Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information

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June 1, 2004

 

WET WEATHER WOES

Although we have escaped much of the torrential rains of NE Iowa, the continued rainy weather is also having an impact in EC Iowa. Some concerns:

 

Nitrogen Losses

Flooding, ponding, and saturated soils can result in significant losses of soil nitrogen through the processes of denitrification and leaching of nitrate N.  Significant loss of soil N will cause nitrogen deficiencies and possible additional yield loss.   Research in the wetter regions of the cornbelt has demonstrated that in May and June, 4 to 5% of soil nitrate can be lost each day a soil is saturated.

For a good, brief explanation of N loss and calculating possible N loss for your situation, go to
http://www.icorn.com/Reports/iNewsltr-volume-4.html
http://corn.osu.edu/archive/2001/may/01-15.html

Another means to estimate N loss available is to use the Late Spring N Test.  The publication, instructions and sample submission sheet is found at:
http://www.extension.iastate.edu/Publications/PM1714.pdf
http://www.agron.iastate.edu/soiltesting/LSN.pdf

 

Weed Control

Some may be needing to change their weed control strategies in corn. Marksman and higher rates of Banvel and Clarity (greater than 8 oz/A) should not be applied if corn is greater than 8 inches tall. For a review of maximum corn sizes and weed sizes for various corn herbicides, see the May 31, 2004 ICM Newsletter at http://www.ipm.iastate.edu/ipm/icm/2004/5-31-2004/weedsinlatecorn.html.

 

 

Soybean Planting

There are still a number of soybean fields to be planted in the area. On average, soybeans planted in early June in central and southern Iowa have yielded about 10% less than those planted in early May. The yield potential does drop more rapidly after early June. Stick with an adapted full season variety through June. A good source of information on soybeans is "Soybean Replant Decisions" (Pm-1851) at http://www.extension.iastate.edu/Publications/PM1851.pdf.

 

 

Stalk Borers

Stalk borer migration from grassy areas to adjacent corn plants begins at about 1,300 Growing Degree days (GDD) Base 41.  As of the end of the day on May 31, the GDD Base 41 was about 1250 in Cedar Rapids and 1300 in Davenport. One way to manage the stalk borers is to spray an insecticide along field edges and waterways during this migration. See pages 81 - 82 of the May 29, 2000 ICM Newsletter or http://www.ipm.iastate.edu/ipm/icm/2000/5-29-2000/stalkincorn.html for scouting and management details.  A tracking of GDD in the Burlington to Dubuque area is at http://www.extension.iastate.edu/Pages/eccrops/stalkborer.html.

 

If you have any questions, please feel free to contact the Iowa State University Extension Office.
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Last Update: June 1, 2004
Contact: Jim Fawcett fawcett@iastate.edu


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