The 2005 Corn Growing Season:
What have we seen? Where are we going?

June 2, 2005  12(12):98-100

Joe Lauer, Corn Agronomist

The early news about the 2005 corn growing season is that planting progressed ahead of schedule while emergence and seedling establishment has been good, but slow due to cool air temperatures. Most field symptoms of problem corn include slow development and a somewhat yellow appearance. This observation is typically seen with corn in most Wisconsin fields in most years. Some of it is due to the natural transition of corn root growth from radicle and seminal roots to the dominant nodal root system the plant uses for the rest of its life cycle.

Figures 1 and 2 are summaries of the weather occurring at Arlington and Marshfield, WI. Figures 1a and 2a represent the precipitation at these sites. Normally (30-year average) about 10 inches of precipitation accumulate by June 1. So far, both sites have accumulated about 7 inches of precipitation, with one major rainfall event (more than one inch) occurring at Marshfield on April 20.

Air temperatures at both Marshfield and Arlington are similar (Figures 1b and 2b). Cool air temperatures occurred between April 20 and May 2 and again between May 10 and 15. The most recent freezing temperature occurred on May 4 at Arlington and May 13 at Marshfield.

Growing degree unit accumulation (Figures 1c and 2c) was ahead of schedule early, but now is behind normal. Corn planted April 15 has accumulated the same GDUs as corn planted May 1. At Arlington, emergence of corn planted April 15, April 29 and May 10 occurred on May 9, May 20, and May 25. Using the model in Figures 1c and 2c, we should have observed emergence about 125 GDUs after planting and should occur on May 9, May 20 and May 24.

Use Figure 1c and 2c to project when various stages of the corn plant will occur for specific planting dates. This model tells you how much time you have left to perform management operations from now until lay-by at V10-12. For example, if the weather is normal from this date forward, corn planted on April 15 should be at V3 and will achieve V6 by June 9-12, V9 by 19-22 and V12 by June 26-July 1.

It is still early in the season and lots can happen, but the corn crop is off to a good start through out much of Wisconsin.

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