Minnesota Crop News > 2001-2008 Archives
D.R. Hicks, Extension
I recently wrote a news release that suggested
thinking about replanting might be premature because the reports
I had indicated the germinating seeds had roots and shoots
that were firm, but growing very slowly. While not a heat wave,
the temperatures have been warmer and corn is emerging. However,
some corn seeds are rotting and I think growers need to look
carefully now at the situation so they can replant if necessary.
Evaluating the Stand Potential. Dig out 10 consecutive
seeds and evaluate their potential to emerge. Some coleoptiles
may have ruptured that lets the seedling "leaf out" under
ground. Count those dead. Seeds that are soft or roots and
shoots that are soft should be counted as dead. Determine the
percent of the 10 seeds that are likely to emerge and determine
the potential plant stand. For example, if 8 of the 10 seeds
would emerge, then the stand should be 80% of the expected
stand. If the desired stand is 30,000 plants per acre, then
the stand should be 80% of that, or 24,000 plants per acre.
Repeat this procedure several times to evaluate the stand for
Compare Yield Potential with Replant Yield Potential.
There are yield and plant population tables in MNCN61 to make
this comparison. For example, planting corn May 25 gives an
86% yield potential. This yield potential is comparable to
a plant stand of 21,000 plants per acre. So if the expected
stand is 21,000 plants per acre or higher, replanting will
not produce a better yield. If the expected stand is less than
21,000 plants per acre, then the decision is more difficult.
One needs to consider the cost to replant and recognize that
maturity will be later and grain will be wetter which will
cost more to dry. Given those facts, I would not replant unless
the stand was lower than 17,000 plants per acre.
Surface Soil Condition. There may be some surface
crusting, particularly in areas that have had an intense rainfall.
If plants are not up and the evaluation is that seeds are germinating
and still alive, then breaking up the surface crust will help
emergence. The rotary hoe is the best piece of equipment to
do this. Operate the rotary hoe with a good speed and inspect
the job it is doing. Rotary hoeing can be done on corn anytime
from before emergence to the seedling 4-leaf stage. If corn
is just about to emerge, there may be an occasional plant that
is injured because a tine hits the corn shoot, but this is
not serious and rarely reduces the stand. With corn that has
just spiked, it is probably best to rotary hoe in the afternoon
when the seedlings are less turgid and less likely to snap
Drags will work, but one needs to use a drag with caution
because there are several different kinds of drags and they
do different things. If there is a wheel track depression,
dragging will move soil into the low area. This covers the
plant deeper, which would not be good for these stressed plants.
And if a preemergent herbicide has been applied, this soil
movement may increase the herbicide rate immediately above
the seed. Drags also get trash in them, which may cause damage
by gouging, as the drag moves across the soil. If a drag is
used, operate it for a distance at the normal speed and then
inspect the job the drag is doing. Then decide if the job can
be improved by adjusting the drag or parking it.