Northwest Iowa Crop Update Newsletter
by Todd Vagts
ISU Extension Crops Specialist
Counties Served: Carroll, Calhoun, Crawford, Ida, Monona, Pocahontas and Sac.

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The remarkable recovery of area corn fields...
One week Later

(Click on images for larger view)

It appears the area corn has gone through a remarkable recovery following last week's storm. Many fields that were flattened from the wind have goose-necked back to the up-right position, and in many cases the damage is no longer visible from the road. I would say the immediate concern for pollination should not be a problem in most fields. The next challenges for the lodged and goose-necked corn will be accessing moisture and nutrients with a reduced root system, potentially decreased photosynthesis, stalk diseases this fall and harvest challenges (the fields are still a jungle even though individual plants have goosenecked). Look to this web page for more information and progress of the area's corn as the season progresses.

Assessment of Storm Damage to Corn
Carroll, Crawford, Ida, Sac and Calhoun Counties

The Storm
A major wind and rain storm traveled through south and eastern Ida, north and eastern Crawford, southwestern Sac and most of Carroll counties on Wednesday morning, July 10, 2002. Wind gusts ranged from 50 to 90 mph in the affected areas. Extensive lodging (uprooting) damage was inflicted to the area's corn crop. Very little to no damage was observed on the soybean crop. One to two inches of rain accompanied the storm; fortunately no major hail was reported.

Why Did The Crop Go Down?
The area was approaching extreme drought conditions before the storm arrived; so much of the corn was already suffering from drought stress. Near 70% of the affected corn was beginning to tassel or was within a few days of tassel. Due to the dry surface soil conditions, the corn may not have been able to establish a good brace root system to help support the plant during the storm. A 1/2 inch rain shower a few hours before the storm may have wetted the soil enough to reduce soil strength, thereby also reducing the plant's ability to stay anchored to the soil. The combination of wind, heavy rainfall, reduced brace roots and reduced soil strength caused entire fields to be uprooted and blown flat.

Will The Plant Upright Itself?
A corn plant has a phenomenal ability to readjust itself after lodging. Corn plants that have not yet tasseled and plants that were not uprooted have the best chance of redeveloping a root-system and “goosnecking” back up. Plants that were tasseled and uprooted will most likely “gooseneck” (to some extent) but will not stand back up.

Prospect For Successful Pollination
The storm damage occurred as most fields were beginning pollination. Successful pollination of the corn kernels requires pollen shed from tassels landing on silks emerging from the ear. For pollination to occur on the storm damaged corn, silks will need to be exposed to receive the pollen. A small portion of the plants with tassels erect will provide enough pollen for pollination, yet some silks on downed plants may not receive pollen because they are physically hidden by stalks and leaves. The result will be missing kernels on the portion of the ear where silks did not receive pollen. The success of pollination improves as the plant returns to an upright position. Plants will attempt to right themselves providing that the stalk is not broken and that the root system is still in contact with the soil. The next issues will be grain fill, maturity and harvesting.

Reduced Photosynthesis, Grain Yield and Test Weight
Leaning and downed plants will suffer from lower photosynthesis due to decreased light interception as a portion of the plants' leaves will not be exposed to sunlight. Grain fill will be affected by the reduced photosynthate supply and may result in lower yields and test weights. Grain yields may also suffer as the plant redirects energy from grain fill to regeneration of roots torn away as the crop tipped. Additionally, plants that were uprooted may incur stress from a reduced ability to extract moisture and nutrients from the soil profile.

Harvest Challenges
Harvest will be complicated by the leaning and goose-necked plants, resulting in slow harvest speeds and above normal harvest losses. Think seriously about harvesting lodged areas earlier than normal, provided that the grain is physiologically mature. An earlier harvest will be recommended to remove the crop before ear rots set in.

Post-Storm Assessment
In many areas, storm damage appears unrelated to corn hybrid, soil insect activity or cultural practices. Yet individual field assessments should be made to help determine why certain fields or hybrids lodged worse than others. Consider time of planting, tillage, crop rotation, cultivation, fertility, soil type, previous precipitation, row direction and hybrid.

Contact Your Insurance Agent
Report any storm damage to crops to your insurance agent now. Your agent will not be able to determine any immediate yield losses, but he/she will asses the situation after pollination is complete or at harvest.

Give Your Crop Time to Recover
Storm damage to crops always looks worse immediately after the storm. Give the crop 7 to 10 days, preferably after pollination is complete, before making any evaluations on potential yield losses.

For more information, contact your local ISU Extension Education Director or area Extension Crop Specialist.

Extension Crop Specialist
Todd Vagts, 712-792-2364, vagts@iastate.edu

Extension Education Directors for the Counties of
Carroll: Dennis Molitor – 712-792-2364
Crawford: Coletta Weeda – 712-263-4697
Ida: Carol Heaverlo – 712-364-3003
Sac: Roger Jensen – 712-662-7131
Calhoun: Jerry Chizek – 712-297-8611

ISU Extension Storm Damage Recovery Homepage
http://www.extension.iastate.edu/Pages/communications/recovery/

ISU Extension Web Page
www.extension.iastate.edu

Northwest Iowa Crop Webpage
www.extension.iastate.edu/carroll/crops/

Pictures of lodged corn
http://www.extension.iastate.edu/carroll/crops/storm-damage-02.htm

Information From "The Ohio State Univeristy"

Recovery And Yield Potential Of Root Lodged Corn - Peter Thomison CORN Questions

Strong winds and heavy rains associated with severe thunderstorms can lodge or knock corn plants over, especially if the nodal root system is not fully developed. Recent hot, dry weather conditions and soil compaction may have inhibited good nodal root formation and predisposed plants to such wind injury. Strong winds can pull corn roots part way out of the soil; a condition referred to as root lodging. The problem is more pronounced when soil are saturated by heavy rains accompanying winds. If root lodging occurs before mid-grain fill, plants usually recover at least partly by "kneeing up." This results in the characteristic gooseneck bend in the lower stalk with brace roots providing above ground support. If this stalk bending takes place before pollination, there may be little effect on yield. When lodging occurs later in the season some yield decrease due to partial loss of root activity and reduced light interception may occur. If root lodging occurs shortly before or during pollen shed and pollination, it may interfere with effective fertilization thereby reducing kernel set. Hybrids differ in their ability to resist root lodging.

In a University of Wisconsin study, root lodging was simulated by saturating soil with water and manually pushing corn plants over at the base, perpendicular to row direction. Wind damage was simulated at various vegetative stages through silking (V10 to R1). Compared to hand harvested grain yields of control plants, grain yield decreased by 2 to 6%, 5 to 15% and 13 to 31% when the lodging occurred at early (V10-V12), medium (V13-V15) and late (V17-R1) stages.

(from the CORN Newsletter, Ohio State University, July 19, 1999)

"Goose-necked" Corn