Wednesday, May 14, 2014

From the Agronomists: Assessing Hail Damaged Corn

Estimating the yield impact requires an understanding of how damage does and does not impact yield at various corn stages. Direct stand reduction from hail is fairly easy to estimate.  Prior to V6 (the six leaf stage), the growing point of the corn plant is located beneath the soil surface and hailstones are therefore, not able to clip off the growing point.  After V6, the growing point of the corn plant is above ground and hailstones can then clip off the growing point.  Plants with removed growing points are dead and should be subtracted from the stand count

The indirect impact of hail can be a little more complicated to estimate.  Corn should be sliced open to determine if there has been any injury to the growing point even if the growing point has not been removed.  Corn post-V6 or corn almost to V6 can struggle given such injury.  Tillering or other symptoms may develop with time, and while the plant may survive, a damaged growing point will likely eliminate the plant’s contribution to yield.  If the growing point appears damaged or discolored, it should be used to further reduce the stand estimate.  

The indirect impact of hail can also be complicated to estimate because leaf loss influences yield as well.  Before V6 and up to V6, elimination of leaf tissue results in negligible direct yield loss.  V7 stage corn plant may encounter slightly more severe losses.  A fifty percent reduction in leaf area, typically results in a 2% yield loss, while a total loss of leaf area at this stage results in 9-10% yield loss.  By V9, a loss of the entire leaf area often results in yield losses in the area of 15%.

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