Joe Lauer, Corn Agronomist
Before 1998 becomes too foggy in our memory, what lessons can we
learn from the corn forage drydown during September 1998? In most
years farmers would most often use the calendar, and typically would
begin thinking about cutting corn forage around 15 Sep. Last year
most farmers would have been ensiling corn that would probably have
turned moldy in the silo because it would have been too dry. Corn
drydown started earlier than normal. Fig. 1 describes corn forage
drydown for 4 counties in Wisconsin. For a concrete stave silo, the
optimum moisture to begin filling the silo is at 65% whole plant
moisture. Last year the average date that these counties would be at
65% moisture was 9 Sep. Nearly a week earlier than normally
expected.
What is interesting though is the rate of drydown that occurred across
the counties. In the past, we have typically seen an average drydown rate of
0.5% per day. Depending on county, the maximum and minimum drydown rate
during 1998 was 0.40 to 0.87 % per day with the average being 0.65% per day.
Since 1996, the slowest corn forage drydown rate reported in various
Wisconsin counties was 0.36 % per day, while the fastest drydown rate was
0.87 % per day (Table 1). Predicted dates when corn forage in the field
would be at 65% moisture range from 11 days in 1997 and 6 days in 1998. The
average predicted date at 65% moisture was 15 Sep in 1997 and 6 Sep in 1998.
|
Table 1. Summary of corn forage drydown rate and
predicted dates for 65% moisture in Wisconsin counties
during 1996 to 1998. |
|
Year
|
County
|
Drydown
rate |
Predicted date
@ 65% moisture |
| |
|
% per day |
|
|
1996 |
Manitowoc |
0.36 |
3 Oct |
| |
|
|
|
|
1997 |
Chippewa |
0.43 |
15 Sep |
| |
Jefferson |
0.55 |
26 Sep |
| |
Manitowoc |
0.60 |
20 Sep |
| |
Sheboygan |
0.78 |
30 Sep |
| |
Waukesha |
0.61 |
26 Sep |
| |
|
|
|
|
1998 |
Dodge |
0.67 |
6 Sep |
| |
Jefferson |
0.67 |
9 Sep |
| |
Manitowoc |
0.40 |
12 Sep |
| |
Marathon |
0.67 |
6 Sep |
| |
Waukesha |
0.87 |
10 Sep |
Some summary points for determining when to harvest corn forage for
ensiling:
- Watch for kernel milkline movement in the cornfields you plan to
ensile.
- Use kernel milkline as a guide to begin checking forage moisture. For
a bunker or bag silo, begin measuring forage moisture when kernels on
ears are around 80% kernel milk; for concrete stave silos, begin
measuring moisture when fields are around 60% kernel milk; and for
oxygen limiting silos, begin monitoring moisture when fields are around
40% kernel milk. Usually about 95% of the time forage moisture will be
too wet at these kernel stages. But, you will know where that field is
at for moisture.
- Once the kernel milkline has begun to move and forage moisture is
known, then use 0.5% per day forage drydown rate to predict the date you
should recheck and/or chop the field to store at the proper moisture for
the storage structure.
