Unfortunately, hail damage is not a rare occurrence in Iowa. Every year hail damage occurs; it is just a matter of how severe it is and how widespread it is. In most cases, hail damage results in varied levels of defoliation. Defoliation will have an impact on crop yield potential at a greater percentage as vegetative development progresses. The following discussion is largely for more severe hail injury that has resulted in moderate to severe stand loss. For readers interested in yield potential on crop stands with defoliation consult the Hail on Corn and Hail on Soybean publications referenced below.
Step 1: Assess the existing stand and associated yield potential
In assessing the existing crop stand consider not how many plants are present but rather how many viable plants are present. Split corn stalks to examine the growing point. A healthy corn growing point will be white to yellow in color. Discolored and soft growing points have been damaged and will likely result in a non-harvestable ear. For soybean, examine the apical meristem. It is the soybean growing point and uppermost node of the soybean stem. If it is not present or damaged, examine the remaining stem nodes to determine if there is regrowth from the auxiliary buds. Regrowth from the auxiliary buds will result in branches that will flower and produce pods and seeds.
In addition to accounting for yield loss from stand loss, defoliation of the existing stand needs to be considered. In early to mid-vegetative stages for both corn and soybean, defoliation has minimal impact on yield potential compared to stand loss. Consult the publications below to assess yield potential from stand and defoliation loss on the remaining stand.
Step 2: Determine what a replanted yield potential would be
Consult the publications below to assess potential yields from replanting in late June
Step 3: Determine profitability of the existing stand and the replanted stand
This is often difficult because it has to take into account insurance claims and expected commodity price. The replant decision must also take into account the seed, fuel, machinery, labor costs associated with replanting. Both replanting and keeping the existing stand may have additional costs associated with weed control that should be factored into the decision making process.
Decision Point: 1: keep the existing stand
- Plan for season long weed control
- Know that bruised stalks and stems will be more susceptible to disease pathogens
- Know that bruised soybean stems will be brittle and can break at the nodes
- Harvest planning for damaged field should be first due to increased likelihood of stalk/stem rots and lodging
Decision Point 2: replant to corn or soybean
- Replanting to corn
- Plant an early adapted hybrid (probably no earlier than 90CRM) to reach maturity ahead of fall frost risks
- Plant at a 10% higher seeding rate
- Replanting to soybean
- Assess if previous herbicide applications will affect germination and emergence
- Plant an early adapted variety (probably no earlier than a 1.0 MG in northern Iowa or 1.8 MG in southern Iowa) to reach maturity ahead of fall frost risk
- Plant at a 10% higher seeding rate
- Plant in a narrow row configuration (drilled to 15-inch rows)
Decision Point 3: replant to something else
- Dry hay options: Foxtail millet, Japanese millet, Teff, Oats
- Silage options: Foxtail millet, Japanese millet, Pearl millet, Sudangrass, Sorghum*Sudan Hybrid, Teff, Oats
- Grazing options: Foxtail millet, Japanese millet, Pearl millet, Sudangrass, Sorghum*Sudan Hybrid, Teff, Oats, Radishes, Turnips
Publications to help make decisions on a hailed crop;
Hail on Corn in Iowa – IPM 0078
Hail on Soybean in Iowa – IPM 0079
Soybean Replant Decisions – PM 1851
Forage and Cover Crop Considerations – ICM News