Corn Yield Loss Due to Defoliation at Various Growth Stages
Spring Frost. Hail. They both reduce yield. But, How much?
Using the growth stage and the amount of defoliation, predict the
probable yield loss you will experience. The reference chart which is
used in this calculation is from the National Crop Insurance
Association's Corn Loss Instructions.
Using this calculator as a guideline, calculate the potential yield loss
due to hail or spring frost damage. Since hail damage prior to 7 leaf
stage, when the growing point is below ground, does not result in yield
loss, there is seldom any reason to replant corn which has been hail
damaged in the spring. Corn which is at later growth stages when hit
hard by hail may need to be salvaged by using silage, since it will be
too late to replant.
The Causes
Spring Frost
Spring frost injury typically takes place when the corn plant
has less than seven leaves and the growing point is still below ground.
In this case, there is little yield loss potential since the growing
point will still send out new leaves which will produce photosynthate
for the plant as it continues to grow.
If the corn plants have more than 7 leaves and the growing point
is above ground, then there is a danger that the growing point has been
killed and the plant will die. In this case, taking a stand count of
viable plants a week after frost will better reflect the yield potential
of the field rather than using the defoliation chart.
Hail
There are 3 factors which will affect final yield in fields which have
had hail damage.
- The percent of leaf surface which has been lost. Decreased photosynthesis results.
- The stage of growth. Small plants continue to grow new leaves replacing lost capabilities.
- Extent of stalk and ear damage. Hail causes severe bruising on the
stalk which can result in breakage or stalk rot. This affects the
general plant health and late season standability. If the ear is
damaged , there is a potential for ear molds to set in.
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