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The Effect of Hail on Corn

Categories: GROWING, CORN
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Hail can be one of the most unpredictable and destructible natural events to impact a growing corn crop. In a matter of minutes, healthy corn can be reduced to a twisted mess of plant material.

Corn, however, is an amazing plant that has the ability to recover quickly depending on the growth stage at the time of the hail event. The resiliency of corn helps maintain as much yield potential as possible.  

The greatest losses to corn from hail are defoliation, especially during the pollination stage. Hail also impacts yield potential from direct plant damage (wounds) and reducing plant stands, depending on the crop stage when the event occurred. When corn reaches the V6 growth stage, the growing point emerges from the soil surface. A hail event can significantly impact the growing point of the plant, resulting in reduced plant stand and yield potential. 

Assessing plant stand and plant health of a field following a hail event is important for replant decisions. A healthy growing point will have a light-colored appearance with a firm texture. New leaves emerging every 3-5 days indicate normal growth. A damaged growing point will have a distinct yellow to brown, water-soaked appearance with a mushy texture.

Evaluating Stands: Plant Population and Distribution 

It is important to determine the plant population and distribution (uniformity) of the existing stands. Count the number of viable plants in 1/1,000th of an acre and multiply by 1,000 to obtain plant population per acre. Take enough counts in the field to represent the existing stand. Plants that are weak or questionable in growth should occasionally be omitted.

After plant population and health have been evaluated, yield potential of the current stand versus replanting can be determined. Table 1 can be used to estimate stand potential. The yield values (expressed as a percent of maximum) are based on uniform distribution of plants within the row(s), which is not usually the case after a hail event.

Simulated Hail Agronomy in Action Trial 

To help visualize the effect of hail on a growing corn crop, a trial at York, NE, was used. Damage treatments were applied to cause a similar loss in leaf area of varying degrees of severity. A string trimmer was used to cause the simulated damage at approximately the V7-V8 growth stage. 4 individual rows were damaged to various levels ranging from 10 to 100% loss of leaf area (Figure 1). No stand loss resulted in this simulated event. Regrowth was monitored weekly up to flowering (Figures 2 and 3).

Recovering Leaf Area Loss
The plants with simulated hail damage defoliation were quickly able to recover, with new leaves emerging from the whorl within 3 days of the original loss. Within 20 days of the simulated event, well over 50% of the defoliation were able to recover even in the most severe treatment. This study saw no “buggy whipping” or twisting of the plant leaf whorl that is sometimes associated with hail events

Impact on Yield Potential 
Hail can reduce corn yield potential in 2 direct ways; by the reduction of crop stand and the loss of leaf area. Final yield is dependent on the severity of damage and the crop growth stage when the hail event occurred. Previous researchers have reported minimal reduction in yield with early season defoliation. For example, at V13, a 60% loss in leaf area only resulted in a 13% loss in yield (Table 2).

Small reductions in final stands prior to V8 typically also result in minimal yield penalty due to the ability of a corn plant to compensate for the stand loss early. However, later season stand loss usually results in a one-for-one ratio in yield loss. For example, a 10% reduction in stand will result in a 10% reduction in yield potential.

Demo Harvest Results
Corn ears were hand harvested at 15% moisture from each treatment row in the demo (Table 3). The row with 100% loss of leaf area resulted in an 18% reduction in yield compared to the other rows with less severe loss of leaf area. Current USDA percent leaf area loss charts based off more extensive trialing suggests 100% leaf loss at V7-V10 would only result in a 9%-16% yield loss (Table 2). The other damaged rows saw no significant variation of yield due to leaf loss. 

Summary
While hail may be one of the most destructive events to a corn crop, corn plants can recover quickly under good growing conditions, depending on the timing of the event and growth of the corn. Hail can be devastating to any crop. Allowing the crop to recover, by assessing the field 5-7 days after a hail event will help make the most informed replant and management decisions. 

For more information on managing hail damage in corn, contact your local Golden Harvest Seed Advisor.

Photos are either the property of Syngenta or used under agreement.
Syngenta hereby disclaims liability for third-party websites.







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