Last week some fields of corn and soybeans in several areas of Iowa were hit by hail. Some escaped with less damaging hail, but more damaging were the high winds. Parts of southeast Iowa were hit, as were areas around Cedar Rapids and Waterloo in east-central and northeast Iowa, respectively. Northwest Iowa had pockets of hail damage, too.
Unfortunately, hail damage on a corn or soybean stand is not a rare occurrence in Iowa. “Every year, hail damage occurs somewhere. It’s just a matter of how severe it is and how widespread it is,” notes Mark Licht, Iowa State University Extension cropping systems agronomist. “In most cases, hail damage results in varied levels of defoliation. This leaf damage or complete loss of leaves in some cases will have an impact on crop yield potential at a greater percentage as vegetative development progresses.”
Assessing yield potential of damaged stands
The following discussion is largely for the more severe hail injury that has resulted in moderate-to-severe stand loss, he explains. If you are interested in assessing the yield potential of corn and soybean stands that have defoliation damage, Licht recommends you consult the “Hail on Corn” and “Hail on Soybean” publications listed at the end of this article. He offers the following guidelines to help you decide whether to rip up a damaged stand and replant; or let it go and take whatever it will produce:
Step 1. Assess the existing stand and its yield potential. In assessing the existing crop stand consider not how many plants are present, but rather how many viable plants are present. Split cornstalks 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 soybeans, 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 soybeans, defoliation has minimal impact on yield potential compared to stand loss. Consult the ISU Extension publications (see listing at the end of this article) to assess yield potential from stand and defoliation loss on the remaining stand.
Step 2. Determine what a replanted yield potential would be. Before you decide to rip up a damaged stand and replant, consult these publications (see below) to assess the potential yield you would get from replanting in late June.
Step 3. Determine profitability of an existing stand and a replanted stand. This is often difficult because you have to take into account insurance claims and expected commodity price. The replant decision must also take into account the seed, fuel, machinery and 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.
If you decide to keep the existing stand, plan for season-long weed control. Also, know that bruised stalks and stems will be more susceptible to disease pathogens, and bruised soybean stems will be brittle and can break at the nodes. Plan to harvest a damaged field first due to the increased likelihood of stalk and stem rots, as well as lodging.
If you decide to replant to corn, plant an early adapted hybrid (probably no earlier than 90CRM) to reach maturity ahead of fall frost risks, and plant at a 10% higher seeding rate.
If you replant to soybeans, assess if previous herbicide applications will affect germination and emergence. Plant an early adapted variety (probably no earlier than a 1.0 maturity group in northern Iowa or 1.8 in southern Iowa) to reach maturity ahead of fall frost risk. Plant at a 10% higher seeding rate and in a narrow-row configuration (drilled or up to 15-inch width).
Or if you decide to replant something else, your options for dry hay would be foxtail millet, Japanese millet, teff and oats. Silage options would be foxtail, Japanese and pearl millet; sudangrass; sorghum-sudan; teff; and oats. And lastly, for grazing, the options are the same as for silage, along with radishes and turnips.
Publications to help make decisions on a hailed crop:
Hail on Corn in Iowa – IPM 0078
Hail on Soybean in Iowa – IPM 0079
Corn Planting Guide – PM 1885
Soybean Replant Decisions – PM 1851
Forage and Cover Crop Considerations – ICM News