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June
1, 2001
Soybean
Stands and Replant Yield Potential
Dale Hick, Professor and Extension Plant Pathologist
The cold and wet seedbed conditions are delaying
soybean emergence and may result in less than full stands. Some
are considering replanting even though there are plants that
are
still emerging in the field. Cutworms are
also reducing some soybean stands as well as corn stands. Evaluate the stand
for
population and distribution of stand before getting the planter out.
Soybeans that were planted three weeks ago are still emerging. Inspect the germinating
seedlings closely for rotting; some may rot because conditions are favorable
to rotting. If the hypocotyls are still turgid, white on the inside, and not
slimy, they should emerge, particularly if we get some warm weather. Soybeans
will compensate very nicely to less than ideal stands by branching and increasing
pod numbers per node such that yield is
very minimally affected.
Replanting at this calendar date may not be the best economic choice for soybeans
with less than ideal stands. Even with a very low stand of soybeans, the yield
potential of the first planted crop may be higher than a replanted crop. Using
an initial stand of 157000 as a 100% stand with 100% yield potential, a stand
or 118000 (25% reduction) should produce a 98% yield and a stand of 78000 (50%
stand reduction) should produce a 90% yield potential with relatively uniformly
spaced plants. If stands are clumpy, reduce these
yield potentials by 5%.
A June 4 planting date has a yield potential of 82% and the yield potential continues
to be lower with later planting dates.
For June 9, the yield potential is 76%, and 70% for June 14. So the yield potential
of fields with poor stands is likely to be higher than a replanting at this date.
Plus there are replant costs and a short supply of seed of most varieties, especially
the roundup ready ones. These numbers are in The
Soybean
Growers Field Guide
for Evaluating Crop Damage and Replant Options, publication MI-7290-S. The
same
publication gives comparable
information for corn. |
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