Will Fond du Lac Corn Mature in 2001?

Mike Rankin
Crops and Soils Agent
University of Wisconsin - Extension

How are we stacking-up in 2001 from a corn maturity standpoint?

           We have now turned the calendar to August and reached a point where an educated guess at corn maturity can be made.  To do this, we use growing degree units (GDU).  Much of the early-planted corn has already silked or will start within the next several days.  One of the "benchmarks" often cited regarding corn development is to have corn silking by the end of July.  To reach physiological maturity (black layer stage), it takes about 1100 GDU's.  On average, we can expect about 930 GDU's from today through October 6^th (near our first frost date).  Clearly, there will some corn that won't reach full maturity.  How much of the corn falls into this category will depend on actual GDU's accumulated and first frost date.  Regardless of corn hybrid maturity, it takes essentially the same amount of days/GDU's to progress from silking to physiological maturity.  For you moon watchers, the full moon falls on second day of both September and October.

On the corn silage side of the ledger, there's still some breathing room.  From silking to "full dent", or when corn reaches 65 to 70 percent whole plant moisture, it takes about 880 GDU's.  The 30-year average number of GDU's accumulated in our area from August 5 to September 29 is 875.  Hence, corn fields silking today will probably be ready to chop during the last week of September assuming we have near "normal" temperature and rainfall conditions.  Obviously, corn that has already silked will be ready to chop slightly sooner.  Like last year, there will be a relatively long corn silage harvest season because of the wide fluctuation in planting dates from late-April to mid-June.  It will be important to monitor corn maturity on a field by field basis.  The Fond du Lac County Forage Council will offer several opportunities beginning later this month for growers to bring in corn plants for a whole plant moisture analysis.

Which fields do I chop for silage and which do I harvest for grain?

           This year, this may be a more difficult decision.  Many fields are maturing at an uneven rate.  Additionally, there is extreme variation from field to field.  Dealing with in-field maturity variation is more problematic than field-to-field variation because it is difficult to harvest silage at a uniform optimum stage of maturity.  In general, I think a good rule of thumb is to harvest your best corn fields for silage.  This may contradict conventional thinking, but good corn silage offers a better return than corn grain.  Or, to put it another way, poor corn silage can cost you a lot of money.