development this year. Corn development is right-on using GDU as a benchmark. We still have a lot of growing season left. Daily GDU accumulation will in all likelihood increase, and corn development can catch up quickly once we return to a more normal temperature pattern.

Table 1. Development benchmarks of corn grown using chisel tillage for an "average" year, during 1995 and 1996 at Arlington, WI
Corn stage Average year 1995 1996
GDU Date GDU Date GDU Date
Planting 0 May 1 0 May 1 0 April 26
VE 125 May 12 138 May 18 130 May 20
V4 380 June 3 397 June 7 340 June 10 @ V3
V8 600 June 15 706 June 23    
V12 900 June 30 929 July 5    

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