Hot, dry weather starts to take its toll on young corn plants

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Dry conditions and a record-setting heat wave have started to stress young, Midwestern corn plants, a Purdue Extension agronomist says.

According to the latest update of the U.S. Drought Monitor (http://droughtmonitor.unl.edu/), Indiana and Ohio both have started to experience abnormally dry weather. Both also have endured several days of temperatures in the 90s. The combination can be extremely stressful to young corn plants, which need enough soil moisture to develop their root systems.

"The success or failure of the initial development of a corn plant's nodal, or permanent, root system greatly influences the success or failure of the young corn plant in transition from 'life support,' using kernel reserves, to relying on the developing nodal root system," Bob Nielsen said.

This transition starts at the V3 growth stage, or when corn has three visible leaf collars.

According to Nielsen, corn younger than V3 can look healthy and uniform because it is still relying on kernel reserves. But if stresses stunt development of permanent roots, plants won't be able to make the transition to relying on a fully developed root system.

Stressors that limit root development can include seedling disease; repeated defoliation events, such as frost or sandblasting; shallow soil compaction; corn rootworm or corn nematode injury; or excessively wet, dry, cold or hot surface soils.

If young plants are exposed to any combination of these conditions, especially during root development, Nielsen said, the crop can go from healthy to unhealthy - seemingly overnight. A large portion of Indiana's corn crop is in the midst of the transition.

"The concern raised by farmers about the recent unusually warm temperatures and the forecast for more of the same is a valid one given the current stage of development of much of the state's corn crop," Nielsen said. "Approximately 76 percent of the crop is currently at growth stage V5 (leaf development) or younger. Maybe one-third or more is at V3 or younger.

"Concerns over hot and dry weather right now are similarly valid, given that many fields have not yet successfully developed their initial set of nodal roots."

Excessively hot, dry surface soils during transition can stop elongation of roots, Nielsen said. And prolonged hot, dry soils can kill young corn plants.

But with no control over Mother Nature, Nielsen said the bottom line is that farmers with vulnerable corn need to "pray for rain or turn on the irrigation."

More of Nielsen's comments about the corn crop and the weather can be found on the Chat 'n Chew Café at http://www.agry.purdue.edu/ext/corn/cafe/.



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